US1687325A

US1687325A - Telephone system

Info

Publication number: US1687325A
Application number: US2744A
Authority: US
Inventors: Thomas F Crocker
Original assignee: Automatic Electric Inc
Current assignee: Automatic Electric Inc
Priority date: 1925-01-16
Filing date: 1925-01-16
Publication date: 1928-10-09
Anticipated expiration: 1945-10-09

Description

Oct. 9, 1928.

Thames F. Emnkr Oct. 9, 1928.'y

T. F, CROCKER TELEPHONE SYSTEM 5 Sheefs-Sheet 2 Filed Jan. 16, 1925 I Thames E Cracker mut-14 Oct. 9, 1928.

T. F, cRockl-:R

TELEPHONE SYSTEM 3 Sheets-Sheet 3 Filed Jan. 16, 1925 Thomas F." Drucker Patented Got. 9,1928.

UNITED STATES `PATENTg OFFICE. f

THOMAS F. CROCKER, DE CHICAGO, ILLINOIS, 'ASS'GNOR, BYy MESNE ASSIGNMENTS,

T0 AUTOMATIC ELECTRIC ENC., OF WARE.

C-ICAGO, ILLINOIS, A CORPORATION OF DELA.

TELEPHONE SYSTEM.

Application filed January This invention relates to telephone systems in general, but more particularly to small automatic telephone systems. In such systems, an operator may be required to give complaint and information service, to complete rural and toll connections, and also to give other miscellaneous service. rThe principal object of this invention is to provide simple and eflicient circuits for the operators switchboard for giving these various kinds of service.

The features of this invention will be fully described in connection with the explanation of the different operationsto be performed by the operator, reference being had to the accompanying drawings.

Referring now to the drawings, the three figures placed end to end in numerical order show enough of the essentialA elements of a telephone system to illustrate and explain the invention. Fig. l shows the circuits `of the apparatus at the operators position; while Figs. 2 and 3 combined show` .the circuits and connections of ythe necessary switches to complete a call from one automatic telephone to another automatic telephone, to complete a call from an automatic telephone `to an operator for information, rural, or toll service, or to complete a call from the operatorto any automatic telephone.

The apparatus will now be explained more in detail. For the sake of convenience, the automatic apparatuson Figs. 2 and 3 will be described first. The substation 'B in Fig. 2 is an ordinary automatic telephone having a line, comprising

conductors

122 and 123, to the automatic exchange. Associated with each telephone line at the automatic exchange is an individual line switch such as C, in 2. The line switches are of the well known rotary type, in which the wipers have no normal position and move in a forward direction only. rlhe total number of line switches may be divided into several groups, reach group havingaccess to a group of selectors. Vilhcn a call is initiated at a substation, the line switch associated. with that substation is operated to hunt an idleselector.

rlhe selectors, one of which is shown in Fig. 2, designated D, are of the well known Strowger vertical and rotary type. The selectors have access to groups of connectors,

' may 16, 1925. Serin No. 2,744.

each level of the selector banks being assigned to a certain group.

The banks of the individual connectors of l any one group are'multipled togetherand serve as the terminating point for the subscribers lines. Each group may accommodate 100 lines in the ultimate.` Besides the several groups of ordinary connectors there may be one or more groups of rotary connectors accessible from a certain one or more selector levels. The rotary connectors, one of which is shown in Fig. 3, denoted by E, besidesv accommodating' individual lines, may have access to groups of lines, all the lines of any one group having the same directory number. ln this case, the rotary connector wipers, after lpicking out the desired group of lines in the connectorbank, commence an automatic rotary trunk hunting movement to pick out the first idle trunk of the group. group of lines. may extend to aprivatesubscriber who has several telephones ora group of lines may be desired for each kind of special service to an operator at the automatic exchange. Substat-ion B is an illustration of an individual line te 1minating inv the banks of the rotary connector E. The

line comprising conductors

32, 33, and 34 is one line of a certain `group of lines for special vservice to the operator.

Having described `the automatic `exchange switches, the description of the apparatus at the operators position will begiven. In a small automatic exchangesuch as is being decribed, several groups of trunks from rotary connector levels may terminate at an operators position to be used for special service. Each group of trunks may be reserved for a certain kind of service. One group of trunks be reserved for information, another group for toll service, `another group for complaint, and other groups for such services may Abe required. In the drawing, Fig. l, the

trunk comprising conductors

32, 33 and 34 may represent one trunk of a group of trunks reserved for rural service. The trunk terminates at the jack J2 with its associated circuit TC. The drop 3 serves to signal the operator. The other trunks to the operator for information, and the several other special services are identical with this described trunk and terminate at jacks like jack J2.

The line represented in Fig. l by conducico ters and 11 and terminating at the jack J is one o1 the rural lines terminating at the oparators position. The reference letters A, A', A2, and .i513 represent the rural telephones, only the bells ot lll, A2, and A3 being shown. Associated with each rural line jack, such as J, is a drop similar' to that shown in Fig. 1,

4designated by the reference numeral 2. 1f

rscribed before.

more than one operator be employed, the aclrs of the rural lines, such as J, be multipled to other jacks similar to il, located at the other operators positions.

Several toll lines may also extend to the operator-s position. These lines terminate in jacks similar to jack J, having signal drops similar to drop 2.

Each operator is provided with a plurality of cords, the circuit of which is shown in Fig. 1, designated by the reference character 0C. The answering plug is designated by the letter l? and the calling plug by the letter P. A ringing and listening lrey K, monitoring lrey K and a ring and dial key l. 2 are provided. rlhe opera-tors dialling circuit and head set are shown above the cord circuit.

