US2331391A - Signaling system - Google Patents

Description

Oct. 12, 1943. A. E. HAGUE 2,331,391

SIGNALING SYSTEM Filed Nov. 19, 1942 3 Sheets-Sheet l FIG. 4

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CENTRAL OFF/CE CONTROL 5 TA T/ON lNl ENTOR A. E. HAGUE A T TORNE Y SIGNALING SYSTEM Filed NOV. 19, 1942 3 Sheets-Sheet 2 T0 ALARM C C T 'INI/ENTOR A. E. HAGUE ATTORNEY A. E. HAGUE SIGNALING SYSTEM Filed Nov. 19, 1942 Oct. 12 1943.

3 Sheets-Sheet 3 V 3/ 7 E M m R k 9% $1 7 m N T HHH h Semi HHH r uHu I. W; A I I 4358i I (m5 3n lg Rm $5 J H A H: W h. b3; w P a M l 3 3mm: :2 i .1 PHI-EU. Wu n/mwn N2, .n 19.; Wu awn W 3 ml W W an W S 11 W Y ."J T hf PI b 3n v r WL|- r) UL l l r ["m. w wam m r] n 8m 3m FL QM n NR 3 H N1 Hu wwl Hu 9% 4 4 wj a E? 2 QNM QNM 2 l m2 0: =35 own Emma 33 NM. .H 9L. n 20R wt .w 655 w 3 Hh md HU d E" l EQG 5 3% 655 T wmm m. UP. Emma 14 g 3% Patented Oct. 12, 1943 UNITED STATES PATENT OFFICE SIGNALING. SYSTEM Alfred E. Hague, WestOrange, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application November 19, 1942, Serial No. 466,157 '5 Claims. (01. 179-5) This invention relates to signaling systems and more particularly to a continuously self-checking arrangement whereby an attendant at a control station can cause the simultaneous operation of a plurality of distant'signal devices in either of two distinctive manners and receive an answer,-"

back signal in the event that all thesign'al devices function in the manner desired. 7 I

Specifically, a feature of the invention resides in a siren control arrangement for emergency warning service comprising a control key station at a police station, firehouse, or other suitable location, a control circuit located in a telephone central office or other suitable switching point,

and a plurality of outlying stations equipped with motor-driven sirens or other suitable signal devices. I

The control station is equipped with. a two- Way keyand a telephone ringer, receives rectified direct current over a pair of conductors from the central office and has two other signal pairs extendingto the central office. When the control key is normal, direct current is connected to both of thesignalpairs in parallel thereby holding two three-position polarized relays at the central oflice in one of their circuit closing positions. When the key is actuated to either of its operated positions it reverses the, current over one of the signal pairs and substitul s' the ringer for the direct current normally connected to the other signal pair. Reversal of current over the one pair causes the corresponding polarrelay at the central office-to open one circuit and close 1 a second circuit and disconnection of the other signal pair from the direct current causes its associated polar relay torelea'se and assume its neutral or open circuit condition. The reversal of the one polar relayandthej release, of the other causes the connection of ringing current to a plurality of siren station lines which ringing current is periodically interrupted, or ,c'ontinw ously applied, depending upon which polar relay is reversed. v When the central oifice circuit functions due to a reversal over one of the signal pairs, ringing current is applied to the other signal pair, to which the ringer is connected at the control key station, which serves as an indication that the anyone ofthe siren stations fails to operate, the ringer at the control key station is silenced, thereby indicating to the control station attendant that the system is not functioning properly. The invention will be understood from the followingdescription when read in connection with the I accompanying drawings, the figures of which, when arranged in accordance with Fig. 4, show an embodiment of the invention in which the control station is shown to the left of the vertical broken line XX' of Fig. 1; the siren stations are shown, above the horizontal broken line, on Fig. 3, and the balance of Figs. 1 and 3 and all of Fig. 2 show the equipment andcircuits atthe telephone central oflice.

