Патент USA US2132857код для вставки
Oct. 11, 1938. A. G. LANG El‘ AL 2,132,857 TELEPHONE SYSTEM Filed March 16, 1937 5 Sheets-Sheet l vN NM. m.ut INVENTORS. A. G.LANG '7TH.NEELV vATTORNEY Oct. 11, 1938. ' ’ ' A. G. LANG ET AL 2,132,857 TELEPHONE SYSTEM Filed March 16, 1937 ' 3 Sheets-Sheet 2 .AGLLANG WVEN-TORSTHNEELV BV ATTORNEY ‘Oct. 11; 1938. - A. G. LANé ET AL " 2,132,857 TELEPHONE SYSTEM Filed March 16, 1937 5 Sheets-Sheet 3 95 92 MARE/MA_L E.206.F3IGS. L(PA1T/.653709DIOA/NP6TT0RUNK AUTOMIEXCHANG PHI-Q ‘ grroR/wsy 1 Patented Oct. 11, 1938 2,132,857 UNl'i‘ED STATES PATENT OFFICE TELEPHONE SYSTEM Albert G. Lang, Whitestone, and Thomas H. Neely, StewartManor, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 16, 1937, Serial Nb. 131,144 3 Claims. (01. 179-27) This invention relates to telephone systems and more particularly to semiautomatic telephone systems. An object of the invention is to facilitate the _ completion of calls through a toll switchboard to subscribers’ lines in’ an automatic community (unattended) exchange over operators’ connect ing ,(cord) circuits primarily arranged for com ‘ pleting calls over trunk circuits to subscribers’ 10 lines in main automatic exchanges at which ex changes a reversal of the line battery occurs when the ?nal selector switch connects with the called line. time and tends to slow up the service, particularly when a considerable number of such calls are completed at certain hours of the day. A speci?c object of the invention is therefore to provide facilities whereby a single cord circuit can be interchangeably used to complete calls to trunks of either of the above described types without any of the objections above described. A feature of the invention whereby the forego ing specific object is obtained, resides in such modi?cations of the present operator’s cord and position circuits and community o?lce trunks that upon completion of dialing on a community office > In toll switchboard cord circuits adapted for 15 luse with trunks of the above-described latter type, the dial circuit, once ‘it is connected to the cord circuit, remains associated therewith until the before-mentioned reversal occurs at which time a polarized relay operates in the toll operator’s V iolposition to disconnect the dial circuit from the cord. The circuits of what are commonly known as community dial o?ices, i. e. relatively small un attended satellite of?ces, are in some cases not 25'; arranged to transmit a battery reversal when the switch connects with the called line and hence a toll cord arranged to function with trunks to a main exchange over which a reversal occurs when the called line is seized could not be operated in trunk, and the releasevof a. positional dial key, the trunk conductors at the toll o?ice will be 15 reversed to supply line battery to the cord in a reversed direction thereby operating a polarized relay in the position dial circuit to disconnect the dial circuit from the cord and condition the cord circuit for conversation in the'same manner as 20 when the call is extended to a main exchange and a line connected to the trunk, the dial is connected and the speech transmission circuit through the cord is opened, all'under control of a polarized relay in $51‘: the position circuit which only operates when the line battery is reversed. ' To overcome this dii‘?culty, in the past, it has been the custom, when community of?ce trunks , are present in the same switchboard with trunks 4.0‘ to main exchange, to provide a special dial jack for each community o?ice trunk and, when a call is to be extended thereover, after plugging up the main trunk jack with the cord circuit to be used in completing the connection, to plug another cord circuit, from that over which the connection 7 is to‘bebompleted, into the dial jack. The oper ator then operates the dial key and actuates the dial now associated with this other cord and upon the completion of dialing removes this other cord 50 'from the dial jack whereupon a talking connec tion is established by means of the ?rst cord. By this sequence of operation, the operator is enabled to complete calls over both types of trunks, but, in the case of connections to community o?ice 7 55ytrunks, the double