US2583642A - Electric signaling system - Google Patents

Description

1952 J. G. GORDON-WRIGHT 8 ELECTRIC SIGNALING SYSTEM Filed May 12, 1948 Patented Jan. 29, 1 952 UNITED J STATES PATENT foFrI'cE' ELECTRIC SIGNALING SYSTEM Application May12, 1948, Serial No. 26,597

In Great Britain June 14, 1947 2 Claims. (01. lit-s53) The present invention relates to electrical sigthe responding units are connected between any nalling systems and :is more particularly conm one of these phase leads and the neutral concerned with systems involving the application of ductoru In the drawing, connection to the live high frequency-signals to electric supply mains lead is represented by the letter L and to the for the purpose of operating a number of re- 5 neutral lead by the letter N and by way of exsponding devices connected thereto at different ample two responding units RI and R2 for propoints. By, high frequency is meant high comducing the desired switching operations are pared with the frequency of the supply and in shown connected between the neutral N and the practice a frequency withinthe audio ,rangeis phase leads LI and L2 respectively. These infound mostappropriate. Systemsof this type clude relays ofthe oscillating magnet type somealready find considerable application for the contimes known as galvanometer relays which are trol of street lighting and may also be used for mechanically tuned to the different cadences effecting tarifi change or some form of load and when energised at suitable intervals build up control. a swing suflicient to operate their contacts.

Such systems have sometimes not provedper- 1 It is found that in suitable circumstances apfectly reliable because the applied signal has plication of the signalling currents to one low been masked or mutilated by surges or other tension network will result in the transmission parasitics fromwhich electric supply systemsare of these currents over thehigh tension network never entirely free. These parasitics maybe due to other low tension networks also. This method to switching operations or possibly to signals of of injection thus avoids the special insulation similar type spilling over from adjacent netdifiiculties which arise if injection is made direct works. It is highly desirable that in the event to the high tension network in order to be effecof any failure for this reason the operator should tive over a plurality of low tension networks have some means of knowing that the transmisconnected thereto. sion has not been effective so that suitable steps The manually operable selector switches SAI may be taken to ensure that the required switch and SAZ are coupled together so that they aling DB at O is in fact performed, The chief ways occupy corresponding positions and they object of the invention is to provide improved are shown resting on unwired' contacts which arrangements for actually testing whetherthe may be the normal position. The remaining signal has been properly applied to the network 3 ,contacts of switch SAI extend to the contacts of and whether the conditions then existing were galvanometer relays i th signal th com such as to enable it to produce itsproper effect. troler SRC for controlling'rhythms which may According to the invention, in an electrical be injected into the alternating current supply signalling system employingaudio frequency cur- 1 network, while the remaining contacts of switch rents SUDBIimDOSBd 0 e c c pp y ma s Or SA2 extend to corresponding supervisory reeilecting switching operations at a-plurality 0f sponding devices such as SR which are conremote points, supervisory equipment associated nected to the network at the transmitting point with thesignal transmitting equipment includes: and are similar to the responding devices which a unit similar to those employed at thelremote 1 are to effect the required switching operations. points for responding to signals, the supervisory 40 If for example the switch arms areset on conequipment; beingar-ranged to-control the signal tacts 3, the-rhythm relevant to a particular re transmitting equipment so asto cause the transmote controlling operation to be effected, say mission of a signal to be repeatedif itfails to the switching on of street lights, is selected over produce satisfactory operation of the supervisory switch SAI, and the lead SLA whose condition lim t. 7 i t is subsequently indicative of the operation or The invention will be, better, understood from non-operation of the supervisory relay SR in rethe following description ofone'methodoi? carrysponse to'the injected signal is selected over ing it into eiiect, reference being bad to the acswitch 8A2.

companying drawing; which shows by means of To initiate the transmission of the signal seacircuit diagram. the application of the invenlected, the push button switch KTS is closed motion to a system using signals of the so-called mentarily, thereby operating relay A which locks cadence type. By this is meant that the same up over itscontacts Al, at contactsA2 operates signalling frequency is employed for a number of relay G and at contacts A3 and A4 closes points different signals and the necessary distinction is in the paths to switches SAI and 8A2 respecmade by applying the signals at different cadences 65 tively. e y G pO op r t n at C a G1 or rhythms towhich the responding devices are prepares a locking circuit forrelay F, at contacts mechanically tuned.- The arrangement contem- G2 energises, the motor starter of the voice freplated is that the audio-frequency signalling curquency motor alternator VFMA. which proceeds rents are injected on to the phaseleads Ll, L2, to run up to speed, at contacts. G3 starts the L3 of a low tension portion of the network and synchronous motor ST which is used for signal v.) timing purposes and at contacts G4 and G connects direct currentpcsitive and n gative to the signal rhythm controller SEC. The synchronous motor ST drives cams which are arranged to actuate contacts STI, STZ and ST3 which are operated cyclically. It will be assumBdtha-t one cycle of operations is executed in sixty seconds and, by way of example, contacts STI close six seconds after the start and remain closed for the remainder of the cycle, contacts ST2 close twelve seconds after STI and remain closed for eighteen seconds and contacts ST3 close for two seconds six seconds before the end of the cycle. Thus the closed periods are: STI, 6-430; 5T2, Ilia-36 and ST3, 5456.