In the following description the two characteristically different signals sounded by the sirens will be 'hereinafter referred to as red and white signals, a red signal being defined as the intermittent sounding of the sirens at such a rate as to produce intermittent or undulating sound and a white signal being defined as the continuous operation of the sirens for a period of about two minutes. i General description Referring to-the drawings, the control station, Fig. l, is equipped with a lever type key I having anormal and two locking positions, one of which positions-is the warningor red" position and the other the all-clear or white position.

The control station key I is connected to the central office over three pairs of line conductors L1, L2 and L3, one pair, L1,-,being a current supply line while the other two pairs, L2 and L3, serve as red-and white signaling lines, respectively.

Associated with the key at the control station is a telephone ringer 2 which sounds upon operation of the key in either direction and continues to do so in unison with the sirens, intermittently .inthe case of the red signal and steadily in the case'oi'thewhite. The ringer 2 ceases operation if any siren fails to receive starting power. Further, when the key is first actuated to either of its looking positions, the, failure of the ringer to respond indicates trouble in the lines between the central ofiice circuit is functioning properly.

control station and central ofiice orin certain of the central office relays.

At the central office, shown at the right of the verticalbroken line X-'X', on Fig. 1, is located a current supply circuit and a set of polar relays associated with the three control station lines L1, Lzand L3, together with various relay equipments 'for transmitting red and white signals to the siren stations simultaneously and for returnmakes the ringer operation ing a response signal to the control station. In addition there shown auxiliary equipment for keeping a continuous check upon the lines and for operating central oflice alarms under trouble conditions.

Supplying the control station with direct current is a va-ristor-rectifier 3 which in turn is supplied from the regular central office ringing generator,- lwl iichl arrangement. affords a. nongrounded source ofdire'ct current which is independent of commercial power failure and is free of the eiiect of ground on the control station lines. Similarly, the non-grounded operation of the control station ringer 2 previously mentioned grounds on the line. This method of supplying direct current to the control station makes it possible to use reverse battery signaling over the red and white lines so that ordinary line troubles do not cause false operation of the polar relays at the central oflice. Short circuits on the control lines are detectable by the release of the polar relays and the operation of an alarm. A continuous check for open'siren station lines, at the top of Fig. 3, is made by means of relays 30I, 302, etc. which are normally held operated in series with marginal relays 304, 305, etc., the station lines, and the siren stations. .Short circuits in the siren station lines are detected by the operation of the respective marginal relays 304, 305, etc., as are also trouble grounds which interfere with signaling. Signaling over the siren station lines is transmitted to the sirens by supplying ringing current through tripping relays 301, 308, etc. to ringing relays, such as 3I0, located at the siren station. The latter relays, 3I0, apply power directly to the siren motor. Upon closure of the power circuit a check relay 3 at the siren station operates to bridge the line with a low resistance shunt which operates the tripping relay, 30 1 for example, at the central oifice. v q

At the central oiiice a red.- signal is communicated to the siren network by intermittent operation of the siren line ringing relays 3I2, 3I3, etc. under control of a relay timing circuit as shown at the bottom of Fig. 2. This timing circuit may be set to produce such closed and open intervals as may be required to give an intermittent or undulating tone on the sirens or other warning devices. The centraloflice control circuit checks to see that allthe siren stations receive local power, as indicated by the operation of all tripping relays in the siren station line and then it continues 'the operation' of the control station ringer in unison with 'the'sirens. If any siren station fails to respond the control station ringer is silenced and a centralofii'ce alarm is given.

The white signal, which is continuous, and usually of about two minutes duration, is transmitted in the same way as the red signal except that in this case the timing relays are notbrought into play to interrupt the ringing current which controls the sirens.

Initiation of a. red signal We will first assume that a so-called red or warning signal is to be sounded by the siren, shown at the top of Fig; 3, which warning signal is initiated by an attendant at the control station, shown in the upper left corner of Fig. 1 by operating the key [iii to the right, or red position.

It will be noted that when key IN is normal, rectified direetIcurrent, supplied over line L1, by the rectifier I03 at the central office, is connected,

independent of] by means of the normal contacts of the key in parallel with the signal lines L2 and L3, which lines in turn are connected in series with respective polar relay pairs I04, I05 and I05, I01 in such a direction that the contacts of relays I04 and I06 are open and the contacts of relays I05 and I01 are closed.

