US1537154A - Multiplex signaling system - Google Patents

Description

May 12, 1925. 1,537,154

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Patented May 12, 1925.

UNITED STATES P rsivr ori-ics WALLACE V. lViI'OLFE, OF CORONA, NEW YORK, ASSIGN'OR' TO yWNESTE".Lfll' ELECTRC COMPANY, INCORPORATED, OF NEW'YORK, N. Y., A CORPORAION OF NEW YORK.

`ifiirixrirL-EX sIGNALiNe SYSTEM;

Application filed November 29, 1922. Serial No. 603,307.`

To all iii/10m 'it may concern:

Be it known that I, 'lVALLAon V. lNoLrn, a citizen of the United States of America, residing at Corona, in the county of Queens and State of New York, have invented certain new and useful Improvements in Multiplex Signaling Systems, of which the following` isa full, clear, concise, and exact description.

The present invention relates tol signaling by means of carrier waves, and more particularly to provisions for the transmission of signals through a plurality of carrier wave channels constituting a multiplex system. f y y The invention relates particularly to the type of carrier transmission system in which the carrier wave is normally continuously7 transmitted, and in which the carrier waves of the various channels may be independently interrupted to transmit a signal over any particular channel. In the embodiment of the` invention to be described, the normal ly continuously transmitted carrier waves are` modifiedor modulated to transmit one kind of signal such as speech, for example7 and are temporarily ,interrupted to. transmit another kind of signal such as' a call signal. i lin systems of this character, sometimes teri'ned closed circuit systems, the entire signaling circuit such as the line must be intact and the terminal apparatus must be in opeiative condition in order that the carrier waves may `be continuously transmitted and received. An interruption to the transmission through the. system due, for example, to a break in the line or in a common terminal circuit, or to adverse nf'eather conditions in the case of aline system, or of a radio system, for example7 may result in an interruption ofeach. or a number of the carrier waves beine; transmitted. and such an interruption of all or a plurality of the received carrier waves may conveniently be taken as an indication of a failure of the system. rThisis imrticularly true since it is very improbable that. all or a number of the carrier waves would be interrupted simultaneously in the normal operation .of transmitting call signals oi'er the various channels.

lt is an object yof theinvention to provide for giving' asigiial in response to interruption of the carrier wares-iii a plurality of channi-ils simultaneously.

This signal or alarm may-be `used to indicate to an attendant a failure in the system, or ka reduced or interrupted transmission of the carrier currents, as'will beexplained The general type of carrier current system to which the invention is particularly applicable, is shown and described in an article entitled Carrier'current telephony and telegraphy by E. H. Colpitts and O. B. Blackwell,,beginning in thei-rpril7 192i Journal of the American Institute of Electrical Engineers, at page 420, Fig. 42.

The drawing` to which the following` description refers illustrates diagrammatically a system of the type shown inthe Golpitts and Blackwell article with an embodiment of the invention'incorporated therein.y

Referring to the drawing, the line ML may be a multiplex carrier current line and the line LLmay be one of a. plurality of low frequency lines such as ordinary subscriloers7 loops arranged for two-way repeating` to and from the carrier line. The main line, or carrier line, is provided with. a balancingnetwork MN and a conjugate repeating` coil, or hybrid coil, H, having a transmittingloop TL and a receiving loop RL associated with the hybrid coil and conjugately related to each other, Each low frequency line is also provided with a balancing network LN and a hybrid coil as shown, having conjugate branches for respectively iii/ipressing currents on the line LL'and ,deriving currents therefrom.

Each branch or repeating` circuit for repeating signals from the low frequency line to the high frequency line comprises a modulator such as M1 normally suppliedh with carrier current from a source such as S, and a band filter such as BF, for selectively transmitting to the transmission loop TL the range of frequencies setaside for the exclusive use of the particular channel. The repeating circuit for. transmitting from the high frequency line to a low frequency line such as LL comprises a band filter such- `as BFL adapte/dito transmit selectively the "ange of frequencies used exclusively bv this channeL-a detector or demodulator DM, and a low frequency or speech frequency filter LF for confining the currents transmitted to the line LL to the voice frequency range. Also associated with the output side of the demodulator DM'l is a high frequency iilter HF, selective of the carrier frequency,

and a rectifier R for su i vilvine the rectified i a y lun carrier frequency current to a control relay 10. Each of the filters BFl, HFl, LF and BF4k may be of the type described in the Colpitts and Blackwell paper referred to and more fully disclosed in the patent to G. A. Campbell No. 1,227 ,113, issued May 22, 1917. The modulator M1 and the rectifier R1 are preferably of the vacuum tube type such as are indicated in Fig. 42 of the Colpitts and Blackwell paper referred to. Also the carrier frequency source indicated at S is preferably of the vacuum tube type having a regenerative connection for causing the continuous production of oscillations, although this source may be of any other suitable type suchv as a machine generator.