To complete incoming rural calls to automatic subscribers, a group ot service trunks, extending from the operators position to the automatic exchange are provided. The trunk comprising conductors 20 and 21 is one oi this group ci trunks. rlhese trunlrs are accessible to the operator at jacks, such as d3, and terminate in line switches, such as C, at the automatic exchange, shown in Fig. 2. rllhese line switches are also oi" the common rotary type and are identical with the line switch C, described above.

Another group of trunks for completing incoming toll calls is provided. These trunks are similar to the service trunks described above, being accessible to the operator at jacks such as J2 in F 1, and terminating in rotary line switches such as C2 in Fig. 2 at the automatic exchange. The rotary line switch C2 is ieentical with line switch C de- The trunk circuits TG2 and 'll 2 ot the service and toll trunks, respectively, differ in that the toll trunlr circuit is supplied with repeating coils in place of the condensers as are used in the service trunk circuit TG2.

Having described the system and the apparatus general, a more detailed description ci" the various operations will be given. For this purpose, th e assumption first made that the rural subscriber at the substation A `wishes to obtain connection with an automatic subscriber at substation B. 'llo initiate a call the subscriber at A turns the crank ot his magneto and removes his receiver. Turning tbe crank of the magneto causes suitiicient current to flow to actuate the signal drop 2 over a circuit by way of conductor 10, through the winding ot the drop magnet 2, spring 30 and its resting Contact, conductor 410, spring 33 and its resting contact, concluetor 11, conductor 11, to the magneto at substation A. The. actuation of the drop 2 signals the operator who answers the call by inserting the answering plug l? into the ack d, whereupon the drop 2 is cut ed at spring 30. rlhe operator, on plugging in, throws the key K to the listening position. This operation bridges the operators head set across the c lling line in the usual manner. She receives the number of the automatic subscriber to be called and inserts the calling plug Pf into an idle servicetrunk jack. lWe may assume this jack to the (la. This 'operation closes the contact springs 48, and, in addition, completes a circuit lor relay 15 from ground by way of springs controlled .by armature 19, lower winding of relay 15, sleeve ci jack J3', sleeve ci plug 13, spring ll2 and its resting contact, lamp li', to battery. Lamp L-is lighted. Relay 15 operates to open the shunt around the condenser 80 at the normally closed contacts of the springs controlled by armature 18, and to open the shunt around the condenser 81 at the normally closed contacts oli the springs controlled by armature 17. The operation ot relay 15 also closes a bridge across the conductors 2O and 21, completing the circuit for the line relay 1141 of Vthe line switch C at the automatic exchange. rl'his bridge across the conductors 20 and 21 includes the winding oi tie polarized relay 16, armature 17 and its working contact, and springs L13. Relay 11-1 encrgizes and closes a circuit for the switching relay and stepping magnet in series at armature 118, wiper 126 to the junction ot switching relay 113 and stepping magnet 115 at armature 117.

In case the trunk upon which the wipers of the line switch are resting is idle, switching relay 113 energizes immediately. Assuming the trunk to be busy, however, switching relay 113 is short circuited from ground at the test wiper, and does not energize. The

wipers

125, 126, and 127 arek rotated step by step inra buzzer-like manner by the action oi the stepping magnet 115, which'operates from groundV on the busy test contacts encountered by the test wiper 126. When an idle trunk is reached, which will be assumed to be the

trunk comprising conductors

150, 151, and 152, the stepping magnet 115 will Vcease its stepping action and relay 113, being no longer short cireuited, energizes in series with stepping magnet 115. Stepping magnet 115 does not operate at this time on account oi the high resistance of switching' relay 113. The operation of switching relay 113 opens the test circuit and prepares the holding circuit at armature 119, and at

armatures

121 and 120 disconnects the line conductors 2O and 21 from the winding ot thev line relay 1111- and ground, and extends them and 135,

conductors

150 and 152, armatures and connects the test y. ilmlll) llii

171 and 168 and their resting contacts, to the upper and lower windings ot the line'relay 153 ot the selector D.

The relay 153 of selector D now operates, closing the circuit for the slow-to-release relay 154. Relay 154 energizes and opensA the circuit of the release magnet 159 and pre pares a circuit for the vertical. magnet 158 at armature 163, and at armature 162 places ground on the release trunk 151, closing the usual holding circuit for the switching relay 113 before the slow-to-release line relay 114 drops back.

After plugging in, the operator throws the key K2 to the dialling position. This operation removes the original battery at lamp L from relay 15, but supplies a new source of current at the resistance 50. The operator may now operate the dialling device CD, to send out the impulses necessary to operate the automatic switches at the automatic exchange in accordance with the digits ot the required number. Moving the dial from its normal position, in the process ot dialling the first digit, closes the contact springs 14. This completes a circuit for the slow-to-release relay 53. Relay 53 energizes and short circuits the operators receiver at armature 54 and its working contact, and places ground at a point between the battery at resistance 50 and relay 15, at armature 55, thereby placing ground on both ends of the lower winding of relay 15. Relay 15 releases, opens the bridge including relay 16, and places a lshunt around each of the condensers 80 and 81. The circuit ci' line relay 153 now includes the dial CD, which was bridged acrossthe conductors otthe cord circuit by the operation of key K2. On the return ot the dial to normal, springs 14 separate and open the circuit :tor the slow-to-release relay 53. Relay 53 releases and opens the short circuit across the receivers at armaturer 54, and removes the shunt around relay 15 at armature 55. Relay 15 will again operate to restore the original bridve at armature 17 and remove the shunt around the condensers'8() and 81. The operators receiver is short circuited during the period of dialling to prevent the impulses from being heard in the receiver.