When key IOI is operated to the right, conductors I and.'I09 of the' lineLz are disconnected at contacts H0 and III of'key IOI from the current supply line L1 and transferred to the ringer I02 whereupon relays I06 and I01 release, permitting their armatures to assume a mid, or neutral position. Key IOI also opens its contacts .I I4 and II and closes its contacts H5 and H1 thereby reversing the polarity of the direct current connected to conductors I I3 and H9 whereupon relays I04 and I05 at the central ofiice move their armatures to the right whereby battery is disconnected from the armature of relay I05 and ground is connected to the armature of relay I04.

Relay I04 in closing its right-hand contacts completes the circuit to operate relay. I20 and relay I01 in releasing opens the normally closed circuit for SIOW-tO-IBIGEISG, relay I2.I, which relay in closing its normal or back contacts operates relay I22 thereby connecting ground over conductors I23, I24 and I25 to one terminal of relays 3I2, 3I3 and 3i4, respectively. 7

Relay I 20 in operating opens its contacts I25 thereby deenerg'izing, relay I21 which relay, however, is slow to release and before it releases is reenergized in a circuit from ground at contacts 33I of relay 3I9 over contact 330 of relay 3I8 and contact 329 of relay 3I1, to be later referred to. Relay I20 also closes its contacts I28 thereby connecting ground to conductor I29 to prepare an operating, circuit for relays I30 and I3I when the tizning circuit functions. Further, relay I20 in operating opens its contacts I32 thereby disconnecting relays I05 and I01 from line L3 and by closing its contacts I33 and I34 prepares a circuit to apply ringing. current to line La, and its connected ringer I02, when relays I22, I30 and I3I all become operated. Still further, relay I20.in operating closes its contacts I35 to operate relay 20I which grounds, at its contact 202, the start, conductor 203 for the timing circuit shown at the bottom of Fig. 2.

The relays of the timing circuit operate as follows: Ground on start conductor 203 causes operation of relays 204 and 205 in the order named. The operating circuit of relay 204 can be traced from ground on conductor 203, contacts 205 of relay 201, contacts 208 of relay 205, conductor 209 and winding of relay 204. Operation of relay 204 in this circuit closes its contacts 2I0 thereby extending ground present on conductor 209, to the winding of relay 205 over contacts 2II of relay 2I2, contacts 2I3 of relay 2I4, and contacts 2I5 of relay 2I6. A parallel operating circuit of relay 205 can also be traced from ground on conductor 203, contacts 242 of relay 204, conductor 244, contact 243 of relay 201 to the winding of relay 205. Relay 205 in operatin locks in a circuit including its contacts 223 and contacts 203 of relay 201 to ground on conductor 203.

When relay 205 operates, if the brush of interrupter 2I1 is on a grounded segment, relay 2 l 8 operates immediately and, While holding relay 204 operated over its own contacts 2I9 and contacts 221 of relay 204, it extends ground over its contacts 220, and contacts 22I of relay 204, to the winding of relay 2I2 whichthereupon operates.

completing a circuit to reoperate relay 204 which When the interrupter. 2171 removes ground from relay 218 this relay f relealsesthus opening its contacts 219whichrelease relay 204 while relay 212 remains operated in a holding circuit completed at its own contacts 222 to ground over contacts 213 of relay 214, contacts 215 of relay 216, contacts 223 of relay 205, and contacts 2060f relay '1to ground on conductor 2G3 maintained at contacts 202 of relay 201. v

'' The next closure of groundat interrupter'211 re operatesrelay 218 which now extends ground over its contacts 220, contacts 224 of relay 204 and contacts 225 of relay 212 to the winding of relay 214 which relay operates and locks, at its contacts 226, over contacts 215 of relay 2111, contacts 223 of relay 205, and contacts 208 of relay 20'1't0 ground on conductor 203.

