US2214908A - Telephone system - Google Patents

Telephone system Download PDF

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Publication number: US2214908A
Authority: US; United States
Prior art keywords: relay; circuit; switch; winding; energizing
Prior art date: 1939-04-21
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.): Expired - Lifetime

Application number

US269139A

Inventor

Clarence E Lomax

Chicago Pier Bakker

Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Associated Electric Laboratories Inc

Original Assignee

Associated Electric Laboratories Inc

Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)

1939-04-21

Filing date

1939-04-21

Publication date

1940-09-17

1939-04-21 Application filed by Associated Electric Laboratories Inc filed Critical Associated Electric Laboratories Inc

1939-04-21 Priority to US269139A priority Critical patent/US2214908A/en

1940-09-17 Application granted granted Critical

1940-09-17 Publication of US2214908A publication Critical patent/US2214908A/en

1957-09-17 Anticipated expiration legal-status Critical

Status Expired - Lifetime legal-status Critical Current

Links

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RYXPMWYHEBGTRV-UHFFFAOYSA-N Omeprazole sodium Chemical compound [Na+].N=1C2=CC(OC)=CC=C2[N-]C=1S(=O)CC1=NC=C(C)C(OC)=C1C RYXPMWYHEBGTRV-UHFFFAOYSA-N 0.000 description 1
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Classifications

- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q3/00—Selecting arrangements