llVhen the operator dials the first digit ot the desired number, the circuit of the line relay 153 is opened a corresponding number oi' times in the usual manner. Each time the line relay 153 falls back in response to lan interruption, a circuit is closed for the ver-- tical magnet 158 which maybe traced from ground by way of the resting contact of armature 169 and said armature,y armature 161 and its resting contact, armature 163 and its working contact, winding of relay 155, through the winding of the vertical magnet 158 to battery. By the operation of the verti- F cal magnet 158,thewipers 184,185, and 186 are raised opposite the proper level of bank contacts, corresponding to the digit dialled. The

slow-to-releaserelay 155 energizes in series with the vertical magnet, retaining its arma! ture attracted throughout the vertical movement. As a result, a circuitl is closed from ground on the release trunk 151 by way of armature 164 and its working contact, o-t normal contacts 172 (which close upon the lfirst vertical step) and interrupter contacts 167, through the winding of stepping relay 156 to battery. The stepping relay 156 energizes and closes a locking circuit for itself at armature 165, and at armature 166, prepares a circuit tor the rotary magnet 160.

At the end of the vertical movement, slow acting relay 155 deenergizes and completes the circuit oi' the rotary magnet 160 at armature 164. Rotary magnet 160, upon energizing, advances the

wipers

184, 185 and 186 into engagement with the iirst set of bank contact-s in the selected level, and, near the end ot this movement, opens again closes its interruptor contacts 167. In

case the trunk terminating in thelirst set or bank contacts is idle, switching relay 157 energizes immediately. Assuming the trunk to be busy, however, switching relay 157 is short circuited by the ground potential encountered' by test wiper' 185. Stepping relay 156 energizes from this same ground potential and'closes the circuit of the rotary magnet- 160 a second time.y The switch wipers are thus rotated into engagement with the next set of bank contacts. This alternate operation of stepping relay 156 and rotary magnet 160 continues until any idle trunk is reached, which may beassumed to be the trunk terminating in

bank contacts

187, 188 and 189. Switching relay 157. being no longer short circuited by a ground on the test wiper 185, energizes in series with stepping relay 156. The stepping relay 156, however.` does not energize at this time on account or the high resistance of switching` relay 157. The operation of relay `157 opens a point in the testing circuit and'prepares the holdingl circuit at armature 170; disconnects ground from armature 161 ot the line relay 153 at armature 169; and at

armatures

171 and 168,

ratesby reason of the bridge across the concompletes the circuit est,

duct-ors 20 and 21 and orthe release relay 212 at armature the circuit of stepping` -relay 156 at interrupter contacts 167. The

Release relay 212 energizes; opens a point in the circuit of the release magnet 221 and prepares a` circuit tor the vertical magnet 222 at rmature 235; and places ground potential on the release trunk conductor 188 and on the holding conductor 209 at armatures 236 and 237, respectively.

lvlhen the operator dials the second digit of the desired number, the dial CD is bridged across the trunk in place of relay 16 the saine as before. Each time the line relay 211 talls back in response to an interruption produced by the dial, a circuit is closed 'for the vertical magnet 222. This circuit may be traced trom ground by Way of armature 2311 and its resting contact, armature 235 and its Working contact, ott normal springs 262 and 264;, Winding of the slovv-to-release series relay 213, through the Winding otvertical magnet 222. rllhe above is the circuit over which the lirst impulse is sent. Upon thelirst vertical step of the switch, the ott normal springs are shifted, so the remaining impulses to the magnet traverse a new circuit which is the same as the one traced above except that it includes the oli"

normal springs

262 and 263, and armature 238 and its Working contact, relay 213 now beingl in an operated position. The vertical magnet 222 operates to raise the switch Wipers 270-273, inclusive, step by step until they are placed opposite the level t bank contacts in Which is located the set of contacts associated With the line of the substation B. The sloW-to-release relay 213 energizes in series With the vertical magnet 222, and maintains its armature attracted throughout the vertical movement oit the switch. At the termination of the vertical movement, relay 213 `deenergizes, transferring the operating circuit to the rotary magnet 220.

The operator novv dials the third. or final digit ci the desired number. As before, a series of interruptions is produced in the circuit ot the line relay 211. Ait each retraction of the armature 2311 an impulse oit current is sent to the rotary maejnet 220 over a circuit extending` from 4round by Way of armature 234 and its resting Contact, armature 235 and its working contact, ott

normal springs

262 and 263. armature 231 and its resting contact, resting contact ot armature 2416 and said armature, winding` ci' sloW-to-release relay 217, armature 255 and its resting Contact. through the Winding ot the rotary magnet 220 to battery. The rotary magnet 220 operates to rotate the switch Wipers 276-273, inclusive, into engagement with the set oi bank contacts associated With the line ot the desired substation which has been assumed t0 be substation B Whose associated bank contacts are 274. 276, and 277. The slow-to-release relay 217 is energized in se ries with the rotary magnet 226 and maintains its armature attracted throughout the rotary movement. Relay 217, being operated,

closes a shunt around the armature 246 and its resting contact, at ari ature 250; complet-es a circuit tor slow to release relay 213 at armature 2119; and holds open a point in the stepping circuit to be described later, at