Relay 214 in operating opens its contacts 213 thereby interruptingthe previously traced holding circuit for relay 212 but this relay is held operated' in a circuit including. its own contacts 228, contacts 229 of'relay204 and contacts 2139f relay 218 during the interval relay 2 I 8 is operated. j The next time relay 21B releases, due to removal of ground by the interrupter, it"opens its contacts 219 which release relay. 212. When relay:

218 again operates it extends ground over its contacts 220 to operate relay 216, which circuit includes contacts 224 of relay 204, contacts 230 of relay 212, and contacts 231 of relay 214 to the Winding of relay216 which now operates therebyopening, at its contacts 215, the holding circuit for relay 214 previously traced. This relay, however, does not release at this time as it is held operated over its contacts 232, contacts 233 of rela 212, contacts .229 of relay204, and contacts 219 of relay 218 while this latter relay remains operated.

, ,Relay 216locks itself at its contacts 234 over contacts 223 of relay 205 and contacts 205 of relay 201 to conductor 203. When relay 218 again releases, it opens its contacts 219 thus releasing relay 214. 1 r i The next operation of relay 2 18 extendsgroundj as before, to operate relay 211! the circuit for which can be traced from groundon conductor 2113 contacts-220 of relay 218, contacts224 of relay 204,

contacts 2300f relay 212, contacts 235 of relay 214, and contacts 236 of relay 216 to the winding of relay 20'1,-which relay operates and opens its contacts 206, thus opening'the original locking circuit for relay 215 but due to the fact that relay 214 is now released an alternative holding cir'-' f cuit for 'relay216 is now established during the period relay 218 is operated which circuit can be traced from ground on conductor 203,- contacts 219 of relay 213, contacts 2230f relay 204, contacts 233 of'relay 212, contacts'240 of relay 214, contacts 241 and the winding of relay-216 to battery. This circuit, just traced, for holding relay 215 also holds start-relay 205 'operated'as long as relay 213 remains operated, although the original locking circuit for relay 2315 is opened'at con-' tactsxwfi of relay 201 when that relay .operated. As'long as relay 205 remains operated, relay 201 is locked in a circuit including its own contacts 231 and 230 and contacts239 of relay 205 to ground on conductor 203.

. The next time interrupter 211 releases relay 218 the circuit just traced for holding relays 216 and 205 is opened and both relays release. The release of relay 285 opens the lockingcircuit of relay; 201 and this relay releases. The release ofrelay 205 also closes its contacts 2118 thereby again mined 'point- 148 cycle of the timing circuit takes place which is repeated as long as relay 201 remains operated. v During the period between the operation of relay 204 and the subsequent release of relay 212 conductors 129 and 245 are connectedat either contacts 246 of relay 204 or contacts 241 of relay 212, thereby operating relays 130 and 131 in parallel, the circuit for which can be traced from ground, contacts 128 of relay'l20, conductor 120, contacts 246 or 241 of relay 204 or 212,.respectively,"conductor'245 and to battery and ground through the winding of relays 130 and 131 in? parallel.

When relays 130 and 131 operate they close a circuit to operate ringer 102 at the controlkey station which can be traced from the lower terminal of the secondary winding of theringing' current transformer I36, condenser 131, contacts 133 of relay 1311, contacts 139 of relay 131, contacts 140 of relay 122, contacts 141 of relay 142,

contacts 243 of relay 249, contacts 133'of-re1ay 120, to conductor 109 of the line L3 extending to the control key station and thence over contacts 143'and 113 of key 101, through the ringer 102,

over contacts 112 and 144 of key 101 to line conductor 1'08, thence over conductor 145, contacts 134 of relay 120, contacts 251! of relay 249, con ductor 145and condenser 14?, to a'predeterin the secondary winding of transformer136. v

Ringer A 102' operates in this circuit and indicates at thecontrolkey station that the central oihc'e circuit has functioned properly. In this connection it will be noted that the circuit for ringer, 102 includes contacts 14 1 of relay 142 which relay is normally held operated from ground overa chain oi: contacts formed by the operated conditionof relays 301, 302 and 303 and the release of any one of which will cause relay 142*to release, thus silencing" the Thisfeature willbe later referred to.