handling of cords consumes occurs the following description and accompanying 25 drawings, Figs. 1, 2 and 3, which ?gures, when arranged as shown in Fig. 4, represent a toll oper ator’s cord circuit together with its associated position and dial circuit (as shown in Figs. 1 t the same manner when connected to a community _ and 2) o?ice trunk for the reason that once the cord is battery reversal , automatically thereat when the called line is seized. Other features will appear hereinafter from adapted to be connected to either a standard trunk circuit terminating at an auto matic central office, arranged to reverse the bat tery supply to the cord when a called line is seized, or tobe connected to, a trunk circuit ex tending to a so-called community dial of?ce not so arranged, as shown in Fig. 3. ' Fig. 1 of the drawings shows the position dial circuit. Fig. '2 shows a cord circuit with the operator’s telephone circuit, and Fig. 3 shows the outgoingjack of a standard out-dial trunk to 40 an automatic exchange and the circuit at the out going end of a trunk to a community dial office arranged to simulate a battery reversal back into a connected dial circuit when‘ the position dial keyis released at the termination of the dial ing operation. ‘ V A description of the operation of thecircuits of this invention follows: Assuming that the operator is what is known as an inward operator and has answered a call by inserting the rear plug of her cord circuit C, Fig. 2, into a calling toll line, not shown, and desires to extend the connection to a station in an auto matic o?ice reachedover trunk l0, she will ?rst operate'the trunk dial key I thereby operating 55 ' 2 2,182,857 relay 2 in a circuit which can be traced from line, if the line is idle, current flowing back over - ground, contacts 3 or‘ key I, contacts 4 of relay 5, the trunk to the dial circuit is reversed thereby contacts 6 of key i and winding of relay 2 to causing polarized relay I’! to operate.‘ Operation battery. Relay‘Z in operating connects battery of this relay opens the circuit including relays it, ill and I2 thus permitting relays i9 and i2 to re to leads ‘l1; ‘52, etc., to operate dial relays, such as ' l2, individual to the respective cords in the posi— tion, when the front plug 9 of the cord is con nected to an out-dial trunk such as H]. . Trunk ‘I0 is a standard out-dial trunk oi‘ the 10 type fully described in Patent 1,653,789. to lease. ' Relay 52 in releasing disconnects the trunk from leads 3! and 32 extending into the dial cir cult, opens contacts l5, and closes contacts 3d and 35. Closure of contacts 34 connects the tip 10 of plug 5 through to the upper armature of relay Stokely dated December 1927 and shown in Figs. 2 and 3 thereof and therefore will not be I I5 anclclosure of contacts 35 connects'sleeve relay 33 to the plug sleeve whereupon relay 83 operates redescribed here. v ' By referring to the above patent it will be noted to ground over the sleeve of the trunk. Relay 33 15 that the ring conductor of ‘the trunk jack 2% in operating closes an obvious circuit to operate 15 relay l5 which relay closes its inner upper and shown in Fig. 2 is grounded through the left hand winding of relay 262 and consequently when lower contacts to connect the tip and ring'of the plug 9 of the present cord is insertedin jack plug 9 through to the cord. > . Release of relay l9 releases relay 2| and if the H, which corresponds to jack 296 of the Stokely 20 patent, a circuit is completed to operate the dial ' operator released dial key 8 at the conclusion of 20 the dialing operation, relay 5 will new release relay i2 which can be traced from battery, con tacts Q3 of relay 2, lead 1'1, upper winding of relay thereby extinguishing lamp 26 which completely l2, contacts ill of relay [5, and the ring conductor restores the dial circuit to normal and conditions of the plug 9 and jack H to ground in the trunk the cord for conversation. 