The filter BF2 and the demodulator DMg are assumed to comprise the receiving side of a second carrier channel leading to a second loiv frequency line Which is not shown, but which may be entirely similar to the line LL. This channel employs a carrier current of a frequency different from that used in the channel previously described and the band filter BF2 is designed in accordance with the principles set forth in the Campbell patent referred to, so as to have a selective transmission range for the currents of the frequency range used exclusively by this channel. Similarly the filter HF2 is selective of the carrier Wave transmitted over this particular channel. The circuit for transmitting from the second low frequency line (not shown) to the multiplex carrier line ML by Way of the common transmission loop TL is indicated by the branch 11.

The band filter BFM demodulator DWS, filter HF,v and rectifier are in a similar manner associated with a third low frequency line which is not shown in thc dra\ving, but which may be a duplicate of the line LL and the circuit for transmitting from this third assumed loW frequency line to the transmission loop TL is indicated by the connectinfr terminals 12. Associated with the rectifier B2 is a relay 13 and associated with the rectifier R3 is a relay The filters HFl, HF2 and HF3 may in each instance be a simple timed circuit if desired. The relay 15, which is adapted to be actuated by tlie relays 10, 13 and la in common in the manner to be described below, is pret'- erably marginal so that its armature is normally retracted and holds open the circuit of the alarm 16, except When a current exceeding a predetermined strength is flowing in the Winding of the relay 15. The resistanccs 17, 18 and 19 may each be any desired type of current consuming indicating device such as a lamp or an electromagnetic signal. The purpose and function of the relays 20, 21 and 22 Will appear from the description of operation of the system which will now be given.

The operation of the system in transmit ting speech is substantially as described in the Colpitts and Blackwell paper referred to. The speech frequency currents received from the subscribers station on the line LL are repeated into the circuit of modulator M1 where they combine with the carrier Wave from the source S in well known mannei to produce a voice modulated high fri quency Wave. This Wave is selectively t ausmitted by band filter BF* to the branch TL and to the multiplex line ML for transmission to a distant station. The manner in which the Wave is received and' again converted into speech at the distant station will be clear from considering a similarly modulated Wave received at the station shown. Such a Wave received -over the uppermost channel in the drawing, for example, is selectively transmitted by the band filter BF1 to the demodulator DMI, which operates in Well known manner to reproduce currents of the speech frequency range. These currents pass selectively through the low pass filter LF from which they are impressed on the line LL.

The relay 21 bridged across the telephone line LL is made selective of ringing or signalmg current adapted to be transmitted from the distant station on the low frequency line, but remains inert when currents of different character such as speech currents or talking currents traverse the line LL. This selectivity maybe secured in a manner Well known in the art such as by including the condenser as shown in the circuit of the relay, and by proportioning the inductance of the Winding and also, if necessary, the mechanical construction of the armature. Except when a ringing or calling signal is received over the line L'L, rela-y 21 allows its armature to close continuously the energizing circuit for the relay Relay 22 by continuously attracting it-s armatures permits a supply of carrier current from the source S to the modulator Ml and through the band filter BF4 to the main line ML. Tu a similar manner it is assumed that the carrier current is normally continuously supplied through the branches 11 and 12 to the line ML under control of other low frequency lines not shown. Similarly also at a distant terminal of the multiplex line ML, thc corresponding lou' frequency .lines with which the lines LL and similar lines at the station shown are adapted to converse, are assumed to maintain normally the supply ol corresponding carrier currents to the multiplex line ML, except when a call signal is to be transmitted. Accordingly at the station shown in the d aiving there is normally being received continuously a sustained carrier Wave in each of the carrier channels associated With the line ML.