Simultaneous with the operation of ringer 102, relay. 130'connects battery to conductors 148,149 and which extendto relays 312, 313 and 314, respectively. and, previously, when relay 122 operated upon the initiation of the red signal it connected ground at itsright-hand contacts to conductorsl23, 124 and 125 which extend to the remaining," terminals of relays 312', 313 and 314, and the'refore, upon the operation of relay 130 'relays312, 313 and 31,4 operate immediately.

-Directing our attention firstto relay 312 it will be noted that its operationdisconnects checking relays 301and 304 from the line SL1 extending to siren station 1.

This relay 312 in operating also closes itscontacts 315 thereby operating relay 153 in a circuit including conductor 316 and contacts 154 of relay 131.. Relay 153 looks to ground at contacts of relay 12.8, opens its lowermost contacts to release relay 151, if operated, andby closing its contacts 155 operates relay 251 which looks to ground at the lowermost contacts of re-,. lay 2111 in the timing circuit. Relay 251 in op-f erating closes, at its contacts 252, a circuit to operate relay 155 which connects ground over; conductors 156, 15'! and 158 to prepare a holding,

ringer 102.

circuit for relays 3I1, H8 and 319; respectively;

when they operate' Reverting to relay 312', which is now operated under control of relay I30, ringing current, from source .320, is connected over its contacts 32I, 322 and 323 to the line SL1, in series with tripping relay 301,'to which line is connected a ring-up relay 3I0 in series with condenser 324. Relay 3I0 operates in response to ringing current supplied by source 320 and by closing its left-hand contacts connects the power supply circuit to the siren motor in parallel with relay 3I I which relay operates if the power supply circuit is energized.

Relay 3 operated closes its contacts which closure, in cooperation with the right-hand contacts of relay 3I0, short-circuits high resistance 326 which is normally connected, inseries with inductance 321, in parallel with the ringing relay 3I0 across the line SL1. This short circuit around resistance 320 lowers the effective resistance of the line SL1, as seen from the ringing current source 320 at the central oflice and consequently an increased current flows through the tripping relay 301 suflicient to cause its operation thus connecting ground to operate relay 3l1 which locks up at its contacts 328 to ground supplied over conductor I56 by relay I55 previously referred to; As the timing circuit continues to function relay I30 continues to operate and release, as determined by the timing circuit, thereby operating and releasing relay 3I2 which in turn causes the siren to operate intermittently.

The foregoing operation also takes place for the other siren stations under control of relays 3I3 and 354, respectively. When relays 3I8 and 3I0 have also operated and looked under control of relay I55 2. chain circuit is established, including contacts 329 -01 relay 3I1, contacts 330 of, relay 3IB, and contacts 33I of relay 3I9 and conductor 332 to hold relay I21 operated, which relay due .to its slow characteristic does not release quickly when relay I20 operated. Relay I21 holds relay I42 thus maintaining the circuit closed for the ringer I02 which continues to operate under control of relays I30.and I3I as they alternatively operate and release under control of the timing circuit.

,Any trouble onthe lines L1, L2 or Lsbetween the control station and the central office, while no signal is being sent, which results in the release of relay I05 or I01, will release relay I2I followed by the release of relay I21 which causes alarm relay I5I to operate thus. lighting lamp I52.

If a siren line,such as SL2, should become open test relay 302 will release thereby opening the normal operating circuit of relay I42 which relay releases and by closing its left back contact energizes relay I59 to light lamps I60 and I 6I..

This same alarm is produced in the case of a short-circuit of line SL2, for example, which opcrates marginal relay 305 thereby connecting ground to conductor 333 which also operates relay I50.

Should the power supply for any siren station fall, for example station I, relay 3I I will not operate and the resistance of the line will remain high and relay 301 will not operate. Consequently, relay 3I1 will not operate and hence relay I21 will not receive holding ground, at contacts 329 of relay 3I1,.and will release thus opening the locking circuit for relay I42 which releases and closes its left contact to operate relay 26 I in a circuit including contacts 260 of relay 25I. Relay 26I lights lamp 262. Relay I42 in opening its right-hand contact silences the ringer I02, which up to this time has been controlled by relays I30 and I3I, as previously described.

