US2184978A - Carrier current telegraphy - Google Patents

Carrier current telegraphy Download PDF

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Publication number
US2184978A
US2184978A US208760A US20876038A US2184978A US 2184978 A US2184978 A US 2184978A US 208760 A US208760 A US 208760A US 20876038 A US20876038 A US 20876038A US 2184978 A US2184978 A US 2184978A
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United States
Prior art keywords
impulses
current
bridge
relay
direct current
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Expired - Lifetime
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US208760A
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English (en)
Inventor
Nyquist Harry
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AT&T Corp
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Bell Telephone Laboratories Inc
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Publication date
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Priority to US208760A priority Critical patent/US2184978A/en
Priority to FR854914D priority patent/FR854914A/fr
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Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
    • H04L27/06—Demodulator circuits; Receiver circuits

Definitions

  • This invention relates to carrier current receiving systems and more particularly to the reception of carrier current telegraph signals.
  • Another object is to secure in the telegraph impulses received over carrier current transmission systems a substantial reproduction of the original direct current impulses actuating the sending relay.
  • a further object is to convert sinusoidal waves into waves having substantially flat tops and straight sides.
  • I may first amplify and then rectify the incoming carrier current impulses, thus producing direct current impulses of fixed polarity, that is, they may be either positive impulses or negative impulses depending upon the point of reference, but with respect to any fixed reference point in the circuit, current flow is in one direction only. Upon this unidirectional current is then superposed an oppositely poled direct current of suitable magnitude with the result that the impulses are now defined by reversals of current. Before this superposition spacing intervals may be characterized by zero currents, markingintervals by positive currents. After superposition spacing intervals may be characterized by negative currents,
  • the next step involves the use of a discriminative network such that it transmits small currents readily, but larger currents are suppressed 5 in proportion as they increase in magnitude, this of course within the designed limits of operation of the device.
  • a discriminative network such that it transmits small currents readily, but larger currents are suppressed 5 in proportion as they increase in magnitude, this of course within the designed limits of operation of the device.
  • Fig. 1 represents the form of the direct current wave at the transmitting end of a carrier current telegraph system
  • Fig. 2 represents the carrier counterpart of the 25 wave of Fig. l;
  • Fig. 3 shows the carrier wave at thereceivih end of a carrier current telegraph system
  • Fig. 4 is a direct current-wave formed from rectification of the received carrier wave
  • Fig. 5 shows the change of axis resulting from the superposition of a fixed opposing potential upon the direct current wave of Fig. 4;
  • Fig. 6 is illustrative of the results obtained in the process of producing steep wave fronts in the wave of Fig. 5;
  • Fig. '7 is a schematic of the circuit involved in making the transformation from the wave of Fig. 3 to that of Fig. 6;
  • Fig. 8 is a complete diagram of a preferred arrangernent as employed to improve the operation of the receiving relay in a carrier current telegraph system in accordance with the invention
  • Fig. 9 is a transformer which may have a nonlinear input-output characteristic
  • Fig. 10 is a. modification of the arrangement of Fig. 8 which may under some conditions afford practical advantages.
  • Fig.7 the input from the carrier current line is applied to the amplifier it and then is led to the rectifier i.
  • the input to rectifier i may have the form shown in Fig. 3 and the output may then have the form shown in Fig. 4 andrepresent the current flowing through the conductor a.
  • the rectifier there are a resistance i3 and two batteries II and I2 so arranged that battery i2 causes direct current to be superposed on the detector or rectified currents, but by reason oi the interposition of battery I! no direct current is sent through the rectifier.
  • the purpose of the batteries H and i2 is to remove the bias from the rectified wave so that the wave shape of the current flowing through conductor 17 has the form shown as Fig. 5.
  • the bridge t is a non-linear device which may be made up for instance of two metallic resistances and two resistances made of a substance the resistance of which decreases as the current through it or the potential across it is increased. This may be a mixture of silicon, carbide and a binder material as described in McEachron Patent 1,822,742, September 8, 1931.
  • the elements are so chosen that the bridge is substantially balanced for large current values and is unbalanced for small current values.- For example, assume resistances l4, iii to be fixed at 100 ohms each and that impedances Z are so designed as to be several thousand ohms at low voltages.
  • impedances Z may be 5000 ohms each at a potential difierence of one volt and 100 ohms each at ten volts. It is apparent that a much greater proportion of the output voltage or bridge rectifier l is applied to relay 8i when this rectified voltage is at its minimum than when at its maximum value, and also that the impedance values selected for bridge 4 are dictated not only by the impedances of the connected circuit but more particularly by the peak value of voltage to be applied to it. The effect of the bridge 4 is to remove the peak and steepen the sides oi the waves as it exists in conductor 2). The current in the conductor will then take the form shown in Fig. 6. If the design is such that the magnitude of the wave at c as shown in Fig. 6, is sufficiently large to operate the relay 8