The carrier current normally continuously meuse' received over amv channel such. as the upper most channel iliustrated in the drawing is selectively passed through the band filter BF, and passes into the demodulator DM1 .Where a partial rectiiication takes place.

larly the carrier current normally received continuously over eachV of the other channels maintains the respective relays 13 and 111 in energized condition.

` When it is desired totransmit a ringing or calling signal from a lovv lrequency line such as LL through the correspondingcarrier channel and out over the cooperating loW frequency at la distant station on the line ML, ringing current of the character to Which relay 21 is selectively responsive is transmite-d over the line LL. Relay 21 in response to this ringing current pulls up its armature, opening the circuit of relay 22 which releases its armatures. The supply ot carrier current to the modulator M1 from the source S is thus interrupted for the duration ot the calling signal received from the line LL. The etl'ect of this interruption or' the distant station will be understood from considering the effect at the station'shown ot an interruption in the carrier current normally continuously received.

yConsidering the uppermost chanel ot the drawing an interruption of the'recei-vedcarrier in this 'channel allows the relay 10 to deenergize, whereupon a circuit is closed for the relay 2O from grounded battery, Winding` of relay 20, armature and back contact ot relay 10, and the armatureland front contact of one or all of the remaining relays 13, 111-, etc. on the assumption that the cary rier Waves normally being received bythese several channels Will not all be simultaneously interrupted in the normal operation" of transmitting calling signals. A circuit in shunt of the relayis also closed from that curients on the line LL can have no etlect upon the carrier terminal apparatus. The ringing current sent out over the line LL from the source 25 may serve, in accordancey with standard practice, to actuate a signal device at the distant station ot the line LL.

In an entirely similar manner, calling or ringing signals may be simultaneously and selectively transmitted through each of the other carrier channels by momentary inter-` `ruption or' thel respective carrier Wave. In

case of the simultaneous interruption of all or a number of the carrier Waves normally being received, all or a plurality o i the relays 10, 13 and 14, etc., Will be simultaneously deenergized. The marginal relay 15, it will be noted, is included in a circuit in shunt to ground of the circuit for energizing relay 2O and signal device 17. In the normal operation of the system in transmitting a ringing current over a single one of the channels, or over a pluralityl of channels less than a predetermined number, re-

'lay 15 will draw insuiiicient current from a path including battery and relay 20, and battery and resistance 17 in parallel, (or a plurality of such paths in parallel it' more than one channel are simultaneously calling) armature and back contact et one or a 'correspon-ding plurality of relays 10, 18, etc., resistance 24, and Winding o1' relay 15 to ground in parallel with one or more resistances 24, and armature and front contact of the relays 13, 14, etc., that may still be in energized condition. However, if all ot the relays 10, 13, 141, etc., are simultaneously deenergized, or il more than a pre-` determined number are deenergized simultaneously, the current through the corresponding plurality or' relays in parallel', through the corresponding indicating devices 17 in parallel, and through the Wind-- ing of relay 15, will be suiiicient to energize this relay and cause it to pull up its armature to actuate the alarm signal 1G. For ere ample, in a live channel system the resistances 17, 18, 19 and 24; and the impedance of the windings or' the relays 2O of the various lines may be so proportioned with respect to the characteristics ofrelay 15 that it' the Carrier current on four of the channels is interrupted simultaneously the re- 'lay 15 will energize, Whereas it three or less than three of the carrier Waves are simulta- -neously interrupted, the relay 15 will receive insuificient current to energize.

It three or less than three carrier Waves are interrupted simultaneously, it follows that two ortheir carrier Waves simultaneously interrupted, the resistances 1i', 8, 19, 'and the relay 15 maybe such `that none of the relays 20 1n question can be operated on account of the single remaining resistance 2l Cil in the single remaining ground circuit, As explained above, however, relay l5 will under these conditions operate. By suitable-adjustinent therefore, the system may be ar- `rangedso that no ringing signal will loe sent out on any low frequency line LL in ease a ringing signal is siini'lltaneously received over a plurality of carrier channels greater than a predetermined number, While under these. sam-e conditions the alarm lo will be actuated. If desired, however, the system may be adjusted so that ringing signals simultaneously received over the various channels Will be repeated over the respective lines, except in the single instance Whenthe carriers in all of the channels are simultaneously interrupted, this being also the only condition on Which the alarm 16 is operated. rlhe invention lends itself, therefore, to various adjustments correspondingto interruption of transmission on all of the channels, or to a condition of reduced transmission through the systen'i due to the cessation of current on a part of the channels only. rlhis latter adjustment may be convenient, for example, in cases Where the alarm 1G is to be actuated to indicate a change in the transmitting conditions which is selective in character and etlects only the channels employing Waves of certain frequencies;