operates and prepares a locking circuit for the rotary magnet 220 at armature and prepares the busy tone circuitat arr; ature 217. A 'further result of the 0pion ot busy relay 216 is the closing of a ont in the circuit of the stepping relay 21o at armature 2114-. Shortly after the coinpletion oit the impulses, the series relay 217 deenereizes and opens the circuit for the sloiv-toreleasc relay 213 at armature 249; opens the circuit for the rotary magnet 220 at armature 250; and closes another pointin the circuit oit the stepping relay 215 at armature 'l-his has no utility in setting up a call to the individual telephone'as is being cescribed since the Contact 275 is not ca'znnected to the-contact 276, as Will be hereinafter described. Since the circuit ont the r .ry magnet 226 is open at armature 250 and held open by busy relay 216 at armature f, the Wipers are prevented from being rotated oft the contacts of the called line by any accidental movement ot the dial at the calling' substation. Since the circuit of the sloW-tdrclease relay 213 has been opened at armature 2419, relay 213 deenergizes, thereby closing the locking circuit rfor the busy rela. by closing the normally closed springs controlled by armature 252 and coinpleting the circuit forv the busy tone to the heavy talking conductor 139 at armature 253. The busy tone is transmittedthrough the dial and the tertiary Winding of the induction coil N, is induced in the secondary ot' the coil 1l, and is reproduced in the-operators receiver. indicating the busy condition on the desired line.

lt Will be assumed, however, that the line oit the desired substation B is idle at this time. Under these circumstances there Will be no ground potential upon the test Contact 27V Y engaged by the test Wiper 272, no cire ci t will be completed tor the test relay 216 and the operator, not hearing the busy signal, will restore lier keys l and K2 to normal. Folle-ving the deenergizstion ot the slow to release relay 213, a circuit is completed er:-

tending trom ground on release'conductor 163, by Way otarmature 2415 and its resting Contact u 3 ier Windinn' ot the switchino re- 9 no b lay 219, resting contact ot armature 252, and

etes the testing circuit for the busy relay F t armature 245; opens the initial cirllt) battery `and ground connections in the liner switch C3. The svitchingielay 219, upon energizing, establishes a locking circuit 'tor self at armature 256; completes the ringing circuit to the substation B at armatures 259 Aand 25a; opens a point in the rotary magnet circuit at armature opens a point in the test circuit at armature 257; and places direct ground on the private wiper at armauro 253. Ringing current is now intermitently projected over the line oi the substaion Bf from the ringing equipment Pt.

Vhen the calledv subscriber answers, removing his receiver, a circuit 'for the ring cut-oli relay 21a is completed over the called line loop. Relay 211i; energizes and establislies a locking ciicuit for itself at armature 249, and at-armatures 239 and 2111 cuts off the ring at the resting contacts and finally completes the talking connection at the working contacts. The back bridge relay 21() now supplies talking current to the called substation B, and is immediately energized. The operation ot relay 21() reverses the direction ot current flow over the calling subscribers line. r)This reverses the current in the polarized relay 1G, now bridged across the trunk, causing relay 16 to operate. At its armature 19, the operation of relay 16 closes a circuit from ground by way ot the workingr contact springot armature 19 and armature 19 `through the winding ot relay 15to battery. At the resting contact ot spring controlled by armature 19, the original ener gizing circuit for relay 15 'over the sleeve` of jack J and plug P, including spring t2 and its resting contact and lamp L', 1s opened. Relay 15 is held operated bythe energizaf tionot its upper winding, but lampL is ezi-y tinguished, thereby signalling the operator that the vcalled party has answered. rPhe callingand called parties may now hold conversation. v

lWhen the conversation is completed, both parties will replace their receivers upon their respective switchhooks. Then the receiver is replacedat the` called substation B', the

yback bridge relay 210 is deenergized, revers'- ing the direction oi2 current flow back to its x original direction. As a result, the polarized relay 16 ialls back again closing the circuit which includes the lower winding of relay 15 and lamp L at the springs controlled by the armature 19. The lamp L is lighted, giving the signal to the. operator that the automatic subscriber B has replaced his receiver.

The subscriber at substation A, in addition to replacinghis receiver, gives the ring down signal by turning the crank of the magneto a i'ew times. This operation energizes the left hand winding of the ring down relay 13. Relay 13 immediately closes a locking lcircuit for itself at armature 29, which may be traced from ground by way otl the right hand winding ot relay 13, armature 29 and its working contact, normally closed springs 31, lamp L to battery. Lamp L is lighted, giving the signal to the operator thatvthe rural subscriber at A has replaced his receiver. y y

The koperator may now release. the connection by removing the plugs P and P from the jacks J and J3, respectively. Inremoving the plug P from jack J3, the circuit for relay 15 is opened.` Relay l'deenergizes andfopens the holding bridge across conductors 20 and 21 at armature 17, which causes the deenergization of the line relay 211 and release relay 212 of connector E. A circuit is thereby completed for the release magnet 221 which operates to restore the connector-to normal. AThe deenergization of relay 212 .also disconnects ground from the release trunk conductor 18S and holding conductor 209. As a result ot' removing ground from the holding conductor 209, the relays 214 and 219 which were held up are permitted to deenergize. The

removal of ground from the release conduc `relay 13 deenergized. All apparatus is again at normal.

Having described the various operations for completing a call trom a rural substation to an automatic substation, the operations in connectionr with completing a toll call to an automatic subscriber will be described. The operationv of the automatic switches will be similar to that in the previous case. Consequently a detailed description of the autoFV matic switches will not be repeated, la generalv description suiiicing. y

VAs explained before, the` toll lines terminate at the'operatofs position in jacks (not shown) -similar to ack (l, with drop signals similar to the associated dropsignal 2.y The operator is given a signal of an incoming'toll call by thek action ot a drop associated with a toll jack. To answer an incoming toll call,

the operator inserts the plug P into thecalling toll jack and throws the key K to the listening position. She may now talk to the distant toll operator to obtain the name or number of the desired subscriber. It is assumed that the called substation is substation E. For toll service, a special group of trunks to the automatic exchange are provided, one of which is the trunk comprising conductors 27 and 28 and the associated trunk circuit TG3. After learning the number of the party to be called, the operator inserts the calling plug i3 into an idle toll trunk jack, which we may assume to be jack J4. This operation 'closes the contact springs 44, and also completes a circuit for relay 23 which may be traced from ground by way of normally closed springs controlled by armature 24, lower winding of relay 23, sleeve of 'ack J4 sleeve of Dluo' P s )rin/142 and its b 7 23 resting contact, and lamp L to battery. lielay 23 is energized over this circuit and operates to open the shunt around the repeating coil M at armatures 25 and 26 by separating the normally closed contacts of springs controlled by armatures 25 and 26.

