CH197444A - Installation of long-distance telephony. - Google Patents

Description

  

  Installation of long-distance telephony. The invention relates to a long-distance telephony installation.



  Its purpose is the economical use e1; of different qualities of trunk lines or equipment associated with trunk lines connecting power plants through which trunk or terminating traffic can pass.



  This long-distance telephone installation comprising a number of interurban centers is characterized by a first group of interurban lines between a first and a second interurban exchange, by a second group of interurban lines connecting the first exchange to the second and having a character different from that of the lines of the first group, and by means for automatically diverting the interurban traffic normally carried by said first group of interurban lines to the second group of interurban lines,

      if said first group of trunk lines is completely occupied.



  The following description, based on the accompanying drawings, relates to working examples of this installation.



  On these: fig. 1 schematically shows a switching point for trunk telephone lines comprising a single step of retrograde search switches with repeaters; fig. 2 shows a switching point with two stages of retrograde search motion switches adapted to be actuated in response to a single digit;

    fig. 8: shows a switching point with two stages of retrograde search motion switches, each adapted to be actuated by a direction digit; figs. 4 to 8 show different types of connections that can be made, as well as arrangements for the control of the bath;

    1a, fig. 9 relates to a trunk line circuit arriving at a switching point; the fi-. 10 shows the gain control circuits of a repeater; the fi-. 11 shows circuits of an outgoing trunk line and switches at a switching point for two subgroups. in the. same direction; the fi-. 12 shows another form of direction and call circuits reta.rdf@s; the fi-. 13 gives in detail the circuits of the installation shown schematically in FIG. 2;

    the. fig. 14 gives details of the circuits of the installation shown schematically in FIG. 3, and the fi-. 15 relates to. a central office network to which a new form of leadership is applied; the fi-. 9 to. 12 together represent the complete circuits of a switching point for the installation shown schematically in. fi-. 1; fig. 10 should be placed under, fig. 9 and fig. 11 and 12 must be placed respectively. right of the fi-. <B> 9 </B> and <B> 10. </B>



  The principles of operation can be explained by first referring to figs. 1 to- 8. After these principles have been clearly stated in this manner, the detailed operation of the installation will be. in face by referring to the simplified circuits giving them. essential parts necessary to understand the invention.



       Co-rmiautation Step <I> of </I> cornnuctatioiz. <I> to </I> süu ple clr i <i> f f </I> re (fig. 1) The <B> fi-. </B> 1 represents a switching step to. single digit and shows how a number of local LL connection circuits or incoming inter-city line circuits <I> IT </I> can have access to.

   interurban lines running in a number of directions, of which only two have been shown in the drawing, namely direction A and direction B.



  In direction B there is shown a single group BL of outgoing interurban lines, while in direction _1 there are two distinct groups of these outgoing interurban lines. This distinction was made for the following various reasons: (a) With regard to the type of signaling equipment.



  It may be possible to serve part of the lines between two networks by means of a simple type of signaling equipment, while for transit operation, or for other reasons. other lines must be served by means of signaling equipment, which is more complicated and more expensive.

   In order to minimize the use of such equipment, the circuits are so arranged that the lines containing the single type of equipment will be chosen whenever possible, while the other type of lines will be chosen only when possible. absolutely necessary. The drawing shows that a sub-group of lines F_1L in direction _I is served by means of equipment at. 50 cycles, and that the other subgroup <B> VAL </B> is served by means of voice frequency equipment.

   It is obvious that a different classification can be made depending on the way of signage used.



       b% With regard to the transmission characteristics of the lines.



  The lines between two networks can be divided into sub-groups: @s containing for example lines with high transmission quality and lines with lower transmission quality, suitable only for certain particular types of calls. Two-conductor trunk lines can be divided into those having characteristics of high transmission speeds and others having lower or lower speeds.

   A distinction can also be made between trunk lines with two conductors and circuits with four conductors, or between lines having. a.ffa.i- weakening and those with a strong weakening.



       c) With regard to the importance of the networks that can be reached by the lines.



  Some lines can be used for: LAN connections at the ingress end only. so that they do not contain the necessary selector equipment and the repeater access equipment that would be required if they were arranged for traffic in transit through the office at their arriving ends. Other lines can be equipped for this purpose.

   In this case the very expensive tandem equipment is reduced to the minimum possible.



       Selection When the local function circuit or the terminating trunk circuit has been selected for a call, the direction to which this call is to be extended is indicated by means of:

  a train of pulses sent from the recorder and received on a direction marker switch DIM forming part of the first circuits mentioned. Following the position occupied by this marker switch, a test potential is connected to a terminal characterizing the incoming circuit in. the arcs of all researchers in the division:

  requested, for example BL, and the wanted seekers -of this direction are simultaneously set in motion. One of them then connects the finish line <I> IT </I> and sends a start pulse to the end: remote from the start line,:

  simultaneously establishing the connection between the incoming and outgoing line circuits via four of these brushes. In the case where. the insertion of a repeater is necessary, a group of RF researchers simultaneously search with the researchers for outgoing trunk lines. and only when both an originating trunk and a repeater have been connected to the terminating trunk, a pulse of:

  boot is sent to the remote end. Simultaneously with the impulse of: starting, <B> the </B> outgoing trunk: circuit sends a pulse in, return via the incoming trunk: to the originating office so that the recorder at that office makes the next selection.

   The time during which the interurban line searchers:, departure and repeaters searchers operate, is therefore independent of the speed at which the subscriber records the various digits on his disk, these being stored at the recorder and transmitted in a timely manner under the control of outgoing trunk circuits.



   <I> Excess appeal cases </I> When the lines in one direction are divided into sub-groups, as indicated for: direction A, each sub-group is characterized by a different position @ of the DIel direction marker switch, so that each subgroup can be chosen individually. It is however possible for:

  calls directed to one of the sub-groups, to be forwarded to the other sub-group in the event of a line failure in the first sub-group. This is usually possible in one direction only. For example in the case in question, it is possible: to direct towards the lines <I> VAL </I> @ at phonic frequencies a call directed first to the FAL lines <I> to. </I> 50 cycles.

   It is not possible to do the reverse, because the reasons which govern the choice of a line with voice frequency prevent the use of a line with 5; 0 cycles.

   This way, one of the two sub-groups will have a: restricted use and the other sub-group will have general use and can be used for:

   calls directed first to the first sub-group than to the others. The way in which a call is transferred from one sub-group to another,:

  is as follows when, fig. 1, all. the 50-cycle lines are busy, a recourse or transfer relay placed in the starting circuit of this sub-group operates each time a call is directed to the sub-group. This transfer relay causes the test potential supplied by the direction marker switch <I> TEN </I> in the calling circuit,

       East. switched of the arc contacts of the FAL searchers <I> to </I> 50 cycles towards those of the lines <B> VAL </B> at vocal frequencies.



       Direction. alternating Fig. 1 also shows how it is possible, for a call directed to _l, to be served via another alternate direction including another office B, if no line in -direction A is available. The call is directed to; B and a selection is made artificially at office B to obtain a line going from B to A.

   This is done as follows: It is assumed that no line at. voice frequencies are not available at the time a call is made to the to lines. direction A voice frequencies (either directly under the control of the DIJI marker switch or indirectly via the 50 cycle lines).

   A transfer relay is energized in the start circuit of the lines to. voice frequencies leading another group of ARF researchers to. search for the call in question. These seekers are each associated with an alternating direction circuit and are multiplied with the seekers of the voice frequency lines, that is, the test and talk multiples are. common.

   One of the AIIF seekers takes the call and extends it to the arcs of the group of trunk searchers BF associated with direction B. When an outgoing trunk line BL in this direction is chosen and it sends the The start pulse to remote office B, it also indicates by means of a feedback pulse in the usual manner that the next selection can take place. However, in this case, the alternating direction circuit intercepts this return pulse, so that it does not reach. not the original office.

   The alternate direction circuit, when it receives the impulse, itself sends an atificial selection to office B in order to cause the. selection of a line of <I> B </I> to <I> A. </I> When a line of <I> B </I> to A has been connected, the starting line circuit. at B to A pulses back in the usual way to indicate that the next selection can take place. The impulse in return is. this time transmitted by the circuit of alternating direction, so that it reaches the office of origin which proceeds to the sending of the next selection.

    This one reaches. office A in the same way as if the transmission took place through a direct line.



       Circuits <I> for delayed calls </I> In a manner analogous to that which has just been explained for circuits at. alternating direction, a group of searchers can be called upon to function whenever no starting line is free, and they extend the call to an operator, or alternatively they provide an auditory signal of occupancy to the calling subscriber. These researchers usually operate after a certain period of time in order to give circuits a chance to reach a free come line.



  Fig. 1 shows a circuit of <B> this, </B> type for delayed call, associated with direction B searchers. When a call takes place in direction B when no line is free, a transfer relay in the starting circuit of direction B, in response, leads the late call seekers to seek the call.

   When one of the researchers has found the call, it determines whether the call was made by a local network or if it arrives via an interurban line circuit. <I> IT. </I> In the first case it is sent to an operator. and in the second case an auditory busy signal is connected to. line.



  It is obvious that a delayed call circuit can also be associated with groups of lines going in direction A. In this case, it can be provided instead of an alternating direction circuit, or if an alternating direction is required, it can be connected in such a way that delayed call seekers operate only when all alternate direction hours are occupied.