Definitions

the present invention relates to telephone systems and, more particularly, to automatic telephone systems in which nder switches are employed to extend connections between calling lines and selector switches.
Another object of the invention is to provide, in an automatic telephone system of the character noted, improved apparatus for testing the operations of the distributor apparatus and the finder switches, which testing apparatus is so connected and arranged that it does not interfere with the handling of tratlic in the system.
a further object of the system is to provide, in an automatic telephone system of the character noted, an automatic switch embodying improved testing apparatus for controlling the operation thereof, which testing apparatus is connected and arranged to prevent false operation of the switch when it engages a busy line having a metering potential connected to the control conductor thereof.
each link including a finder switch and a selector switch, rst and second groups ofl connector switches, and first and second distributors respectively associated with the rst and second groups of links.
These switches are so connected and arranged that each finder switch has access to each line of the system; each selector switch has access to each connector switch; and the connector switches in the rst and second groups of connector switches respectively have access to the lines in the first and second groups of lines.
each of the finder switches includes rst and second' wiper sets movable in vertical and rotary4 directions and respectively having access to the first and second groups of lines, vertical and rotary magnets operative' respectively to control the vertical and the rotary movements of the wiper sets, a trunk line normally disconnected from the wiper sets, first and second switching relays operative respectively to connect the rst and. Sond wiper sets to the trunk line, and means responsive to the operation of one of the switching relays for preventing the operation of the other of the switching relays.
the distributor associated with each group of nder switches comprises a rotary switch operative to select an idle one of the nder switches in the group, means for governing the rotary and the vertical magnets of the selected nder switch, a first test relay operative in response to the seizure of a calling line by the first wiper set in the selected nder switch, a second test relay operative in response to the seizure of a calling line .
the second wiper set in the selected finder switch means responsive to the operation of the rst test relay for causing the operation of the first switching relay in the selected finder switch, means responsive to the operation of the second test relay for causing the operation of the second switching relay in the selected finder switch, and means responsive to the operation of either one of the switching relays in the selected finder switch for causing the operation of the rotary switch.
the rst and second test relays in the distributor are individually provided with operating circuits, each operating circuit including a uni-directional current conducting device in the form of a copper oxide rectifier.
the arrangement of the copper oxide rectifier in the operating circuits of the first and second test relays prevents these relays from being energized when these operating circuits are completed in such a manner that current tends to flow therein in a direction opposite to that of the normal flow of current therein. This arrangement prevents false operation of the first and second test relays when the rst and second ⁇ wiper sets in the selected finder switch respec-a tively engage busy lines having a metering potential connected to the control conductors 40 thereof.
each of the distributors includes a transfer relay provided with an operating circuit; and means is included in each idle nder switch in the associated group of nder switches for completing the operating circuit of the transfer relay, whereby the voperating circuit of the transfer relay is interrupted when all of the finder switches in the associated group are busy.
First and second start conductors are provided which are operatively associated with the rst 'and second groups of lines, whereby start potentials are connected to the start conductors in re- Spouse t9 the creatien 0i calling conditions 0n Cil - restored position.
the first start conductor is associated with the first distributor, when the transfer relay in the first distributor occupies its operated position, and is associated with the second distributor, when the transfer relay in the first distributor occupies its
the transfer relay in the second distributor controls the association of the second start conductor with the first and second distributors in a similar manner. Operation of each of the distributors is initiated when a start potential is connected to a start conductor associated therewith; and each of vthe distributors is effective when operation thereof is initiated to cause a selected one of the finder switches in the associated group to find a line having a calling condition thereon. Also, each of the distributors includes timing means operative to interrupt the operating circuit of the transfer relay therein in the event the finder switch selected thereby fails to operate. In order to test the operations of the distributors and the finder switches associated therewith, manually operable means comprising a busy switch and a number of test jacks is individually associated with each of the distributors.
the selector switch of each of the links comprises a test relay having a field structure provided with a first magnetic path including a shunt leg and a second magnetic path including a movable armature, first and second windings being associated with the field structure.
a first circuit is provided for energizing the first winding; and a s econd circuit'including atest'wiper of the finder switch is provided for energizing the second winding.
the first winding is effective, when energized with current flowing in the first circuit, to produce a magnetic flux in the field structure traversing the first magnetic path;
the second winding is effective, when energized with current flowing in a first direction in the second circuit, to produce a magnetic flux in the field structure traversing the first magnetic path; and when energized with current flowing in a second direction in the second circuit to produce a magnetic flux in the field structure opposing the magnetic flux traversing the shunt leg, thereby to 'divert magnetic flux from the first magnetic path into the second magnetic path.
the test relay is so constructed and arranged that it is operated when magnetic flux traverses the second magnetic path.
the selector switch comprises automatic means operative to drive the test wiper thereof step by step over a group of test contacts in the contact bank thereof; lwhich test contacts are adapted to have connected thereto an idle potential, a busy potential, or a metering potential, depending upon the condition of the associated line.
the second circuit is so connected and arrangedthat no current flows therein, when the test wiper engages a test contact having a busy potential connected thereto; that current flows therein in the first direction, when the test wiper engages a test contact having a metering potential connected thereto; and that current flows therein in the second direction, when the test wiper engages a test contact having an idle potential connected thereto.
each selector switch comprises means controlled by the operation of the test relay therein for arresting the operation of the automatic means.
the telephone system there illustrated comprises an exchange including an operator position 2I0 and terminating a plurality of subscriber lines, including the subscriber lines IUI and 230.
the exchange comprises a number of links, including the links 60 and 10, and a number of connector switches including the connector switch 2
Each of the links comprises a 200 point finder switch having access to each line in the system and a 100 point selector switch having access to each of the connector switches; while the connector switches are of the 100 point type and are arranged in first and second groups, respectively, Vhaving access to the first and second groups of lines of the system.
the links are arranged in first and second groups, each group of links being provided with a distributor individual thereto for assigning idle ones of the links in the group to the use of calling ones of the lines.
the number of links included in each group is determined by the amount of traiiic which the exchange is required to handle and usually satisfactory service may be rendered when each of the two groups of links includes ten links.
the number of connector switches required is determined by the amount of traffic which the exchange is required to handle and usually satisfactory service may be rendered when each of the two groups of connector switches includes ten connector switches.
the first group of links includes the link 60, which comprises the finder ⁇ switch
the first and second groups of lines are respectively associated with the distributors 300 and 3
2 are so connected and arranged that a. call initiated on a line in the first group of lines is assigned for use an idle link in the second group of links in the event all of the links in the first group of links are busy; and a call initiated on a line in the second group of lines ⁇ is assigned for use an idle link in the first group of links in the event all of the links in the second group of links are busy.
a subscriber substation is associated with each of the subscriber lines, the subscriber substations A and B being respectively associated with the subscriber lines and 230.
Each of the subscriber substations is provided with a telephone instrument, a dial mechanism and a ringer.
a line circuit is individually associated with each of the subscriber lines, the line circuits
these line circuits are identical, each including a line relay and a cutol relay, these relays in the line circuit
a meter relay is associated with each of the line circuits, these relays associated with the line circuits
each of the links is connected and arranged in a manner similar to that of the link 60 which comprises the finder switch
30 comprises a switching mechanism
40 comprises upper and lower wiper sets respectively including the wipers
this Strowger mechanism includes a vertical magnet M
this Strowger mechanism Associated with this Strowger mechanism are two sets of switch springs SI15 and SI1! which are actuated by the movement of the carriage in the vertical direction away from its normal position, and a set of switch springs S
30 comprises a start relay R
the selector switch 200 comprises a switching mechanism of the Strowger type including a bank of xed contact sets arranged in ten vertical levels, each level including ten circumferentially disposed contact sets, each contact set terminating a line extending thereto. Also, the Strowger mechanism 20
this Strowger mechanism includes a vertical magnet M236 for moving the carriage in the vertical direction, a rotary magnet M231 for a line relay R260, a hold relay R210, a transfer l relay R290, a test relay R265 and a switching relay R2
each of the distributors is connected and arranged in a manner similar to that of the distributor 300 individually associated with the first group of links which comprises, as best shown in Fig. 3, a rotary switch 30
includes a rotary magnet M308 for driving the wipers associated with the contact banks in a rotary direction.
the distributor 300 also comprises a start relay R345, a busy transfer relay R340, a ⁇ step relay R310, a transfer relay R360, a timing relay R315, rst and second test relays R320 and R325, respectively, and a number of control relays R350, R380, R390 and R330. Also associated with the distributor 300 are a supervisory lamp L309, a number of jacks J33I, J332 and .1333 and a busy switch S334 which are utilized for test purposes in a manner more fully described subsequently.
the distributor 300 is of the preselective type in that an idle link in the rst group of links is selected to be assigned to the use of a calling line in the first group of lines prior to the initiation of a call on the line therein and another idle link in the first group of links is automatically selected to be assigned to the use of the next calling line in the first group of lines as soon as the selected link operates to find a calling line in the first group of lines.
the distributor 300 is so connected and arranged that, when all of the links in the rst group of links are busy, the start circuit of the distributor 300 is transferred to the distributor 3
each of the connector switches is connected and arranged in a manner similar to that of the connector switch 2
4 extends to the connector switch 2
the operator position 2IU is of conventional connection and arrangement and includes apparatus thereat for answering an incoming call extending thereto.
the call is first initiated at the substation A by removing the receiver of the telephone instrument thereat from its hook, thereby to complete a bridge path at the substation A between the line conductors CIU2 and C
a circuit is completed for energizing the line relay RI2U -in the line circuitgIUU individually associated with the subscriber line IUI, which circuit extends from ground, at RAI I2, by Way of RAI
2U When energized over the above-traced circuit the line relay R
this application of ground potential to the control conductor CI90 marks, by way of the circuit network
20 completes, at RAI2I, a path for applying battery potential to the control conductor CI04 of the subscriber line IUI, thereby to mark the rotary positions of the contact sets in the contact banks of the Strowger mechanisms included in the tinder switches terminating the subscriber line IUI.
This path for applying battery potential to the control conductor CIU4 of the subscriber line IUI extends from battery at the winding of the cutoff relay RII U, by way of the winding of RI IU andRA
This application of ground potential to the start conductor C3I6 extending into the distributor 300 completes a circuit for energizing the start relay R345, this circuit extending from ground, at RAI 25, by way of the control conductor CI'3I, a resistor included in the circuit network ISI, the start conductor C3IU, RA34I, RC343 and the winding of R345 to battery.
the start relay R345 When energized over the above-traced circuit, the start relay R345 operates to initiate operation of the distributor 300. thereby to cause the preselected idle one of the links in the first group of links to be assigned to the use of the calling subscriber line.
the start relay R345 completes, at RA343, a circuit for energizing the control relay.R350 in series with the winding of the rotary magnet M303 of the rotary switch 30
the control relay R35U does operate.
the control relay R350 completes.
the busy transfer relay R340 is normally energized by way of a number of multiple circuits completed in idle ones of the finder switches of 'the first group of links, one ofA these multiple circuits being completed at this time in the finder switch
the relay R350 completes, at RA355, a point in a circuit traced hereinafter for energizing the timing relay R315, prepares,
a point in a circuit traced hereinafter for energizing the lower winding of the transfer relay R300 prepares, at RA353, a point in an alternative circuit traced hereinafter for energizing the winding thereof in series with the winding of the rotary magnet M300 of the rotary switch 30
control relay R350 completes, at RAI, a circuit traced hereinafter for energizing the start relay RI of the finder switch
link 5U in the rst group of links has been previously selected by the distributor 300 ,for the use of a calling line in the first group of lines.
engage the contacts in the associated contact banks terminating the control conductors extending to the finder switch
30 extends from ground, at RA35I, by way of RA35I, the wiper 303 and associated contact of the rotary switch 30
the start relay RI40 When energized over the abovetraced circuit, the start relay RI40 operates to complete,l at RAI4I, an obvious path between the line conductors CI I6 and CI I1 of the trunk line II5 extending between the ilnder switch
the line relay R260 When energized over the above-traced circuit, the line relay R260 operates to interrupt, at RA26I and RC263, a point in a circuit, traced hereinafter, for energizing the winding of the release magnet M238, and to complete, at RA26I and RC262, a circuit for energizing the hold re-y lay R210, the last-mentioned circuit extending from ground at RA2I0 by way of RA2
the hold relay R210 When energized over the above-traced circuit, the hold relay R210 operates to complete, at RA21I, a multiple path for applying ground potential to the control conductor CI I8 of the trunk line I I5, to complete, at RA212, a circuit for energizing the winding on the core leg L261 of the field ⁇ structure of the test relay R265, to prepare, at RA213, a circuit, traced hereinafter, for energizing the winding on the core leg L268 of the fleld structure of the test relay R265, to interrupt, at RA214 and RC216, a further point in the previously mentioned circuit for energizing the winding of the release magnet M230, and to prepare, at RA214 and RC215, a point in a circuit, traced hereinafter, for energizing in multiple the lower winding of the transfer relay R290 and the winding of the vertical magnet M236.
the application of ground potential to the control conductor CI I8 of the trunk line I I5 completes a circuit for energizing the upper winding of the transfer relay R290, this circuit extending from the grounded control conductor CI I8 by way of the set of switch springs S211 and the upper winding of R290 to battery.
the transfer relay R290 When energized over the above-traced circuit, the transfer relay R290 operates to interrupt, at RA29I, a point in a circuit, traced hereinafter, for energizing the winding of the rotary magnet M231 and to interrupt, at RA292, a point in the previously mentioned circuit for energizing the winding of the release magnet M238.
the selector switch 200 is conditioned to be responsive to a digit .aled thereinto, thereby to cause the wiper set if the Strowger mechanism 20
the start relay RI40 prepares, at RAI42, a circuit, traced hereinafter, for energizing the second test relay R325 in the distributor 300, interrupts, at RA
the circuit for energizing the vertical magnet MI10 extends from ground, at RA352, by way of RA352, RA31i, RA36I, RC362, the wiper 304 and associated contact of the rotary switch 30
the vertical magnet MI10 When energized over the above-traced circuit, the vertical magnet MI10 operates.
the vertical magnet MI10 drives the carriage of the Strowger mechanism
the circuit for energizing the step relay R310 extends from ground, at MAI10, by way of MAI10, the interrupter conductor C3I9 and the winding of R310 to battery.
the step relay R310 When energized over the above-traced circuit, the step relay R310 operates to interrupt, at RA31 I, a point Vin the previously traced circuit for energizing the winding of the vertical magnet MI10, thereby to cause the vertical magnet MI10 to restore. Upon restoring, the vertical magnet MI10 interrupts, at MAI10, the previously traced circuit for energizing the step relay R310, thereby to cause the latter relay to restore.
the step relay R310 completes, at RA31I, a point in the previously traced circuit for energizing the winding of the vertical magnet MI10, whereupon the vertical magnet MI10 operates to drive the carriage of the Strowger mechanism
30 continue to interact in the above-described manner, thereby to cause the carriage of the Strowger mechanism
30 is driven two steps in the vertical direction, whereupon the control wiper
a circuit is then completed for energizing the lower Winding of the transfer relay R360 in series with the winding of the step relay R310, this circuit extending from the grounded contact
the above-traced circuit for energizing the lower winding of the transfer relay R360 in series with the winding of the step relay R310 is completed immediately the carriage of the Strowger mechanism
the transfer relay R360 Shortly after the transfer relay R360 is energized over the above-traced circuit it operates, this relay being of the slow-to-operate type. Upon operating, the transfer relay R360 completes, at RA369, a holding circuit traced hereinafter for energizing the upper winding thereof, interrupts, at RA366 and RC361, a point in the previously traced circuit for energizing the lower winding thereof in series with the step relay R310, and prepares, at RA366 and RC368, a circuit traced hereinafter for energizing the first test relay R320.
the transfer relay R360 interrupts, at RA365, a point in the previously traced original circuit for energizing the control relay R350 in series with the winding of the 6 l rotary magnet M303, an alternative circuit for energizing the control relay R350 in series with the winding of the rotary magnet M308 being completed at this time; interrupts, at RAIBI and RC362, a further point in the previously traced circuit for energizing the vertical magnet Ml10; and prepares, at RA36
the control relay R350 completes, at RA356. a point for energizing the timing relay R315, this circuit extending from ground, at RA356, by way of RA356, RA333, RC334, and the winding of R315 to battery.
the timing relay R315 When energized over the above-traced circuit, the timing relay R315 operates to complete, at RA316 and RC318, RC313, a circuit for energizing the control relay R380, this circuit extending from ground, at 'RA356, by way of RA356, RA316, RC318, RC319, and the winding of R380 to battery.
control relay R380 Shortly after the control relay R380 is energized by Way of the abovetraced circuit, this relay operates, this relay being of the slow-to-operate type. Upon operating, the control relay R380 completes, at RA386, a holding circuit for energizing the winding thereof, this circuit extending from ground, at RA356, by Way of RA356, RA316, RC318, RA386, and the winding of R380 to battery. Also, upon operating, the control relay R380 interrupts, at RA382 and RC383.- a point in a.
t'he control relay R380 completes, at RA38
control relay R380 completes, at RA385, an obvious circuit for energizing the upper winding of thecontrol relay R330, thereby to cause the latter relay to operate.
control relay R330 completes, at RA336, a holding circuit for energizing the lower Winding thereof, this circuit extending from ground at RA35
control relay R330 interrupts, at RA330 and RC33I, a point in the previously traced original circuit for energizing the control relay R350 in series with the winding of the rotary magnet M308, and completes, at RA330 and RC332, a multiple alternative circuit for energizing the control relay R350 in series with the winding of the rotary magnet M308.
control relay R330 interrupts, at RA333 and RC334, a point in the previously traced circuit for energizing the timing relay R315; prepares, at RA333 and RC335, a point in the previously mentioned holding circuit for energizing the upper winding of the transfer relay R360; prepares, at RA331, a point in a circuit traced hereinafter for energizing the first test relay R320; and prepares, at RA338, a point in a circuit traced hereinafter for energizing the second test relay R325.
the 1r-tter relay restores, thereby to cause-the weighted armature RA316 thereof to vibrate between the rssociated contacts RC311 and RC318, in order to. complete intermittently the previously traced holding circuit for energizing the control relay R380. It is noted that the weighted' armature RA310 vibrates between the contacts noted for a predetermined time interval, thereby to retain the control relay R380 in its operated position during this time interval.
the previously mentioned holding circuit for energizing the upper Winding of the transfer relay R360 extends from ground, at RA355, by way of ,RA353, RA333, RC3, RA382, RC3, RAS, and
the circuit for energizing the step relay R310 extends from ground, at MA
the step relay R310 When energized over the abovetraced circuit, the step relay R310 operates to interrupt, at RA31
interrupts, at MAI1I, the previously traced alternative'circuit for energizing the step relay R310, thereby to cause the step relay to restore and recomplete, at RA31
30 continue to interact in the manner described above until the carriage of the Strowger mechanism
a circuit is completed for energizing the winding of the cutoff relay RI I0 in the line circuit
the last-mentioned circuit extends from ground at RA331 by way of RA331, the unidirectional current conducting device or copper oxide rectifier 341, the winding of R320, RC368, RA366, the wiper 302 and associated contact of the rotary switch 30
00 When the cutofl' relay RI I0 in the line circuit
60 extends from ground, at RA352, by way of RA352, RA31I, RA36I, RC36I, RA32I, RC323, the wiper 306 and associated contact ofthe rotary switch 30
60 When energized over the ⁇ above-traced circuit, the switching relay R
are respectively connected, at RAIGi, RA
0 When energized over the above-traced circuit, the cutoi relay R
the cutoff relay RI Il completes, at RAI I4, a circuit for energizing the winding of the meter relay R
This circuit extends from the grounded control conductor CIII of the subscriber line
This circuit extends from ground by Way of the upper winding of R260, RC2
11 of the set of switch springs SI are actuated into disengagement and the switch springs
is interrupted; and when the switch springs
30 interrupts, at RA
60 interrupts, at RA
This application of ground potential to the guard conductor C322 completes a circuit for energizing the Winding of the rotary magnet M308 of the rotary switch 30
the rotary magnet M308 When energized over the above-traced circuit, the rotary magnet M308 operates, thereby to condition the wipers of the rotary switch 30
the rotary magnet M308 interrupts, at MA308, a point in the previously traced alternative circuit for energizing the winding thereof in series with the winding of the control relay R350, thereby to cause the control relay R350 to restore.
the control relay R350 interrupts,I at RA353 and RC355, a point yin the pre- Viously traced circuit for energizing the winding of the rotary magnet M308, thereby to cause the rotary magnet M308 to restore.
the rotary magnet'M308 drives the wipers 302 to 301, inclusive, of the rotary switch 30
the previously ytraced circuit for energizing the start relay R345 in the distributor 300 is interrupted, thereby to cause the start relay R345 to restore.
the start relay R345 interrupts, at RA346, the previously traced original circuit the control relay R350 in series with the winding of the rotary magnet M300.
the control relay R350 restores, as previously noted, it interrupts, at RA359, a further point in the circuit for energizing the winding thereof in series with the winding of the rotary magnet M308.
is connected by way of the self-interrupting contact MA308 and the winding of the rotary magnet M308 to battery, this connection extending from the wiper 305 by way of RA353, RC354, RA345, MA308, and the winding of M300 to battery.
ground potential appears upon the guard conductor thereof, corresponding to the guard conductor C322 of the finder switch
the rotary magnet M308 operates tocondition the wipers of the rotary switch 30
the rotary magnet M308 When the previously traced circuit for energizing the winding of the rotary magnet M308 is interrupted, the rotary magnet restores, thereby to drive the wipers of the rotary switch 30
the rotary magnet M308 continues to operate in the above-described manner in order to cause the wipers of the wiper set 30
the finder switch of an idle link of the first group is found, further operation of the rotary magnet M300 is interrupted, due to the fact that no ground potential appears upon the guard conductor thereof, corresponding to the guard conductor C322 of the nder switch
the distributor 300 operates automatically to preselect an idle link in the first group of links immediately after the previously selected link in the first group of links is taken for use by a calling line and operates to nnd the calling line.
the distributor 300 operates in the above-described manner in order to preselect an idle link in the nrst group of links only in the event that idle link is available in the first group of links, due to the fact that the busy transfer relay R340 is retained in its operated position at this time only in the event that ground potential is present upon the all-trunks-busy conductor C32
the busy transfer relay R340 interrupts, at RA344, a further point in the alternative holding circuit for energizing the winding thereof, interrupts, at RA345, a point in the previously traced circuit for energizing the winding of the rotary magnet M308, thereby to prevent operation of the rotary magnet M300, and interrupts, at RA34
6 extending to the distributor 300 is connected, together with the start conductor C3l5, to the conductor C321 extending to the distributor 3
2 is operative to assign idle links in the second group of links to the use of calling lines in both the first and second groups of lines.
an alternative path for applying Agli und potential to the guard conductor C322 is path extending from ground, at the switch spring
This application of ground potential to the guard conductor C322 insures that the distributor 300 will not operate to select the busy link 60 at this time.
40 interrupts, at RAI" a further point in the previously traced circuit for energizing the rotary magnet Ml 1
control relay R350 in the distributor 300 interrupts, at RA352, the previously traced original circuit for energizing the switching relay R
the transfer relay R360 interrupts, at RA369., a further point in the holding circuit for energizing the upper winding thereof, interrupts, at RA366 and RC368, a point in the previously traced circuit for energizing the first test relay R320, and prepares, at RA36-6 and RC361, a point in the previously traced circuit for energizing the lower winding thereof.
the transfer relay R360 prepares, at RA365, a point in the previously traced original circuit for energizing the winding of the control relay R350 in series with the winding of the rotary magnet M308, interrupts, at RA36
the control relay R380 Upon restoring, the control relay R380 interrupts, at RA386, a further point in the holding circuit for energizing the winding thereof, interrupts, at RA385, a point in the holding circuit for energizing the upper winding of the control relay R330, thereby to cause theflatter relay to restore, and interrupts, at RA382 and RC384, a further point in the holding circuit for energizing the upper winding of the transfer relay R360.
control relay R380 prepares, at RA382 and RC383, a point in a circuit traced hereinafter for energizing the upper winding of the control relay R390, and interrupts, at RA38I, a point in the previously traced alternative circuit for energizing the winding of the control relay R350 in series with the winding of the rotary magnet M308.
control relay R330 interrupts, at RA336, a further point in the previously traced holding circuit for energizing the 'lower winding thereof, interrupts, at RA331, a further point in the previously traced circuit for energizing the first test relay R320, and interrupts, at RA338, a point in thepreviously mentioned circuit for energizing the second test relay R325.
control relay R330 interrupts, at RA333 and RC335, a further point in the holding circuit for venergizing the upperV winding of the transfer relay R360, prepares, at RA333 andv RC334, a point in the previously traced circuit for energizing the timing relay R315, interrupts, at RA330 and RC332, ⁇ a further point in the pre;
the first test relay R320 interrupts, at RA32
the subscriber substation A is operatively'connected by Way of the previously traced circuit to the selector switch 200.
the distributor 300 is complet-ely released each time a finder switch of a link selected thereby operates to nd a calling line in spite of the fact that the start relay R345 therein remains operated, due to the presence of other calling lines in the iirst group of lines.
the start relay R345 in the distributor 300 remains in its operated position, and, when the transfer relay R360 and the control relay R330 restore, the previously traced original circuit for energizing the control relay R350 is recompleted, assuming that the rotary magnet M308 has already operated to cause the rotary switch 30
the distributor 300 is operative to cause the finder switch of a selected link in thel first group of links, such as the finder switch
2 operates.r thereby to cause the conductors C321 and C328 therein to be connected together, in a manner similar to that previously explained, incident to the restoration of the busy transfer relay R340 in the distributor 300 when all of the links in the ilrst group of links are busy.
5 is extended by way of the conductor C321 and the distributor 3
30 of the link 00, incident to the operation of the start relay R345 in the distributor 300, are the same as previously explained, assuming that the calling line in the second group of lines is also accessible to the upper wiper set of the Strowger mechanism 40 of the flnder switch
the iinder switch 30 of the link 60 is operative in a manner substantially identical to that previously explained to find a calling line in ⁇ either ⁇ the rst group of linesor the second group of lines and accessible to the lower wiper set of the switching mechanism
30 is rotated in the rotary direction to the position of the contact set terminating the calling subscriber line, battery potential is encountered by the wiper
the second test relay R325 When energized over the above-traced circuit, the second test relay R325 operates to interrupt, at RA326 and RC32I, a point in the previously traced circuit for energizing the rotary magnet M
the second -test relay R325 completes, at RA325 and RC320, the previously mentioned circuit for energizing the switching relay R
50 When energized over the above-traced circuit, the relay R
the path for applying ground Potential to the guard conductor C322 extends from ground, at the switch spring
'I'his application of ground ⁇ potential to the guard conductor C322 causes the distributor 300 to be released and the rotary switch 30
50 interrupts, at RAI, a point in the previously traced pleteS
50 connects, the trunk line
35 is connected to the trunk line III, the line circuit individually associated with the calling subscriber line and the selector switch 200 operate in the previously described manner.
the ilrst test relay R320 comat RA32
30 operates to iind the calling line accessible to the upper wiper set of the Strowger mechanism
40 may engage contacts in the associated contacts of contact sets in the associated contact bank terminating the control conductors of subscriber lines having either ground or booster battery potential "appearing thereupon; ground potential appearing upon the control conductors of the subscribers lines when the subscriber lines are bus tery, ⁇ potential appearing upon lines when the subscriber lines are being metered.
the control relayy is completed substantially identical to the abovetraced path, tending to energize the winding of the iirst test relay R320.
the copper oxide rectiiier 341 is so connected and arranged that current is prevented from traversing this circuit ina direction extending from the wiper
the iirst test relay R320 does not operate when the wiper
a path is completed for short-circuiting the winding of the second test relay R325 when the wiper
the copper oxide rectifier 348 prevents the winding of the second test relay R325 from being effectively energized in the last-mentioned case.
the vibratory armature RA316 of the timing relay R315 in the distributor 300 assumes an intermediate position between the associated contacts RC311 and RC318, thereby to interrupt the previously traced holding circuit for energizing the control relay R300 in order to cause the control relay R380 to restore.
the control relay R380 interrupts, at RA382 and RC384, the previously traced holding circuit for energizing the upper winding of the transfer relay R360,'and completes, at RA382 and RC383, a. point in the previously mentioned circuit for energizing the upper winding of the control relay R390.
the circuit for energizing the upper winding of the control relay R390 extends from ground, at RA356, by way of RA356, RA333, RC335, RA382, RC383, and the upper battery.
R390 When energized R390 operates to complete, at RA392, a holding circuit for energizing the lower winding thereof, this circuit extending from the grounded conductor C330 by way of the switch springs 330 and 331 of the busy switch S334, RA302, and the lower winding of R390 to battery.
ground potential appears upon the conductor C330 in the distributor 3
the relay R390 completes, at RA39I, a path for short-circuiting the winding of the control relay R350, this path extending from the upper terminal of the winding ofV R350, by way of RA39I, RA353, RC355, MA308, RA345, and the winding of R350 to the upper terminal thereof.
the winding of the control relay R350 When the winding of the control relay R350 is short-circuited, it restores to interrupt, at RA353 and RC355, a point in the previously traced path for short-circuiting the winding thereof, and to complete, at RA353 and RA354, an alternative path for short-circuiting the winding thereof.
the alternative path for short-circuiting the winding of the control relay R350 extends from the upper terminal of the winding of R350 by way of RA39I, RA353, RC354, and the winding of R350 to the upper terminal thereof. Also, upon restoring, the control relay R350 interrupts, at RA358, a point in the previously traced alternative circuit for energizing the winding of the busy transfer relay R340.
control relay R390 interrupts, at RA333, the previously traced original circuit for energizing the winding of the busy transfer relay R340, and interrupts, at RA334, the normal connection between the conductor C329 extending into the distributor 3
the busy transfer relay R340 completes, at RA34
the control relay R380 completes, at RA392, a circuit forilluminating the supervisory lamp L300, this circuit extending from the grounded conducor C330 by way of the switch springs 338 and 331 of the busy switch S334, RA392, and the lamp L303 to battery. Illumination of the supervisory lamp L30! indicates to the exchange attendant that the distributor 300 is locked out of service. The release of the remainder of the operated relays in the distributor 300, incident to the restoration of the control relay R350 and the busy transfer relay R340, is the same as that previously described. At this time, the distributor 300 is locked out of service, as previously noted.
the distributor 300 remains locked out of service until the busy switch S334 is operated away from its normal position and returned thereto, which switch will not be thus operated until the defective iinder switch of one of the unks in the Vietnamese group of links is found and again placed in working order.
the busy switch S334 is operated away from its normal position, the switch springs S331 and S333 are actuated into disengagement, thereby to interrupt the previously traced holding circuit for energizing the lower winding' of the control relay R390 in order to cause the control relay R390 to restore.
the control relay R390 reconnects, at RA394, the conductor C328 extending into the distributor 3
30 of the link 60 embodies an arrangement for causing the distributor 300 to select another idle link in the iirst group of links for the use of the calling subscriber line
the nder switch 30 of the link 60 may be rendered busy .by operating the busy switch SI83.
the busy switch SI 83 When the busy switch SI 83 is operated, the switch springs
an arrangement for testing'the operation of the distributor 300 and the finder switches of the links associated therewith.
This arrangement comprises the busy switch S334 and the test jacks J33I, J332 and J333.
the busy switch S334 is operated away from its normal position and plugs are inserted into the jacks J33
the busy transfer relay R340 thenrestores to interrupt, at RA344, a further point in the previously traced alternative holding circuit for energizing the winding thereof, to interrupt, at RA345, a point in the previously traced circuit for energizing the winding of the control relay R350 in series with the winding of the rotary magnet M308, to interrupt, at RA34
2 is operative to assign idle links in the second group of links to the use of calling lines in both the rst and second groups oi' lines. Accordingly, the test of the distributor 300 at this time does not interrupt trailc on the subscriber lines in the rst group of lines.
an alternative circuit traced hereinafter, is prepared for energizing the winding of the control relay R350 in series with the winding of the rotary magnet M308; and, when the' plug is inserted into the jack J332, an alternative circuit is completed for energizing the winding of the start relay R345.
the last-mentioned circuit extends from ground by way of the jack J 332 and associated plug, the resistor 339, and the winding of R345 to battery.
the start relay R345 When energized over the above-traced circuit, the start relay R345 operates to complete, at RA346, the previously mentioned alternative circuit for energizing in series the winding of the control relay R350 and the winding of the rotary magnet M308, this circuit extending from ground, at RA330, by way of RA330, RC33I, RA365, RA346, the winding of R350, the jack J33
control relay R350 When energized over the above-traced circuit, the control relay R350 operates. However, the rotary magnet M308 does not operate due to the high series resistance of the winding of the control relay R350.
control relay R350 Upon operating, the control relay R350 prepares, at RA351, a point in the previously traced circuit for energizing the lower winding of the transfer relay R380, and completes, at RA356, the previously traced circuit for energizing. the winding of the timing relay R315, thereby to initiate the timing operation of the relay R315 and the control relays R380, R390 and R330 in the previously described manner.
the control relay R350 prepares, at RA359, a point in an alternative circuit for energizing the winding thereof in series with the Winding of the rotary magnet M308; prepares, at RA353 and RC355, a point in the previously traced circuit for energizing the winding of the rotary magnet M308 directly from the guard conductor C322; prepares, at RA352, a point in the previously traced circuit for energizing the vertical magnet of the iinder switch of the selected link, and completes, at RA35
30 operates, in the previously described manner, in order to seize the calling subscriber line.
30 is i'lrst driven 'in the vertical direction ten steps away from its normal position, whereupon the control wiper
the transfer relay R360 completes, at RA36
then operates to drive the carriage of the Strowger mechanism
the distributor 300 When another idle link in the first group of links is selected in the previously described manner, the distributor 300 again operates to cause the nder switch of this link either to seize a calling vline in the iirst or second group of lines or to be operated, in the above-described manner
the distributor 300 and the idle links in the first group of links are reoperated in the above-described manner so long as the busy switch S334 remains operated away from its normal position and the plugs are retained irl the jacks J 33
the busy switch S334 In o-rder to restore the operation of the distributor 300 to normal, the busy switch S334 is returned to its normal position and the plugs are removed from the Ijacks .133
plugs are inserted into the jacks J 332 and J 333, while the busy switch S334 remains in its normal position.
the previously traced alternative circuit for energizing the start relay R345 is completed; and, when the plug is inserted into the jack J 333, an alternative circuit is completed for energizing the winding of the step relay R310.
'I'he last-mentioned circuit extends from ground by way of the jack J 333 and associated plug, and the Winding of R310 to battery.
the step relay R310 When energized over the above-traced circuit, the step relay R310 operates to interrupt, at RA31I, a point in the previously traced circuit for energizing the vertical magnet of the nder switch of the selected link, thereby' to prevent operation of the finder switch of the selected link,
the operation of the start relay R345 causes operation of the control relay R350, ⁇ as previously explained.
the control relay R350 completes, at RA356, the previously traced circuit for energizing the timing relay R315, which latter relay operates to complete, at RA316 and RC318, RC319, the ⁇ previously traced circuit for energizing the winding of the control relay R380, thereby to cause the latter relay to operate shortly thereafter.
control relay R380 completes, at RA385, the previously traced circuit for energizing the upper winding of the control relay R330, thereby to cause the latter relay to operate.
control relay R330 completes, at RA336, the previously traced holding circuit for energizing the lower winding thereof, and interrupts at RA333 and H0336, the previously traced circuit for energizing the timing relay R315, thereby to cause the latter relay to restore.
the Ytiming relay R315 sets the weighted armature RA316 into operation, thereby to retain the control relay R380 in its operated position for a predetermined interval, after which the relay R380 restores,
the control relay R380 completes, at'RA382 and RC383, the pre- Vviously traced circuit for energizing the upper trol relay R330 locks the distributor 300 outoi service and the illumination of the supervisory lamp L30! indicates to the exchange attendant this condition of the distribuer 300, as previously explained.
the plugs are removed from. the jacks -I332 and J333, and the busy switch S330 is operated away from its normal position and then returned to its normal position, as previously explained.
the selector switch 200 is rendered operative in response to impulses transmitted thereto from the subscriber substation A.
the line relay R260, the hold relay R210 and the transfer relay R290 in the selector switch 200 occupy their operated positions, as previously explained.
test relay R265 in the selector switch 200 is of the shunt ileld type and comprises a ileld structure including an L- shaped leg L266, -two core legs L261 and L263, a shunt leg L269 and a movable armature RA265, two windings being respectively carried on the core legs L261 and L266.
the 'I'he test relay R265 is so connected and arranged that, when the winding on the core leg L261 is energized, a magnetic ilux is produced in the field structure which traverses a first magnetic path extending from the core leg L261 by way of the base of the leg L266, the core leg L266, and the shunt leg L269 to the core leg L261, thereby to polarize .the eld structure of the test relay R265.
the armature RA265 of the test relay R265 is not operated with respect to the eld structure thereof.
the armature RA265 is attracted to the field structure of the :est relay R265, thereby to operate the test re-
the subscriber at the substation A then dials the'iirst digit of the directory number of the called subscriber substation B at the dial mechat the substation A, thereby to transmit a nrst series of impulses by way of the subscriber loop circuit to the line relay R260 in the selector switch 200.
the relay R260 follows the dialed impulses in the usual manner. restoring each time the loop circuit is interrupted and operating each time the loop circuit is completed. Each time the line relay R260 restores,-
the hold relayR210 and the transfer relay R200 are oi the slow-to-release type. Thus, these relays remain operated during impulsing.
the vertical magnet M230 is energized, the ⁇ carriage of the Strowger mechanism 20
the sets of switch -springs S211, S218, and S239 are actuated. More particularly, the set of switch springs S211 is actuated into disengagement, thereby to interrupt the previously traced circuit for energizing the upper winding of the transfer relay R290; the set of switch springs S216 is actuated into engagement, thereby to prepare a circuit. traced hereinafter, for energizing the winding of the rotary magnet M231; and the set of switch springs S239 is actuated into engagement, thereby to prepare a circuit traced hereinafter for energizing the winding of the release magnet M230.
the relay R260 reoperates, thereby to interrupt, at RA26
this circuit is interrupted, further operation of the vertical magnet M236 is positively arrested, thereby to arrest the carriage of the Strowger mechanism 20
the rotary magnet M231 continues to operate buzzer fashion, thereby to drive the carriage of the Strowger mechanism 20
the connector switch 2I5 is the li'lrst idle connector switch in this group of connector switches
further operation of the rotary magnet M231 is arrested when the wiper 204 of the wiper set of the Strowger mechanism 20
test relay R265 interrupts, at RA266 and RC261, a point in the previously traced circuit for energizing the rotary magnet M231, and completes, at RA266 and RC268, a circuit for energizing the switching relay R2 I0, this circuit extending from ground, at RA212, by way of RA212, RA266', RC268, and the winding of R2I0 to battery.
the switching relay R2I0 When energized over the above-traced circuit, the switching relay R2I0 operates to complete, at RA2I9, a holding circuit for energizing the windingthereof, .this circuit extending from the grounded control conductor CI I8 of the trunk line II5 by way of RA2I9eand the winding of R2I0 to battery. Also, upon operating, the switching relay R2I0 interrupts, at RA2I8, a further point in the previously traced circuit for energizing the winding of the rotary magnet M231, and connects the trunk line II5 to the wiper set of the Strowger mechanism 206,
the line conductor CI I6 of the trunk line H5 is conneced by/way of RAMI, RC2I2, and the wiper 20
the line conductor CI I1 of the trunk line Ii5 is connected by way of RA2I6, RC2I5, and the wiper 203 and associated contact tothe line conductor C2I3 of the trunk line 2
the control conductor CI I8 of the trunk line H5 is connected by way of RA2I1 and the wiper 200 and associated contact to the control conductor C2i@ of the trunk line 2H.
ground potential appearing upon the control conductor CHS of the trunk line H5 is extended by Way. of the control conductor C2I4 of the trunk line 2H to the connector switch 2I5, thereby to cause the connector switch to operate and complete a loop circuit between the line conductor C2I2 and C2 I3 of the trunk line 2II and extending tothe subscriber substation A.
the connector switch 2I5 operates to cause ground potentialtherein' to be applied to the control conductor C2I4 of the trunk line 2
the switching relay R2I0 interrupts, at RA2I0, a. point in the previously traced circuit for energizing the hold relay R210, and interrupts, at RA2II and RC2I3, and at RA2I4 and RC2 I6,.points in the previously traced circuit for energizing in series the upper and lower windings of the line relay R260.
the line relay R260 immediately -restores and, shortly 1thereafter, the hold relay R210 restores.
the hold relay R210 interrupts, at RA212, the previously traced circuit for energizing the winding on the core leg L261 of the field structure of the test relay R265, and interrupts, at RA213, the previously traced circuit for energizing the winding on the core leg L268 of the field structure of the test relay R265, thereby to cause the test relay R265 to restore.
the switching relay R2I0 in the selector switch 200 remains inits operated position due to the completed holding circuit for energizing the winding thereof including the control conductor C2I4 of the trunk line 2II.
the connector switch 2I5 is conditioned to be responsive to impulses transmitted thereto .by way of the Iloop ⁇ circuit extending thereto from the calling subscriber substation A.
ground potential appears upon the control'conductor C2 I4 of the trunk line 2
booster battery potential appears upon the control conductor C2 I4 of the trunk line 2
the selector switch 200 is so connected and arranged that it will not operate to seize the trunk line 2II when either ground potential or booster battery potential appears upon the control conductor C2I4.
engages the contact in the contact set terminating the control conductor C2I4 of the trunk line 2
a path is completed for shortcircuiting the winding on the core leg L260 of the eld structure of the test relay R265 when ground potential appears upon the control conductor C2I4 of the trunk line 2
the subscriber at the calling subscriber substation A dials two additional ldigits into the connector switch 2
ground potential appears upon the control conductor C234 thereof, thereby to cause the connector switch 2
5 then operates to cause direct ground potential to be applied to the wiper 228 of the wiper set of the Strowger mechanism 225, thereby to complete a circuit for energizing the cutoff relay R245.
the circuit for energizing the cutoi relay R245 extends from ground potential appearing in the connector switch 2
the cutoil' relayv R245 operates to interrupt, at RA248 and at RA249, the circuit for energizing the line relay R250, and to complete, at RA24'I, a path for applying ground potential to the control conductor C235 oi' the subscriber line 230, this path extending from ground potential appearing upon the control conductor C234 of the subscriber line 230, by way of RA252, RC253 and RA24I to the control conductor C235.
'I'his application of ground potential to the control conductor C235 marks the called subscriber line 230 as busy to the nder switches of the links having access thereto.
the cutoff relay R245 completes, at RA245, a circuit for energizing the winding of the meter relay RZIS, assuming that the upper terminal of the meter relay R2
9 is energized over the above-traced circuit, this relay does not operate at; this time due to theL fact that it is oi' the marginal type.
5 After seizing the called subscriber line 230, the connector switch 2
the subscriber at the substation B answers the call by removing the telephone receiver of the telephone instrument thereat from its hook, a'loop circuit is completed by way ot the line conductors of the subscriber line 230 to the connector switch 2
5 operates to complete a connection between the calling subscriber loop circuit extending theretov from the subscriber substation A and the called subscriber loop circuit extending thereto from the substation B.
5 completes, at RA22I and RA223, the previously traced path for connecting booster battery potential to the control conductor C2
09 When energized over the above-traced circuit, the meter relay R
5 Shortly after the connector switch 2
the release of the established connectionl between the subscriber substations A and B is under the control of the subscribers thereat and, when both of the subscribers replace the receivers of the telephone instruments upon their associated switchhooks at the substations A and B, the connector switch 2 I5 iirst releases.
the connector switch 2 I5 is released, the Strowger mechanism 225 thereof is returned to its normal position and ground potential is removed in the connector switch 2
5 is returned to its normal position, the previously traced circuit for energizing the cutoi relay R245 in the line circuit 240 is interrupted, thereby to cause the cutoff relay R245 to restore.
the cutoir relay R245 interrupts, at RA248, a point in the previously traced circuit for energizing the meter relay R2Il, intertrunk rupts, at RA241, a point in the previously tracedv path for applying ground potential to the control conductor C235 of the subscriber line 230, and prepares, at RA248 and at RA248, points in the previously mentioned circuit for energizing the line relay R250.
the line circuit 240 individually associated with the subscriber line 230 is completely released.
the switching relay R2I0 interrupts, at RA2I9, a further point in the holding circuit for energizing the winding thereof, prepares, at RA2I8, a point in the previously traced circuit for energizing the winding of the rotary magnet M231, and interrupts, at RA2II and RC2
the switching relay R2I0 completes, at RA2I0, the previously mentioned circuit for energizing the release magnet M238.
this circuit extending from ground, at RA2I0, by way of RA2I0, RA26I, RC263, RA214, RC216, RA292, the set' of switch springs S239, and the winding of M238 to battery.
the release magnet M238 When energized over the above-traced circuit, the release magnet M238 operates, thereby to release the carriage of the Strowger mechanism'20l in order.
the sets of switch springs S239, S211 and S218 are actuated. More particularly, the set of switch springs S239 is actuated into disengagement, thereby to interrupt the previously traced circuit for energizing the winding of the release magnet M238; the set of switch springs S211 is actuated into engagement, thereby to prepare a point in the previously traced circuit for energizing the upper Winding of the transfer relay R290; and the set of switch springs S218 is actuated into disengagement, thereby to interrupt a further point in the previously traced circuit for energizing the winding of the rotary magnet M231. At this time, completely released. ⁇
the selector switch 200 is and interrupts, at Ram, at nam and at asm,
81 the previously traced circuit for illumihating the supervisory lamp LI28, and completes, at RAISB and RCI68, the previously mentioned circuit for energizing the winding of the release magnet. MI12.
the last-mentioned circuit extends from groun ⁇ d, at RAI44,'by way of RAI44, RCI45, the switch springs
the release magnet When energized over the ,above-traced circuit, the release magnet release the carriageof the Strowger Amechanism
the sets of switch springs SI15 and SI19 are actuated.
80 and I8I ofthe set of switch springs SI19 are actuated into disengagement, thereby to interrupt a further point in the previously traced path for applying ground potential to the guard conductor C322; the switch springs I8I and
82 are actuated intol engagement, thereby to connect the guard conductor C322 to the control conductor CI I8 of the trunk line I'I5; the switch springs
18 of the set of switchv springs SI15 are actuated into disengagement, thereby to interrupt the previously traced circuit for energizing the winding of the release magnet MI12; and the switch springs
trunk line II5 extends