25 25 circuit, as previously mentioned. Call to a community dialomce Dial relay l2 operates in this circuit, discon nectsrelay 33 from the plug sleeve, and at its contacts l6 completes a holding circuit for itself, including its lower winding, which can be traced 30 from battery, contacts of polarized relay l1, re In case the called subscriber is reached over a trunk to a so-called community dial of?ce'which is not arranged to send a current reversal back to operate polarized relay I? to release the dial cir 30 lays !8 and IQ, lead 29, lower Winding and con cuit from the cord when (the called subscriber’s tacts E6 of relay l2, sleeve conductors of plug 9 and'jack H to ground over the left-hand contacts line is reached, some means must be provided to simulate such a reversal in order to free the dial of relay 202 and the right-hand winding of relay 35. 283 shown in the above-noted Stokely patent. Qperation of relay l2 also connects, at its con tacts 29 and 36, the tip and ring conductors of the trunk to leads 3i and 32 extending to the dial circuit of Fig. 3. ‘ Relay i8 is marginal and does not operate in the above traced circuit but relay l9 and trunk relay 263 do operate which latter relay, it will be observed, operates relay 2E3] to extend the trunk to pulsing relay 2M thereby connecting ground 45 and battery respectively to the tip and ring con 40, ductors of the connected cord plug 9. . Relay ill in operating causes thesuccessive op eration of relays 2i and 5, The latter relay locks up over its contacts 22 to ground on the dial. key 1, opens the operating circuit of relay 2 and at its contact 23 closes a circuit from the dial 2G over lead 3i and contacts 29 of relay E2 to the tip con ductor of the cord plug 9. When relay, 2 releases it disconnects battery from lead 71 and all other - corresponding leads to other cords thereby open circuit and condition the cord for conversation and to accomplish this the trunk T (Fig. 3) has 35 beenprovided, the operation of which is as fol lows: I I When the operator desires to reach a commu nity dial of?ce subscriber, she ?rst operates dial key l as before described, thereby operating relay 40 2 which connects battery over leadsli, l2, etc. to operate the respective dial relays such as l2 when the respective plug, such as 9, is inserted'in trunk jack 3% at which time a circuit is completed to operate relay 12 which can be traced from bat 45 tery, contacts l3 of relay 2, lead '11, upper winding of relay 52, contacts id of relay 15, ring conduc tors of plug 9 and jack 36, contacts 3? of relay 38, contacts 39 of relay I30 and lower winding of relay 6! to ground. Relays l2 and ii operate in . this circuit. Operation of relay‘ 12 extends the tip and ring of the plug 9 to the dial circuit (Fig. 1) over its contacts 29 and 39 and leads]?! and 32, and prepares a locking circuit for itself at con tacts it. Relay 4! inaoperating operates relay 42 55 ing the circuits previously traced which caused r in a circuit which can be traced from battery, operation of relay 202 in the trunk. Relay I2, - contacts of polarizedrelay ll of the dial circuit, windings of relays l8, l9 and the locking winding however, remains locked up over its lower wind and contacts lb‘ of relay l2, sleeve of the plug 9 ing as previously described. . . . . 60 Relays l9, 2! and 5 are su?iciently slow in and jack 3%, contact 43 of. relay 4! and lower ' operating, however, to permit relays 2m and 262 V winding of relay 42 to ground. In the standard out-dial trunk IE, before‘dis in the trunk to lockup before the original operat ing circuit for relay 292 is opened by the release 7 cussed and described in Patent 1,653,789, the right-hand winding of sleeve relay 293 is of su?i of relay 2. Release of relay'Z closes, at its con tact 25, a circuit to light the dial pilot lamp 25 ciently'high resistance to prevent operation of which can be traced from battery, contacts 25 of marginal relay l8 in the dial circuit, but the lower winding of sleeve relay A2 in the community trunk relay 2, contacts 7270f relay 2%, lamp 28 andcon tacts 22 of relay 5 to ground over contacts 3 of T (Fig. 3 or‘ the present application) is made low' dial key I. ' . enough to permit this relay (A) to operatethere 70 The circuit is now inrcondition for dialing and by closing a circuit to operate relay '15 which can actuation of the dial 2% transmits pulses over the be traced from battery’, winding of relay 15, con trunk to operate vthe pulsing relay 266 in the tacts of relay l8 and the upper normal contacts