  • I represents a full wave rectifier which may be of the bridge type
  • 2 is a second rectifier which may for convenience be similar to rectifier I but is not necessarily of the full wave type although so shown
  • 3 represents a Wheatstone type of bridge having resistance arms l8, l9 and 20, the fourth arm of bridge 3 being formed by non-linear bridge 4.
  • the bridge 4 is so designed that for large values of current, the four arms l4, l5, l6 and I! approach equality and consequently the current output from the bridge into conductors 3'! and 38 approaches zero. For small values of current the bridge output is thus large comparatively.
  • Conductors 37 and 38 connect the bridge 4 into the direct current amplifier 3
  • is through the transformer 32 into the receiving relay 8
  • the direct current amplifier may consist of one or more stages of amplification as required.
  • the relay 8! shown as a two-winding polarized relay may, of course, take any suitable form.
  • the connection of the condenser 36 in series with the second winding of therelay 8i may be one form of such equalization.
  • the relay BI is shown in spacing position. On
  • operates to marking position and the battery 33 is then connected through contacts 34 and 35 to relay 28, so that contacts 29 and 36 of relay 28 are closed.
  • the output of rectifier 2 is thus connected across the condenser 21 which is permanently connected between grid 23 and cathode 24 of electron discharge device 26, the output circuit of. tube 26 including anode 22, bridge 3, anode battery 2! and cathode 24.
  • Incoming signals such as those shown in Fig. 3 may be amplified as required in amplifier l0 and are then impressed on both rectifiers l and 2.
  • Rectifier i produces biased impulses such as shown in Fig. 4 which are impressed on bridge 3.
  • bridge 3 had four equal arms l8, I9, 20 and a fourth of the same magnitude, then since across one diagonal of the bridge is impressed the biased signal from rectifier 4 and across the other diagonal a fixed potential representative of the magnitude of the incoming signal as produced by rectifier- 2 and vacuum tube 26, if these potentials were properly poled and properly proportioned, there would appear across any one arm a biased wave form such as shown in Fig. 5 and resulting from the superposition of the two potentials. It is apparent that the bridge 3 is thus a device for permitting the superposition of the output of rectifier 2 upon the output of rectifier I while yet maintaining the two circuits substantially conjugate. In a preferred arrangement as shown in Fig. 8, the fourth arm of bridge 3 is replaced by bridge 4. By reason of the characteristics of bridge 4 as aibove described, the wave form of the signal as shownin Fig. 5 is transformed substantially to that shown in Fig. 6.
  • This amplifier may employ one or more stages as required.
  • is shown interposed between the bridge 4 and the receiving relay 3
  • FIG. 9 An alternate method for the production of steep wave fronts might involve a transformer.
  • Fig. 9 having a highly permeable core 15, as for example a core of permalloy and designed to saturate on small currents.
  • This transformer might have two primary windings 16 a 11, one (16) to carry the rectified signaling wa output of bridge I and the other (11) to carry he bias compensating current.
  • the secondary 1 would be connected into the grid circuit of thedirect current amplifier, thus the transformer would replace bridges 3 and 4 of Fig. 8.
  • Fig, 9 the connections have been so laid out and n nbered that it may be figuratively transposed in 0 Fig. 8 to replace bridges 3 and 4.
  • the rectifier 2 As shown in Fig. 8, one of the imperfect rectifiers such as those employing coppereoxide, which functions by virtue of considerable variations in resistance with change in polarity of the applied potential. Such a rectifier would ordinarily permit the discharge of condenser 21 of Fig. 8 to an extent which would prevent proper functioning of the biasing circuit. Under these conditions there may be used the arrangement of Fig. 10 which is designed to function substantially in the manner described above for the arrangement of Fig. 8 and differs from it essentially only in the details of the biasing circuit, that is, the apparatus designed to convert the signal as shown in Fig. 4 to that shown in Fig. 5.
  • the rectifier 2 is connected through the high resistance to the contact 50 of the relay 48 which has a polarizing winding 52 activated by battery 65 and an operatingwinding 5
  • of relay 48 is completed through contact and battery 53 or through contact 59 and battery 62 and then to the ground return.
  • the receiving sounder 64 may also be operated from batteries 52 and 63.
  • the condenser 41 is shunted by the very high resistance 53 and in series with these is the grid biasing battery 54.
  • the condenser 41 and the resistance 55 are so proportioned as to permit substantially full charge of condenser 41 from the potentials appearing across terminals 4
  • the time constant of the resistance 55 and the condenser 41 may thus be of the order of one-tenth second.
  • the resistance 53 which under some circumstances may comprise the unavoidable leakages of the assembled apparatus is of a value so high as to have no appreciable efiect upon the time constant of condenser 41 and resistance 55.
  • Fig. 10 The conditions shown in Fig. 10 may be assumed to be those of spacing position. Assuming that no signal has come through for a considerable time, condenser 41 will have substantially discharged itself into resistance 53 and grid 23 of tube 23 will be biased substantially to the potential of battery 54. The potential of battery 54 is so chosen as to cause the apparatus to remain in an operating condition even after a very long mark or space. The potential across bridge 3 from tube 26 will not be ideal under such conditions but the apparatus is so maintained that it will not fail to operate at the first incoming signal and will quickly adjust itself to provide the proper bias.
  • operates and battery 62 begins to charge condenser 51 through winding 5
  • the relay will operate and will remain operated until the point is reached where as the charge of condenser 51 approaches completion the charging current and hence the flux due to current in winding 5