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Engineering & Computer Science (AREA)
Computer Networks & Wireless Communication (AREA)
Monitoring And Testing Of Exchanges (AREA)

Description

Sept. 17, 1940. c. E. oMAx Er Ax.

TELEPHONE SYSTEM Filed April 21. 19259 5 Sheets-Sheet l I7 JNHUIQI @me NSG S l :SQ

i wm w mm@ m WLM m EK AP a.

Timm Sept. 17, 1940. c. E, LoMAx ET AL TELEPHONE SYSTEM Filed April 21, 1939 5 Sheets-Sheet 2 ON Oem BY PIER BAKKER ATTORNEYS.

INVENToRs ATTORNEYS.

25l Sheets-Shee't 3 Sept. 17, 1940- c. E, LoMAx Er AL TELEPHONE SYSTEM Filed April 21, 1939 CLARENCE E. LOMAX BY I P/EP BAKKER MIM,MV0MJ Patented Sept. 17,

i TELEPHONE SYSTEM Clarence E. Lomax, Oak Park, and Pier Bakker?- Chicago, Ill., assignors to Associated Electric Laboratories, Inc., Chicago, lll., a corporation of Delaware Application April 21, 1939, Serial No. 269,139

10 Claims.

The present invention relates to telephone systems and, more particularly, to automatic telephone systems in which nder switches are employed to extend connections between calling lines and selector switches. f

It is an object of the present invention to provide, in an automatic telephone system, improved distributor apparatus for selecting idle finder switches for the use of calling lines and for lclantrolling the operations of the selected finder switches.

Another object of the invention is to provide, in an automatic telephone system of the character noted, improved apparatus for testing the operations of the distributor apparatus and the finder switches, which testing apparatus is so connected and arranged that it does not interfere with the handling of tratlic in the system.

A further object of the system is to provide, in an automatic telephone system of the character noted, an automatic switch embodying improved testing apparatus for controlling the operation thereof, which testing apparatus is connected and arranged to prevent false operation of the switch when it engages a busy line having a metering potential connected to the control conductor thereof.

The features of the present invention are illustrated as being incorporated in a telephone system provided with an exchange terminating first and second groups of lines and comprising rst and second groups of finder-selector links, each link including a finder switch and a selector switch, rst and second groups ofl connector switches, and first and second distributors respectively associated with the rst and second groups of links. These switches are so connected and arranged that each finder switch has access to each line of the system; each selector switch has access to each connector switch; and the connector switches in the rst and second groups of connector switches respectively have access to the lines in the first and second groups of lines.

In accordance with one feature of the invention, each of the finder switches includes rst and second' wiper sets movable in vertical and rotary4 directions and respectively having access to the first and second groups of lines, vertical and rotary magnets operative' respectively to control the vertical and the rotary movements of the wiper sets, a trunk line normally disconnected from the wiper sets, first and second switching relays operative respectively to connect the rst and. Sond wiper sets to the trunk line, and means responsive to the operation of one of the switching relays for preventing the operation of the other of the switching relays. The distributor associated with each group of nder switches comprises a rotary switch operative to select an idle one of the nder switches in the group, means for governing the rotary and the vertical magnets of the selected nder switch, a first test relay operative in response to the seizure of a calling line by the first wiper set in the selected nder switch, a second test relay operative in response to the seizure of a calling line .by the second wiper set in the selected finder switch, means responsive to the operation of the rst test relay for causing the operation of the first switching relay in the selected finder switch, means responsive to the operation of the second test relay for causing the operation of the second switching relay in the selected finder switch, and means responsive to the operation of either one of the switching relays in the selected finder switch for causing the operation of the rotary switch.

More particularly, the rst and second test relays in the distributor are individually provided with operating circuits, each operating circuit including a uni-directional current conducting device in the form of a copper oxide rectifier. The arrangement of the copper oxide rectifier in the operating circuits of the first and second test relays prevents these relays from being energized when these operating circuits are completed in such a manner that current tends to flow therein in a direction opposite to that of the normal flow of current therein. This arrangement prevents false operation of the first and second test relays when the rst and second` wiper sets in the selected finder switch respec-a tively engage busy lines having a metering potential connected to the control conductors 40 thereof.

In accordance with another feature of the invention, each of the distributors includes a transfer relay provided with an operating circuit; and means is included in each idle nder switch in the associated group of nder switches for completing the operating circuit of the transfer relay, whereby the voperating circuit of the transfer relay is interrupted when all of the finder switches in the associated group are busy. First and second start conductors are provided which are operatively associated with the rst 'and second groups of lines, whereby start potentials are connected to the start conductors in re- Spouse t9 the creatien 0i calling conditions 0n Cil - restored position.

lines in the respective groups oi' lines. The first start conductor is associated with the first distributor, when the transfer relay in the first distributor occupies its operated position, and is associated with the second distributor, when the transfer relay in the first distributor occupies its The transfer relay in the second distributor controls the association of the second start conductor with the first and second distributors in a similar manner. Operation of each of the distributors is initiated when a start potential is connected to a start conductor associated therewith; and each of vthe distributors is effective when operation thereof is initiated to cause a selected one of the finder switches in the associated group to find a line having a calling condition thereon. Also, each of the distributors includes timing means operative to interrupt the operating circuit of the transfer relay therein in the event the finder switch selected thereby fails to operate. In order to test the operations of the distributors and the finder switches associated therewith, manually operable means comprising a busy switch and a number of test jacks is individually associated with each of the distributors.