trunk as shown in Patent 1,653,789. As described of the dial to ground. Operation of relay 15 opens in the above patent, when the connector switch at its contact 76 the normal short-circuit around 75 in the distant o?ice comes to rest onthe'called resistance’ 17 and closes its contact 18 thereby 60" 65 70 75 3 2,132,857‘ transferring the lead 19, which extends'lto ground through the transformer winding 80 of the oper ator’s induction coil in the telephone circuit OT, shown at the bottom of Fig. 2, from the lead 8| normally connected to the tip of the plug 9, to the lead 32 and thence to the ring conductor of the trunk in order to receive dial tone from the dis tant'community office 'over the ring conductor of . the trunkh Relay l9 also operates in this circuit, as previously described, which operates relays 2| and 5 in turn. Relay 5 releases relay 2 which completes the circuit of dial pilot lamp 26'. Relay The resistance of this circuit, due to resistance ' 11, is such that marginal relay'51 does not oper ate, but pulsing relay 51 does operate, over its lower winding, thereby closing its lower contact 86lto operate relay 81 in an obvious circuit. Relay 31 in operating closes its locking contact 88. thereby completing a locking circuit for itself from ground at contact 89 of relay 54, and at its co'ntact‘90 short-circuits the lower, and high re sistance, winding of relay‘ 9| thereby decreasing 10 the resistance of the loop to the community dial office su?iciently to operate a marginal line relay 5 in operating also closes its contacts 23 which thereat, not shown, thereby causing the circuit at extends lead 3| to the dial 24. With relay I2 ‘that point to be conditioned to ‘receive dial pulses, 16 operated and locked when relay ‘5, which is slow in a well-known manner, and as trunk T is a two to operate, ?nally closes its contacts dial 24 is con— way circuit, to make the outgoing terminals of nected across the tip and ring springs of the trunk this trunk busy to any switch which may attempt jack 36 in series with polarized relay I1. ‘Oper toisei'zeit to originate a call in the opposite direc ation of trunk relay 42 ~completes, ‘at its‘ lower tion, i. e. toward the toll oi’rlce'~ end. ' contacts an obvious circuit to energize‘relay. 40, ' ' The toll operator now actuates the dial 24 to which circuit was prepared by the operation of’ transmit the proper ‘impulse code corresponding relay 4|, and a second obvious and parallel‘cir to the wanted line. When the dial is moved off cuit to operate slow acting relay ~44. normal, the upper‘or oil-normal contacts of the ‘Relay 49 in operating completes a'locking cir . dial are opened thereby releasing relay 15 which cuit for relay 4| which can be traced from ground, thereupon transfers the busy test lead 19 from contacts 41 of relay 49', contacts 48 of‘ relay 38, . lead, 3| back to its normal connection to lead 8| and contacts 49 and upper winding of relay4| to and reestablishes the short circuit around resist battery. Relay 46 also opens its contacts 39 and ance 11 thereby removing this resistance. from the closes contacts 59 thereby transferring the con previously traced pulsing circuit which includes nection of the ring conductor of the jack 36 from the dial, relay I1, pulsing relay 51 and marginal the lower or operating winding of relay 4| to the relay 61 whereupon relay 6'! now operates which lower winding of relay 5|, which latter relay now, in turn ‘operates relay 9| in a circuit traced from operates. Further, relay 49 opensits lowermost battery, contact 63 of relay 54, winding of relay contact thereby disconnecting battery from'the 9|, contact 92 of relay 61 to ground over contact 35 lower or primary winding of relay 38 and prevent‘ 41 of relay 40. Relay 9| closes an obvious circuit ing that relay from falsely operating in response to operate relay 62, which relay opens its contact to the operation of relay 45 which immediately 93 andcloses contact 94 thereby connecting the‘ follows. When relay 44, closes its contacts it tip conductor. 