Checking the timing circuit Interrupters 253 and 254 are provided for the purpose of checking the operation of the timing circuit. When relay 20! operates, in response to operation of relay I20, upon the initiation of a red signal, the timing circuit is started upon its cyclic operation, as previously described. At the same time, relay 20I closes its contacts 255 to prepare a circuit to operate a so-called pick-up relay 256 when interrupter 253 connects ground thereto. When relay 256 operates it closes its bottom contacts to establish a locking circuit for itself under control of relay 201 in the timing circuit which can be traced from ground at contacts 251 of relay 201, lower contacts of relay 256, contacts 255 of relay 20I, and winding of relay 256. The interrupters 253 and 254, whose commutators are mounted on the same shaft, operate at such a slow rate that under normal conditions relay 201 will operate and remove the holding ground for relay 256 before ground is applied at the contacts of interrupter 254. If, however, the timing circuit should stop before relay 201 operates, thus holding relay 256 operated until interrupter 254 applies ground, a circuit will be established to operate relay 258 and light lamp 250 over contacts I63 of relay I20.

White signal Now we will assume that a so-called white or all-clear signal is to be sounded by the siren which signal is identified as a continuous or noninterrupted blast lasting for a considerable interval of time, for example, for upwards of two minutes.

The white signal is initiated, as previously indicated, by operating key IOI to the left thereby disconnecting conductors II 8 and H9 of the line L2 from the direct current source supplied over line Li and connecting them to the ringer I02, and also reversing the conductors I08 and I00 of line L3 with respect to the conductors of the current supply line L1 thereby reversing the current flowing through the polar relay pair I06 and I01 whereupon relay I06 moves its armature to the right to connect ground to conductor I62 thus operating relay 249. Relay I05 releases and relay I01 moves its armatures to the right thus opening at two points the normally closed circuit for relay I2 I which releases.

Relay I2I in releasing opens its left front contact thus opening the normal energizing circuit for relay I21 but this relay is slow to release and will be reenergized and held operated by ground on-conductor 332 if relays 3I'I, M8 and 3I9 operate immediately responsive to the sirens at stations I, 2 and 3 receiving power, as previously described.

When relay I2I closes its back contacts it connects ground to operate relay I22 which in turn connects ground to one terminal of each of the ringing control relays 3I2, M3 and 3M. Relay 249, which is now operated, connects ground at its contacts 263 to operate relays I30 and I3I directly which relays, at their contacts I38 and I33, respectively, complete a circuit for actuating the ringer I02 at the control station which includes contacts 264 and 265 of relay 249. Relay I30 in operating connects battery to conductors J48, 149 and I50 thereby completing operating circuit for relays 3l2, 3l3 and '3l4 to initiateloperation' ofethe sirens at stations I, 2 and-3 .in the same manner as described in connection with the'red signal.

Due to the factthat relay I04 is deenergized during the transmission of the while signal, relay I20 remains released and consequently the timing circuit does not function and, therefore, as long as the key I! is operated to the left or white position, relay 249 will hold relays 3l2, 3| 3 and 3M operated thus causing the sirens to sound a continuous (all-clear) signal.

Trouble on the lines L1, L2 or L3, failure of power supply at any of the siren stations, or trouble on any of the sirenstation lines will be indicated in the same manner as previously described.

Except for the elimination of the timing circuit and holding relays I30 and |3I operated as long as the key llll is operated, the circuit functions in the same manner as previously described for the sending of a red signal.