In accordance with another feature of the invention, the selector switch of each of the links comprises a test relay having a field structure provided with a first magnetic path including a shunt leg and a second magnetic path including a movable armature, first and second windings being associated with the field structure. A first circuit is provided for energizing the first winding; and a s econd circuit'including atest'wiper of the finder switch is provided for energizing the second winding. The first winding is effective, when energized with current flowing in the first circuit, to produce a magnetic flux in the field structure traversing the first magnetic path; the second winding is effective, when energized with current flowing in a first direction in the second circuit, to produce a magnetic flux in the field structure traversing the first magnetic path; and when energized with current flowing in a second direction in the second circuit to produce a magnetic flux in the field structure opposing the magnetic flux traversing the shunt leg, thereby to 'divert magnetic flux from the first magnetic path into the second magnetic path. The test relay is so constructed and arranged that it is operated when magnetic flux traverses the second magnetic path. The selector switch comprises automatic means operative to drive the test wiper thereof step by step over a group of test contacts in the contact bank thereof; lwhich test contacts are adapted to have connected thereto an idle potential, a busy potential, or a metering potential, depending upon the condition of the associated line. The second circuit is so connected and arrangedthat no current flows therein, when the test wiper engages a test contact having a busy potential connected thereto; that current flows therein in the first direction, when the test wiper engages a test contact having a metering potential connected thereto; and that current flows therein in the second direction, when the test wiper engages a test contact having an idle potential connected thereto. Further, each selector switch comprises means controlled by the operation of the test relay therein for arresting the operation of the automatic means.

Further features of the invention pertainto the particularl arrangement of the circuit elements of the system and to the particular connection and arrangement of the elements of the distributors and the links incorporated therein, whereby the above-outlined and additional features are attained.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings in which Figures 1 to 3, inclusive, illustrate a telephone system embodying the present invention.

Referring now more particularly to Figs. 1 to 3, inclusive, of the drawings, the telephone system there illustrated comprises an exchange including an operator position 2I0 and terminating a plurality of subscriber lines, including the subscriber lines IUI and 230. Also, the exchange comprises a number of links, including the links 60 and 10, and a number of connector switches including the connector switch 2|5 for setting up connections between the various lines. More specifically, the exchange `has an ultimate capacity of 200 lines, these lines being arranged in first and second groups of lines each. Each of the links comprises a 200 point finder switch having access to each line in the system and a 100 point selector switch having access to each of the connector switches; while the connector switches are of the 100 point type and are arranged in first and second groups, respectively, Vhaving access to the first and second groups of lines of the system.

Furthermore, the links are arranged in first and second groups, each group of links being provided with a distributor individual thereto for assigning idle ones of the links in the group to the use of calling ones of the lines. The number of links included in each group is determined by the amount of traiiic which the exchange is required to handle and usually satisfactory service may be rendered when each of the two groups of links includes ten links. Also, the number of connector switches required is determined by the amount of traffic which the exchange is required to handle and usually satisfactory service may be rendered when each of the two groups of connector switches includes ten connector switches.

More particularly, the first group of links includes the link 60, which comprises the finder `switch |30 and the selector switch 200, and is provided with the distributor 300; while the second group of links includes the link 10, which comprises the nder switch 3|!) and the selector switch 3| I, and is provid-ed with the distributor 3| 2. The first and second groups of lines are respectively associated with the distributors 300 and 3|2; whereby calling lines in the first group of lines are normally assigned for use idle ones of the links in the first group of links, and calling lines in the second group of lines are normally assigned for use idle ones of the links in the second group of links, thereby rendering it possible to extend simultaneously a call initiated on a line in each of' the two groups of lines. Furthermore, the distributors 300 and 3|2 are so connected and arranged that a. call initiated on a line in the first group of lines is assigned for use an idle link in the second group of links in the event all of the links in the first group of links are busy; and a call initiated on a line in the second group of lines `is assigned for use an idle link in the first group of links in the event all of the links in the second group of links are busy.

A subscriber substation is associated with each of the subscriber lines, the subscriber substations A and B being respectively associated with the subscriber lines and 230. Each of the subscriber substations is provided with a telephone instrument, a dial mechanism and a ringer. Also, a line circuit is individually associated with each of the subscriber lines, the line circuits |00 and 240 respectively illustrated in Figs. 1 and 2 being respectively associated with the subscriber lines |0| and 230. Preferably, these line circuits are identical, each including a line relay and a cutol relay, these relays in the line circuit |00 being respectively' indicated at R|20 and R||0, and these relays in the line circuit 240 being respectively indicated at R2 50 and R245. Furthermore, a meter relay is associated with each of the line circuits, these relays associated with the line circuits |00 and 240 being respectively indicated at Rl09 and at R2l9.

Preferably, each of the links is connected and arranged in a manner similar to that of the link 60 which comprises the finder switch |30 and the selector switch 200. The finder switch |30, as best shown in Fig. 1, comprises a switching mechanism |40 of-the Strowger type including a bank of fixed contact sets arranged in ten vertical levels, each level including upper and lower rows of contact sets, each row of contact sets including ten radially disposed contact sets, each contact set terminating a line extending thereto; and a row of fixed contacts arranged in vertical alignment. Also, the Strowger mechanismv |40 comprises upper and lower wiper sets respectively including the wipers |4I, |42, |43`and |44, |45, |46 carried by a carriage movable in both vertical and rotary directions, the upper and lower wiper sets being respectively associated with the upper and lower rows of contact sets in the bank of xed contact sets; and a control wiper |41 carried by the carriage, the control wiper |41 being associated with the row of xed contacts. Also, this Strowger mechanism includes a vertical magnet M|,10 for moving the carriage in the vertical direction, a rotary magnet M|1| for moving the carriage in a rotary direction, and a release magnet M|12 for releasing the carriage and for causing it to be returned to its normal position. Associated with this Strowger mechanism are two sets of switch springs SI15 and SI1!) which are actuated by the movement of the carriage in the vertical direction away from its normal position, and a set of switch springs S|14 which is actuated by the movement of the carriage into its eleventh rotary position. Also, it is noted that the upper and lower wiper sets respectively terminate the trunk lines |3| and |35 included in the finder switch |30, which trunk lines are operatively associated with the trunk line ||5 extending between the finder switch |30 and the selector switch 200. Also, the

The selector switch 200, as best shown in Fig. 2, comprises a switching mechanism of the Strowger type including a bank of xed contact sets arranged in ten vertical levels, each level including ten circumferentially disposed contact sets, each contact set terminating a line extending thereto. Also, the Strowger mechanism 20| comprises a wiper set including the wipers 202,

203 and 204 carried by a carriage movable in both vertical and rotary directions, the wiper set being associated with the bank of fixed contact sets. Also, this Strowger mechanism includes a vertical magnet M236 for moving the carriage in the vertical direction, a rotary magnet M231 for a line relay R260, a hold relay R210, a transfer l relay R290, a test relay R265 and a switching relay R2|0.

Preferably, each of the distributors is connected and arranged in a manner similar to that of the distributor 300 individually associated with the first group of links which comprises, as best shown in Fig. 3, a rotary switch 30| including six banks of xed contacts and six wipers individu# ally associated therewith, the corresponding contacts in each bank terminating the control conductors extending to the respective links in the rst group of links, and the wipers terminating the control conductors extending to the distributor. Also, the rotary switch 30| includes a rotary magnet M308 for driving the wipers associated with the contact banks in a rotary direction. The distributor 300 also comprises a start relay R345, a busy transfer relay R340, a `step relay R310, a transfer relay R360, a timing relay R315, rst and second test relays R320 and R325, respectively, and a number of control relays R350, R380, R390 and R330. Also associated with the distributor 300 are a supervisory lamp L309, a number of jacks J33I, J332 and .1333 and a busy switch S334 which are utilized for test purposes in a manner more fully described subsequently.

The distributor 300 is of the preselective type in that an idle link in the rst group of links is selected to be assigned to the use of a calling line in the first group of lines prior to the initiation of a call on the line therein and another idle link in the first group of links is automatically selected to be assigned to the use of the next calling line in the first group of lines as soon as the selected link operates to find a calling line in the first group of lines. Also, the distributor 300 is so connected and arranged that, when all of the links in the rst group of links are busy, the start circuit of the distributor 300 is transferred to the distributor 3|2 associated with the second group of lines, whereby the distributor 3| 2 assigns idle ones of the links in the second group of links to the use of calling lines in the rst group of lines.

Preferably, each of the connector switches is connected and arranged in a manner similar to that of the connector switch 2| 5, which connector switch is of conventional connection and arrangement and includes a Strowger mechanism 225 anda battery reversing relay R220. It is noted that a trunk line 2|| including a control conductor C2|4 extends to the connector switch 2|5 and that a battery 223 is included in the connector switch 2|5 and operatively associated by way of a switching arrangement with the control conductor C2|4 of the trunk line 2| whereby booster battery potential may be applied to the control conductor C2|4 of the trunk line 2II for metering purposes in a manner more fully described hereinafter.

Preferably, the operator position 2IU is of conventional connection and arrangement and includes apparatus thereat for answering an incoming call extending thereto.

A better understanding of the connection and arrangement of the apparatus incorporated in the telephone system will be facilitated from a consideration of the operation thereof incident to the extension of a call from the subscriber substation A to the subscriber substation B. The call is first initiated at the substation A by removing the receiver of the telephone instrument thereat from its hook, thereby to complete a bridge path at the substation A between the line conductors CIU2 and C|U3 of the subscriber line IUI extending to the substation A, When' this bridge path is completed between the line conductors of .the subscriber line' IUI, a circuit is completed for energizing the line relay RI2U -in the line circuitgIUU individually associated with the subscriber line IUI, which circuit extends from ground, at RAI I2, by Way of RAI |2, CIU2, the bridge path between the line conductors C|U2 and CI03 of the subscriber line IUI, C103, RAI I I, and the winding of RI to battery. When energized over the above-traced circuit the line relay R|2U operates to complete, at RAI22 and RC |23, an obvious path for applying ground potential to the control conductor C|U5 of the subscriber line IUI, thereby to mark the subscriber line I'UI as busy to the connector switches having access thereto. Also, the line relay RI'20 completes, at RAl25, an obvious path for applyingground potential to the control conductor CIUU, thereby to cause ground potential to be applied by way of the circuit network IUI to the start conductor C3I6 extending into the distributor 300, assuming that the subscriber line IUI is included in the first group of subscriber lines. Also, this application of ground potential to the control conductor CI90 marks, by way of the circuit network |9| and the contacts in the rows of contacts in the Strowger mechanisms included in the nder switches, the levels wherein the subscriber line IUI is terminated, the contact in the row of contacts in the Strowger mechanism |40 included in the finder switch |30 being indicated at |48. Also, upon operating, the line relay R|20 completes, at RAI2I, a path for applying battery potential to the control conductor CI04 of the subscriber line IUI, thereby to mark the rotary positions of the contact sets in the contact banks of the Strowger mechanisms included in the tinder switches terminating the subscriber line IUI. This path for applying battery potential to the control conductor CIU4 of the subscriber line IUI extends from battery at the winding of the cutoff relay RII U, by way of the winding of RI IU andRA|2|,toC|U4.

This application of ground potential to the start conductor C3I6 extending into the distributor 300 completes a circuit for energizing the start relay R345, this circuit extending from ground, at RAI 25, by way of the control conductor CI'3I, a resistor included in the circuit network ISI, the start conductor C3IU, RA34I, RC343 and the winding of R345 to battery. When energized over the above-traced circuit, the start relay R345 operates to initiate operation of the distributor 300. thereby to cause the preselected idle one of the links in the first group of links to be assigned to the use of the calling subscriber line. Moreparticularly, upon operating, the start relay R345 completes, at RA343, a circuit for energizing the control relay.R350 in series with the winding of the rotary magnet M303 of the rotary switch 30|, this circuit extending from ground, at RA330, by way of RA33U. RC33I, RA335. RA343, the winding of R350, RA345, MA3U3, and the winding of M303 to battery. When the above-traced series circuit is completed, the rotary magnet M303 does not operate due to the high series resistance of the winding of the relay R350. However, the control relay R35U does operate. Upon operating, the control relay R350 completes. at RA353, an alternative holding circuit for energizing the busy transfer relay R340, this circuit extending from ground, at RA344, by way of RA344. RAI"V and the winding of R340 to battery. It is noted that the busy transfer relay R340 is normally energized by way of a number of multiple circuits completed in idle ones of the finder switches of 'the first group of links, one ofA these multiple circuits being completed at this time in the finder switch |30 of the link 5U and extending from ground, at RAI44, by way of RAI44, RCI45, the switch springs |85 and |31 of the busy switch SIU3, the switch springs |13 and |11 of the set of switch springs SI15, the'all-trunks-busy conductor C32I, the switch springs 335 and 330 of the busy switch S334, RA 333, and the winding of R340 to battery. Also, it will be understood that a similar multiple circuit will be completed in each of the finder switches of idle ones of links in the first group of links.

Also, upon operating, the relay R350 completes, at RA355, a point in a circuit traced hereinafter for energizing the timing relay R315, prepares,

at RA351, a point in a circuit traced hereinafter for energizing the lower winding of the transfer relay R300, prepares, at RA353, a point in an alternative circuit traced hereinafter for energizing the winding thereof in series with the winding of the rotary magnet M300 of the rotary switch 30|, prepares, at RA353 and RC355, a point in a circuit traced hereinafter for energizing the winding of the rotary magnet M303 directly from the guard conductor C322, and prepares, at RA352, a point in a circuit traced hereinafter for energizing the vertical magnet M|1U of the finder switch |30 of the link 5U, assuming that the link 5U has been preselected by the distributor 300. Also, the control relay R350 completes, at RAI, a circuit traced hereinafter for energizing the start relay RI of the finder switch |30 of the preselected link 3U. As previously noted, the link 5U in the rst group of links has been previously selected by the distributor 300 ,for the use of a calling line in the first group of lines. Accordingly, the wipers 302 to 301, inclusive, of the rotary switch 30| engage the contacts in the associated contact banks terminating the control conductors extending to the finder switch |30.

The circuit for energizing the start relay RI40 in the finder switch |30 extends from ground, at RA35I, by way of RA35I, the wiper 303 and associated contact of the rotary switch 30|, the ilnder start conductor C3I3, and the winding of RI40 to battery. When energized over the abovetraced circuit, the start relay RI40 operates to complete,l at RAI4I, an obvious path between the line conductors CI I6 and CI I1 of the trunk line II5 extending between the ilnder switch |30 and the selector switch 200 of the link UU, and to complete, at RA|44 and RCI, an obvious path for applying ground potential to the control conductor CIIB of the trunk line IIS. When the path is completed between the line conductors CI I6 and C| I1 of the trunk line H5, a circuit is completed for energizing in series the upper and lower windings of the line relay R260 in the selector switch 200, this circuit extending from ground by way of the upper winding of R260, RC2| 6, RA2I4, CII1, the resistor |21, RAI4I, CII6, RA2I I, RC2|3, and the lower winding of R260 to battery. When energized over the above-traced circuit, the line relay R260 operates to interrupt, at RA26I and RC263, a point in a circuit, traced hereinafter, for energizing the winding of the release magnet M238, and to complete, at RA26I and RC262, a circuit for energizing the hold re-y lay R210, the last-mentioned circuit extending from ground at RA2I0 by way of RA2|0, RA26I, RC262 and the winding of R210 to battery. When energized over the above-traced circuit, the hold relay R210 operates to complete, at RA21I, a multiple path for applying ground potential to the control conductor CI I8 of the trunk line I I5, to complete, at RA212, a circuit for energizing the winding on the core leg L261 of the field` structure of the test relay R265, to prepare, at RA213, a circuit, traced hereinafter, for energizing the winding on the core leg L268 of the fleld structure of the test relay R265, to interrupt, at RA214 and RC216, a further point in the previously mentioned circuit for energizing the winding of the release magnet M230, and to prepare, at RA214 and RC215, a point in a circuit, traced hereinafter, for energizing in multiple the lower winding of the transfer relay R290 and the winding of the vertical magnet M236. The application of ground potential to the control conductor CI I8 of the trunk line I I5 completes a circuit for energizing the upper winding of the transfer relay R290, this circuit extending from the grounded control conductor CI I8 by way of the set of switch springs S211 and the upper winding of R290 to battery. When energized over the above-traced circuit, the transfer relay R290 operates to interrupt, at RA29I, a point in a circuit, traced hereinafter, for energizing the winding of the rotary magnet M231 and to interrupt, at RA292, a point in the previously mentioned circuit for energizing the winding of the release magnet M238. At this time, the selector switch 200 is conditioned to be responsive to a digit .aled thereinto, thereby to cause the wiper set if the Strowger mechanism 20| thereof to be driven away from its normal position in the vertical direction in a manner more fully described hereinafter.

Also, the start relay RI40 prepares, at RAI42, a circuit, traced hereinafter, for energizing the second test relay R325 in the distributor 300, interrupts, at RA|43, a point in a path traced hereinafter for applying ground potential to the guard conductor C322, interrupts, at RAIN and RCI45, a point in the previously traced path for applying ground potential in the finder switch |30 to the alltrunks-busy conductor 032|, prepares, at RAi'l, a circuit traced hereinafter for energizing the winding of the rotary magnet MIN, and completes, at RAIB, a circuit for energizing the vertical magnet MI10. The circuit for energizing the vertical magnet MI10 extends from ground, at RA352, by way of RA352, RA31i, RA36I, RC362, the wiper 304 and associated contact of the rotary switch 30|, the vertical conductor C320, RAI48, and the winding of MI10 to battery. When energized over the above-traced circuit, the vertical magnet MI10 operates. Upon operating, the vertical magnet MI10 drives the carriage of the Strowger mechanism |40 of the finder switch |30 one step in the vertical direction and completes, at MAI10, a circuit for energizing the step relay R310 in the distributor 300. The circuit for energizing the step relay R310 extends from ground, at MAI10, by way of MAI10, the interrupter conductor C3I9 and the winding of R310 to battery.

' When energized over the above-traced circuit, the step relay R310 operates to interrupt, at RA31 I, a point Vin the previously traced circuit for energizing the winding of the vertical magnet MI10, thereby to cause the vertical magnet MI10 to restore. Upon restoring, the vertical magnet MI10 interrupts, at MAI10, the previously traced circuit for energizing the step relay R310, thereby to cause the latter relay to restore. Upon restoring, the step relay R310 completes, at RA31I, a point in the previously traced circuit for energizing the winding of the vertical magnet MI10, whereupon the vertical magnet MI10 operates to drive the carriage of the Strowger mechanism |40 of the iinder switch |30 an additional step in the vertical direction and to recomplete, at MAI10, the previously traced circuit for energizing the step relay R310 in the distributor 300.