  • a carrier current receiving system comprising means for transforming carrier current impulses into direct current impulses of fixed polarity, means for superposing upon said direct current impulses a potential of opposite polarity whereby said impulses are characterized by reversals of direct current polarity, means for proportioning the magnitude of said oppositely poled potential in accord with the magnitude of said carrier current impulses whereby said reversals are made substantially symmetrical with respect to zero direct current potential, and means for producing steep wave fronts in said reversals.
  • a carrier current receiving system comprising rectifying means for producing unidirectional direct current impulses from received carrier current impulses, means for biasing said unidirectional impulses to produce equivalent biclirectional impulses, vacuum tube means for weighting said biasing means on the basis of the amplitude of the said received carrier current impulses, and means for producing steep wave fronts in said bi-directional impulses.
  • a carrier current receiving system in which the means for producing steep wave fronts incorporates a Wheatstone bridge having resistance arms, two opposite arms equal and constant, the other opposite arms equal but having a resistance value which is a function of the current through them.
  • a carrier current receiving system as in claim 2 in which the means for producing steep wave fronts comprises a transformer wound on a high permeability core such that saturation is reached for very small currents.
  • a carrier current receiving system in which the superposing means comprises a balanced Wheatstone. type bridge.
  • a carrier current receiving system in which the'means for transforming carrier current impulses into direct current impulses comprises a Wheatstone-bridge type of rectifier.
  • a carrier current receiving system comprising a bridge-type rectifier for converting carrier current impulses into' unidirectional direct current impulses, an electron discharge device having anode, cathode and condenser biased control grid, said condenser charged by rectified carrier current impulses to a potential proportional to the amplitude thereof whereby said electron discharge device delivers a unidirectional direct current potential proportional to the magnitude of the received carrier current impulses, a balanced Wheatstone bridge adapted to permit the superposition of said substantially constant direct current potential upon said direct current impulses in opposition such that said direct current impulses are converted into, equivalent bidirectional impulses of substantially equal positive and negative valence, and means for producing steep wave fronts in said bidirectional impulses.
  • said steep wave front producing means comprises a Wheatstone type of resistance arm bridge having two opposite arms equal and of constant resistance and the other opposite arm equal but of a resistance value which is a function of the current through them.
  • a carrier current receivingsystem in which said steep wave front producing means comprises a Wheatstone type of resistance arm bridge having two opposite arms equal and of constant resistance and the other opposite arms equal but of a resistance value which is a function of the current through them.
  • a carrier current telegraph receiving system comprising means for the conversion of received carrier current telegraph impulses into unidirectional direct current impulses, means for the conversion of said unidirectional direct current impulses into equivalent bidirectional direct current impulses of substantially equal positive and negative valence, means for the conversion of said bidirectional direct current impulses into equivalent direct current impulses having substantially vertical sides and substantially flat tops, and electromechanical means responsive to said impulses.
  • a carrier current telegraph receiving system in which said electromechanical means comprises a direct current amplifier and a polarized relay. 4
  • a carrier current telegraph receiving system in which said electromechanical means comprises a direct current amplifier transformer coupled to a polarized, relay, and an equalizing circuit is connected to a winding of said relay, said equalizing circuit being adapted to neutralize and prevent signal distortion due to said transformer.
  • a carrier current telegraph receiving system comprising means for the conversion of received carrier current telegraph impulses into unidirectional direct current impulses, means comprising a Wheatstone bridge and condenser biased electron discharge device for superposing upon said unidirectional direct current impulses an oppositely poled potential adapted to convert said unidirectional direct current impulses into substantially equivalent reversals of substantially equal positive and negative valence, a Wheatstone-type bridge means for producing steep wave fronts in said reversal, a direct current amplifier transformer coupled to a polarized relay responsive to said steep wave front reversals, and auxiliary contacts on said polarized relay adapted to connect said condenser biased anode, cathode, a source of potential and a load circuit, and a control circuit comprising a condenser permanently connected between said grid and said cathode, and arranged to be automatically connected across the output of said recti fler during and in response to the reception of the carrier current impulses and to be disconnected therefrom during spacing intervals whereby the load
  • An impulse receiving'system comprising a source of biased direct current impulses, means superposing upon said biased impulses an opposing direct current potential, meansproportioning said opposing direct current potential according to magnitude of said biased impulses whereby said biased impulses are converted to unbiased reversals, and means for producing steep wave fronts in said reversals.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
US208760A 1938-05-19 1938-05-19 Carrier current telegraphy Expired - Lifetime US2184978A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US208760A US2184978A (en) 1938-05-19 1938-05-19 Carrier current telegraphy
FR854914D FR854914A (fr) 1938-05-19 1939-05-17 Systèmes de transmission à courants porteurs