What is claimed is:

1. In a signaling system, a source of direct current, first and second pairs of conductors, multiposition switching means adapted when in a first position to connect one end of each pair of conductors in parallel with said source, when actuated to a second position to reverse the conductors of the first pair with respect to the source and disconnect the second pair therefrom, and when actuated to its third position to reverse the conductors of the second pair with respect to the source and disconnect the first pair therefrom, a polarized relay terminating the other end of each pair of conductors, each relay having a neutral or open circuit position when the relay is deenergized and being adapted to close one or the other of two circuits, depending upon the direction of the flux therein when the relay is energized, a signal device and means controlled by said polarized relays for selectively actuating said signal device in either of two manners depending on whether said switching means as actuated to its second or third position.

2. In a signaling system,,a source of direct current, first and second pairs of conductors, multiposition switching means adapted when in a first position to connect one end of each pair of conductors in parallel with. said source, when actuated to a second position to reverse the conductors of the first pair with respect to the source and disconnect the second pair therefrom, and when actuated to its third position to reverse the conductors of the second pair with respect to the source and disconnect the first pair therefrom, a pair of polarized relays terminating the other end of each pair of conductors, each relay of each pair having a neutral or open circuit position when deenergized and each pair being adapted to close one or the other of two circuits, depending upon the direction of the flux therein when energized, .a plurality of signal devices, means controlled by said polarized relaysfor simultaneously actuating all of said devices in either of two distinctive manners, depending on whether said switching means is actuated to its second or third position, and means for giving an alarm if any one of said signal devices fails to respond.

3. In a signaling system, a source of direct current, first and second pairs of conductors, multiposition switching means adapted when in a first position to connect one end of each pair of conductors parallel with said source, when actuated to a second positiontoreverse the conductors of the first pairiWith respect-to the source and disconnectthesecond pairtherefrom, and when actuated to its third position to reverse the-conductors; ofv the second pair with respect to the source and disconnectthe firsti pair therefrom, a pair ofpOlarlZed relays -;terminating the other end of each pair ;of;conductors, each relay of each pair, having a neutralior .openpircuit position when deenergized and each pair being adapted to close one or the other of two'circuits, depending upon the direction of flux therein when energized, a plurality of signal devices, a local source of electrical power for operating each ,of'

said devices, means controlled by said polarized relays for selectively applying said power to said devices in either of two distinctive manners depending on whether said switching means is actuated to a second or third position, and means for giving an indication if any of said devices fail to receive power. 1

4. In a signaling system, a control station, a central station, a source of direct current, first and second pairs of conductors between said'control and central stations, multiposition switching means at said control station adapted when in a first position to connect one end of each pair of conductors in parallel with said source, when actuated to a second position to reverse the conductors of the first pair with respect to the source and disconnect the second pair therefrom, and when actuated to its third position to revers the conductors of the second pair with respect to the source and disconnect the first pair therefrom, a pair of polarized relays terminating theother end of each pair of conductors, each relay having a neutral or open circuit position when the relay is deenergized, one relay. of each pair being adapted to close a circuit when said pairs of relays are energized in one direction and the other relay of each pair being-adapted to close a circuit individual thereto when energized in an opposite direction, a plurality of signal devices,

a local source of electrical power foreach 'of said devices, means controlled by said polarized relay for selectively applying said power to said device, in either of two distinctive manners depending on the energized direction of said polarized relay, a check signal device at said control station, mean for operating said check signal responsive to the deenergization of one of said pairs of polar relay and a reversal of energization of the other pair, and means responsive to failure of any one of said signal devices to receive power to silence said check signal device.

5. In a signaling system, a control station, a central station, a source of direct current, first and second pairs of conductors extending between I said control and central stations, multiposition switching means at said control station adapted when in a first position to connect one end ofeach pair of conductors in parallel with said source, when actuated to a second position to reverse the conductors of the first pair with respect to the source and disconnect the second pair therefrom, and when actuated to its third DOSi-r tion to reverse the conductors of the second pair with respect to the source and disconnect the first device at said control station, means for operat- 10 p in'g said check signal responsive to the deenergization of one of said pairs of polar relays and a reversal of energization of the other pair, and means responsive to failure of any one of said signal devices to receive power, to silence said check signal device, said means for operating said check signal device including the conductor pair disconnected from the direct current source.

ALFRED E. HAGUE.

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