The step relay R310 in the distributor 300 and the vertical magnet MI10 in the iinder switch |30 continue to interact in the above-described manner, thereby to cause the carriage of the Strowger mechanism |40 of the iinder switch |30 to be driven step by step in the vertical direction until the carriage wiper |41 engages a contact in the row of contacts associated therewith having marking ground potential thereon. In the present instance, the carriage of the Strowger mechanism |40 of the finder switch |30 is driven two steps in the vertical direction, whereupon the control wiper |41 engages the contact |48 in the row of contacts having marking ground potential thereon. A circuit is then completed for energizing the lower Winding of the transfer relay R360 in series with the winding of the step relay R310, this circuit extending from the grounded contact |48 in the row of contacts by way of the control wiper |41, the rst test conductor C3I1, the wiper 302 and associated contact of the rotary switch 30|, RA366, RC361, the lower wind,- ing of R360, RA351, and the winding of R310 to battery. It is noted that the above-traced circuit for energizing the lower winding of the transfer relay R360 in series with the winding of the step relay R310 is completed immediately the carriage of the Strowger mechanism |40 of the finder switch |30 is driven the second step in the vertical direction. Accordingly, the step relay R310 does not restore incident to the restoration of the vertical magnet MI10 at this time.

Shortly after the transfer relay R360 is energized over the above-traced circuit it operates, this relay being of the slow-to-operate type. Upon operating, the transfer relay R360 completes, at RA369, a holding circuit traced hereinafter for energizing the upper winding thereof, interrupts, at RA366 and RC361, a point in the previously traced circuit for energizing the lower winding thereof in series with the step relay R310, and prepares, at RA366 and RC368, a circuit traced hereinafter for energizing the first test relay R320. Also, upon operating, the transfer relay R360 interrupts, at RA365, a point in the previously traced original circuit for energizing the control relay R350 in series with the winding of the 6 l rotary magnet M303, an alternative circuit for energizing the control relay R350 in series with the winding of the rotary magnet M308 being completed at this time; interrupts, at RAIBI and RC362, a further point in the previously traced circuit for energizing the vertical magnet Ml10; and prepares, at RA36| and RC3, a point in a circuit traced hereinafter for energizing the rotary magnet M|1|.

As previously noted, upon operating, the control relay R350 completes, at RA356. a point for energizing the timing relay R315, this circuit extending from ground, at RA356, by way of RA356, RA333, RC334, and the winding of R315 to battery. When energized over the above-traced circuit, the timing relay R315 operates to complete, at RA316 and RC318, RC313, a circuit for energizing the control relay R380, this circuit extending from ground, at 'RA356, by way of RA356, RA316, RC318, RC319, and the winding of R380 to battery. Shortly after the control relay R380 is energized by Way of the abovetraced circuit, this relay operates, this relay being of the slow-to-operate type. Upon operating, the control relay R380 completes, at RA386, a holding circuit for energizing the winding thereof, this circuit extending from ground, at RA356, by Way of RA356, RA316, RC318, RA386, and the winding of R380 to battery. Also, upon operating, the control relay R380 interrupts, at RA382 and RC383.- a point in a. circuit traced hereinafter for energizing the upper winding of the control relay R390, and prepares, at RA382 and RC384, a point in a holding circuit traced hereinafter for energizing. the upper winding of the transfer relay R360. Also, t'he control relay R380 completes, at RA38| the previously mentioned alternative circuit for energizing the control relay R350 in series with the winding of the rotary magnet M308, this circuit extending from ground, at RA38I, by way of RA38I, RA359, the winding of R350, RA345, MA308, and t'he winding of M308 to battery. Finally, upon operating, the control relay R380 completes, at RA385, an obvious circuit for energizing the upper winding of thecontrol relay R330, thereby to cause the latter relay to operate. Upon operating, the control relay R330 completes, at RA336, a holding circuit for energizing the lower Winding thereof, this circuit extending from ground at RA35| by way of RA35|, RA336, and the lower winding of R330 to battery. Also, the control relay R330 interrupts, at RA330 and RC33I, a point in the previously traced original circuit for energizing the control relay R350 in series with the winding of the rotary magnet M308, and completes, at RA330 and RC332, a multiple alternative circuit for energizing the control relay R350 in series with the winding of the rotary magnet M308. Furthermore, the control relay R330 interrupts, at RA333 and RC334, a point in the previously traced circuit for energizing the timing relay R315; prepares, at RA333 and RC335, a point in the previously mentioned holding circuit for energizing the upper winding of the transfer relay R360; prepares, at RA331, a point in a circuit traced hereinafter for energizing the first test relay R320; and prepares, at RA338, a point in a circuit traced hereinafter for energizing the second test relay R325.

When the previously traced circuit for energizing the timing relay R315 is interrupted, the 1r-tter relay restores, thereby to cause-the weighted armature RA316 thereof to vibrate between the rssociated contacts RC311 and RC318, in order to. complete intermittently the previously traced holding circuit for energizing the control relay R380. It is noted that the weighted' armature RA310 vibrates between the contacts noted for a predetermined time interval, thereby to retain the control relay R380 in its operated position during this time interval.

The previously mentioned holding circuit for energizing the upper Winding of the transfer relay R360 extends from ground, at RA355, by way of ,RA353, RA333, RC3, RA382, RC3, RAS, and

the upper winding of R360 to battery; while the previously mentioned circuit for energizing the rotary magnet MI1| extends from ground, at RA352, by -way of RA352, RA31|, RA36I, RC3, RA32I, RC322, RA326, RC321, the rotary conductor C324, RAISS, RA| 51, RAI41, and the winding of M|1| .to battery. When energized over the above-traced circuit, t'he rotary magnet M|1| operates to drive the carriage of the Strowger mechanism |40 of the finder switch |30 one step in the rotary direction and to complete, at MA|1|, an alternative circuit for energizing the step relay R310 in the distributor 300. The circuit for energizing the step relay R310 extends from ground, at MA|1|, by way of MA|1|, the interrupter conductor C3l3, `and the winding of R310 to battery. When energized over the abovetraced circuit, the step relay R310 operates to interrupt, at RA31|, a point in the previously traced circuit for energizing the rotary magnet M I1|, thereby to cause the rotary magnet to restore. Upon restoring, the rotary magnet M|1| interrupts, at MAI1I, the previously traced alternative'circuit for energizing the step relay R310, thereby to cause the step relay to restore and recomplete, at RA31|, the previously traced circuit for energizing the winding of the rotary magnet Mill.

The step relay R310 in the distributor 300 and the rotary magnet M |1| in the finder switch |30 continue to interact in the manner described above until the carriage of the Strowger mechanism |40 of the finder switch |30 is rotated in the rotary direction to the position of the contact set terminating the calling subscriber line |0|, at which time the wiper |43 of the upper wiper set engages the contact of the contact set terminating the control conductor CI04 of the subscriber line |0|, assuming that the line |0| is accessible to the upper wiper set of the Strowger mechanism |40 of the finder switch |30. whereupon a circuit is completed for energizing the winding of the cutoff relay RI I0 in the line circuit |00 inseries with the first test relay R320 in the distributor 300. The last-mentioned circuit extends from ground at RA331 by way of RA331, the unidirectional current conducting device or copper oxide rectifier 341, the winding of R320, RC368, RA366, the wiper 302 and associated contact of the rotary switch 30|, the rst test conductor C3|1, the wiper |43 of the upper wiper set, the associated'contact terminating the control conductor CI04 of' the subscriber line 0|, CI04, RA|2| and the winding of the cutoff relay RI l0 to battery.

When the cutofl' relay RI I0 in the line circuit |00 is energized by way of the above-traced circuit, it does not operate due to the high series resistance of the first test relay R320 in the distributor 300. However, the first test relay R320 does operate. Upon operating, the first test relay R320 interrupts, at RA32| and RC322, a point in the previously traced circuit for energizing the Winding of the rotary magnet M|1I and completes, at RA32| and RC323, a circuit for ener- `switch gizlng the switching relay R|60 in the finder |33. 'I'he circuitV for energizing the switching relay R|60 extends from ground, at RA352, by way of RA352, RA31I, RA36I, RC36I, RA32I, RC323, the wiper 306 and associated contact ofthe rotary switch 30|, the conductor C323, RAI55, and the winding of R|60 to battery. When energized over the` above-traced circuit, the switching relay R|60 operates to interrupt, at RAI65, a further point in the previously traced circuit for energizing the winding of the rotary magnet M|1| and to complete, at RAI64, a hold-` ing circuit for energizing the winding thereof, this circuit extending from the grounded Aconductor CI |8 by way of RAIN, and the winding of R|60 to battery. Also, upon operating, the switching relay R|60 connects the trunk line |3| terminated by the upper wiper set to the trunk line ||5 extending between the finder switch |30 and the selector switch 200. Specifically, the conductors C|32, C|33 and C|34 of the trunk line |3| are respectively connected, at RAIGi, RA|62 and RA|63, to the conductors CIIG, C||1 and CIIB, respectively, of the trunk line I|5. When the grounded control conductor CI|8 of the trunk line ||5 is connected to the control conductor C|34 of the trunk line |3|, an alternative circuit is completed for energizing the cutol relay RI I0 in the line circuit |00, this circuit extending from the grounded control conductor CII 8 of the trunk line ||5 by way of RAI63, the control conductor C|34 of the trunk line |3I, the wiper |43 of the upper wiper set, the associated contact terminating the control conductor CI03 of the subscriber line |0I, CIM, RAI2I, and the winding of R||0 to battery. When energized over the above-traced circuit, the cutoi relay R||0 operates to complete, at RAI I3, a holding circuit for energizing the winding thereof, this circuit extending from the grounded control conductor CIM of the subscriber line III by way of CIM, RA||3, and the winding of RI Il to battery. Also, upon operating, the cutoi relay R||0 interrupts, at RAI and RAII2, points in the previously traced circuit i'or energizing the line relay R|20, thereby to free the subscriber line |0| of impedance elements and to cause the line relay R|20 to restore. Also, upon operating, the cutoff relay RI Il completes, at RAI I4, a circuit for energizing the winding of the meter relay R|03 associated with the line circuit |00, assuming that the upper terminal of the winding of the meter relay RIOS is connected to the conductor CI08. This circuit extends from the grounded control conductor CIII of the subscriber line |0| by way of RAII3, RAIIl, CI08, and the winding of R|03 to battery. Although the winding of the meter relay RIOS is energized, this relay does not operate at this time as this relay is of the marginal type.

When the line conductors C|32 and C|33 of the trunk line |3| are connected to the line conductors CI I6 and C I1, respectively, of the trunk line IIS, an alternative circuit is completed for energizing in series the upper and lower windings of the line relay R260 in the selector switch 2li. This circuit extends from ground by Way of the upper winding of R260, RC2|6 and RA2|4 to the line conductor CI I1, and from battery by way of the lower winding of R260, RC2|3 and RA2|| to the line conductor C2|6, the line` conductors C2|6 and C2|1 of the trunk line 2|5 being connected together by Way of the bridge path connected between the line conductors C|02 and CI03 of the subscriber line III at the subscriber substation A.

It is noted that,A when'the carriage Aof the Strowger mechanism of the ilnder switch |30 is operated away from its normal position the iirstA step in the vertical direction, the sets of switch springs S|15 and S|19 are actuated. More specifically, the switch springs |8| and |82 of the set of switch springs S|10 are actuated into disengagement; while the switch springs |8| and |80 of the set of switch springs S|19 are actuated into engagement. When the switch springs |-8| and |80 of the set of switch springs S|19 are actuated into engagement, a point is prepared in a path traced hereinafter for applying ground potential to the guard conductor C322. Also, the switch springs |18 and |11 of the set of switch springs SI are actuated into disengagement and the switch springs |16 and |16 of the set of switch springs SI15 are actuated into engagement. When the switch springs |18 and |11 of the set of switch springs SI15 are actuated into disengagement, a further point in the previously traced path for applying ground potential to the all-trunks-busy conductor C32| is interrupted; and when the switch springs |18 and |16 of the set of switch springs SI15 are actuated into engagement, a point is prepared in a circuit traced hereinafter for illuminating the supervisory lamp L|28.

Also, upon operating, the switching relay R|60 in the iinder switch |30 interrupts, at RA|66 and RC 68, a point in a circuit traced hereinafter for energizing the release magnet MI12, and prepares, at RA|66 and RC|61, an additional point in the previously mentioned circuit for illuminating the supervisory lamp L|28. Furthermore, the switching relay R|60 interrupts, at RA|60, a point in a circuit traced hereinafter for energizing the switching relay RI50, thereby to prevent operation of the switching relay R|50 at this time; and completes, at RAISS, the previously mentioned path for applying ground potential to the guard conductor C322, this path extending from ground, at the switch spring |80 of the set of switch springs SI19, by way of the switch springs |80 and |8| of the set of switch springs SI10, RAi69, and the switch springs |85 and |84 of the busy switch S|83 to the guard conductor C322. This application of ground potential to the guard conductor C322 completes a circuit for energizing the Winding of the rotary magnet M308 of the rotary switch 30|, this circuit extending from the grounded guard conductor C322 -by way of the wiper 305 and associated contact of the rotary switch 30|, RA353, RC355, and the winding of M308 to battery. When energized over the above-traced circuit, the rotary magnet M308 operates, thereby to condition the wipers of the rotary switch 30| to be driven one step in the' rotary direction. Also, upon operating, the rotary magnet M308 interrupts, at MA308, a point in the previously traced alternative circuit for energizing the winding thereof in series with the winding of the control relay R350, thereby to cause the control relay R350 to restore.

Upon restoring, the control relay R350 interrupts,I at RA353 and RC355, a point yin the pre- Viously traced circuit for energizing the winding of the rotary magnet M308, thereby to cause the rotary magnet M308 to restore. Upon restoring, the rotary magnet'M308 drives the wipers 302 to 301, inclusive, of the rotary switch 30|.one

step in the rotary direction and into engagement with the contacts in the associated contact banks terminating the control conductors extending to the nder switch of the next link. 'I'he subse` quent operation of the distributor 300 depends upon the idle or busy condition of the finder switch of the next link, in a manner more fully described subsequently.

Assumingthat there are no other calls in the ilrst group of lines at this time, when the line relay R|20 of the line circuit |00 associated with the subscriber line restores it interrupts, at RAI25, the previously traced path for applying ground potential to the control conductor C|90, interrupts, at RA|22 and RC|23, the previously traced path for applying ground potential to the control conductor C| of the subscriber line |0I, and completes, at RA|22 and RC|24, an alternative path for applying ground potential to the control conductor CI 05, thereby to mark 'the subscriber line I0| as busy to the connector switches having access thereto. 'I'he last-mentioned path extends from the grounded control conductor C|04 of the subscriber line |0| by way of RAI I3, RCI 24 and RA|22, to the control conductor C|05.

When ground potential is removed from the control conductor C|90, the previously ytraced circuit for energizing the start relay R345 in the distributor 300 is interrupted, thereby to cause the start relay R345 to restore. Upon restoring, the start relay R345 interrupts, at RA346, the previously traced original circuit the control relay R350 in series with the winding of the rotary magnet M300. Also, when the control relay R350 restores, as previously noted, it interrupts, at RA359, a further point in the circuit for energizing the winding thereof in series with the winding of the rotary magnet M308. Also, at RA353 and RC354, the wiper 305 of the rotary switch 30| is connected by way of the self-interrupting contact MA308 and the winding of the rotary magnet M308 to battery, this connection extending from the wiper 305 by way of RA353, RC354, RA345, MA308, and the winding of M300 to battery.

In the event the nder switch of the next link in the rst group is busy at this time, ground potential appears upon the guard conductor thereof, corresponding to the guard conductor C322 of the finder switch |30, as previously noted, thereby to complete a circuit extending by way of the previously traced connection for energizing the winding of the rotary magnet M308. When thus energized, the rotary magnet M308 operates tocondition the wipers of the rotary switch 30| to be driven an additional step in the rotary direction and to interrupt, at MA308, the previously traced circuit for energizing the winding thereof. When the previously traced circuit for energizing the winding of the rotary magnet M308 is interrupted, the rotary magnet restores, thereby to drive the wipers of the rotary switch 30| an additional step in the rotary direction. The rotary magnet M308 continues to operate in the above-described manner in order to cause the wipers of the wiper set 30| to be driven step by step in the rotary direction until the nder switch in an idle link of the rst group is found. When the finder switch of an idle link of the first group is found, further operation of the rotary magnet M300 is interrupted, due to the fact that no ground potential appears upon the guard conductor thereof, corresponding to the guard conductor C322 of the nder switch |30.

for energizing Accordingly, the distributor 300 operates automatically to preselect an idle link in the first group of links immediately after the previously selected link in the first group of links is taken for use by a calling line and operates to nnd the calling line.

It is noted that the distributor 300 operates in the above-described manner in order to preselect an idle link in the nrst group of links only in the event that idle link is available in the first group of links, due to the fact that the busy transfer relay R340 is retained in its operated position at this time only in the event that ground potential is present upon the all-trunks-busy conductor C32|, which condition obtains only in the event that there is an idle link available in the rst group of links. In the event that all of the links in the ilrst group of links are busy at this time, no ground potential appears upon the all-trunks-busy conductor C32I, whereby the circuit for energizing the busy transfer relay R340 is interrupted in order to cause' the'busy transfer relay R340 to restore. Upon restoring, the busy transfer relay R340 interrupts, at RA344, a further point in the alternative holding circuit for energizing the winding thereof, interrupts, at RA345, a point in the previously traced circuit for energizing the winding of the rotary magnet M308, thereby to prevent operation of the rotary magnet M300, and interrupts, at RA34| and RC343, the connection b etween the start conductor C3|6 and the Winding of the start relay R345. Also, upon restoring, the busy transfer relay R340 connects, at RA34| and RC342, the conductors C328 and C321 extending to the distributor 3| 2. Accordingly, at this time, the start conductor C3|6 extending to the distributor 300 is connected, together with the start conductor C3l5, to the conductor C321 extending to the distributor 3|2. Hence, at this time, the distributor 3|2 is operative to assign idle links in the second group of links to the use of calling lines in both the first and second groups of lines.