The n operation of relay 23 also closes a bridge across the conductors 27 and 28 which includes closed contact springs 44, working contact of the spring controlled by ari'nature 25 and said armature, upper right hand winst ing of repeating coil M, winding of polarized relay 227 and lower right hand winding of rei peating coil M. This bridge across conductors 27 and 28 closes a circuit for the line relay of the rotary line switch C2. Line switch C2, being similar to line switch C, operates to select a trunk to an idle selector in the same manner as was described in conn-ection with the description of the operation of C. A suming

trunk comprising conductors

150, 151 and 152 is the trunk selected, the line'relay 153 and release relay 154 of selector D energize to prepare the selector for operation.

After plugging in, the operator throws the key K2 in the dialling position. This operation removes battery at lamp L from relay 23 but supplies a new source of battery at resistance 50, as explained before. rllhe operator may now dial the desired number. Each time the dial is moved from its normal position in the process of dialling, the contact springs 14 are closed. Relay 28 is thereby shunted and deenergized. The dial is then bridged directly across the conductors 27 and 28 ahead of the repeating coil, the original bridge across the line being open at armature 25.

When the operator dials the first digit of the called number, the selector raises its

wipers

184, 185 and 186 to the particular level of contacts which is assigned to the group of connectors having access to the desired substation, and selects a trunk to an idle connector.

Assuming the trunk comprising conductors 187,188, and 189 is this selected trunk, the line Leanser,

relay 211 and release relay 212 energize and prepare the connector' E for operation.

When the operator dials the second digit, the connector raises its wipers 270-2i`3, inclusive, to the desired level. lWhen the third and last digit is dialled by the operator, the con nestor rotates its wipers to engage the contacts at which the conductors of the called line terminate. lf this line is busy, the busy relay 216 will be energized to give the operator the busy signal. Assuming the line is noty busy, the switching relay will energize to complete the connection to the called substation. Ringing current will then be sent out on the line to signal the called subscriber. When the called subscriber lifts his receiver to answer, the ring cut-off relay 214 is energized to cut orf the ring and make the lfinal connection between the called subscribed and the incoming toll line. Lifting the receiver at substation B" also causes the operation of the baclr bridge relay 210, which reverses the direction of current flow in

conductors

187 and 189 and through the polarized relay 22. Polarized relay 22 is thereby operated, closing a new circuit for relay 23, which extends from ground by way of the working contact of armature 24 and said armature, upper windingof relay 23 to battery. Art springs controlledby armature 24, the original circuit for relay 15, including sleeve of jack J4 and plug l, springs 42 and lamp L, is opened. Lamp L is thereby extinguished, giving the operator a signal indicating that the called subscriber has answered.

Should the operator wish to supervise or listen in on the conversation, she may throw her monitoring keyl K in the listening position. it springs 45, la circuit is closed for relay 12. Upon energizing, relay 12 opens the transmitter circuit at armature 45; opens the shunt around the receiver and connects the same across the line in series with the two secondary windings of the repeating coil N at armatures 46 and 47; and at armatures 48 and 49 disconnects the grounded impedance coils 52 from the vlistening circuit. The purpose of the impedance coils 52 is to give the listening circuit a ground potential for line testing purposes. Opening the transmitter circuit prevents any oiiice noises from being trans mitted to the line. Since the two secondary windings of the repeating coil N are connected in series forming a high impedance, only a minmum amount of voice currents are shunted away from their normal path when the. monitoring key K is thrown and conversation is not interfered with.

TWhen the conversation is completed and the talking subscribers hang up their receivers, the operator receives the usual disconnect signals. `When the automatic subscriber' at B hangs up his receiver, the back bridge relay 210 of the connector E deenergizes, thereby reversing the; direction of current flow back to normal. The polarized relay 22 re- -leases and closes the circuit for lighting the lamp L. The originating toll operator at the distant end of the toll line will ring off when the party at her end hangs up. This operates relay 13 which immediately establishes a locking circuit for itself through lamp L, lighting said lamp. rlhe operator now removes the plugs P and l from their respective jacks and thek automatic switches release as described before.

Let us now assume that an automatic subscriber such as B wi shes to talk to a rural subscriber. To complete this connection, the subscriber at B must first call the operator. When the calling subscriber at B removes his receiver, a bridge is placed across the

conductors

122 and 123, which completes a circuit tor the line relay of the line switch C. Line switch C, being similar' to line switch C', op-

erates to selecta trunk'to an idle selector in the same manner as was described in connection with the description of the operation ot C. f l

Assuming the

trunk comprising conductors

150, 151 and 152 is the trunk selected, the line relay 153and release relay 154 of selector D energize and prepare the selector for operation.