85 of the trunk to the ring con completes a circuit for relay 45 whichis slow act ductor 96 through the pulsing contact 91 of relay Ill) ing. After a short interval this latter relay oper 51 to the exclusion of the repeating coil 56, upper ates and in turn operates relay 46. Relay 45 is 3 winding of polarized relay I01 and contact 99 o made slow to operate in order to insure that relay relay 81. ' 40 has operated and removed battery from relay . The return of the dial interrupts the circuit 38 before relay 45 closes its lowermost contact through relay 51 the required number of times which otherwise would cause the premature oper- ‘ which relay releases and reoperates thereby al ation of that relay (38) which is not desired at ternatelyopening and closing the trunk loop to this time. ' ~ . control the switching‘ circuit at the distant o?ice. Relay 45 in operating closes, at its contact 52,’ Relay 61 also follows the interruption of the dial an obvious circuit for operating relay ‘I I3 and at thereby alternately opening and closing the cir .» its contact 53 closes an equally obvious circuit for cuit previously traced for relay 9|, but this relay, operatingrelay 54. Operation of relay ‘I I3 con which is slow' to release, holds operated over nects ground through resistance 55 to the right these brief open-circuit intervals thereby holding hand terminal of the upper winding of pulsing relay 62 operated.v Further, due to the closure relay 5?. Operation of relay 54'closes its contact of contact 98 of relay 62, relay 9| is held operated 93 thereby connecting battery through the'lower 157 20$ 40 50 3 as long as relay’51 is released, under control of winding of relay 5? and thence to. the left-hand relay 54.‘ When‘the dial restores to normal, relay armature of relay 5 in the dial circuit (Fig. 1) 7 15 reoperates which again removes the short cir which due to its slow-acting characteristic has cuit from resistance 11 thereby again increasing not yet operated. This circuit can be traced from ' the‘ resistance of the pulsing circuit including 60 battery, contact'53 of relay 54, leads 64 and 165, . marginal relay 61 which latter relay thereupon 60 contact 93 of relay 38, winding. of 'marginal relay releases which permits relays‘ 9| and 62 to re 61, contact 68 of relay 46, lowerwinding of puls ing relay .51, contact 59 of re1ay59, resistance 19, lower left-hand winding of repeating coil 56, lead 84, contact 85 of relay 4 | ,' tip spring of‘ jack 36 and tip of plug 9, contact 29 of relay I2 and lead 3| to the left armature of relay 5. Relay 5, however, '70 lease in turn. ‘ _ " The release of relay62 ‘opens its contacts 94 and '> 98 and recloses'contact 93 thereby recon~ necting the trunk conductors 95 through the up per right winding of repeating coil 56, upper low resistance winding of relay I01, contact 90 of operates almost immediately after relay 54 and -. relay 91, and‘ lower rightwinding of repeating the foregoing circuit may be continued over con coil 55 to the ring conductor 96. This restores tact 23 of relay 5, pulsing contact82 of dial24, ,3 the original condition which existed before the resistance 11,‘ winding of polarized relay I1, lead ?rst digit was dialed. _' 32, contact 35 of relay l2, contact l4 oi=relay l5, When the dial is moved 011‘ normal to transmit ring conductor of plug 9 and ring‘spring of jack ' the next'digit, the ‘same sequence of operations 35, contact 31 of relay 38, contact 59 of relay 40 to takes place, and so on, until the dial comes to 75 ground through the lower winding of relay. 5|. . rest at thesconclusion of the dialing operation at 2,132,857. which time the operator must release the dial key I in order to free the dial circuit from the trunk and condition the cord for conversation. When dial key I is released, due to the fact that _ relay 51 is now operated, ground at the right; hand contact of relay 15 will be applied‘ over contact 99'of rear dial key I00 and contacts IOI of the front dial key I to junction point I02 be tween resistance ‘I1 and relay I‘I thereby ground 10 ing both the tip and ring of the trunk. This , ground is connected through relay I‘! to the ring spring of the trunk jack and thence over contact ' 3‘! of relay 38 and contact 50 of relay 40 to the lower winding of relay 5| thereby short-circuiting 15 it. During the pulsing period although the puls ing circuit includes the lower winding of relay 5!, and consequently is