Continuing now with the release of the distributor 300 incident to the restoration of the start relay R345 and the control relay R350, when the control relay R350 restores it interrupts, at RA35I, the previously traced circuit for energizing the start relay R|40 in the finder switch |30. Shortly thereafter the start relay R|40, being of the slow-to-release type, 'restores to interrupt, at RAMI, the mst-'mentioned path between the line conductors C||6 and. CIII of the trunk line 5 and to complete, at RAI43, an alternative path for applying Agli und potential to the guard conductor C322, is path extending from ground, at the switch spring |00 of the set of switch springs S|`|9 by way of the switch springs |00 and |0| of the set of switch springs SHS, RAI43, and the switch springs |05 and |04 of the busy switch S|03 to the guard conductor C322. This application of ground potential to the guard conductor C322 insures that the distributor 300 will not operate to select the busy link 60 at this time. Also, upon restoring, the start relay R|40 interrupts, at RAI", a further point in the previously traced circuit for energizing the rotary magnet Ml 1|, interrupts,

at RA|40, a further point in the previously traced circuit for energizing the vertical magnet MI10, interrupts, at RAI42, a point in the previously mentioned circuit for energizing thesecond test relay R325 in the distributor 300, and completes, at RA|44 and RC |45, the previously mentioned circuit for illuminating the supervisory lamp L| 28, this circuit extending from ground,-at RAI, by way of RAI, RCHS, ythe switch springs |86 and |81 of the busy switch S|83, the switch springs |18 and |16 of the set of switch springs SI15, RA|66, RC|61 and L|28 to battery. The illumination of the supervisory lamp L|28 indicates to the exchange attendant that., the link 60 is busy upon a call routed therethrough from a line included in the rst group of lines.

Also, upon restoring, the control relay R350 in the distributor 300 interrupts, at RA352, the previously traced original circuit for energizing the switching relay R|60 in the nder switch |30,

interrupts. at RA351, a further point in the previously traced circuit for energizing the lower wind-ing of the transfer relay R360 in the distributor 300, and interrupts, at RA356, a point in the previously traced circuit for energizing the upper winding oi' the transfer relay R360 and a point in the previously traced holding circuit for energizing the winding of the control relay R380, thereby to cause the transfer relay R360 and the control relay R380 to restore. Upon restoring, the transfer relay R360 interrupts, at RA369., a further point in the holding circuit for energizing the upper winding thereof, interrupts, at RA366 and RC368, a point in the previously traced circuit for energizing the first test relay R320, and prepares, at RA36-6 and RC361, a point in the previously traced circuit for energizing the lower winding thereof. Also, upon restoring, the transfer relay R360 prepares, at RA365, a point in the previously traced original circuit for energizing the winding of the control relay R350 in series with the winding of the rotary magnet M308, interrupts, at RA36| and RC364, a further point in the previously traced circuit for energizing the switching relay R|60 in the nder switch |30, and prepares, at RA36| and RC362, a point in a circuit for energizing the vertical magnet in the finder switch of a selected link when thel distributor 300 operates to select an idle link in the first group of links to the use of a calling line.

Upon restoring, the control relay R380 interrupts, at RA386, a further point in the holding circuit for energizing the winding thereof, interrupts, at RA385, a point in the holding circuit for energizing the upper winding of the control relay R330, thereby to cause theflatter relay to restore, and interrupts, at RA382 and RC384, a further point in the holding circuit for energizing the upper winding of the transfer relay R360. Also, the control relay R380 prepares, at RA382 and RC383, a point in a circuit traced hereinafter for energizing the upper winding of the control relay R390, and interrupts, at RA38I, a point in the previously traced alternative circuit for energizing the winding of the control relay R350 in series with the winding of the rotary magnet M308.

Upon restoring, the control relay R330 interrupts, at RA336, a further point in the previously traced holding circuit for energizing the 'lower winding thereof, interrupts, at RA331, a further point in the previously traced circuit for energizing the first test relay R320, and interrupts, at RA338, a point in thepreviously mentioned circuit for energizing the second test relay R325. Also, the control relay R330 interrupts, at RA333 and RC335, a further point in the holding circuit for venergizing the upperV winding of the transfer relay R360, prepares, at RA333 andv RC334, a point in the previously traced circuit for energizing the timing relay R315, interrupts, at RA330 and RC332,\a further point in the pre;

viously traced alternative circuit for energizing the winding of the control relay R330 in series with the winding of the rotary magnet M308, and prepares, at RA330 and RC33I, a point in the previously traced original circuit forenergizing the winding of the control relay R350 in series with the winding of the rotary magnet Upon restoring, the first test relay R320 interrupts, at RA32| and RC323, a further point in the previously traced original circuit for energizing the switching relay R|60 in the finder switch- |30, and prepares, at RA32| and RC322, a point in a circuit for energizing the rotary magnet in the finder switch of a preselected unir. At this ume'tne distributor soo lis completely released for further use and the subscriber substation A is operatively'connected by Way of the previously traced circuit to the selector switch 200.

As previously noted, as soon as the finder switch |30 operates to seize the calling subscriber line ground potential; is applied therein to the guard conductor C332, thereby to complete the previously traced path for short-circuiting the winding of the control relay R350 in order to cause the controlrelay R350 to restore and initiate the release of the distributor 300. It is noted that it is not possible to reoperate the relay R350 unil the distributor 300 is completely released in spite of the fact that there may be present a calling line in the first group of lines. which causes the start relay R315 to remain in yits operated condition, due to the fact that, upon restoring, the control relay R350 interrupts, at RA358, the previously traced alternative circuit for energizing the winding thereof in series with the winding of the rotary magnet M308, and the original circuit for energizing the winding of the control relay R350 in series with the Winding of the rotary magnet M308 is not recompleted until subsequent to the restoration of the transfer relay R360 and the control relay R330, as previously explained. Accordingly, the distributor 300 is complet-ely released each time a finder switch of a link selected thereby operates to nd a calling line in spite of the fact that the start relay R345 therein remains operated, due to the presence of other calling lines in the iirst group of lines.

In the event another calling line is present in the iirst group of lines at this time, the start relay R345 in the distributor 300 remains in its operated position, and, when the transfer relay R360 and the control relay R330 restore, the previously traced original circuit for energizing the control relay R350 is recompleted, assuming that the rotary magnet M308 has already operated to cause the rotary switch 30| to find an idle link in the rst group of links. 'Ihe control relay R350 then operates, thereby to cause the nder switch of the previously selected link to operate and seize the calling subscriber line in the first group of lines, as explained above.

As previously noted, the distributor 300 is operative to cause the finder switch of a selected link in thel first group of links, such as the finder switch |30 of the link 60, to operate and seize a calling line in the second group of lines, which condition may arise when all of the links in the second group of links are busy. In this event, the distributor 3|2 operates.r thereby to cause the conductors C321 and C328 therein to be connected together, in a manner similar to that previously explained, incident to the restoration of the busy transfer relay R340 in the distributor 300 when all of the links in the ilrst group of links are busy. At this time, ground potential applied to the start conductor C3|5 is extended by way of the conductor C321 and the distributor 3| 2 to the conductor C320, in order to cause the start relay R345 in the distributor 300 to be energized and to operate in the previously described manner. The subsequent operations of the distributor 300 and the ilnder switch |30 of the link 00, incident to the operation of the start relay R345 in the distributor 300, are the same as previously explained, assuming that the calling line in the second group of lines is also accessible to the upper wiper set of the Strowger mechanism 40 of the flnder switch |30.

Furthermore, the iinder switch 30 of the link 60 is operative in a manner substantially identical to that previously explained to find a calling line in `either `the rst group of linesor the second group of lines and accessible to the lower wiper set of the switching mechanism |40 thereof. However, in this case, when the carriage of the Strowger mechanism |40 of the nder switch |30 is rotated in the rotary direction to the position of the contact set terminating the calling subscriber line, battery potential is encountered by the wiper |46 in the lower wiper set appearing upon the contact terminating the control conductor of the calling subscriber line. This application of battery potential to the wiper |46 completes the previously mentioned circuit for energizing the second test relay R325 in thedistributor 300, this circuit extending from ground at RA338 by way of RA338, the unidirectional current conducting device or copper oxide rectiiler 343, the winding of the second test relay R325, the second test conductor C326, RAI 42, and the control conductor C'I38 of the trunk line |35 to battery potential appearing upon the wiper |45. When energized over the above-traced circuit, the second test relay R325 operates to interrupt, at RA326 and RC32I, a point in the previously traced circuit for energizing the rotary magnet M|'|| in the finder switch |30, thereby to arrest further operation of the ilnder switch. Also, upon operating, the second -test relay R325 completes, at RA325 and RC320, the previously mentioned circuit for energizing the switching relay R|50 in the nder switch |30, this circuit extending from ground, at RA352, by way of RA352, RA3||, RA30I, RC3, RA32I, RC322, RA326, RC320, the wiper 301 and associated contact of the rotary switch 30|, the conductor C325, RAIGO, and the winding of R|50 to battery. When energized over the above-traced circuit, the relay R|50 operates to interrupt, at RA|5'|, a further point in the previously traced circuit for energizing the rotary magnet MITI, and to complete, at RAISE, a path for applying ground potential to the guard conductor C322. The path for applying ground Potential to the guard conductor C322 extends from ground, at the switch spring |00 of the set of switch 'springs SH3, by way of the switch springs |00 and |0| of the set of switch springs SI10, RAI53, and the switch springs |05 and |04 of the busy switch S|03 to the guard conductor C322. 'I'his application of ground `potential to the guard conductor C322 causes the distributor 300 to be released and the rotary switch 30| therein to Operate and select an idle link in the ilrst group of links, as previously explained.

Also, upon operating, the switching relay R|50 interrupts, at RAI, a point in the previously traced pleteS,

ilnder switch |30,

circuit for energizing the switching relay R|00, and completes, at RAIN. a holding circuit for the winding thereof, this circuite from the grounded control conductorC|`|0 oi! the trunk line v'III by way oi' RAI54. and the winding of R|50 to battery. Finally. the switching relay R|50 connects, the trunk line |30 extending to the lower wiper set of the Strowger m |40 to the trunk line H5. More specitlcally, the conductors C|30, CI3'| and CI30 of the trunk line |35 are respectively connected, at RAIII, RAIIZ and RAIN, to the conductors C||0, C||`| and CH3, respectively, of the trunk line H5. When the trunk line |35 is connected to the trunk line III, the line circuit individually associated with the calling subscriber line and the selector switch 200 operate in the previously described manner.

It is noted that there is a possibility that the upper and lower wiper sets of the Strowger mechanism |40 of the ilnder switch |30 may simultaneously encounter contact sets in the contact bank terminating calling subscriber lines. In this event, the presence of battery potential appearing upon the contacts in the two contact sets respectively engaged by the wipers |43 and |46 in the upper and lower wiper sets, respectively, of the Strowger mechanism |40 complete the' previously traced circuits for respectively energizing the windings of the ilrst and second test relays R320 and R325, respectively, thereby to cause both of these test relays to operate. Upon operating, the ilrst test relay R320 comat RA32| and RC323, the previously traced circuit for energizing the switching relay R|60, thereby to cause the switching relay R|60 to operate, and interrupts, at RA|2| and RCIZZ, the previously traced circuit for energizing the switching relay R|50, thereby to prevent operation of the switching relay Rl50. Accordingly, under this' conditio the switching relay R|00 is operated and the switching relay R|50 is not operated. Hence, the ilnder switch |30 operates to iind the calling line accessible to the upper wiper set of the Strowger mechanism |40 thereof in preference to the calling line accessible to the lower wiper set of the Strowger mechanism |40 thereof.

It is noted that, incident to operation of the the wipers |43 and |40 in the upper and lower wiper sets, respectively, oi.' the Strowger mechanism |40 may engage contacts in the associated contacts of contact sets in the associated contact bank terminating the control conductors of subscriber lines having either ground or booster battery potential "appearing thereupon; ground potential appearing upon the control conductors of the subscribers lines when the subscriber lines are bus tery,` potential appearing upon lines when the subscriber lines are being metered. When the wiper |43 or the upper wiper set of the Strowger mechanism |40 engages a contact having ground potential appearing thereupon, a path is completed for short-circuiting the winding oi the rst test relay R320 in the distributor 300, this circuit extending from the grounded control conductor of the subscriber line, by way of the wiper |43 and associated contact, Cl33, the rst test conductor C3|'|, the wiper 302 and associated contact of the rotary switch 30|, RA300, RC3, the winding of R320, the copper oxide rectifier 341, and RA33`| to ground. When the wiper |43 oi.' the upper wiper set of the Strowger mechanism |40 engages a contact having boosterbattery potential appearing thereupon, a circuit winding of R390 to over the above-traced circuit, the control relayy is completed substantially identical to the abovetraced path, tending to energize the winding of the iirst test relay R320. However, the copper oxide rectiiier 341 is so connected and arranged that current is prevented from traversing this circuit ina direction extending from the wiper |43 to ground at RA331. Accordingly, the first test| relay R320 is not effectively energized. Thus, the iirst test relay R320 does not operate when the wiper |43 of the upper wiper set of the Strowger mechanism |40 engages a Contact terminating the control conductor of a subscriber line having either ground or booster battery potential appearing thereon.

In a similar manner, a path is completed for short-circuiting the winding of the second test relay R325 when the wiper |46 in the lower wiper set of the Strowger mechanism |40 engages a contact terminating a control conductor of a subscriber line having ground potential appearing thereon; and a circuit is completed tending to energize the winding of the second test relay R325 when the wiper |46 engages a contact terminating a control conductor of a subscriber line having booster battery potential appearing thereon. However, the copper oxide rectifier 348 prevents the winding of the second test relay R325 from being effectively energized in the last-mentioned case. Hence, the arrangements of the copper oxide rectifiers 341 and 348 in the circuits for respectively energizing the windings of the first and second test relays R320 and R325, respectively, prevent false operation of the iinder switch |30 and the consequent seizure thereby of a busy'subscriber line having booster battery potential appearing upon the control conductor thereof.

In the foregoing description of the operation of the finder switch |30 of the link 60 to seize the calling subscriber line |0I, it was assumed that the finder switch |30 operated properly to seize this calling subscriber line. However, it may occur that the finder switch |30 fails to operate properly to seize the calling subscriber line I0| when the operation thereof is initiated by the distributor 300, due to the fact that the finder switch |30 has become temporarily inoperative. In this event, the inder switch |30 fails to seize the calling subscriber line |0I. Accordingly, ground potential is not applied in the finder switch |30 to the guard conductor C322 in order to cause the distributor 300 to be released, as previously explained. Hence, after a predetermined time interval, the vibratory armature RA316 of the timing relay R315 in the distributor 300 assumes an intermediate position between the associated contacts RC311 and RC318, thereby to interrupt the previously traced holding circuit for energizing the control relay R300 in order to cause the control relay R380 to restore. Upon restoring, the control relay R380 interrupts, at RA382 and RC384, the previously traced holding circuit for energizing the upper winding of the transfer relay R360,'and completes, at RA382 and RC383, a. point in the previously mentioned circuit for energizing the upper winding of the control relay R390. The circuit for energizing the upper winding of the control relay R390 extends from ground, at RA356, by way of RA356, RA333, RC335, RA382, RC383, and the upper battery. When energized R390 operates to complete, at RA392, a holding circuit for energizing the lower winding thereof, this circuit extending from the grounded conductor C330 by way of the switch springs 330 and 331 of the busy switch S334, RA302, and the lower winding of R390 to battery. It is noted that ground potential appears upon the conductor C330 in the distributor 3|2 so long as ground potential appears upon the all-trunks-busy conductor associated with the nder switches of the links in the second group of links, just as ground potential appears upon the conductor C323 in the distributor 300 so long as ground poential appears upon vthe all-trunks-busy conductor'CSIl associated with the finder switches of the links in the rst group of links. Also, upon operating, the relay R390 completes, at RA39I, a path for short-circuiting the winding of the control relay R350, this path extending from the upper terminal of the winding ofV R350, by way of RA39I, RA353, RC355, MA308, RA345, and the winding of R350 to the upper terminal thereof. When the winding of the control relay R350 is short-circuited, it restores to interrupt, at RA353 and RC355, a point in the previously traced path for short-circuiting the winding thereof, and to complete, at RA353 and RA354, an alternative path for short-circuiting the winding thereof. The alternative path for short-circuiting the winding of the control relay R350 extends from the upper terminal of the winding of R350 by way of RA39I, RA353, RC354, and the winding of R350 to the upper terminal thereof. Also, upon restoring, the control relay R350 interrupts, at RA358, a point in the previously traced alternative circuit for energizing the winding of the busy transfer relay R340.

Also, upon operating, the control relay R390 interrupts, at RA333, the previously traced original circuit for energizing the winding of the busy transfer relay R340, and interrupts, at RA334, the normal connection between the conductor C329 extending into the distributor 3| 2 and the winding of the busy transfer relay R340, thereby to cause the busy transfer relay R340 to restore and to insure that it remains in its restored position. Upon restoring, the busy transfer relay R340 completes, at RA34| and RC342, the previously mentioned connection between the conductors C321 and C328 extending to the distributor 3|2, thereby to cause the distributor 3| 2 to assign links in the second group of links to the use of calling lines in both the rst and second groups of lines, as previously explained.

Also, upon operating, the control relay R380 completes, at RA392, a circuit forilluminating the supervisory lamp L300, this circuit extending from the grounded conducor C330 by way of the switch springs 338 and 331 of the busy switch S334, RA392, and the lamp L303 to battery. Illumination of the supervisory lamp L30! indicates to the exchange attendant that the distributor 300 is locked out of service. The release of the remainder of the operated relays in the distributor 300, incident to the restoration of the control relay R350 and the busy transfer relay R340, is the same as that previously described. At this time, the distributor 300 is locked out of service, as previously noted.