The subscriber at B now dials the number assigned to the rural service trunks. In response to the first digit dialled, the selector raises its wipers opposite the level which has access to that group of connectors in whose banks the trunks for rural service terminate, and then rotates its wipers to select a trunk to any idle connector of this group. Assuming the

trunk comprising conductors

187, 188, and 189 is the trunk selected, the line relay.211 and release relay Y212 energize immediately, and prepare the connector' E for operation. In response to the impulses of the second digit dialled, the connector raises its wipers 270-278, inclusive, opposite the level of contactsin which the rural service trunks terminate.` lfilhen the third and last digit is dialled, the connector rotates its wipers into engagement with the contacts of the vfirst trunk.

The operation of the connector 'romfthis point issomewhat diiierent-*than it was in the previous case. In addition to'having `a vertical and rotary motion, each responsive to impulses corresponding to a digit dialled, the connector has also an automatic rotary motion Jr'or selecting the tirst idle trunk of a group of trunks.

This is accomplished in the Ytollowing manner: ln a group of trunks, the test contacts similar to

contacts

281 and 282 of each trunk are connected together on all exceptthe last trunk ot the group. rllhus when a line becomes busy, ground is present upon both these contacts. Assuming that. the rst trunk ofl the group of rural service-trunks with which the wipers 2704278, inclusiveare f now engaged, is busy, ground lwillloe lpresent on

wipers

271 and 272. It will be remembered that relay 2171s energized in. series with the rotary magnet 22() and that relay 218 1s held operated during the rotary movement over a circuitcompleted at armat-ure 249 and its working contact. From ground on wiper 272, the test relay 216 will be energizedk as described hereinbetore and will operate to prepare a locking circuit for itselfat armature v245 and closeva point in the circuit of steppingrelay 215 at armature 244. ySoon after the termination of the impulses of the last digitdialled, relay 217 tails back and closes a circuit extending from ground on.

wiper 271 by way of the working contact of armature'251 and armature 251, resting contact of armature 248 and armature 248, working contact oit armature 244 and armature 244, armature A285 and its resting contact through winding of stepping relay 215 to battery. Relay 215 energizes and establishes al locking circuit for itself at'armature242 and completes the circuit of the rotary magnet 220 at armature 243. Relay 218 is also maintained operated in parallel with the rotary magnet. Magnet 220 attracts its armature 255, thereby rotating the connector wipers into engagement with the next set or' bank contacts of the selected level, and opening the-locking circuit ot the stepping relay 215. Relay 215-.falls back Aand breaks the circuit of the magnet ing magnet 220.

It' this next trunk line is busy, the stepping relay 215 will again energize from ground on switch wipers 'will be rrotated into engagement with the contacts of the third line o the group. The alternate operations of the stepping relay 215 and the rotary magnet 220 will continue until` an idle -line in the group is found or until the switch wipers are rotated into engagement with the'last line in the group. L If the lastline is also busy, there'will be ground potential present only upon the test contact `engaged by the test` wiper 272, since the test contacts ot the last line of the group similar to 281 and 282 are not joined together, and the stepping relay 220 thereby deenergiz-` test wiper 271 and the connector cannot again be energized. The testrelay 216 will remain operated, however, and a1 busy tone .will vbe given to the calling subfscriberin the same mannerr aswas described hereinbe'fore.

i It will Abe'assurned that the trunk compris ing conductors 82,83 andV 34 terminating inl i

contacts

280, 281, 282,' and 283 is the lirst idle trunk ot vthe groupl of rural service trunks. ln this case there will be no ground potential upon the test contacts 281- and.282 engaged'by the

test wipers

271 and 272.'

' Cond sequently, test relay 216 Will deenergize and stepping relay 215 will not be energized. As

`a result, the circuit for the rotary magnet 220 and relay 218 in parallel is opened at armature 243. Following the deenergization of the slovv acting relay 218, a circuit is i test contact 282, conductor 32, resting cont-ac;

of armature 8 and said armature through Winding of relay to battery. Relays 5 and 219 are energized over this circuit. The switching relay 219 operates and establishes a locking circuit for itself and completes a circuit for ringing current over the

conductors

33 and 34, as described hereinbefore. Relay 5, upon energizing, prepares 'the bridge including the upper Winding of relay 4, and normally open contact springs 52. Ringing current over

conductors

33 and 34 operates "the drop magnet 3 over a circuit which eirtends from conductor 34 through Winding of drop magnet 3, normally closed contact springs 61, and through condenser 84 to conductor 33. The release of the drop signals the operator Who inserts the answering plug P into the jack J2. This operation opens the circuit for the drop magnet 3 at springs 61, and closes the bridge across the

conductors

33 and 34 at contact springs 62. Relay 4 and ring cut-oil relay 214 are energized over this' circuit. Relay 4 operates to remove ground from the sleeve of the jack J2 at armature and opens the circuit of slovv-torelease relay 5 at armature 8. The ring cut-oil" relay 214, upon energizing, establishes a locking circuit for itself and cuts off th-e ring and linally completes the talking connections as pre- CII viously described. After the ring cut-oli' relay 214 has established its locking circuit, relay 5 falls back and, at armature 9, opens the shunt around the high resistance loiver Wind-l ing of relay 4. The baclr bridge relay 210 may or may not operate before this shunt is removed, depending largely on the adjustmentof relay 5, but after the back bridge re-V lay 210 is in'series With the two windings of relay 4, the current flow is insufficient to operate relay 210 or hold it in operation if it be operated. l

Ordinarily, in a connect-ion between one automatic subscriber and another automatic subscriber, the release of the selector is under the control of the calling party, but the connector is released by the party last to hang up his receiver, which may be either the called or calling party. When the calling party replaces his receiver first, the line relay 211 and release relay 212 are deenergized, but the connector is held up by the energization of the back bridge relay 210' Which supplies ground to the holding conductor 209 at armasivitchhoolrs.

ture 230, and holds the circuit of the release as soon as the calling subscriber replaces his receiver, giving the operator supervision as will be described hereinafter.