       Step <I> of </I> switching <I> to </I> figure <I> with intermediate researchers </I> The arrangement shown in fig. 1, can be used in inter-city central offices where the total number of local LL trunking circuits and incoming trunk circuits <I> IT, </I> does not exceed the number of terminals available on the arcs of interurban line searchers,

  . For example, it is assumed that line seekers of 200 points are used, the total number of local trunk circuits and terminating trunk lines being limited to 200.



  For offices of larger capacity, the arrangement shown in fig. 2 can be used. This assumes that the number of selectable directions does not exceed the capacity of the direction marker switch DIM. According to this Fig. 2, the local trunk circuits LL, and the incoming trunk lines <I> IT, </I> are divided into groups of 2i00 or groups of a size corresponding to the capacity of the researchers used.

       It is assumed that researchers of 2-00 points are employed. Consequently, each group of circuits, local or arrival, has access to as many groups of intermediate researchers as there are departing directions. :

  In fig. 2 we only consider id @ them starting directions. Therefore, each group of 200 circuits has - access to, - two groups of intermediate researchers. So if there are no more than 400 circuits there will be two groups of intermediary researchers for each direction. For capacities up to 6.00 selector circuits there will be three groups of intermediate seekers for each direction, and so on.



  In order to ensure that each circuit has the possibility of reaching all the outgoing trunk lines circuits, the intermediate seekers in each direction are connected to the arcs of a group of secondary seekers associated with the lines in that direction.

    Due to the division of traffic that takes place on circuits between the different directions, the number of intermediate searchers per direction, for each group of 200 circuits, is only a fraction of 200, and therefore a secondary searcher of 200 points can,

  serve all. intermediary researchers for the various sub-groups of 200 circuits. This arrangement may be suitable until such time as the traffic to one direction is so great that the number of lines for that direction approaches 200. So, up to that capacity per direction of departure, satisfaction can be given.



       D $ the same way as for fig. 1, direction A has been shown with two subgroups of lines, and direction B with only one group.

   However, a fact of the proposed circuits is that for the two sub-groups of lines only one group of intermediary researchers is required. This obviously achieves a considerable saving in the number of these intermediary researchers.

   Die the same way as explained for fig. 1, the DIJI direction marker switch to the selector circuit (that is, either the local selector junction circuit LL, or the trunk line of the incoming trunk line. <I> IT) </I> is set in motion, under the control of the recorder, not shown,

   to a position characterizing the group or sub-group of line & mandated. So, there is a determined position of this marker, for each of the two subgroups of direction A and another for the -direction <B> B </B>.



  The direction marker switch is connected to the intermediate seekers, in such a way that for the first mentioned positions it causes the search of the common group of intermediate seekers for direction A, -and for the third position it causes the search. of the group of intermediate researchers for the B.



  In the case of a call for direction A, one of the intermediate seekers for that direction takes the call and circuit 1 AF of the intermediate seeker now makes a test to see if the direction marker switch DI31 <I> a </I> been brought to the position corresponding to the 50-cycle lines or to the voice-frequency lines.

   Depending on the result of this test, the intermediate seeker circuit connects a test potential via the contact <I> DC, </I> either in the ares of: FAF researchers associated with the 50 cycle lines, or in the FAF arcs associated with the to lines. voice frequencies and a line in one of the two subgroups is then connected.



  It is assumed that a call has been directed to the subgroup of lines at. 50 cycles of direction A, at the time when no such line is available. A transfer relay in the starting circuit of this sub-group of researchers energizes, bringing on operation. a relay in the intermediate finder circuit, which relay switches the test potential of the lines to. 50 cycles to lines at, vocal frequencies. The relay in the intermediate seeker circuit is the one controlling the contact; D ('which serves both purposes.



  An alternating maneuver can take place in the same way as that applied in fig. 1, when a call has. take place to a line at, voice frequency in direction A, either directly or by transfer interconnection, and this when no such line is available. The operation does not differ from that described with reference to the, fig. 1.



       Multiple searches <I> of </I> researchers <i> i </I> tterrnedia <I> and </I> researchers <I> of </I> trunk lines It has been explained above that with the method shown in fig. 2, it is necessary that a call be. chosen by two successive researchers.

       In order to reduce the search time, an arrangement has been devised whereby while simultaneously with the research of the primary researchers (i.e. the intermediate researchers in Fig. 2), the secondary researchers here that is to say, the interurban line searchers of FIG. 2) are brought in .ii. re looking for the particular group of primary researchers in which the call takes place.



  This is done by connecting the primary researchers of a group of 200 lines consecutively in the arc of the secondary researchers and by providing a marker terminal vis-à-vis such a group of terminals in the arc. secondary researchers, when the direction marker switch MAI of the selector circuit has indicated a requested direction in application <iiit a test potential in the arc (intermediate researchers, for example IBF, it simultaneously causes the connection of a potential to.

   the marker terminal, vis-à-vis the corresponding group of terminals in the searchers of interurban BF lines of the requested direction, and the search of these searchers for this marked terminal. This potential is disconnected when an IBF intermediary researcher <I> a </I> found, the call. and, therefore, if a searcher for BF trunk lines has stopped at the marked terminal, he will become free at that time and may still participate ii. research for the particular intermediate researcher who chose the call.

   The number of terminals through which this seeker must search dear is therefore very low, since the maximum is equal to the number of intermediate searchers of the direction requested in the particular group of the two selector circuits.



  In the description of FIG. 2 we have established (read each group of the 200 selection circuits, local or arrival, has access to as many groups of intermediate researchers as there will be directions of departure. In addition, it has been shown that each group Intermediate seekers have access to two subgroups of trunk lines in the same direction, which can be individually selected by means of the direction marker switch DIIl associated with the selector circuit. It has been assumed that the two subgroups of lines were different kinds of lines with the same destination.

   It is, however, possible to employ exactly the same arrangement in the case where a group of intermediate searchers gives access to two groups of trunk searchers, each of them being associated with a different direction.

   This is only possible with two directorates which each have only one group of outgoing lines, which can be the case with end offices connected to tandem offices. It is therefore possible, with precisely the same circuits as those described, to give access to trunk seekers from two departure directions through a group of intermediate seekers, and to determine by means of the direction marker in the chosen circuit which direction must be chosen.

   It is however obvious that, in this case, the relay in the circuit of the intermediate researcher which serves to distinguish between a group of interurban line seekers and the other, can only function under the control of the marker of directions, and it is not controlled by a transfer relay in any starting circuit. For example, no interconnection is possible from one group of researchers to another.



  This arrangement, the aim of which is to reduce the number of intermediate searcher groups, also offers the advantage that the total number of intermediate searcher circuits is less, with one large group serving two directions than with two smaller groups. each serving a directorate, and this is due to the greater number of researchers available per group. As a result, the search time is reduced and a uniform type of circuits is provided to achieve various purposes.



       Step <I> two-digit switching </I> A central interurban office can be partially or fully equipped according to the fi-. 3 where two selections must be made to connect an outgoing interurban line with an incoming interurban line <I> IT, </I> or with a local trunk circuit LL. In this way,

   the number of directions that can be reached is theoretically increased to the square of the number of points available on the direction marker switch DIM.



  The first selection is received on the incoming trunk line circuit switch D1111 <I> IT </I> or the local junction circuit LL, and depending on the position occupied by this switch, a group of a certain number of groups of intermediate selector circuits IF1 or IF2 is connected.

    When such a circuit is connected, a feedback pulse is sent to the registrar circuit at the originating central office, causing the next selection to be sent which is now received on the direction marker switch DIM2 associated with the cir cuit intermediate selector. From this moment, the maneuver is identical to that described in connection with FIG. 1.



  The transfer facilities and alternate directions provided in the second stage are identical to those relating to. fig. 1.



   <I> Layout </I> allowing <I> the passage </I> of a <I> line without </I> selection <I> in tandem </I> <I> to </I> a <I> line with tandem selection </I> We now consider the possibility of having two subgroups of lines in one direction, only one of these being capable of making tandem selections at the far end. Such a case is represented by FIG. 8 ..

   The subgroup of so-called "non-tandem" NTL lines leaving the office <I> A, a </I> office B access only to local OLL connection circuits leading to local office dropouts.

   The other sub-group of so-called "tandem" interurban lines <I> TL </I> have access to office B, the outgoing interurban lines OL in addition to the local OLL connection circuits.



  In order to distinguish between the various directions to which a tandem trunk line has access when it arrives at office B, a selection can be made at the terminating end of such a line in B. However, this selection is not required. when a call is directed via a non-tandem NTL line to B since this line has access exclusively to local connections, so that in this case the recorder does not need to include means for making this selection.

   However, if a call directed to a non-tandem NTL trunk line is. transferred to a tandem trunk line <I> TL, </I> a selection is required in B to choose the local direction at the terminating end of this tandem line in B. The following arrangement satisfies this case: The local direction OLL is. always ac cessible from tandem interurban lines <I> TL </I> by sending a single additional pulse to the start pulse to the direction marker switch D1312 in B. In addition, the recorder is always set to send a digit "1" for local selection. .