It is noted that the distributor 300 remains locked out of service until the busy switch S334 is operated away from its normal position and returned thereto, which switch will not be thus operated until the defective iinder switch of one of the unks in the erst group of links is found and again placed in working order. When the busy switch S334 is operated away from its normal position, the switch springs S331 and S333 are actuated into disengagement, thereby to interrupt the previously traced holding circuit for energizing the lower winding' of the control relay R390 in order to cause the control relay R390 to restore. Upon restoring, the control relay R390 reconnects, at RA394, the conductor C328 extending into the distributor 3|2 to the winding of the busy transfer relay R340, and prepares, at RA393, a. point in the previously traced original circuit for energizing the winding of the busy transfer relay R340 by way of the al1-trunksbusy conductor C32 I is returned to its normal position, there is completed at the switch springs 335 and 338 thereof the previously traced original circuit for energizing the winding of the busy transfer relay R340 by way of the all-trunks-busy conductor rC32I, in the event one of the links in the first group of links is idle at this time, as previously explained.

It is notedthat the ilnder switch |30 of the link 60 embodies an arrangement for causing the distributor 300 to select another idle link in the iirst group of links for the use of the calling subscriber line |0| in the event that the nder switch |30 of the selected link 60 in the rst group of links fails to find the calling line |0| incident to the operation thereof.` More particul-arly, the set of switch springs S|14 in the iinder switch |30 is actuated into engagement when the carriage of the Strowger mechanism |40 of the finder switch |30 is driven eleven steps in the rotary direction away from its normal position, due to the failure of the inder switch |30 to iind the calling line 0 I. When the set of switch springs S|14 is actuated into engagement, a path is completed for applying ground potential to the guard conductor C322, this path extending from ground, at the set of switch springs SI14, by way of the set of switch springs SI14, the switch springs |85 and |84 of the busy switch S|83 to the guard conductor C322. This application of ground potential to the guard conductor C322 completes the previously traced circuit for energizing the winding of the rotary magnet M308 and for short-circuiting the winding of the control relay R350, thereby to cause the distributor 300 to release and to cause the rotary switch 30| therein to operate and select another idle link in the rst group of links for the use of the calling subscriber line I0|, in the previously described manner.

It is noted that the nder switch 30 of the link 60 may be rendered busy .by operating the busy switch SI83. When the busy switch SI 83 is operated, the switch springs |86, |81 and |84, |85 thereof are actuated into disengagement, and the switch springs |86, |84 thereof are actuated into engagement. When the switch springs |86 and |81 of the busy switch S|83 are actuated into disengagement, the previously traced path for applying ground potential in the nder switch |30 to the all-trunks-busy conductor C32| is lnterrupted; when the switch springs |84 and |85 of the busy switch SI83 are actuated into disengagement, a point in the previously traced path for applying ground potential to the guard conductor C322, incident to the operation of the switching relays R|50 and RISO, is interrupted; and, when the switch springs |86 and |84 of the busy switch S 83 are actuated into engagement, a path is completed in the nder switch |30 for applying ground potential to the guard conductor C322. The last-mentioned path for applying ground potential to the guard conductor C322 When the busy switch S334,y

extends from ground, at RAI, .by way oi.' RAI 44, RCI45, and the switch springs |08 and |84 oi.' the busy switch SI83, to the guard conductor C322. This application of ground potential to the guard conductor C322 marks the link 80 as busy, thereby to prevent the distributor 300 from selecting the link 80 in the ilrst group of links, or causes the rotary switch 30| in the distributor 300 to operate and select another idle link in the rst group oi' links in the event that the distributor 300 has previously operated to select the link 00 prior to the operation oi' the 4busy switch SI83 therein. .In the event the distributor 300 has operated to select the link 60 in the ilrst group of links prior to ,operation of the busy switch SI83 therein, as explained abov the application of ground potential to the guard conductor C322, incident to the operation of the busy switch SI83, causes the rotary switch 30| in the distributor 300 to operate and select another idle link in the first group of links. Speciilcally, this application of ground potential to the guard conductor C322 completes the previously traced circuit for energizing the winding of the rotary magnet M308 of the rotary switch 30| in the distributor 300. The operation of the rotary magnet M308 to cause the rotary switch 30| to select an idle link in the ilrst group of links is the same as that previously explained.

As previously noted, an arrangement is provided for testing'the operation of the distributor 300 and the finder switches of the links associated therewith. This arrangement comprises the busy switch S334 and the test jacks J33I, J332 and J333. In order to test the operation of the distributor 300 to select idle links in the ilrst group of links and to test the operation of the selected links in the rst group of links, the busy switch S334 is operated away from its normal position and plugs are inserted into the jacks J33| and J332. When the busy switch S334 is operated away from its normal position, a point in the previously traced holding circuit for energizing the lower winding of the control relay R390 is interrupted at the switch springs 331 and 338 thereof, and the previously traced original circuit for energizing the winding of the busy transfer relay R340 is interrupted at the switch springs 335 and 336 thereof. The busy transfer relay R340 thenrestores to interrupt, at RA344, a further point in the previously traced alternative holding circuit for energizing the winding thereof, to interrupt, at RA345, a point in the previously traced circuit for energizing the winding of the control relay R350 in series with the winding of the rotary magnet M308, to interrupt, at RA34| and RC343, a point inthe previously traced circuit for energizing the start relay R345, and to complete, at RA34| and RC342, a connection between the conductors C328 and C321 extending into the distributor 3|2. As previously noted, when the conductors C321 and C328 are connected together, the distributor 3| 2 is operative to assign idle links in the second group of links to the use of calling lines in both the rst and second groups oi' lines. Accordingly, the test of the distributor 300 at this time does not interrupt trailc on the subscriber lines in the rst group of lines. When the plug is inserted into the jack J 33| an alternative circuit, traced hereinafter, is prepared for energizing the winding of the control relay R350 in series with the winding of the rotary magnet M308; and, when the' plug is inserted into the jack J332, an alternative circuit is completed for energizing the winding of the start relay R345. The last-mentioned circuit extends from ground by way of the jack J 332 and associated plug, the resistor 339, and the winding of R345 to battery. When energized over the above-traced circuit, the start relay R345 operates to complete, at RA346, the previously mentioned alternative circuit for energizing in series the winding of the control relay R350 and the winding of the rotary magnet M308, this circuit extending from ground, at RA330, by way of RA330, RC33I, RA365, RA346, the winding of R350, the jack J33| and. associated plug, MA308,

and the winding of M308 to battery. When energized over the above-traced circuit, the control relay R350 operates. However, the rotary magnet M308 does not operate due to the high series resistance of the winding of the control relay R350.

Upon operating, the control relay R350 prepares, at RA351, a point in the previously traced circuit for energizing the lower winding of the transfer relay R380, and completes, at RA356, the previously traced circuit for energizing. the winding of the timing relay R315, thereby to initiate the timing operation of the relay R315 and the control relays R380, R390 and R330 in the previously described manner. Also, upon operating, the control relay R350 prepares, at RA359, a point in an alternative circuit for energizing the winding thereof in series with the Winding of the rotary magnet M308; prepares, at RA353 and RC355, a point in the previously traced circuit for energizing the winding of the rotary magnet M308 directly from the guard conductor C322; prepares, at RA352, a point in the previously traced circuit for energizing the vertical magnet of the iinder switch of the selected link, and completes, at RA35|, the previously traced circuit forenergizing the start relay of the nder switch of the selected link. Assuming that the rotary switch 30| has previously operated to select the link 60, when the control relay R350 operates it completes, at RA35|, the previously traced circuit for energizing the start relay RI 40 in the nder switch |30 of the link 60. Upon operating, the start relay R|40 completes, at RAI48, the previously traced circuit for energizing the vertical magnet M|10, thereby to initiate operation of the finder switch |30, in the previously described manner. 'I'he vertical magnet M|10 and-the step relay R310 in the distributor 300 interact in the previously described manner, thereby to cause the carriage of the Strowger mechanism |40 of the finder switch |30 to be driven step by step in the vertical direction. In the event that there is la calling line in either the first or second group of lines at this time, the finder switch |30 operates, in the previously described manner, in order to seize the calling subscriber line. However, in the event there is no calling line at this time in either the iirst or second group of lines, the carriage of the Strowger mechanism |40 of the nder switch |30 is i'lrst driven 'in the vertical direction ten steps away from its normal position, whereupon the control wiper |41 associated with the row of contacts engages the grounded contact |48', thereby to complete the previously traced circuit for energizing the lower wrindingof the transfer relay R360 in order to cause the transfer relay R360 to operate. Upon operating, .the transfer relay R360 completes, at RA36| and RC364, the previously traced circuit for energizing the rotary magnet M|1|. The rotary magnet M|1| then operates to drive the carriage of the Strowger mechanism |40 in the finder switch |30 step by step in the rotary direction eleven steps away from its normal position, whereupon the set of switch springs S|`|4 is actuated into engagement. When the sct of switch springs -S|`|4 is actuated into engagemennthe previously traced path for .applying ground potential to the y `guard conductor-C322 is completed, thereby to cause the distributor 300 to release and to cause therotary switch 30| to operate and select another idle link in the flrst group of links in the previously described manner. When another idle link in the first group of links is selected in the previously described manner, the distributor 300 again operates to cause the nder switch of this link either to seize a calling vline in the iirst or second group of lines or to be operated, in the above-described manner The distributor 300 and the idle links in the first group of links are reoperated in the above-described manner so long as the busy switch S334 remains operated away from its normal position and the plugs are retained irl the jacks J 33| and J 332. In o-rder to restore the operation of the distributor 300 to normal, the busy switch S334 is returned to its normal position and the plugs are removed from the Ijacks .133| and .1332.

Inorder to test the timing operation of the distributor 300, plugs are inserted into the jacks J 332 and J 333, while the busy switch S334 remains in its normal position. When the plug is inserted in the jack J 332, the previously traced alternative circuit for energizing the start relay R345 is completed; and, when the plug is inserted into the jack J 333, an alternative circuit is completed for energizing the winding of the step relay R310. 'I'he last-mentioned circuit extends from ground by way of the jack J 333 and associated plug, and the Winding of R310 to battery. When energized over the above-traced circuit, the step relay R310 operates to interrupt, at RA31I, a point in the previously traced circuit for energizing the vertical magnet of the nder switch of the selected link, thereby' to prevent operation of the finder switch of the selected link, The operation of the start relay R345 causes operation of the control relay R350, `as previously explained. Upon operating, the control relay R350 completes, at RA356, the previously traced circuit for energizing the timing relay R315, which latter relay operates to complete, at RA316 and RC318, RC319, the `previously traced circuit for energizing the winding of the control relay R380, thereby to cause the latter relay to operate shortly thereafter. Upon operating, the control relay R380 completes, at RA385, the previously traced circuit for energizing the upper winding of the control relay R330, thereby to cause the latter relay to operate. Upon operating, the control relay R330 completes, at RA336, the previously traced holding circuit for energizing the lower winding thereof, and interrupts at RA333 and H0336, the previously traced circuit for energizing the timing relay R315, thereby to cause the latter relay to restore. Upon restoring, the Ytiming relay R315 sets the weighted armature RA316 into operation, thereby to retain the control relay R380 in its operated position for a predetermined interval, after which the relay R380 restores, Upon restoring, the control relay R380 completes, at'RA382 and RC383, the pre- Vviously traced circuit for energizing the upper trol relay R330 locks the distributor 300 outoi service and the illumination of the supervisory lamp L30! indicates to the exchange attendant this condition of the distribuer 300, as previously explained. l

. In order to restore normal operation of the distributor 300, the plugs are removed from. the jacks -I332 and J333, and the busy switch S330 is operated away from its normal position and then returned to its normal position, as previously explained.

Continuing now with the operation of the selector switch 200 to extend a call from the subscriber substation A to the subscriber substation B, when the finder switch |30 operates to seize the calling subscriber line |0|, the selector switch 200 is rendered operative in response to impulses transmitted thereto from the subscriber substation A. At this time, the line relay R260, the hold relay R210 and the transfer relay R290 in the selector switch 200 occupy their operated positions, as previously explained.

It is noted that the test relay R265 in the selector switch 200 is of the shunt ileld type and comprises a ileld structure including an L- shaped leg L266, -two core legs L261 and L263, a shunt leg L269 and a movable armature RA265, two windings being respectively carried on the core legs L261 and L266. 'I'he test relay R265 is so connected and arranged that, when the winding on the core leg L261 is energized, a magnetic ilux is produced in the field structure which traverses a first magnetic path extending from the core leg L261 by way of the base of the leg L266, the core leg L266, and the shunt leg L269 to the core leg L261, thereby to polarize .the eld structure of the test relay R265. When the winding on the core leg L266 is energized with current of one polarity, an additional magnetic flux is produced in the eld Accordingly, the armature RA265 of the test relay R265 is not operated with respect to the eld structure thereof. On the .other hand, when the winding on the core leg 1.268 is energized with current of the opposite polarity, a magnetic flux is produced in the shunt leg L269 which is in opposition to the magnetic flux traversing the shunt leg L26! by way of the iirst magnetic path. Accordingly, the magnetic ux produced by the winding on the core leg L261 of the i'leld structure is diverted from the shunt leg L269 into a second magnetic path extending from the leg L206 by way of the core legs L261 and 1.268, and the armature RA265 to the leg 1.266. Accordingly, the armature RA265 is attracted to the field structure of the :est relay R265, thereby to operate the test re- The subscriber at the substation A then dials the'iirst digit of the directory number of the called subscriber substation B at the dial mechat the substation A, thereby to transmit a nrst series of impulses by way of the subscriber loop circuit to the line relay R260 in the selector switch 200. The relay R260 follows the dialed impulses in the usual manner. restoring each time the loop circuit is interrupted and operating each time the loop circuit is completed. Each time the line relay R260 restores,-

it interrupts', at RA26| and RC262, the previously traced circuit for energizing the hold relay R210, and completes, at RA26| and RC2, the previously mentioned circuit for energizing in multiple the lower winding of the transfer-'relay R200 and the winding of the vertical magnet M230. The last-mentioned ground, at RA2II, by way of RA2|0, RA20|, RC203 andRA210 to RC216, one branch of this circuit extending from RC2" by way of the lower winding of R230 to battery, and the other branch of this circuit extending from RC215 by way of the winding of M236 to battery. The hold relayR210 and the transfer relay R200 are oi the slow-to-release type. Thus, these relays remain operated during impulsing. Each time the vertical magnet M230 is energized, the `carriage of the Strowger mechanism 20| of the selector switch 200 is driven one step in the vertical direction.

When the carriage of the Strowger mechanism 20| is moved away from its normal position one step inthe vertical direction, the sets of switch -springs S211, S218, and S239 are actuated. More particularly, the set of switch springs S211 is actuated into disengagement, thereby to interrupt the previously traced circuit for energizing the upper winding of the transfer relay R290; the set of switch springs S216 is actuated into engagement, thereby to prepare a circuit. traced hereinafter, for energizing the winding of the rotary magnet M231; and the set of switch springs S239 is actuated into engagement, thereby to prepare a circuit traced hereinafter for energizing the winding of the release magnet M230. At the conclusion of the first digit dialed, the relay R260 reoperates, thereby to interrupt, at RA26| and RC263, the previously traced circuit for energizing in multiple the lower winding of the transfer relay R290, and the winding of the vertical magnet M236. When this circuit is interrupted, further operation of the vertical magnet M236 is positively arrested, thereby to arrest the carriage of the Strowger mechanism 20| circuit extends from of the selector switch 200 in a vertical position magnet'M231 to re: rotary magnet M231 thereby vto cause the rotary store. Upon restoring, the recompletes, at MA231, the previously traced circuit for energizing the winding thereof.

l The rotary magnet M231 continues to operate buzzer fashion, thereby to drive the carriage of the Strowger mechanism 20| step by step in the rotary direction until the wiper set thereof engages a contact set in the contact bank terminating a trunk line extending to an idle connector switch in the group of connector switches including the connector switch 2I5. Assuming that the connector switch 2I5 is the li'lrst idle connector switch in this group of connector switches, further operation of the rotary magnet M231 is arrested when the wiper 204 of the wiper set of the Strowger mechanism 20| engages the contact in the contact set terminating the control conductor C2I4 of the trunk line 2II extending to the connector switch 2I5, the connector switch 2 I5 being marked as idle by the presence of battery potential upon the control conductor C2I4 of the trunk line 2| I. This application ,of battery potential to the control conductor C2I4 of the trunk line 2| I completes the previously mentioned circuit for energizing the winding on the core leg L268 of the eld structure of the test relay R265, this circuit extending from ground, at RA213, by way of RA213, the winding on the core leg L268, the wiper 204 and associated contact, and the control conductor C2 I4 ofI the trunk line 2II to battery in the connector switchr 2I5. When energized over the above-traced circuit, the winding on the core leg L268 of the eld structure of the test relay R265 causes the test relay R265 to operate, as previously explained. Upon operating, the test relay R265 interrupts, at RA266 and RC261, a point in the previously traced circuit for energizing the rotary magnet M231, and completes, at RA266 and RC268, a circuit for energizing the switching relay R2 I0, this circuit extending from ground, at RA212, by way of RA212, RA266', RC268, and the winding of R2I0 to battery. When energized over the above-traced circuit, the switching relay R2I0 operates to complete, at RA2I9, a holding circuit for energizing the windingthereof, .this circuit extending from the grounded control conductor CI I8 of the trunk line II5 by way of RA2I9eand the winding of R2I0 to battery. Also, upon operating, the switching relay R2I0 interrupts, at RA2I8, a further point in the previously traced circuit for energizing the winding of the rotary magnet M231, and connects the trunk line II5 to the wiper set of the Strowger mechanism 206,

' thereby to complete a loop circuit between the subscriber substation A and the connector switch 2 I5. At this time, the line conductor CI I6 of the trunk line H5 is conneced by/way of RAMI, RC2I2, and the wiper 20| and associated contact to the line conductor C2I2 of the trunk line 2| I; the line conductor CI I1 of the trunk line Ii5 is connected by way of RA2I6, RC2I5, and the wiper 203 and associated contact tothe line conductor C2I3 of the trunk line 2| I; and the control conductor CI I8 of the trunk line H5 is connected by way of RA2I1 and the wiper 200 and associated contact to the control conductor C2i@ of the trunk line 2H. Thus, ground potential appearing upon the control conductor CHS of the trunk line H5 is extended by Way. of the control conductor C2I4 of the trunk line 2H to the connector switch 2I5, thereby to cause the connector switch to operate and complete a loop circuit between the line conductor C2I2 and C2 I3 of the trunk line 2II and extending tothe subscriber substation A. -Also, the connector switch 2I5 operates to cause ground potentialtherein' to be applied to the control conductor C2I4 of the trunk line 2| I, thereby to retain the nder switch |30 and the selector switch 200 of the link 60 in their operated positions.