alternately opened and closed, this relay (5|) remains operated, i. e., while the dial circuit is opened, relay 5| is held winding of'relay I‘I, lead 32, contact 30 of relay I2, contact I4 of relay I5, contacts of the plug 9, ring spring of jack 36, contact ‘II of relay 38, lower left winding of repeating coil 56, resistance ‘I0, contact 69 of relay 59, lower winding of relay 5 51, contact 68 of relay 45, winding of relay 61, re sistance I09, leads 65 and 64 and contact 63 of relay 54 to the negative pole of battery. Opera tion of relay‘ I‘I releases relays I8, I9 and I2. Relay‘ I2 in releasing opens its contacts 29 and 39 thereby disconnecting the dial circuit (leads 3| and 32) from the tip and ring of the trunk, closes its contact 34 to extend the tip of plug 9 to the upper armature of relay I5, opens contacts I6 and closes contacts 35 thereby connecting bat tery through the cord sleeve relay 33 to the sleeve of plug 9 and consequently to the sleeve of the trunk thereby holding the trunk sleeve relay 42 operated which otherwise would also release. 20 ‘operated by its upper winding in a circuit traced I Cord'sleeve relay 33 now operates in series with 20 from battery, contact 63 of relay 54, lead 64, re v.the trunk sleeve relay 42 thereby operating relay sistance. I03, upper winding and contacts I04 of I5. Relay I5 closes through the tip and ring relay 5| and contact 89 of relay 54 to ground. of the cord. When the dial circuit is. closed, thereby operat ‘i5 and release of relay I9 releases relays 2| and 25. ing relay 51, the holding winding of relay 5| is short-circuited in the following path: Ground, contact 86 of relay 51, contact I05 and the upper winding of relay 5|, contact I04 of this relay and contact 89 of relay 54 back to ground. Ground connected at the junction point I02, by the release of dial key I, is also connected through resistance 11, contact 82 of the dial and contact'23 of relay 5, to lead 3| and thence over the previously traced pulsing circuit including the 35 lower winding of relay 5‘! and marginal relay G‘I to battery. As before mentioned, resistance: 11 is 30 su?iciently high to prevent the operation of relay 51, but relay 51, however, holds operated in this circuit. 40 . ' I ' The short-circuiting ofrelay 5| and its conse quent release at this time completes a circuitto operate relay 38 which cain be traced from ground at- the still closed contacts 86 of relay 5?, con . tacts I06 of relay 5|, now released, upper con 45 tacts of relay H3 and upper winding of relay Release of relay I8 releases relay 5 thereby restoring the position dial'circuit (Fig. l) to normal. With relay I2 released and relay I5 operated the tip and ring conductors of the cord are connected through and the‘ supervisory bridge, comprising retard coil IIO,and relay II I 'in par-_ allel across the cord, holds relay 5'! operated. Relay III operates at this time and lights super visory lamp II2. ' .When the called subscriber answers battery and ground are reversed in the usual manner, over 35 the trunk from the community dial of?ce, causing operation of polarized relay I0‘! in the trunk. Operation of relay I01 closes a circuit to operate relay 59 which can be traced over the lower con tacts of‘relay 81 and lowermost normal contacts I of relay 40 to battery. Operation‘ of relay 59 opens its contacts 58 and 59 thereby disconnect ing the two windings of relay 5‘I from the previ ' ously traced circuit through the cordwhich has held this relay operated and at its ‘upper and lower front contacts substitutes a local holding circuit for relay 51. This, however, opens the cir cuit for supervisory relay III in the cord which 38 to battery. Operation of relay 38 closes its contacts ‘I2 and ‘II thereby connecting the tip. and ring springs of the jack 36 to the respective terminals of the left-hand windings of repeating 50 coil 55. Operation of this relay also opens its contact 48 thereby opening the locking circuit for releases and extinguishes the supervisory lamp relay 4| which thereupon releases which in turn opens the circuit for relay 40‘which also releases. Release of relay 4| opens its contact 85 which up 55 to this time has connected. the tip spring of the jack 36 to the lower left-hand terminal