The direct current connected up by relay G to e si nal rhythm contr ler is pp d simultaneously to relay WG, the operation of which is slightly delayed since it is of the slow-to-operate type, and. to the lower coils of the galvanometer relays GA, GB and G0 in, series. When the coils of. t e relays are thus energised steadily, the magnets are. deflected so as to open contacts GAL G13 and-G0 contacts GB! and CI r ain effectual, however since it is assumed that the arm of switch SA! is s on Contact When relay WG operates, the lower galvanometer relay oils are dis nneeted to p m t the magnets to swing in the reverse direction and their repective contacts then lose. Wh n t ts A los h upper coils o the relays are ener is d momentarily nti the peration of lay XG and the oscil ating. magnet of. re y GA i age-in fliected in suc d rection as to op n its contacts whe eupon relay re as s. It will be ap hat the mo ing system of relay G i p e to osc llate. at i s natural .fr u ncy a at lay wi l operate and r lease in y hr i m- Contactors CA! and CA2 are normally'closed o that the output of he ice equency o r alternator VFMA is normally short-circuited and is consequently not initially transmitted over leads Ll L2 and L3 to the supply network; However, eighteen seconds after the start of the signalling cycle contacts ST2 closeto cause relay H to operate and, release in synchronism with contacts whereupon the actuating coil CA associated with the contactors is also alternately energised and de-energised to actuate the contactors accordingly. By this time the motor alternator has run up to speed so that each time th contactors open, its output at an appropriate frequency is extended over the resonant circuits including inductor IA and capacitor QA, inductor IB and capacitor QB and. inductor IC and capacitor QC to leads L| L2 and L3 whence it is applied to the supply network; In this manner regular pulses of voice frequency current are injected into the network, as selected by the switch SAI, for the eighteen seconds during which contacts S'Ift remain closed.

It will be apparent that had the selector switch been set to a different position, the rhythm of the pulses would have been determined by the frequency ofoscill'ation of the galvanometer relay associated with that position.

A already mentioned a number of supervisory responding; units such; as SR, eachof which conveniently embodies, two galvanometer relay elements individually tuned to respond to the pulses derived from two corresponding transmitting galvanometer relays, are connected tolive and neutral conductors of the supply network at the t ansm tti g. P n

. If the cadence signal is; injected correctly into 4: the network and is not appreciably mutilated or masked, the appropriate galvanometer relay of the supervisory responding unit SR will be set n operation and will close its contacts. The voice frequency signal superposed on the supply is applied to the resonant circuit comprising capacitor QD and inductor ID which is loosely coupled with a second resonant stage comprising inductor IE and capacitor QE to provide a resonant band pass filter. The signal is rectified by the rectifier bridge RB and extended to the local circuit containing the series. connected galvanometer relays on and off. It will be assumed that relay on" is tuned to the rhythm of the signal used for switching on street lights while relay oil is tuned to the rhythm for switching oil the street lights. The oscillating magnets of both relays are deflected slightly due to the initial D. C. pulse but only relay on will beat with the rhythm of the signal and eventually after a plurality of pulses close its contacts on whereupon the latching relay S is operated over its left-hand coil to close contacts SI. These contacts then complete a circuit over lead SLA to relay B which operates and at contacts Bl prepares a circuit for relay D, at contacts B2 opens a point in the circult for relay E and at contacts B3 completes a locking circuit for itself and lights lamp LSR to indicate that the signal has beencorrectly re-.

ceived.

When the contacts ST3 subsequently close after 54 seconds, relay D' operates, lock up at contacts DI and at contacts D2 releases relay A which in turn releases relay G. The interaction of relays XG and GA is then stopped and relay WG also releases. Relay D releases when contacts .ST3 open and when contacts STI open at the end Of the cycle the motor ST comes to rest. The lamp indication may now be cancelled and relay B re-.

leased by operating the push button KCSR, mo-

mentarily so that the circuit is fully restored to normal.

When it is required later to switch the street lights off, the selector switches SAI and SAZ are set on contacts 5 and the push button switch KTS is operated. The circuit functions in substanti'ally the same manner as beforev but in this case pulse signals appropriate to the galvanometer relay GB are injected into the network and'the galvanometer relay off embodied in the supervisory responding unit SR operates so that the right-hand coil of the latching relay S is energised' and contacts SI are restored to the position shown. A circuit is then completed over lead SLB and switch SA2 to operate relay B which functions as before.