After plugging in, the operator throws the hey K to the listening position and may then hold conversation with the calling subscriber and obtain the number of the rural subscriber With which connection is desired.

Assuming substation A to be thisy desired party, the-operator tests the line to substation A in the usual manner by touching the tip of plug l?" to the sleeve of jack J. If this line to substation A, comprising conductors 10 and 11, `is busy through one of the other operators cords, there will be battery potential present on the sleeve at a lamp similar to L of cord circuit OC. Because of the ground potential on the talking strands of the cord at the impedance 52, there Will be a sudden drop in potential across the operators receiver, causing the cliclr in the receiver Which indicates a busy line.

Assuming the line to substation A is idle, the operator, hearing no click When testing, inserts the answering plug P into jack J and t irovvs the lrey K2 to the ringing positionv one or more times in accordance with the proper code to signal the substation A. The oper` ator keeps her listening key depressed until the subscriber A answers. lhen theftvvo parties begin conversing, she may release the listening lrey. f i

At the end of the conversation, both parties Will replace theirreceivers on their respective Subscriber A, in addition to replacing his receiver, rings off in the usual manner, as described hereinbefore. The ring-down relay 13 is thereby energized, closing a locking circuit for itself and lighting the disconnect signal lamp L. VhenA sub scriber B i replaces his receiver, the. bridge across the talking

conductors

122 and 123 is opened. Relays 211 and 212 of the connector fall back, thereby removing ground from the release conductor 188 and holding conductor 209 and closing the circuit for the release niagnets'of the selector l) and connector E as described before. The release of connector E, by disengaging its vvipers from contacts 280-284, inclusive, opens the circuit for the relay 4. Y a circuit extending from ground at resistance coil 6, by Way'of armature 7 .and its resting Relay 4, upon deenergizing, closes contact, sleeve of jack J2, sleeve of plug P, through lainp' L to battery. The lamp L is lighted over this circuit indicating to the operato'r that the subscriber at substation B has replaced his receiver and that she may pull down the connection.

Provisions have been made for giving the automatic subscribers outgoing toll service. 'Io make a long distance call an automatic subscriber, such as B, removes his receiver and dials the code number for long` distance service. Connection is extended through the line switch G, a selector and connector, such as D and E to an idle trunk of a group of toll trunks, which is similar to the trunk comprising conductorsBQ, 53 and 34, terminating at the operators switchboard in the jack J 2 and trunk circuit TC.

rIhe operator answers the call as described in the previous case, and obtains the name or number of the distant substation with which connection is desired and the number of the calling automatic subscriber. The operator records this information on a ticket and informs the calling subscriber that she will call'him when she has obtained connection with the distant substation. The subscriber at substation B may now replace his receiver, thereby releasing the connection.

rI`lie operator proceeds to establish the long distance connection. When notified of the completion of the connection to the distant subscriber, the operator recalls the automatic subscriber at substation B over one of the toll service trunks similar to the trunk comprising conductors 27 and 28. The connection is extended through the automatic switches, such as the line switch C, the selector D, and the connector E, containing the bank contacts 130, 131, and 132, to the substation B. The subscriber at substation B may now converse with the distant subscriber. v

At the termination of the conversation, the subscriber at B replaces his receiver. The lamp L is thereby lighted as described hereinbefore, indicating to the operator that she may disconnect. Before removing the plug- I? from the toll trunk jack, she givesthe disconnect signal to the distant toll operator by throwing the key K in the ringing position for a. short interval.

In order `to explain another method for completing a toll call, especially to a station easily obtainable, it will be assumed that a subscriber, as B, again calls the operator, as described above. The operator, after obtaining the number of the desired distant subscriber, may instruct the calling subscriber B to vhold the connection, keeping the plug P in' the jack of the toll recording trunk.

'By inserting the plug P into the liack of an outgoingtoll line, she may proceed to complete tlie connection in the usual, manner. es soon as the connection is completed, the

' of said jack loperator notifies the calling subscribers who may then commence conversation with the distantsubscriber. The method just described is similar to the method followed in extending calls to rural lines.

An automatic subscriber. at a substation such as B may wish to call the operator for information or for complaint. the code number for information or complaint service, connection is obtained to the operator over one of the information or coinplaint trunks which is similar to the

trunk comprising conductors

32, 33, and 34, `terminating at jack J 2 and trunk circuit TC', themanner of connection being similar to that described hereinbefore.

Any automatic subscriber may, of course, call any other automatic subscriber. i A connection lfrom the substation B to substation B extends through the line switch C, a selector such as D, and a connector such as E,`in whose banks the line to the substation B terminates.

That is claimed is:

l. In a telephone system, a trunk extending from a manual jack to an automatic switchboard, said trunk comprising two inductively connected sections, a cord circuit for connecting with said ack, a calling device and means for bridging the saine across the talking strands of said cord circuit, and means responsive each tiine'said calling device is operated for conductively connecting the two sections of said trunk line'together to enable said calling device to controlv the Vswitches at the saidautomatic switchboard over said trunk.