Thile the invention has been described as applied to a specific type of transmitting system, itis to be understood that the invention isnot limited to the particular type-of system disclosed, nor to systems in which the carri-cr Waves are transmitted over a conductive circuit, but thatl it is equally applicable to other types of line transmission systems than that disclosed and also to radio systems.

that is claimed is:

l. In a signaling system a plurality` ofY carrier Wave transmission channels, means to transmit signals through the respective channels comprising means for withdrawing the respective carrier waves from transmission, and a signal device actuated only in a signalingdevice` and means for actuating said signaling` device in response to the conditionof withdrawal of the normally transmitted carrier wave in a plurality of said channels at the same time.

3. In a multiplex carrier signaling lsystem a. plurality of carrier channels, means for normally continuously transmitting the carrier Waves through the respective carrier channels, means for independently transmitting a signal through each' of said channels in response to the Withdraw-al-from transmission of the normally transmitted carrier Wave, a .signaling device, and means dependent upon the condition of withdrawal of the carrier Waves existing. simultaneously in a plurality of channels in excess only of a predetermined nuniber for controlling said signaling device.

4. In a multiplex carrier wavesystem a plurality of distinct carrier wave transmission channels superposedr onv the same medium, means for normally continuously tansmitting the carrier wave through each of said channels, a `relay foreach of said channels normally energized' in response to the carrier'transmitted through the respective channel, a signaling element associated with each of said relays, a signaling device common to said relays andmeans responsive to the deenergization of each of said relays for actua-ting thev corresponding signaling element and responsive only to the simultaneous deenergization of a plurality of said relays in excess of .a predetermined iniinbei'for controlling,actuation of said signaling z device.

5.y In a multiplex carrier Wave transmissionsystem, av Aplurality of distinct carrier wave transmission channels, means for transmitting signalsithrough said respective channels, an alarm signaland means controlled by carrier Waves receivedover said channels and responsive to a .failure in the `transmission system resulting in the=condition of Withdrawal.from transmission of all of said carrier iva-ves atthesametimeffor actuating said alarm signal.

6. In a multiplex carrier wave transmission systm, means to transmit normally and continuously a plurality of carrier waves of respectively different frequency, a corresponding plurality of signals, means responsive to the Withdrawal from transn'iission of a carrier Wave for actuating the corresponding signal, an iudicatingdevice and means dependent upon the condition of Witlnlraival at the same` time of a plurality of said carrier waves for actuating saidindicatingl device.

7. In a multiplex carrier Wave transmission system', means for normally and continuously transmitting a plurality of carrier Waves of respectively different frequency.` a corresponding plurality of signals, means responsive to the Withdrawalfrom transmission of a carrier wave for actuating the corresponding signahmeans responsive `to the condition of withdrawal at thesame time of a plurality of said carrier Waves for pre- CII llltl lfll) 8. In a multiplex carrier Wave signaling system, means for normally continuously transmitting al pluralityof carrier Waves of respectively different frequency, a plurality of receiving circuits for the respective carrier Waves, interlocking circuits betweenk said receiving circuits, a plurality of signals each having a circuit controlled in the interlocking circuits of said receiving circuits, a marginal relay also controlled in said interlocking circuits, means responsive.

to the Withdrawal 'from transmission of a carrier Wave for actuating the corresponding signal and means responsive to the condition ofwithdrawal at the saine time oi' a plurality of said carrier Waves oishifting said interlocking circuits to prevent the actuation of any of said signals and to actuate said marginal relay and an indicating device controlled by said marginal relay.

9. In a carrier Wave signaling svstem, a plurality of carrier Wave channels, signa-ls corresponding to said channels and arranged to be controlled individually over the respective channels, a signal common to a plnk rality of said channels, and means controlled simultaneously over said plurality of channels for actuating said last-mentioned signal.

In Witness whereof, I hereunto subscribe my name this 25th day of November A. D.

WALLACE v. WoLFE;

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