A further function of the circuit is to perform automatic remote control operations at predetermined times under'control of a time switch. The signal's'appropriate to such operations are in- 2 jected and supervised independently of the selectorswitches but otherwise the'circuit functions as previously described. 7 V In this case the time switch TS assumed to be driven by a synchronous motor is set to close its 7 contacts T5! at a predetermined time and when this occurs relay TA operates, locks dependent upon relay D and performs the same functions as relay A. However, whereas contacts A3 extend a positive battery connection to the coils of galvanometer relays GA, GB. and GC by way f selector switch SAI, contacts TAZ extend the connection direct to those relays. Similarly contacts, TA3' connect relay B direct to the appropriate switched live lead of the appropriate.

supervisory responding unit. It will be understood that the circuits could readily be arranged to prevent the sending of signals by manual control while the time switch control was effective or vice versa and this might be desirable in practice.

Assuming now that switching on of the street lights is again required to be effected but that during the injection mutilation of the signal occurs to such an extent that the relay on a in the supervisory responding unit does not operate effectively. Consequently contacts SI are not changed over and relay B fails to operate. In this case when contacts ST3 close, relay E operates over normal contacts B2 and thereupon at contacts El provides a locking circuit for itself, at contacts E2 prevents the operation of relay D and at contacts E3 operates relay C. Relay C looks at contacts Cl, at contacts C2 operates relay F, and at contacts C3 completes a circuit for the signal failure alarm bell AB. Relay F locks up at contacts Fl, at contacts F2 opens the initial circuit for relay E and at contacts F3 prepares a circuit for relay D. Relay E releases when contacts ST3 open. may be cancelled at any time by operating the push button switch KCA momentarily to release relay C.

Since relay D is not operated, relays A, G, F

and WG remain operated so that the motor ST continues to run and the signal sequence is repeated as before when contacts STZ close. If this second injection is successful, as will generally be the case since it is improbable that muti- The audible alarm 3 lation or masking will be of so long a duration as to prevent it, relay B subsequently operates to indicate the correct response of the supervisory equipment as before. Relay B also operates relay D which results in the release of relays A, G,

WG and F. Finally relay D releases when contacts ST3 open. The indication lamp LSR may be extinguished by operating switch KCSR, and the circuit is then fully restored to normal.

If however the second injection also is unsuccessful, relay B again remains inoperative and lamp LSR again fails to light. When contacts ST3 close, relay D operates over contacts E2 and F3 and brings down relays A, G, WG and F assuming that relay C has already been released by operation of key KCA. A circuit is then again completed for relay E which in turn re-operates relay C so that the alarm is again sounded. If relay C has not previously been released, it maintains relay F operated so that re-energisation of relay E is not possible. Relay D releases when contacts ST3 open and no further injection operation takes place since relays A and G are deenergised. Clearly there would be no difficulty in arranging for the injection operation to be repeated until successful if such an arrangement were found to serve any useful purpose but in practice it is likely that if two successive injections have been unsuccessful some more serious trouble has developed which will require investigation by the operator.

It may be mentioned that the arrangement shown whereby the coils of the galvanometer relays in the equipment SRC are connected in series is a convenient one in practice but the coils could also be connected separately to the contacts of the switch SAI, if necessary in series with suitable resistors. Moreover the provision of two coils for each relay is a convenient arrangement to ensure an adequate initial swing but the effect could also be produced with a single coil.

The invention therefore provides a simple arrangement for improving the operation of equipment for signalling over electric supply mains whereby greater reliability and convenience are secured without any appreciable increase in the amount of equipment required.

I claim:

1. An electrical signalling arrangement for operating a plurality of switching devices connected to electric supply mains at separated points and responsive respectively to signalling currents of audio frequency of different cadences superimposed on said mains comprising a source of signalling current located at a control station, means at said control station for applying said source to said supply mains at difierent cadences, a manually operable rotary selecting switch, a first Wiper on said switch arranged to select the particular cadence at which signalling current is applied, a plurality of switching devices connected to said supply mains at said control station and responsive respectively to the different cadences at which signalling current may be connected to said mains in accordance with circuits completed over said first wiper, contacts controlled by said switching devices connected to the bank contacts co-operating with a second wiper of said switch and means connected to said second wiper for terminating the application of said signalling current to said mains after a predetermined period if the switching device corresponding to the desired cadence has been operated.

2. An electrical signalling arrangement for operating a plurality of switching devices connected to electric supply mains at separated points and responsive to periodic currents of audio frequency superimposed on said mains comprising a source 1 of signalling current located at a control station,

means at said control station for applying to said supply mains a signal of predetermined cadence,

a manually operable key and a time switch each arranged to render said means effective, a manually operable rotary switch for selecting the cadence of said signal by circuits completed over a first wiper of said switch, a circuit controlled by said time switch independently of said manually operable switch for determining the cadence of said signal, a plurality of switching devices responsive respectively to signals of difierent predetermined cadences and individually connected to the bank contacts associated with a second wiper of said switch, a further switching device responsive to signals of the cadence determined by said time switch and means controlled by each of said switching devices for terminating the application of said signal after a predetermined period.

JOHN G. GORDON-WRIGHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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