Also, upon operating, the switching relay R2I0 interrupts, at RA2I0, a. point in the previously traced circuit for energizing the hold relay R210, and interrupts, at RA2II and RC2I3, and at RA2I4 and RC2 I6,.points in the previously traced circuit for energizing in series the upper and lower windings of the line relay R260. The line relay R260 immediately -restores and, shortly 1thereafter, the hold relay R210 restores. Upon restoring, the hold relay R210 interrupts, at RA212, the previously traced circuit for energizing the winding on the core leg L261 of the field structure of the test relay R265, and interrupts, at RA213, the previously traced circuit for energizing the winding on the core leg L268 of the field structure of the test relay R265, thereby to cause the test relay R265 to restore. At this. time, the switching relay R2I0 in the selector switch 200 remains inits operated position due to the completed holding circuit for energizing the winding thereof including the control conductor C2I4 of the trunk line 2II. Also, at this time, the connector switch 2I5 is conditioned to be responsive to impulses transmitted thereto .by way of the Iloop `circuit extending thereto from the calling subscriber substation A.

It is noted that, when the connector switch 2I5 is busy, ground potential appears upon the control'conductor C2 I4 of the trunk line 2| I extending thereto, this ground potential being derived at RC222 of the battery reversing relay R220 therein and extending from RC222 by Way of RC222, RA223 and other elements, not shown, to

the -control conductor C2I4. Also, during the course of operation of the connector switch 2I5, booster battery potential appears upon the control conductor C2 I4 of the trunk line 2| I extending thereto, this booster battery potential being derived at the battery 223 in the connector switch 2I5 and extending therefrom by way of RA22 I RA223 and other elements, not shown, to the control conductor C2 I4.

It is noted that the selector switch 200 is so connected and arranged that it will not operate to seize the trunk line 2II when either ground potential or booster battery potential appears upon the control conductor C2I4. When the wiper 204 of the wiper set of the Strowger mechanism 20| engages the contact in the contact set terminating the control conductor C2I4 of the trunk line 2| I, a path is completed for shortcircuiting the winding on the core leg L260 of the eld structure of the test relay R265 when ground potential appears upon the control conductor C2I4 of the trunk line 2| I, this circuit extending from ground, at RA213, by way of RA213, the winding on the core leg L268, and the wiper 200 and associated contact to the grounded control conductor C2I4 of the trunk line 2H. When the wiper 204 of the wiper set of the Strowger mechanism 20| engages the contact in the contact set terminating the control conductor C2i4 of the trunk line 2| I, a path is completed for venergizing the winding on the core leg L268 of the eld structure of the test relay R265 when booster battery potential appears upon the conthe core leg L200 o! the ileld structure of the test relay R255 is energized in the present instance, the magnetic ilux produced in the shunt leg L260 of the field structure of the test relay R205 is accumulative with the magnetic flux produced therein by the winding on the core leg L26`| thereof. Accordingly, the test relay R235 is not operated at this time, as previously noted.

Continuing now with the operation of the connector switch 2|5 to seize the called subscriber line 230 extending to the subscriberl substation B, the subscriber at the calling subscriber substation A then dials two additional ldigits into the connector switch 2|5, thereby to cause the connector switch 2|5 to operate, in the usual manner, and seize the called subscriber line 230. In the event the called subscriber line 230 is busy, ground potential appears upon the control conductor C234 thereof, thereby to cause the connector switch 2|5 to operate and return busy tone current over the loop circuit extending to the calling subscriber substation A, in the usual manner. On the other hand, in the event the called subscriber line 230 is idle, battery potential appears upon the control conductor C234 thereof, this battery potential being derived at` the upper terminal of the winding oi.' the cutoif relay R245 of the line circuit; 240, individually associated with the subscriber line 230, and extending therefrom by way of the winding of R245, RC253 and RA252 to the control conductor C234. I

'Ihe connector switch 2|5 then operates to cause direct ground potential to be applied to the wiper 228 of the wiper set of the Strowger mechanism 225, thereby to complete a circuit for energizing the cutoff relay R245. The circuit for energizing the cutoi relay R245 extends from ground potential appearing in the connector switch 2|5 .by way of the wiper 228 and associated contact of the Strowger mechanism 225, the control conductor C234 of the subscriber line 230, RA252, RC253 and the winding of R245 to battery. When energized over the above-traced circuit. the cutoil' relayv R245 operates to interrupt, at RA248 and at RA249, the circuit for energizing the line relay R250, and to complete, at RA24'I, a path for applying ground potential to the control conductor C235 oi' the subscriber line 230, this path extending from ground potential appearing upon the control conductor C234 of the subscriber line 230, by way of RA252, RC253 and RA24I to the control conductor C235. 'I'his application of ground potential to the control conductor C235 marks the called subscriber line 230 as busy to the nder switches of the links having access thereto. Also, upon operating, the cutoff relay R245 completes, at RA245, a circuit for energizing the winding of the meter relay RZIS, assuming that the upper terminal of the meter relay R2|9 is connected to the conductor C2|8, this circuit extending from the grounded control conductor C234 of the subscriber line 230, by way oi' RA252, RC253, RANG, the conductor C2| 8, and the winding of R2I9 to battery. Although the winding of the meter relay R2|9 is energized over the above-traced circuit, this relay does not operate at; this time due to theL fact that it is oi' the marginal type.

After seizing the called subscriber line 230, the connector switch 2|5 operates to cause ringing current to be projected over the line conductors C23| and C232 of the subscriber line 230 in the usual manner, thereby to cause the ringer at the called substationB to operate. When the subscriber at the substation B answers the call by removing the telephone receiver of the telephone instrument thereat from its hook, a'loop circuit is completed by way ot the line conductors of the subscriber line 230 to the connector switch 2|5, thereby to cause the battery reversing relay R220 in the connector switch 2I5 to operate in the usual manner. Also, the connector switch 2| 5 operates to complete a connection between the calling subscriber loop circuit extending theretov from the subscriber substation A and the called subscriber loop circuit extending thereto from the substation B. Upon operating, the battery reversing relay R220 in the connector switch 2|5 completes, at RA22I and RA223, the previously traced path for connecting booster battery potential to the control conductor C2|4 of the trunk line 2| I, and interrupts at RA223 and the previously traced path for connecting ground potential to the control conductor C2|4 of the trunk line 2| I. 'I'his application of booster battery potential to the control conductor C2|4 of the trunk line 2I| completes a circuit for effectively energizing the winding of the meter relay R |00 associated with the line circuit |00 individually associated with the calling subscriber line |0I, this circuit extending from booster battery potential appearing upon the control conductor C2|4 o1 the trunk line 2|| by way oi the wiper 204 and associated contact of the Strowger mechanism 20| of the selector switch 200, RAZII, CI I8, RA| 63, CI34,v the wiper |43 and associated contact of the Strowger mechanism |40 of the inder switch |30, the control conductor C|04 of the subscriber line |0I, RAI I3, RAII4, C|08, and the winding of R|00 to-battery. When energized over the above-traced circuit, the meter relay R|09 operates, thereby to cause a call register associated therewith to be actuated in the usual manner. It is noted that booster battery potential appearing uponthe control conductor CI I8 oi.'- the trunk line ||5 extending between the iinder switch |30 and the selector switch 200 of the link 80, and upon the control conductor C|04 of the subscriber line |00, retains these switches and the line circuit |00 in their operated positions. Shortly after the connector switch 2|5 operates to cause booster battery potential to be applied to the control conductor C2|4 of the trunk line 2| I, it again operates to cause booster battery potential to be removed from the control conductor C2| 4 and ground potential to be reapplied thereto, thereby to retain the link 50 and the line circuit |00 in their operated positions.

The release of the established connectionl between the subscriber substations A and B is under the control of the subscribers thereat and, when both of the subscribers replace the receivers of the telephone instruments upon their associated switchhooks at the substations A and B, the connector switch 2 I5 iirst releases. When the connector switch 2 I5 is released, the Strowger mechanism 225 thereof is returned to its normal position and ground potential is removed in the connector switch 2|5 from the control conductor C2| 4 of the trunk line 2| I. When the Strowger mechanism 225 of the connector switch 2|5 is returned to its normal position, the previously traced circuit for energizing the cutoi relay R245 in the line circuit 240 is interrupted, thereby to cause the cutoff relay R245 to restore. Upon restoring, the cutoir relay R245 interrupts, at RA248, a point in the previously traced circuit for energizing the meter relay R2Il, intertrunk rupts, at RA241, a point in the previously tracedv path for applying ground potential to the control conductor C235 of the subscriber line 230, and prepares, at RA248 and at RA248, points in the previously mentioned circuit for energizing the line relay R250. At this time, the line circuit 240 individually associated with the subscriber line 230 is completely released.

When ground potential is removed from the control conductor C2 I4 of thel trunk line 2| I, the previously traced path for connecting ground potential to the control conductor CII8 of the line II5 extending between the ilnder switch |30 and the selector switch 200 of the link 50 is interrupted. When ground potential is removed from the control conductor CI.I 8 of the trunk line II5, the previously traced holding circult for energizing ,the winding of the switching relay R2I0 is interrupted, thereby -to cause the latter relay to restore. Upon restoring, the switching relay R2I0 interrupts, at RA2I9, a further point in the holding circuit for energizing the winding thereof, prepares, at RA2I8, a point in the previously traced circuit for energizing the winding of the rotary magnet M231, and interrupts, at RA2II and RC2|2, at RA2I4 and RC2I5 and at RA2 I1 the connection between the trunk line II5 and the wiper set of the Strowger mechanism 20|, and prepares, at RA2I I and RC2I3, and at RA2I4 and RC2I6, points in the previously traced circuit for energizing in series the upper and lower windings of the line relay R260. Also, upon restoring, the switching relay R2I0 completes, at RA2I0, the previously mentioned circuit for energizing the release magnet M238. this circuit extending from ground, at RA2I0, by way of RA2I0, RA26I, RC263, RA214, RC216, RA292, the set' of switch springs S239, and the winding of M238 to battery. When energized over the above-traced circuit, the release magnet M238 operates, thereby to release the carriage of the Strowger mechanism'20l in order.

to cause it to be returned to its normal position. When the carriage of the Strowger mechanism 20| is returned to its normal position, the sets of switch springs S239, S211 and S218 are actuated. More particularly, the set of switch springs S239 is actuated into disengagement, thereby to interrupt the previously traced circuit for energizing the winding of the release magnet M238; the set of switch springs S211 is actuated into engagement, thereby to prepare a point in the previously traced circuit for energizing the upper Winding of the transfer relay R290; and the set of switch springs S218 is actuated into disengagement, thereby to interrupt a further point in the previously traced circuit for energizing the winding of the rotary magnet M231. At this time, completely released.`

When ground potential is removed from the control conductor CII8, the previously traced circuit for energizing the switching relay, RI60 in the finder switch |30 is interrupted, thereby to cause the latter relay to restore. Upon restoring, the switching relay RI60 prepares, at RAI55, a point in the previously traced circuit for energizing the winding of the rotary magnet MI1I, Y

interrupts, at RAI69, a point in the previously traced path for applying ground potential to the guard conductor C322, interrupts, at RAI64, a further point in the holding circuit for energizing the winding thereof, prepares, at RAI60, a point in the previously traced circuit for energizing the' winding of the switching relay RI50,

the selector switch 200 is and interrupts, at Ram, at nam and at asm,

the connection between the trunk line II5 andthe trunk line I3I. Also, upon restoring, the switching relay RISO interrupts. at-RAI88 and RC|81, the previously traced circuit for illumihating the supervisory lamp LI28, and completes, at RAISB and RCI68, the previously mentioned circuit for energizing the winding of the release magnet. MI12. The last-mentioned circuit extends from groun`d, at RAI44,'by way of RAI44, RCI45, the switch springs |88 and |81 of the busy switch SI83, the switch springs |18 and |18 of the set of switch springs SI15, RAI68,'RCI88, RAI58, andthe winding of MI12 to battery. When energized over the ,above-traced circuit, the release magnet release the carriageof the Strowger Amechanism |40 and to cause it to be returned to its normal position. When the carriage of ythe Strowger mechanism .is returned to its normal' position, the sets of switch springs SI15 and SI19 are actuated. More particularly, the switch springs |80 and I8I ofthe set of switch springs SI19 are actuated into disengagement, thereby to interrupt a further point in the previously traced path for applying ground potential to the guard conductor C322; the switch springs I8I and |82 are actuated intol engagement, thereby to connect the guard conductor C322 to the control conductor CI I8 of the trunk line I'I5; the switch springs |16 and |18 of the set of switchv springs SI15 are actuated into disengagement, thereby to interrupt the previously traced circuit for energizing the winding of the release magnet MI12; and the switch springs |11 and |18 of the set of switch springs SI15 are actuated into engagement, thereby to complete the previously traced path for applying groundA potential in thev finder switch |30 to the all-trunks-,busy conductor C 32I. The previously mentioned connection between the guard conductor C322 and the control conductor CII8 of the from the guard conductor C322, by way of the switch springs |84 and |85 of the busy switch SI83, RAI43, and the switch springs I8I and |82 of the set of switch springs ySI19 to the control conductor CI I8 of the' trunk line |I5. The connection of the guard conductor C322 to the control conductor CI I8 of the trunk line II5 insures that the link 60 will not be selected by the distributor 300 for the use of a calling one of the lines unless both the iinder switch |30 and the connector switch 200 thereof are completely released. At this time,- the nder switch |30 is completely released. Accordingly, the link 60 is completelyrelease and is available to beselected by the distributor 300 for the use of a calling one of the lines. r

When ground potential is removed from the control conductor CI I8 of the trunk line I|5, the previously traced circuit for energizing the cutoff relay RI I0 in the line circuit |00 individually associated with the subscriber line IOI is inrelay RI09-associated with the line circuit I00.,

At this time, th'e `line circuit |00 is completely releasedand the subscriber line IOI is marked as MI12 operates, thereby, tol

trunk line II5 extends

US269139A 1939-04-21 1939-04-21 Telephone system Expired - Lifetime US2214908A (en)

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Application Number	Priority Date	Filing Date	Title
US269139A US2214908A (en)	1939-04-21	1939-04-21	Telephone system

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Application Number	Priority Date	Filing Date	Title
US269139A US2214908A (en)	1939-04-21	1939-04-21	Telephone system

Publications (1)

Publication Number	Publication Date
US2214908A true US2214908A (en)	1940-09-17

Family

ID=23025962

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Application Number	Title	Priority Date	Filing Date
US269139A Expired - Lifetime US2214908A (en)	1939-04-21	1939-04-21	Telephone system

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US (1)	US2214908A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number	Priority date	Publication date	Assignee	Title
US2615092A (en) *	1947-03-05	1952-10-21	Automatic Elect Lab	Discriminating service telephone system
US2668194A (en) *	1949-09-13	1954-02-02	Stromberg Carlson Co	Finder-allotter circuit for telephone systems
US2690479A (en) *	1952-10-15	1954-09-28	Automatic Elect Lab	Overflow arrangement for line finders in telephone systems
US2761906A (en) *	1953-03-10	1956-09-04	Automatic Elect Lab	Rotary finder and secondary
US3037084A (en) *	1959-05-11	1962-05-29	Itt	Linefinder and control circuits

1939
- 1939-04-21 US US269139A patent/US2214908A/en not_active Expired - Lifetime

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number	Priority date	Publication date	Assignee	Title
US2615092A (en) *	1947-03-05	1952-10-21	Automatic Elect Lab	Discriminating service telephone system
US2668194A (en) *	1949-09-13	1954-02-02	Stromberg Carlson Co	Finder-allotter circuit for telephone systems
US2690479A (en) *	1952-10-15	1954-09-28	Automatic Elect Lab	Overflow arrangement for line finders in telephone systems
US2761906A (en) *	1953-03-10	1956-09-04	Automatic Elect Lab	Rotary finder and secondary
US3037084A (en) *	1959-05-11	1962-05-29	Itt	Linefinder and control circuits

Publication	Publication Date	Title
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US2335473A (en)	1943-11-30	Telephone system
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US2115320A (en)	1938-04-26	Automatic telephone system
US2289896A (en)	1942-07-14	Telephone system
US2419282A (en)	1947-04-22	Telephone system
US2333038A (en)	1943-10-26	Telephone system
US1585909A (en)	1926-05-25	Code signaling system
US2370239A (en)	1945-02-27	Special service telephone system
US2177069A (en)	1939-10-24	Telephone system
US2274760A (en)	1942-03-03	Telephone system
US1670252A (en)	1928-05-15	Automatic telephone system
US2286431A (en)	1942-06-16	Telephone system
US2214256A (en)	1940-09-10	Telephone system
US2352107A (en)	1944-06-20	Telephone system
US1902186A (en)	1933-03-21	Automatic telephone system
US2224517A (en)	1940-12-10	Telephone system
US2285282A (en)	1942-06-02	Telephone system
US2706747A (en)	1955-04-19	Selector repeater for telephone systems
US2218850A (en)	1940-10-22	Telephone system
US1688656A (en)	1928-10-23	Automatic telephone system
US1542958A (en)	1925-06-23	Automatic telephone system
US1694615A (en)	1928-12-11	Automatic telephone system
US2713616A (en)	1955-07-19	Finder distributor permanent timer

US2214908A - Telephone system - Google Patents

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Priority Applications (1)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23025962

Family Applications (1)

Country Status (1)

Cited By (5)

Cited By (5)

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