   If a long distance line tan dem <I> TL was </I> chosen, either directly or by transfer from the NTL non-tandem group, the digit ,, 1 "causes the D131? Marker to be moved to the corresponding position towards the local direction. However, if the call uses a non-trunk line. tandem NTL, this line will be arranged so that it does not send a start pulse after being selected to office A, but sends the ordinary pulse back to the recorder indicating that the next digit is to be transmitted. The recorder, receiving this pulse back, transmits.

    the number "1" which is transmitted to :; the. NTL line to office B and acts there as a start pulse, i.e. it is not received on a direction marker switch, but serves to activate and block some relays which, from that moment, check that the call is maintained. <i> Control says </I> gaha The gain control operation will be explained with reference to figs. 4 to 7.



  For reasons not explained here, repeaters are automatically inserted into a connection at tan dems so that the total loss between the trunk line terminals of a connection is always approximately 9 decibels (db). In addition, the system adopted is such that if several are used in a connection, all of these repeaters except the last one are adjusted in order to cancel the loss in the finish line.

   while the last repeater in the connection is adjusted so that the total loss of the interurban connection between the terminals is cicada at 9 di). Or will see that in the latter case, the gain of the last repeater will be equal to the sum of the weakening of two sections of interurban line connected by this repeater minus 9 db.



       ITlilisar / ion of a single dream-ar snirarrt fig. -'f If a connection is made to, through two trunk lines from A to B and from <I> B </I> to C with a repeater <I> RF </I> connected to the junction point, the gain of it is brought to a value which is equal to. the sum of the attenuation of the two sections of interurban lines <I> a </I> and <i> b </I> minus 9 <B> dl). </B>



  The establishment of the gain according to the formula <I> a </I> - <I> b - </I> 9 is obtained by indicating the attenuation of the two line sections a and b as a code to the control equipment or control of the gain at the repeater which is associated with each repeater. The two values thus received are, by this control equipment, translated into the establishment of the desired gain.



   <I> Using two repeaters </I> next <I> the </I> fig. <i> 5 </I> When a trunk connection is established by means of three lines, two repeaters RP1 and RP2 are connected to interconnect trunk lines a and b and trunk lines b and c respectively.

    The repeater RP1 at office B, i.e. between lines a and b is adjusted for a gain corresponding to the attenuation of line a alone, while the repeater RP? at office C establishes a gain equal to the sum of the attenuation of lines b and c minus 9 db. We can see that the total gain introduced by the two repeaters is a -f- b 1- c - 9 db, or in other words, that the total loss is 9 db,

      as the difference between the total loss a -E- b -f- c and the total gain a -I- b -i- c - 9 db.



  The way in which the office repeater C is adjusted to the value b -f- c - 9, is the same as that explained in fig. 4, the way in which the repeater at the office <I> B </I> is adjusted to the value <I> a </I> is explained as follows: Assuming that the offices <I> A, B, C </I> of fig. 4 and 5 are identical, it should be observed that a similar selection is made from office A to reach office C through office B. However in one case the gain of repeater B is established according to the formula a -I - b - 9, and in the other case it is established according to the value a.

   This difference is characterized only by the fact that in the first case (fig. 4) the call terminates at office C while in the other case it is transmitted in tandem through. this office C.



  In order to indicate this difference to the equipment in office B, the recorder must bring the marker switch of the trunk line, arriving at office B, to one of the two positions which serve direction C. For the case shown fi.g. 4, the switch- Their marker at office B is brought to the. first of these positions.

   As a result, the circuit of the incoming trunk line <I> a </I> in <I> B </I> allows. the loss of the outgoing trunk line b to be reported to the monitoring equipment. of the gain of the repeater, so that. can establish itself, as explained above.



  In fig. 5, the marker switch associated with the incoming trunk line <I> a to B </I> is taken to its position corresponding to. the. direction C. Therefore the incoming circuit in B prevents the outgoing circuit B from signaling its loss to the gain control equipment at the repeater and instead sends an artificial code to the control equipment of gain.

   This code has a value of 9 @db. The repeater in B is therefore set to the gain which should occur if the start line b really has a loss of 9 db. The gain control equipment at the repeater always establishes the gain according to the formula <I> a </I> -f- b - 9, and like <i> b </I> has been artificially reported as 9 db, the .gain at which the repeater is set corresponds to the value a.



       Direction <I> alternate </I> next <I> the f </I> ig. <I> 6 and 7 </I> Fig. 6 shows a case similar to that shown in FIG. 5, i.e. a connection from office A to office D, but,

   with the call transmitted from B to C via another office E. It can therefore be seen that the transmission of the call is established differently to a tandem office which is not the last in the chain represented by the fi g. 5, that is, office B.



  By the fact that the call is made to a tandem beam which is not the last, the establishment of the gain at this tandem office can remain unchanged.



       Fig. 7 also represents a case similar to that shown in FIG. 5, but here the call is directed differently from the last tandem office according to FIG. 5, i.e. at office C, and instead of being connected to a terminus line, the repeater at C is now connected to a line which is transmitted in tandem through the neighboring office E. It follows that the gain of the repeater in C,

   which, following fig. 5 has been set in, concordance with formula b -f- c - 9, must be changed when the call is, directed through office E, so that its value becomes equal to the weakening of line d 'arrival b.



  It should therefore be observed that there is a certain difference in the operation for the alternating direction between figs. 6 and 7 opposite the establishment of the gain control at the office where the alternating direction circuit is carried out. In the case <B>, </B> of fig. 6, the establishment of the -gain at the C-repeater remains unchanged, st in the case of fig. 7, the gain setting at the repeater at office C is changed <I> -de b </I> -I- c - 9 in b.



  Another -difference can be noted with regard to the adjustment of the repeater at the E office, that is- <i say the office through which the call is alternately directed.



  In the case of <U> fi-. </U> 6, office E is not the last tandem office in the, con nexion and. therefore the gain of this repeater must be set to match the weakening of the finish line d. In the case of fig. ï, office E is the last tandem office, and therefore its gain must be established in accordance with the rule applied for the last tandem office in one or the other connection, that is to say following the general formula a -f- <I> b - </I> 11.



  As the establishment of gain at office L 'depends on the position of the direction marker switch associated with the terminating trunk line at office I', as it has. been explained in connection with the fi-. 5, and more to. Because the marker switch at E is actuated under the control of an artificial selection sent by the alternate direction circuit to the previous office, it follows that the alternate direction circuit must make a distinction with regard to the number of pulses to be sent for this artificial selection in order to indicate whether office E is the last tandem office in the. connection or not.

    



  It should also be noted that the. question of whether office E will be. the last tandem office in the. connection or not depends on the condition of the tandem desk to which the circuit baked to, alternate direction is placed since the desk E simply takes. the place of this office. In the case of the fi-. 6, office E is not the last tandem office, while in fi-. 7, it becomes the last of the connection, because otherwise desktop C would have been the last tandem point.



  As it already has <B>, </B> been explained in Con nexion with the fi. 5, the indication whether or not it connects the last tandem point in the connection is given to. the automatic equipping of any tandem office by giving the direction marker switch an appropriate movement under the control of the recorder. So in the case of fi-- fi, the marker switch to.

    the terminating end of trunk line a at office B has been brought to a position which indicates (read office B is not the last tandem point, while in fig 7 the marker switch to. the end of trunk line b at office C has been moved to a position which indicates that office C will normally be the last tandem point of the connection.



  The circuit for alternating directions is arranged so that it can check this difference in the operation of the direction marker switch in the arrival circuit of the trunk line immediately preceding it, and it will change the artificial selection sent to the circuit. office E in accordance with the result of this verification.

   In the case of fig. 6. the ARF alternate direction circuit has found that the direction marker stops in a position indicating that it is not the last tandem office,

   and therefore the alternating dirCtiorm circuit sends an artificial selection to office E to place the direction marker associated with the incoming trunk line d at the office in the desired position to indicate that E is not the last point tandem.



  In the case of FIG. 7, the alternating directions circuit has office C found by checking the position of the direction marker associated with the. incoming trunk line b that This indicates that E must be the last tandem point in the connection, and therefore this circuit flies towards office E an artificial selection, placing the direction marker associated with the line interurban d has office E in the desired position to indicate that this office E is now holding the last tandem office.

   At the same time the circuit of alternating directions takes care that instead of the loss @of the starting interurban line d, the artificial loss of db is signaled. ii the gain control equipment at the office C repeater, so that in this way this gain control equipment is artificially set. the value of the arrival line, as has been explained previously.



       Sinople <I> step of </I> Switching A detailed description of the circuits is now given of a single-selection switching step with reference to fi-. 9 to 12.



  The arrival circuit of the interurban line <I> IT, </I> fig. 9, is chosen by a d.e, start pulse which -is received by the receiver assembly and which prepares the IRU circuit for the .reception. Of a digit.

   This number is sent by an auxiliary recorder attached to the remote starting end of the connection, and the number of pulses is determined by the translator switch forming part of this auxiliary recorder. These. pulses in a manner not shown place the DEVI direction marker at the desired position.



  Following this marker position, a test potential is brought over the searcher arcs of the outgoing trunk lines in the desired direction which is assumed to be the group of 50 cycle lines in direction A (Fig. 1).