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US208760A US2184978A (en) 1938-05-19 1938-05-19 Carrier current telegraphy

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE741391C (de) * 1940-06-29 1943-11-10 Telefunken Gmbh Schaltungsanordnung zur Versteilerung von Telegrafiezeichen
US2467308A (en) * 1945-03-17 1949-04-12 Rca Corp Interference reducing radio pulse receiver
US2501574A (en) * 1945-10-02 1950-03-21 Morrison Montford Carrier-current signal system
US2511485A (en) * 1940-10-25 1950-06-13 Howard M Strobel Inertia control system for indicators
US2662114A (en) * 1950-11-03 1953-12-08 Marconi Wireless Telegraph Co Frequency shift telegraph receiver

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE741391C (de) * 1940-06-29 1943-11-10 Telefunken Gmbh Schaltungsanordnung zur Versteilerung von Telegrafiezeichen
US2511485A (en) * 1940-10-25 1950-06-13 Howard M Strobel Inertia control system for indicators
US2467308A (en) * 1945-03-17 1949-04-12 Rca Corp Interference reducing radio pulse receiver
US2501574A (en) * 1945-10-02 1950-03-21 Morrison Montford Carrier-current signal system
US2662114A (en) * 1950-11-03 1953-12-08 Marconi Wireless Telegraph Co Frequency shift telegraph receiver

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