of re in turn thereby reconnecting the winding of relay 51 to the cord and reoperating supervisory relay III which lights supervisory lamp IIZ. The toll operator then challenges on the line and- ?nding peating coil 55 which extends to battery through relays 01 and 57. ' Relay 38 in operatingalso'closes its contact I08 60 thereby maintaining‘ a connection between the sleeve of jack 35 and relay 42 and holding this relay operated, which otherwise would have re leased due to the release of, relay 4|. Further, operation of relay 38 opens its contact 83, thereby removing the short circuit heretofore connected around resistance I09. The effect of ~ the closure of contacts ‘I2 and H and opening of ' contact 83 of relay 38 and the opening of contact I I2. ' When the conversation is ended and the called subscriber disconnects, relays I0‘I and 59 release the conversation ?nished removes plug 9 from jack 36 whereupon the trunk circuit restores to normaLwhich operation, as it forms no part of the invention, ‘will not be described in detail. a What is claimed is: 8 ~ 1. In a telephone system, a trunk circuit, an operator’s cord circuit adapted to be connected to said trunk, a dial adapted to be connected and locked to said cord circuit, a dial key, a polarized relay adapted to be connected inseries with said dial when the dial is connected to the cord, means responsive to the joint connection'of said cord circuit to said trunk and operation of’ saiddial key 35 of relay 4| is to reverse and reduce the current 70 ?owing back into the dial circuit through a to connect said dial to said cord andlock it under polarized relay [1 and due to this reversal of cur- ' control of saidpolarized relay, a source of direct rent, relay I‘I now operates. . current adapted to be connected to said trunk re Thereversed circuit for operating relay I“! can sponsive to the connection of said dial and in a, be traced from ground,. right-hand contact of non-operate direction with respect to saidpolar 75 relay ‘I5, contacts 99 and IM of keys I00'an-d I, ' ized relay, and means responsive to therelease 5 2,182,857 of said dial key to cause said current source to be reversed in polarity with respect to said trunk to operate said polarized relay and release said dial from the cord. 7 I 2. In a telephone system, an operator’s cord circuit, a trunk circuit,‘ a dial, a dial key, means responsive to operation of said dial key and cone nection of said cord to‘the trunk to 'connectand lock the dial to the cord, a polarized relay in nected and locked to any of said cord circuits jointly responsive to connection of the cord to any one of said trunk circuits and the operation of the key, polarized relay means at said manual exchange in series with said dial when it is con nected to a cordadapted when operated to dis connect said dial from its connected cord circuit, means at certain of said automatic exchanges re sponsive to seizure of the called line thereat to 10 series with the dial controlling the locking circuit , reverse thec'onnection of the exchange battery 10 of said dial, a source of direct current, and means responsive to release of said dial key to connect said source to the trunk in such a polar direction as to operate said polarized relay to disconnect 15 the dial from the cord.‘ , r 3. In a telephone system, a manual exchange, a plurality of automatic exchanges, trunk cir cuits from said manual exchange to each of said automatic exchanges, cord circuits at said manual ‘ 20 exchange for making connection to said trunk circuits, a position circuit including an impulse transmitting device and a key at the manual exchange, said device being adapted to be con to the calling trunk circuit to operate said polar ized relay means at the manual exchange, and means-associated with said position circuit, cord circuits, and trunk circuits extending to automatic exchanges not arranged to reverse battery to the 15 trunk when the called line is seized,vresponsive to release of the dial key, to cause direct current to be connected to the trunk circuit at the manual exchange in such a direction, as to operate said polarized relay means to release the dial from its associated cord circuit. ’ THOMAS H. NEELY. ALBERT G. LANG.