   This test potential is given via <I> collar, </I> rc2, dima broom, <I> of 1, </I> and contacts in the brush banks <I> f a f 5 </I> FAF correspondent researchers. At the same time, the circuit for starting FAF researchers is completed:

      Earth, <I> collar, </I> dimb, of3, Fsl. The FSL and Fcl relays get excited and all the FAF free searchers are looking for this in terurban arrival line. <I> IT. </I> When the test potential is reached by a researcher, his release <i> Tt </I> gets excited through the faf5 brush, which stops the seeker and energizes the relay <I> Th. </I> The last relay introduces the low resistance left winding of the test relay <i> Tt </I> in order to perform the double test,

      and at the same time it shunts Fs via inca and Re2, so that all remaining seekers stop.



  More. -of the direction, the position -of the marker also determines whether it is necessary to use a circuit connector repeater (fig. 10). Finally, the position of the marker indicates whether this tandem office is the last or not in the automatic long distance connection.

   When the marker is brought to the required terminal, battery current is supplied to the meal contact <I> of </I> Rc broom c. Terminals <I> A, B and </I> C, are connected to the -various terminals of the arc c.

   Terminal A is connected to all terminals reached in response to the numbers indicating the last points tanë @ ms in your autcmatic trunk connections. To terminal I3 are connected those .of the arc terminals which correspond to the tandem connections.

   which are not the last ones. Connections which do not require a repeater are connected to terminal C.



       When terminal A is connected, relay 19g alone operates, while if B is connected, both relays. 1c and <I> Ag </I> operate.

   So the re lais <I> Ag </I> works in both cases and places the @ d'cs.sai potential on the arcs - of the repeater connectors searchers earth, trl, ag2, and towards the corresponding contacts in the rf terminals <I> k. In </I> at the same time, the starting relays Fs. And <i> St </I>. Are excited and the researchers.

   RF of all free repeater connector circuits search for incoming trunk line <I> IT: </I> RFM, stl, <I> d6, </I> t1. When the test potential is reached by the rf brush <I> k, </I> the relay <I> T </I> gets excited and stops the researcher <I> RF. </I> The relay <I> T </I> is blocked through its low resistance winding in series with,

  S which operates and the common starting circuit is neutralized. The blocking circuit is closed via the working contact s1 of the relay, S which protects against the double test, the relay D of the repeater connector circuit and the relay Tr. In the incoming inter-urban line operating in series:

   battery, upper winding -of Tr (fig. 9), broom rfi, s1, <I> D </I> and earth. The Tr relay breaks the conversation conductors and removes the test potential * from the rfk terminal. The relays <I> T </I> and .S neutralize each other, but the relay <I> D </I> stays excited through own d5 working contact.



  After the repeater connector circuit - and the outgoing trunk line have been connected to the incoming trunk line <I> IT, </I> the blocking circuit enters. the two circuits of interurban lines is closed: the. drums., Co, tr6, faf3, <I> 11o, </I> flil, and. Earth.

    In this circuit, the Co and Ilo relays operate. The Co relay removes the arc test potential from the outgoing trunk line. while Tf and <I> Th, </I> neutralize each other.

   Relay <i> Ho </I> remains excited through her. own blocking earth in hol. 3u working contact lool. the relays Clh., Bg <I> and </I> <3o get excited. Relay <I> Ch. </I> connects to. through the br ', ines of the c.li:

  FAF connector plug. A start pulse at. alternating current is now sent to the. trunk line from d @ - part, to the far end by Fi dut excited via:

   <I> beats, </I> lto3, bg5. The Ao relays and <i> Ba </I> which are excited are slow to- op (-rer and the signal persists until <B> this </B> that <i> Ba </I> gets excited and opens his contacts ba? to release Ft.



  Simultaneously, with this start-up impulse sent forward, a. AC pulse is sent back through the incoming trunk line to the recorder at the end <the origin which at.

   present proceeds to send other
EMI0012.0051
  
     <I> Terminals </I> <SEP> uses <SEP> to <SEP> <I> the <SEP> land <SEP> and <SEP> relcais <SEP> actio ief # s </I>
 <tb> Line <SEP> long distance <SEP> of arrival <SEP> Line <SEP> long distance <SEP> of <SEP> departure
 <tb> Losses
 <tb> in <SEP> db <SEP> <U> 1 </U> <SEP> <B> 1 </B> <SEP> <U> 2 <SEP> 3 </U> <SEP> 1 <SEP> <U> 4 <SEP> 1 </U> <SEP> 2 <SEP> 3 <SEP> 4
 <tb> G1 <SEP> G2 <SEP> I <SEP> G3 <SEP> G4 <SEP> H1 <SEP> H2 <SEP> I <SEP> H3 <SEP> H4
 <tb> 1 <SEP> +.

    <SEP> @ <SEP> l <SEP> I <SEP> I <SEP> +
 <tb> 2 <SEP> + <SEP> +
 <tb> +
 <tb> 4 <SEP> + <SEP> + <SEP> + <SEP> +
 <tb> + <SEP> + <SEP> + <SEP> +
 <tb> 7 <SEP> + <SEP> + <SEP> - + f-- <SEP> 4 <SEP> -i + <SEP> + <SEP> + <SEP> + <SEP> +
 <tb> 10 <SEP> I <SEP> + <SEP> + <SEP> + <SEP> i
 <tb> 11 <SEP> + <SEP> \ <SEP> + <SEP> +
 <tb> 12 <SEP> + <SEP> + <SEP> + <SEP> +
 <tb> 13 <SEP> + <SEP> - @ <SEP> - (- <SEP> i
 <tb> 14 <SEP> + <SEP> + <SEP> + <SEP> + <SEP> # <SEP> -E 1 @ <SEP> + <SEP> + <SEP> I <SEP> + <SEP> + <SEP> + <SEP> + digits.

   This return pulse is supplied by relay 13s which is energized via: I3d, faf4, <I> ch 3, </I> bg5 until <I> that </I> Bg be released by Ba. Lrdication <I> losses </I> The repeater bath will be adjusted in accordance with the interurban line losses and the type of m1 tandem connection.

   If this tandem point is not the last, only the losses of the terminating trunk line must be compensated by the repeat. If this is the last tandem point in the automatic trunk connection, the gates of the incoming and outgoing trunk lines should be considered and the gain should be adjusted to the value a + b - 9 where it is. loss in the finish line and b loss in the start line.



  The loss in the incoming trunk line (1 # e is indicated at the mo '# en of the _dg relay which operates in both cases.

   Terminals 1 to: 4 connected to relay contacts _4g have been earthed in accordance with the weakening of the incoming trunk line <I> IT, </I> as shown in the following table: As soon as the relay D has operated in the circuit connecting the repeaters, these four terminals are connected to the relay Gl-G4, and as soon as there is a combination of these four relay corresponding to the code shown.



  The loss of the outgoing trunk line is indicated in a similar manner. The relay Bg in this circuit energizes during the start pulse and connects terminals 1 to 4 to the conversation and network conductors leading to the circuit connecting the repeaters. These four terminals are connected to earth according to the weakening of the outgoing line, as shown in the table above. The conversion and network conductors pass through the contacts of relay Ic and consequently the indication received by the circuit connecting the repeaters will depend on the position of this relay.



  It is assumed that this tandem office is the last in the connection, and that consequently the relay Ic is not actuated. The code given by the relay Bg of the outgoing trunk line passes through the rest contacts of Ic, the rest contact of C and the open contact of E, which was actuated by D to the relays Hl-H4 in the connecting circuit. repeaters.

   A combination of these relays is established according to the code received, when the starting impulse is sent and the relay Bg is neutralized, moving the earth away from the conversation and network conductors, each of the relays H1-H3, if they are excited, block in series with K at the work contact e2 of relay E. The relay H4, if it is energized, block in series with J also through the make contact of E.

   If the loss in the outgoing trunk line is less than 9 db, the relays <i> J </I> and K get excited, while if this loss exceeds 9 db, relay K alone gets energized and, finally, if the loss is exactly 9 db, relay J alone is energized.



  If the tandem office is not the last on the trunk connection, only the losses of the terminating trunk line need to be offset by the repeater. This case can be considered as being identical to that described in the previous paragraph for which the loss of the outgoing trunk line is exactly 9 db, because then the gain will be equal:

  at a if b, the loss of the outgoing trunk line, is equal to 9 db. It follows that the code sent by the originating circuit of the trunk line must be canceled and replaced by an artificial code of 9 db, as shown in the previous table, for a loss of 9 db, only the relay H4 is energized. This is achieved by the operation of Ic in the incoming trunk line circuit which concentrates all talk and network conductors on relay H4.

   So whatever the loss of the outgoing trunk line, the relays <I> H4 </I> and <i> J </I> will only be excited as required.



  When either or both of the J and K relays energize, they actuate relays B and C which connect the talk and network conductors to both East and West sides, indicator relays for gain at terminals 1 ... 4, 5 ... 8, which are connected to the -line and -of the artificial line terminals of the mixed West and East terminals of the repeater.

   At the same time, a circuit is closed for the relay M to the repeater circuit fig. 10 and for BC in the trunk line circuit fig. 9: <I> H, </I> 12, j3, or <I> k2, </I> rf <I> j, </I> rdl, Rc. The rcl contacts move the battery away from the dimc brush, causing the relays to be reset <I> Ag </I> and Ic. Via the rest contacts of these relays, normal con versation conditions are re-established to the repeater.

    



  The relays L, in the circuit connecting the repeater, energize via ml and block itself towards the control circuit of M which is released. Relay L moves the shunt away from the midpoint of the mixed coil. This shunt is necessary during the periods of sending of the pulses to prevent the initiation of hissing.

   For this purpose, the blocking circuit of L is controlled through the rest contact rd1 of the relay Bd which is inserted in the impulse conductor between the receiving units IRÜ, ORÜ of the incoming and outgoing trunk lines. So every time a pulse goes in either direction the Bd relay energizes and releases L which reconnects the above mentioned shunts. Relay 12d can follow the impulses of the disc,

   but the relay 41 operates slowly and does not energize during the opening periods of the transmitted pulses. The relay Bc, which operated in series with 31, is blocked independently with its second in rolling through contacts not shown. Determination <I> from </I> level of, gataa The gain of the repeater is regulated by the insertion of paths which are introduced between the mixed coil and the potentiometer on both the East and West sides.

   These paths, representing a total loss of 15 db, are normally inserted and compensate for the gain of the repeater which is brought by means of the potentiometer to a value of 15 db. The paths are controlled by relays P1 - P4, and by making a combination of these relays, the paths can be bypassed or, in other words, a corresponding bath can be introduced. The values of the paths are 1,?, 4 and 8 decibels, and therefore any combination ranging from 1 to. 15 db can be "obtained.

    The fourth. relays P1 to, P4 are operated under the control of relays H1 to, H-1 and Gl to, G4 which have received the codes indicating the losses of the trunk lines.



  The control circuits of the Pl to P4 relays are controlled as follows: <I> Case where, the loss in the </I> line itaterttrbaine <I> starting </I> n .'- infl-aterace <I> pus </I> the establishment, <I> from </I> gaina In the event that the loss of the incoming inter-urban line must be considered alone, the relays <I> H4 </I> and <i> J </I> and a combination of relays G1-4, are excited. The relay Ii remains at rest.

   The operation of Gl for example, which indicates a loss of 1 db, causes the operation of Pl which, by short-circuiting the path of 1 db, introduces a corresponding bath of 1 db, or G3, representing a loss of 4 db causes the excitation of P3 and the corresponding gain of 4 db is obtained, and so on.

   In addition, if G1 and G3 are both added, P1 and P3 energize, and the gain is set -i 5 db. In this way, the loss of the terminating trunk line will be exactly balanced by the operation of the corresponding relays P1-4 for any value between 1, to. 15 db, each varying by 1 db.



       Example 1: The swim should equal the loss in the finish line, which is i db.



  a) In the incoming trunk line, terminals 1.2 and 3 are earthed so that the relays Gl, G2, G3 are energized.



  b). Following the operation <I> of </I> Ic <I> to </I> the incoming trunk line (terminal B being connected directly to the arc contact of DIII on which it stops), 1a or the grounds of the outgoing trunk line circuit cause HI to operate only one that hangs in series with J.



  e) Control relays <I> P1, </I> P-2, P3 are excited as follows: P.l via the rest contact 1a14 and the working contact gll to earth via F; P2 via the normally closed contact 1a21, and the normally closed contact g21 to earth via <I> F; </I> P3 via break contact h31 and work contacts 934, g24, to earth via F.



  Note: P4 is not energized since its operating circuits are open to the make contacts -de i, 4 and g45.



  d) The inserted gain corresponds to 1 -f- 2 -I- 1 dl) = î db.



       Case oai <I> the loss in the </I> interurban line <I> starting </I> influence <I> setting the </I> gain If the loss of the outgoing trunk line is less than 9 db, terminals 1 to 1 connected to the working contact of Bg are set to. the.

       earth in such a way that the codes <I> 1I1 ... 113 </I> indicate less loss of 1 db Ù, the actual loss compared to terminating trunk line codes. This loss recorded by the relays Hl to <B> 113 </B> will be added to the loss of the arrival interurban line recorded by the Gl-GI relays of 1a. way <RTI

   ID = "0014.0106"> next: When relay G1. or <B> 111 </B> is the only one excited, the corresponding relay Pl operates and introduces a 1 db bath. If both relays are energized simultaneously, P2 representing a gain of 2 db is energized via. 1z21, g22, 1a14, g11, via relay F.

   If with Gl and Hl, one of the relays G2 or 112 is actuated, P3 is energized instead of P2 in order to provide a gain of 4 db: P3, 1a31, g32, make contact of h.21 or break contact h22, make or break contact g22, h14, g11, via.

   F. In the event that all four relays Gl, Hl, <I> G2, 1I2, </I> are excited, indicating a total loss - of 6 db, then P2 (via h, 212, g2-2, h14, gll) and P3 (via h31, g3 @ 2 @, h2l, g21, g24, h25 and F) are excited to provide a total gain of 6 db, and so on.

       When the total loss indicated by relays Gl-G3 and Hl-H3 reaches 8 db, transfer relay 1 energizes. The operation of this relay 1 in this case has no effect, because both relays J and K are actuated. as explained above.

         The gain of the receiver will depend on the G1-G3 and H1-H3 relays which can be activated in excess of I. This gain is therefore 1 -I- 8 = 9i, db. less than the total loss of the two lines (1 4b dîi at the artificial indication of the outgoing trunk line, and 8 db -dict at the simultaneous operation of J and K which prevent K from being influenced).

    



       Exeïrapde <i> 2: </I> The gain must be equal to the sum of the losses of the incoming trunk line (7 db) and the outgoing trunk line (8 db) minus 9 db.



  a) In the incoming trunk line, terminals 1, 2, 3 are set to. Earth. The relays Gl, G2, G3 are energized.



   <i> b) </I> The terminal <I> A </I>. Of the incoming trunk line -is connected directly to the terminals. : arc <I> c -de </I> DIM on which it remains, .so that the is not excited.



  c) In the outgoing interurban line, terminals 1, 2., .3. and 4 are connected to. Earth. The relays <i> Hl, </I> I12 ,, <I> 113, H4 </I> are excited. Relay H4 is blocked in series with J.



   <I> d) </I> The emergency relay <i> I </I> get excited via h31, g31-, g31, h.35 to the, earth via F.



  e) P2 and P3 relays are actuated as follows: P2 via h22, g22, h1.4, g11, to earth via F; P3 via h3,2, g32, h21, g24, Ib25, to earth via F.



       Note: Pl does not work since the operating circuits are open in g11, h14 and g43. Relay P4 does not work since its circuits: are opened by the simultaneous operation of Jet K.



  f) The inserted gain corresponds to 2 + 4 = 6db. If the loss of the outgoing trunk line is precisely 9 db, relay J operates but not K. No relay <I> Hl to. H'3 </I> does not operate, and the -gain is therefore adjusted to the loss of the. incoming trunk line recorded by the operation of relays Gl to. G4.

   If G4 is actuated, the relay. corresponding P4 is also, its circuit being closed via g45, j5, 1c1, 14. The total. gain of the repeater. in this case will correspond to the formula a + b - 9 since the loss, of the line outgoing interurban b = 9.



       Example <i> 3: </I> The gain must be equal to the sum of the losses of the incoming trunk line 7 @db and the trunk line, outgoing 9 db minus .9 db.



  a) As for the case of example 2. b) As for the case of example 2. c) In the outgoing interurban line circuit, terminal 4 alone is earthed. Relay H4 is energized and blocked in series with J.



  d) Relay 1 does not work, its circuit being open to make contact h14. The conditions for the repeater gain control circuit are identical to that of example 1 and therefore a gain of 7 db is provided.



  If the loss at the originating trunk line is greater than 9 db, then the code sent from that line indicates a loss that is -9 db less than. the actual loss of the outgoing trunk line circuit.

    Relay J does not operate in this case and therefore if relay 1 operates, indicating a total loss of 8.4b, relay P4 energizes and introduces a gain of 8 4b. The total gain cor- r.,. Spon.d will therefore correspond to the formula a -i- b - 9 because the outgoing trunk line directly indicates the value b - 9.



       Exew.ple É: The gain must be equal to. the sum of the losses of the incoming trunk line (î db) and the outgoing trunk line (14 db) minus 9 db.



       R) As for example 2. b) As for example ?.



  c) In the outgoing interurban line, terminals 1 to. 3 are set to. Earth. Relays 111 and: 113 are energized and blocked in series with K.



  d) Relay 1 is energized via 31, g3,1, g: 31, 1% 35 and la. land via. F.



  e) Relays P3 and P4 are activated (@s as follows: P3 via, hic. <I> g3 ?, </I> h-22, g2-, 1a14, gll and earth via F; P4 via il, j4, k1 and earth.



  Note: The relay Pl is not energized then its circuit. order is opened in 1a14. Relay P 2 is not energized since its control circuit -is open in h22, 1z24, 1a245, <I> g13 and </I> 1z11.



  f) The inserted bath corresponds to 4 -f- 8 = 12 db.



  If the loss of the incoming trunk line is at least 8 db, G4 is energized and if simultaneously I acts (this relay has all the losses recorded by relays G1-13 and 1111-3). So, through the serial contacts of G4 and <I> I, </I> all relays <I> P </I> are excited, and the entire repeater gain is. introduced.



       Logout <I> repeaters </I> When, in the case of the last tandem point in the connection, the sum of the losses of the two lines is equal to or less than. 9 db, the repeater disconnects. This, of course, can be: only the case when the. loss in the originating trunk line is less than 9 .db, and then 7 is. actuated as can be seen on the table.

   If, under these conditions, neither G4 nor 1 are energized, the repeater is released by short-circuiting relay D via. i5, g-16, j.1, k1 .. In addition, the repeater is also released when one of the relays G4 or I is energized, while the relay F remains neutral, because <I> D </I> is bypassed via <B> <I> f l, </I> </B> i 5 activated, g46 at rest (or directly via g46 at work),, j4,

          hkl. 1st relay G.1 or I indicates, as we know, a loss of 8 db. If however. if no other loss is shown at the same time, the 8 db represents the total loss. This is the case when F, connected in the control circuit, the relay Pl-3, is not energized.

         In any case, the earth, which bypasses D in order to free the repeater, is controlled through the make contact k1. This is because K is only excited when this tandem office is the last in the connection.

   while if only the loss of the terminating trunk line is to be balanced by the repeater, K is not energized and the repeater remains attached in any case. Relay K is also not energized if the loss in the outgoing trunk line is exactly 9 <B> dl), </B> because in this case the repeater will remain connected since the incoming trunk line will also have a loss.

     <I> Appeal case in, excess </I> So. as explained above, interurban lines are divided, in certain directions, into two groups with respect to the different characteristics of the lines. For example, a group may have united signaling equipment to. 50 cycles and the other group is signaling equipment <B> he </B> phonic frequencies.

   Fig. 11 shows the circuit arrangement, whereby calls directed to the first group of trunk FAL lines in direction a can be transferred to the second group of trunk lines <I> VAL </I> with sound frequency signaling equipment. These two groups of circuits are characterized by two different positions on the marker switchDlal. Either of these groups can be called up directly by bringing the marker <RTI

   ID = "0016.0114"> respectively on its third or fifth terminal, as shown in the drawing.



       Suppose the marker is brought to its third terminal, which assumes that a trunk line with 50 cycle equipment is required, and that at this time all such lines are busy. Relays Fsl and Fcl of the corresponding starting circuit are energized, but no researcher is available and relay Nf 1, which is in multiple series with the electromagnets of the researchers of the group,

   cannot work. Consequently, an earth -is connected from f c121 via nf 11, contact 3 and brush dimd, coi, relay <I> Of </I> and battery.

   Relay <I> Of </I> is quoted and in: ofl switches the test potential, from the arcs of the first key group FAF outgoing trunk searchers to those of the second VAF group provided with phonic frequency signaling equipment .



  The contact of3 changes the corresponding starting conductor and the circuit of the second group of VAF trunk seekers is energized. One of them chooses and then connects the incoming trunk line.

   Relay <I> Of </I> is provided with a hold relay if necessary to provide the number of starting .directions having, subgroups with ease of transfer. <I> Directions </I> Alternate If the excess call could not be transferred due to @de, the occupation of outgoing interurban lines in the second group, the call will be directed through another direction to. the requested office.

   When the circuit, start-up of the second group of trunk lines is excited, and no searcher is available, the relay. Nf2 does not work, and thus the starting circuit of the alternate direction seekers (fi-, <I> 12.) </I> Fe3 and Nf <I> 3, </I> will operate.

   Through the contact @ work key of Fc3, all the free ARF researchers are set in motion, and one. @two connects the terminating trunk line. Relay <i> At </I> gets excited, stops the researcher and activates the relay <i> Ah </I> which introduces the winding at low resistance of <I> At. </I> By this means the starting circuit is neutralized in the well-known way,

   and the drunkenness stop. Through ahl and ga4, the test potential is connected to the arcs of. Outbound trunk lines in direction B through which an attempt must be made to complete the call, and the Fsb relay is energized to turn on the BF seekers. Relay <i> Ah </I> excites Mbl:

      earth, ah, 3, ia4, Mb, and battery. A check is made by the relay Oc via ial, inbl, towards the broom arfd, to determine whether the position of the marker in the trunk line, of iodic arrival at a last tandem point or not.

   In the first case, relay Ic. In the incoming trunk line is not actuated and no earth is connected via iel (fié. 9) col, to arfd, <i> d </I> so that the Oc relay cannot operate. So the connection, from terminal A to are b of switch A <B> S </B> (fie. 12) will be effective.

   However, if the number received by the incoming trunk line <I> IT </I> indicates an intermediate tandem point, relay Ic - is energized and actuates relay Oc which changes the connection of the terminal <I> A </I> at the terminal <I> B </I> .in the .circuit of alternating direction.

   When the trunk line from, d @ leaves, which is similar to fié. 11, is connected, the blocking circuit is connected, and when the circuit connecting the repeater is also attached to the incoming trunk line, the Cwv relay (fie. 12) is energized via arf <I> e, </I> tr6 (fié. 9), Co and drums.

   Relay <i> Ga </I> is quoted in turn. Relay <i> Ga </I> disconnects the test potential of arcs from searchers of trunk lines. starting., and at the same time disconnecting the test. <i> At </I> which frees and brings about the recovery of <i> Ah. </I>



  The interurban line which @ chose this circuit cooked at. alternate direction, sends the start pulse to the far end to cause a call.

   At the same time it transmits in the manner already described above a pulse back through the pulse conductor. This feedback pulse energizes the relay. <I> Br -à </I> in turn energizes the slow recovery relay <I> Bd. </I> When the impulse is transmitted,

      relay Bs is energized via bd2, brl, and blocked via rs3, ia4, gal, while <i> As </I> get excited via rs4, gal, and crash via as3. The conversation and network conductors are connected through the working contacts of. <i> As </I> which operates when the feedback received from the outgoing interurban line is terminated.

   Thus the code for the loss of the outgoing trunk line, which is:. Given simultaneously with the return pulse. does not reach the circuit connecting the repeater, of. so that said repeater is not connected.



  When the relay <I> Bd </I> is neutralized, the IS switch is connected through <B> <I> bd], </I> </B> rsI and the asa broom. The first closing, which can be partial, brings the switch <B> <I> AS </I> </B> out of its normal position.

   The next closing closes a circuit via bdl, rsl., Asa, @ s2, ia3, to energize relay 1r which sends the pulses to. direct current in one direction to the outgoing trunk line via ipl, as6, and at the same time activates the switch <B> AS </B> via. ip2. The number of pulses sent in this way is determined by the.

   way in which terminals _l and B are connected to arc b of t1SDl. When the terminal which is connected is reached by the asb brush, the relay <I> the </I> operates via Oc2: and cuts the switch circuit at ia3.



  When the relay <I> the </I> operates, it opens the circuit of 11b1 which recovers slowly, and during this restoration a land is connected via ial, nabl, arfd, ro? (fig. <I> 9), </I> reflected. (fi-. 10), c-1, e6,, <B> he, </B> to 111 in the repeater connector circuit.

   This is the equivalent of a loss indication of 9 db. Relay <I> 114 </I> excites <I> J. </I> Therefore, the repeater gain is adjusted to only balance the loss of the. terminating trunk line, which is correct since this tandem point can no longer be the last in the. automatic long distance connection.



  The operation of Ia also causes the reestablishment of Rs in ia.-1 with, as a result that the marker AS returns to its normal position: AS'JI, switch, rsl, asa, rs2 and earth. The resistance in series with the CTT'c relay in the blocking circuit a.

    the following purpose: When a connectian is released, a recovery pulse language is produced by means of slow relays placed at the originating trunk line in the originating trunk office. This reinstatement impulse is relayed through all the tandem offices engaged in the connection to the terminus interurban offices, and it prepares for the reestablishment. from all circuits to all these offices simultaneously.



  The equipment of a tandem office relays this impulse and is maintained in the condition in which this relaying can be carried out until the end of the impulse. For this reason, it is unnecessary for the outgoing interstate lines engaged at a tandem office to create a recovery momentum at the time of recovery.

   The indication to the outgoing trunk line to suppress the restoration pulse is the increase in current in the holding circuit which causes the operation called marginal relay Fa connected in parallel with the relay <i> Ho. </I> The relay <I> Co </I> from. the incoming interurban line has a low resistance, while the corresponding relay in the local selector circuit has a higher resistance.

   Relay <i> Fa </I> therefore operates only for tandem connections and prevents the relay from activating the slow recovery pulses.



  In the case of alternating direction connections, the recovery pulse. cannot be transmitted in the event of a premature recovery, until the artificial digit is sent by the alternate direction circuit (the. because this circuit cannot transmit a pulse from the incoming line until after, artificial selection.

   Therefore the resistance of the blocking circuit is increased by the insertion of the mentioned resistor, in order to delay the suppression of the restoration pulse in the outgoing interur line BL (fig. 12) until the selection artificial is completed.

   When this happens,: lb is neutralized and by short- circuiting the resistor, the marginal relay <i> Fa </I> in the outgoing trunk line BL gets excited and prepares for the removal of the recovery pulse. The way in which the recovery pulse itself is sent, and how it is suppressed by <i> Fa, </I> is not shown in the drawing as it is well known.



       The circuits of! alternating directions can easily be changed to suit the following network arrangement: Assume four central offices A, B, C and D (fig. 15) placed geographically so that <I> A </I> and <I> D </I> be the offices furthest from each other, while <I> that B </I> and C are located somewhere between these.



  It is conceivable that there are direct lines between offices B and C and between offices <I> A and D. </I> Calls from <I> A </I> to <I> D </I> can therefore be sent in tandem through to B or C. The following variation of the alternating direction method described above is applicable in this case.



  If no direct line: from <I> A </I> to <I> B </I> is found, an alternate -direction circuit is established at A and chooses a line going to C. This circuit then sends to the recorder at A an indication to make the new selection. This is received at the alternate directing circuit, but is not. sent to C. It is only used to indicate to the circuit the destination of the call.

   The number received in this way indicates that the next selection must direct the call to office D and this call ends. With this information, the alternate-direction circuit can now send an artificial number to office C, so that a selection takes place at C to choose a direct line from C to D. Next.

    when this has occurred, the feedback from the C-equipment passes through the alternate direction circuit to the recorder, signaling this fact to make the selection. The value of the artificial digit received indicates that the gain of the C-repeater should be controlled in accordance with the attenuation of both incoming and outgoing trunk lines.



  It can be seen that arrangements can be made for calls to be transmitted in transit through, office D, and in this case the selection is different in order to adjust the gain of the repeater at C in accordance with the. weakening of the interurban line from A to C only.

   Suppose for example that for a call ending in <I> D </I> and transmitted regularly <I> via B, </I> a digit comprising four pulses is sent to the selector circuit of B, while for a call transmitted in tandem through D the digit sent consists of five pulses. The alternating direction circuit at A can then be arranged for an artificial digit different from the digit transmitted in the case of a connection terminating at D.

   For example, seven and eight pulses respectively are required. in C for a call ending in D and for a call transmitted in tandem through <B> <I> D </I> </B>.



  The alternate direction circuit at A is arranged to send back to the recorder the signal for the next digit which will be received on a recorder in said circuit. A sender controller switch then operates, in accordance with the movement of the recorder, to control the transmission through the alternate steering circuit of one of:

  es, two possible digits, of direction towards the office C in order to control the selection there. The alternate direction circuit connects through the conductors. to allow the signal back to the recorder to be sent from the C.

   This modification includes simple recording and transmission arrangements well known in telephony, and it is therefore not necessary to describe the circuit in detail here.

           Circuit <I> to </I> calls <I> delayed </I> When all trunk lines in the requested direction are busy, and no alternate direction circuits are available, the call is directed to a delayed call circuit shown in fig. 12.

         The start circuit for researchers of delayed call circuits is energized via the working contact FcM and the rest contact N3,1. First the time switch TS is actuated and gives a certain delay before St is excited to set the seekers in motion, and this in order to give time for the call to be chosen by a circuit. working,

  just released <i. this moment.



  * When the switch to. TS time closes the contact, the ST relay energizes and all delayed call seekers that are. free, now start to search for the incoming trunk line. and one of them ends up connecting it.

   The Dt relay energizes: and stops the searcher. do: by energizing relay D1, which introduces the â winding. low resistance of the test relay, and at the same time the blocking circuit is closed. The De relay energizes in this blocking circuit and a check is made by <i> Di </I> to see if the DLF researcher dllfe arc terminal is grounded or not.

       the limits of this arc. dlfe are connected; l earth for finder positions corresponding to incoming trunk lines <I> IT </I> and are not updated. the. earth for local selector junction circuits.

   Due to this fact, the relay Di energizes on tandem connections and sends a busy signal to subscribers calling BTC, dcl, dr2, dlfa, dlf <I> b, </I> ic ?, ic3 (fi-. <i> 9) </I> rfe, rf <I> f (fi-. </I> 10), e1, e \ 3. <I> e3. </I> e-1, capacitors, <I> d3. </I> d-1, <I> b3. </I> <B> b l, </B> rf <I> b, </I> rf <I> a,

   </I> (fig. <B> <i> 10) </I> </B> ayd, <I> aga, </I> (fi ,. <I> 9). HE. </I> For (locally produced connections, relay Di. is not energized, and the call is directed to an attendant, the lamp <I> CL </I> being on.



  It should be observed that if the tan dem connection ends in the delayed call circuit, the repeater will not be switched and no loss indication is sent to the circuit connecting the repeaters. t11t @@ rna._ tively. the call can be held until. what a junction line in the. direction requested. becomes free.

   It will be understood that a simple group of jone.tiou line without alternating directions can be provided in certain offices, and. that, also in this case, if all the trunk lines of the group are busy, the call can be maintained, until * < < <B> this </B> that a trunk line becomes free or transferred directly to a circuit; to. i i.13_ 1c 1s delayed.



       If @ iialisatioii <I> to </I> travers nie bureau taiideiu If both receiving units, or either of these units, are of the 50 cycle type, the selection and signal pulses must be transmitted at.

       these tandem points. Pets forward pulses are received by the IRU receiving unit from the incoming trunk line <I> IT </I> and are repeated by the Ft relay in the FAL starting interurban line. Of the. Likewise, the unit reeptrim ORL% of the.

   starting line iii FAL responds to the return pulses, which are reproduced by relay Bs in the arrival line <I> IT. </I>



  If both trunk lines have equipment. signaling signal, impulses in both directions pass through the repeater and are not repeated by relays.



  Irish <I> Id, </I> shown in dotted lines in the incoming trunk line fg. 9), has been foreseen only if the receiving unit of the same circuit is voice frequency tS-pe.

   The same remark applies to the. resistance R, shown in the outgoing trunk line and connected to. battery. when this has a vocal frequency receiver unit. This resistance, if expected, is. immediately connected to the faf5 test brush. that the start pulse sent by the By e: relay has been received.

   If the relay <I> Id </I> is now provided in the line. long distance arrival. it will energize and cut off the pulse driver with the result that the other pulses are not. not repeated by the relay equipment. The pulse conductor can only be opened after the feedback pulse produced locally in the depara trunk line. is sent.



       Sripl, i-essioia <I> of </I> i pulses at tan.deuis offices In some cases it is required to suppress either the return impulse or the forward impulse produced by the outgoing interurban line, as previously been explained previously.



  The originating trunk line has been arrayed so that any one of these pulses can be removed by simply cutting a connection. For the suppression, of the forward impulse, the conductor marked by a circle in the free departing trunk (fig. 11) must be removed, while the return impulse -is suppressed by the removal of the conductor. marked with a triangle.



       Step Single digit switch <I> </I> <I> with intermediate researchers </I> This circuit for intermediate researchers is shown in fig. 13. It is inserted between the incoming and outgoing trunk lines. The incoming trunk line in this stage remains the same as before, except that the back-up relays are removed for directions where intermediate seekers are introduced. The originating trunk line does not change.



       The selection .in the incoming trunk line is made as before by the action of the .direction marker by a number. The intermediate searcher circuit carries traffic in direction A which has two groups of circuits, for example one group with 50 cycles and another with signaling equipment at voice frequencies. These two groups of starting interurban lines are presented by two separate positions in the direction marker.

   However, the circuit of intermediate seekers is common to both groups and a check is made of this circuit to determine which direction is requested. The fact of excess calls, that is, the transfer of a call from the 50 cycle group to the tone group, is also incorporated in this circuit.



  The test potential to find intermediate researchers is expected on the di.ina arc (Fig. 9) of the DIel marker. The terminals which correspond to the same direction are connected to each other. The starter circuit is energized through the dim arc but these starter terminals are kept separate for reasons explained later.



       When either the Fs3 or Fs4 start relay (fig. 13) energizes, the Fco relay acts. LAF searchers from all free intermediate searcher circuits start moving until one arrives at the incoming trunk line <I> IT. </I> When the test potential -is reached, It gets excited, stops the finder and closes the relay circuit <I> there. </I> This,

  last relay introduces the low-resistance right-hand winding of It, and the starting circuit is neutralized. The other researchers stop.



  The position of the marker in the incoming trunk line is checked by the Of relay. As soon as the ih5 contacts close, <I> Of </I> is connected to the iafc broom. A land is possible through the arch <I> lime </I> (fig. 9), co4 and iaf <I> c, </I> if the voice group of trunk lines is desired, and in this case <I> Of </I> gets excited. The poten:

            tiel for the starting trunk line is directed via the spring combination of <I> Of </I> to one or the other group of FAF or VAF researchers depending on whether <I> Of </I> is or is not excited. In the same way, the starting circuit is also controlled by the relay. <I> Of. </I>



  When an outgoing trunk line is connected, relay CwI energizes in the blocking circuit and activates relay Ib which connects through conductor c, which was used for verification by relay Of, as well as this has been explained previously.

   In addition, 1b disconnects the relay It which, together with ih, neutralize each other, and the test potential is removed from the arcs of the outgoing trunk lines. All the seven brushes are connected to each other, -and the circuit remains maintained under the control of the Cw1 relay inserted: in the blocking circuit.



  If the call is directed to the first group, ei of originating trunk lines, i.e. if the relay Of is not energized across the arriving trunk line at a time when all the lines interurban lines in this group are occupied, the earth supplied by fc13 via the idle contact iifll and ili.1 causes the operation of the relay, <I> Of </I> (changes him at the.

   times the test potential and the starting circuit to the second group.



  If, at this moment, all the outgoing interurban lines of the second group are also occupied, then via. the work contact <B> f </B> c-) 3. and the rest uf <I> 21, </I> the circuit starting circuit < <. alternate directions is actuated and an attempt is made to complete the call to. through the circuit.



  The reason why the start terminals of the arc cIiiiib of the marker of directions in the incoming trunk line are kept separate, is. reduce the search time for outgoing trunk line seekers.

   In fact. when the circuit for: start-up of international researchers I_-IF is closed via, fs3? or fs41. a test potential is simultaneously supplied to a marker terminal in the arcs of interurban line searchers from FAF or VAF in front of the terminals belonging to the group request for intermediate searchers <i> 1 </I> AF via <I> f s31 </I> or f s 4 2, and the searchers look for the marked terminal.

       A free outgoing trunk line will be chosen by this test potential and will wait until. that a circuit of intermediate researchers is attached to the. interur line finish line <I> IT. </I>: after that the starter circuit is brought to rest. The test potential at. the. marker terminal is then removed and; the FAF or VAF seeker of the outgoing trunk line begins again to search to find the intermediate seeker circuit I AF which is engaged.

    



       Step <I> of </I> coiiiii-ittatioii. <I> to </I> two c) i.if fres (fig. 14) The first selection is made in the. incoming trunk line As previously, the starting circuit Fs5 and Fc: 5 is closed and the searchers of all the intermediate selector circuits of, junction which are free, search for the incoming trunk line. When the test potential is reached, the relays <I> Ut, </I> and Uk get excited.

   Relays to. slow operation Sil <I> and </I> Sit are excited in series via 17a4 at work and during their operating time a feedback pulse is sent via si23, -uhl, ef2, iaff, to relay Bs in fig. 9 in the incoming trunk circuit <I> IT </I> which sends a pulse to.

   alternating current through the incoming trunk line to the auxiliary recorder, which now proceeds with the number: next.



       After the operation of Si-2 .. the pulse conductor is directed through the relay Lin to the electromagnet of the marker switch IFJI. earth in IIIU (fig. 9) <I> Rd, </I> iaff (fig. 14), ef2, uh1, si -) 3. L11, IF.Il. The digit received by receiving unit II, L from the terminating trunk line will be,

   transmitted to this intermediate junction selector circuit, and will operate the direction marker <I> IF. </I> When the pulse train is transmitted, the relay <i> Lin </I> which remains energized while sending the pulses, neutralizes and connects the test potential <I> via </I> Liiil, -ucl, ua5, arc <I> fa, </I> to the outgoing trunk line terminals, in the direction requested. At the same time, the corresponding starting circuit is excited ic through the arc ifb.



  As explained previously in connection with the single digit switching step, any group of outgoing trunk lines can be divided into sub-gi, oupes, each of which is represented by a separate soot terminal on the IFM marker switch, and can be called directly. The case of excess calls is resolved in exactly the same way as that described in connection with the single-digit switching step.

   The relay Of 1 serves the same purpose as the relay <I> Of </I> in incoming trunk lines (fig. 9), since by the introduction of intermediate selections, excess calls can be transmitted from the incoming trunk line to this intermediate selector circuit.



  When the outgoing trunk line is connected, ('u @ \ 2 energizes in the blocking conductor and energizes Ua. This last relay disconnects the test potential of the outgoing trunk line arcs, and disconnects in following the test relay <I> Ut </I> which are released together with Uh and Sil, Sit.



  In addition to the direction, the position of the marker indicates whether this tandem office is the last in the connection or is an intermediate office. In the first case, the inherent loss of the outgoing trunk line must be indicated to the repeater connector circuit, while in the case of an intermediate tandem point the outgoing trunk line must artificially indicate a loss of 9 db, in order to 'adjust the repeater gain only for loss of the terminating trunk line.

    Relay <I> Cc, </I> which has the same function as Ic in the incoming trunk line, in this case operates through terminal B and a terminal in the arc <I> i f c. </I> The relay <I> Cc </I> focuses conversation and network conductors on the relay <I> Pb, </I> which operates when the code is received from the originating trunk line and which is followed by the excitation of Ef. Regardless of the code, the land is given only via iaf <i> d </I> to the repeater, which, as we know,

   indicates a loss of 9 db. When the starting interurban line takes the land away from the drivers mentioned, <B> Pb </B> is neutralized, but Ef remains blocked via aca7, and now via <i> f </I> b1 at rest and ef <i> 3 </I> at work. Relay <I> Cc </I> is bypassed and neutralized. Normal conversation conditions are restored via the Cc idle contacts. The Ef relay, in addition <I> to </I> ef2, transfers the driver, pulse via iaf <i> f </I> of the marker <I> IF </I> to the originating interurban line.

    



  In the case of a last tandem point, the terminal <I> A, </I> connected to the arc ifc and the relay Ef operates directly. After the operation of Ef, all the conductors are connected, and the circuit remains under the control of Cw2 connected to the blocking circuit. The correct weakening code is transmitted to the repeater in this case.

 

Claims (1)

CLAIM Long-distance telephone installation comprising a certain number of interurban centers, characterized by a first group of interurban lines between a first and a second interurban center, a second group of interurban lines between said first center and the second and of a different character from said first group of interurban lines, and means for automatically diverting the interurban traffic, normally carried by said first group of trunk lines, through said second group of trunk lines when said first group of trunk lines is completely occupied. S0 US-CLAIMS 1 Installation @ds telephony with long distances @- according to claim, characterized in that said first group of trunk lines is provided only for traffic terminating in said second trunk station, while the second group of interurban lines is intended primarily for interurban traffic intended .à pass in tandem through said second central and being transmitted on an interurban line leaving this central. 2 Long-distance telephony installation according to claim, characterized by a first group of interurban lines between a first and a second interurban center for traffic terminating in the latter center, a second group of interurban lines between said first central and the second, arranged for inter-city traffic intended to pass in tandem, through said second central to be extended on at least one additional interurban line, and means for automatically diverting interurban traffic terminating in said second exchange through said second group of trunk lines when said first group of trunk lines is fully occupied, 3 Long-distance telephone installation following the sub-station. claim 1, ca ractérisée in that. circuits provided in a trunk central and associated with outgoing trunk lines are arranged to transmit a start pulse to the selection equipment of the incoming trunk to prepare said equipment for. the performance of its selective functions. 4 Long-distance telephony installation according to claim, "characterized in that interurban centers, such as said second central, include digital selection devices associated with the end points of the trunk lines normally used for traffic intended to pass in tandem through the central, and non-digital selection devices associated with the terminating ends of trunk lines used to terminate trunk traffic. 5 Telephone installation at. long distance as claimed in claim, characterized in that said first trunk station and similar trunk stations comprise circuits associated with outgoing trunk lines arranged to carry trunk traffic intended to pass in tandem through trunk stations to. their arrival end these circuits being arranged to transmit a starting pulse to the circuits of the arrival ends of said interurban lines, the same central units comprising circuits associated with other outgoing interurban lines used for terminating interurban traffic at the interurban plants at the arrival ends of said other interurban lines, the circuits second mentioned not being arranged to transmit a starting pulse to the arrival ends of said terminating interurban lines. 6 Installation of long distance telephony according to subclaims 1, 3, 4 and 5, characterized by recorders arranged to transmit the digit "1" whenever a digital selection of lines giving access to the local telephone network is required and devices; t, digital selection in said second trunk central and in similar trunk stations which are associated with the terminating ends of trunk lines normally used for trunk traffic destined to, pass in tandem through said stations and which are arranged to give access, in response to the number "1", to lines corresponding to the local telephone networks. i Installation of long-distance telephony according to. sub-claim?, characterized in that for trunk connections terminating at said second exchange and similar stations and arriving on trunk lines used only for terminating traffic, the digit "1" of the recorder controlling the establishment of the connection is received <<the terminating interurban center as a starting impulse in order to cause the operation of a device with automatic selection to prolong the connection to local equipment. while for intercity connections terminating at said second intercity exchange and similar stations and arriving on trunk lines normally used for tan dem traffic, the circuit start pulse at, the outgoing end of the interurban line is preparing the digital selection device at. the end of arrival to respond to the digit "1" of the recorder, said selection device, in response to the digit "1" choosing the local equipment. 8 Installation. long-distance telephone system according to sub-claim 1, characterized in that said outgoing trunk line circuits are arranged to transmit a retro grade pulse when the digit for controlling the equipment of the next trunk exchange is to be transmitted. 9 long-distance telephony installation following sub-claims 4 and 8, characterized in that all of said outgoing trunk line circuits are arranged to transmit said retrograde impulse. 10 Long-distance telephony installation according to sub-claim 2, characterized in that said digitally-selectable devices comprise switches with retrograde search motion, the brushes of each of which are connected with an outgoing trunk line or with a local telephone line, and to the pins to which the incoming interuban lines are connected, and marker switches associated with the terminating trunk lines and arranged to respond to digital pulses transmitted across trunk lines to cause the operation of the retrograde paging switches connected to the desired group of originating trunk lines or local telephone leagues. 11 .Long-distance telephony installation according to sub-claim 9, characterized in that switches with retrograde search movement are interposed between the incoming trunk lines and the individual retrograde search mode switches of the trunk lines departure, that a group of intermediate switches with retrograde search movement are arranged to be connected to the arcs of each of a plurality of groups of individual switches of the departure interurban lines, and in response to each of a plurality of digit values received across an incoming inter-city line said intermediate switches are turned on while the intermediate switch which establishes the connection to the incoming inter-city line is automatically connected to the arcs of a group of outgoing trunk line switches determined by the particular value of the digit received. 12 long-distance telephony installation according to sub-claim 11, characterized in that a group of intermediate switches provides access to the terminal line switches and tandem lines to the same next inter-urban center.