2. In a telephone system a cord circuit and trunk line temporarily connected bya plug and jack, said trunk line comprising two inductively connected sections, a bridge across onesection, a calling device bridged across saidcord circuit, and means operated automatically each time the calling device is set for opening said first bridge and for by-passing said inductive connections sothat the calling device can transmit impulses over the trunk line on restoring to normal.v

3. In a telephone system, a cord circuit and trunk line temporarily connected by a plug and jack, said trunk yline comprising two inductively connected sections, circuits for conductively connecting lay in the trunk held energized'over the sleeve to hold said circuits open, and the cord circuit for deenergize the same.

means associated with shunting said relay to 4f. In a telephone system, a cord circuit and trunk line temporarily connected by a plug and jack, said trunk line comprising two inductively connectedisections, circuits for conductively connecting saidl sections, a relay in the trunkheld energized over the sleeve 'of said `j ack to hold said circuits open, a calling device associated with said cor eir- By (inning,

said sections, Va recuit, said calling device having a dial, and means responsive to the movement of said dial from normal position for shunting said relay to deenergize the same.

5. ln telephone system, a cord circuit and trunk line temporarily connected by a plug and jack, said trunk line comprising tivo inductively connected sections, circuits for conductively connecting said sections, a relay in the trunk held e; ergized over the sleeve ot said jack to Vheld said circuits open, a calling device bridged across the cord circuit, oil' normal spri s actuated in the operation ci' said calling device, and means controlled by said springs for decnergizing said relay.

6. ln a ntclephene system, a temporarily established connection including a cord circuit and. a jack ending trunk circuit, a signal in the cord circuit and a relay in the trunk ci cuit energized in series over a circuit including the sleeve et said j ack, a supervisory relay bridged across said trunk circuit by the energization ci' said relay, contacts on said supervisory relay 't opening the sleeve circuit to restore said signal, a second circuit for holding said iirst relay energized While the sleeve circuit is open, said second circuit excluding the Winding of said first relay Which is included in said lirst circuit.

'l'. ln a telephone system, a temporarily stablished connection including a cord circuit a jack ending trunk circuit, a signal in the cord circuit and a relay in the trunk circuit energized in series over a circuit including the sleeve of said jack, a second circuit for said relay, and a relay connected with the trunk by said .tiret relay and controlled thereover to open the sleeve circuit and close the said second circuit, whereby the signal is restored Without restoring said first relay.

8. ln a jack ending trunk circuit, two condensers inserted in the tivo talking leads, respectively, a relay having a circuit including the sleeve or said ack, shunt circuits tor said condensers controlled by said relay, a supervisory relay arranged to be bridged across the trunk by the operation of said lirst relay, contacts on supervisory relay for opening the said sleeve relay circuit, and a local circuit for said sleeve relay also controlled by said supervisory relay.

9. ln a `iack ending trunk circuit comprising two inductively connected sections, a relay controlled over the sleevev of said jack, contacts on said relay for opening and closing conductive connections between said sections, and a second relay controlled over one of said conductive connections for controlling said lirst relay independent of the sleeve of said jack. v Y

10. In combination, a cord circuit, a battery Y for supplying current, a sleeve conductor connected to a supervisory signal, the other termin al of which is connected to one pole of the battery, a calling device, a key for associating said device with the talking. strands of said cord circuit, said key having contacts for shifting said sleeve conductor from said signal to a similarly connected resistance, and a relay responsive to the operation of said calldevice for connecting the said sleeve conductor to the other pole ot the battery.

ll. ln a telephone system, a trunk line terminating in a jack at a manual switchboard, a relay individual to said trunk line, aV second relay controlled over the sleeve of the jack for bridging said first relay across the talking conductors of said trunk line When a plug is inserted in said jack, a battery, a conductive connection from one pole ot the battery to the sleeve oi said jack, and contacts on said iirst relay for disconnecting said battery fr m the sleeve of said ack and for closing a local circuit for said second relay.

l2. In a telephone system, a temporarily established connection including an automatic connector switch, a trunk line kseized by such switch, and a manual cord circuit, the trunk line and cord circuit being connected through a plugl and jack, a signal in said cord circuit having circuit including the sleeve of Said j ack, and a relay individual to said trunk line held energized thcreover by current supplied from said switch to hold the circuit ot' said signal open.

13. ln a telephone system, a trunk line eX- tending to a jack at a manual switchboard, a connector switch for connecting with said trunk line, said connector including means for projecting ringing current over said trunk line to signal the operator, a battery feedrelay and a ring` cut-oil1 relayin said connector,V

a double Wound relay individual to the trunk line having high and lo\v resistance windings in series, a slow acting relay energized when the connector connects with said trunk line to short circuit said high resistance Winding, means for bridging said double Wound relay across the trunk line when the operator responds, said double Wound relay thereupon having its loiv resistance Wincing energized in series With the said ring cut-oil relay, contacts on said ring cutoli relay for bridging said battery feed relay across the connected trunk line, and contacts on said double Wound relay for opening the circuit of said slow acting relay, whereupon the latter is deenergized to remove the short circuit from said high resistance Winding to prevent the energizainductively con? ot said repeating coil so that the calling de.-

vice can transmit impulses over the trunk .line on restoring to normal.

JluO and 'ack said trunk line comorisinv two C 7 .L Y C sections, a repeating coil inductively connecting said sections, circuits for conduetively connecting said sections, a relay in the trunk held energized over the sleeve olf vsaid jack to hold said circuits open, a calling device associated with said cord circuit, and means responsive to the movement of said device from normal position tor shunting said relay to deenergize the saine.

`17. in a telephone system, a cord circuit and a trunk line temporarily connected by a plug and jack, said trunk line comprising two sections, a. repeating .coil inductively connecting said sections, circuits for conductively connecting said sections, a relay in the trunk held energized over the sleeve of said jack to hold said circuits open, a calling device bridged across the cord circuit, oit normal springs actuated in the operation of said calling device, and means controlled by said springs for deenergizing said relay.

18. In a jack ending trunk circuit, a repeating coil dividing said trunk circuit into two inductively connected sections, a relay having a circuit including the sleeve of the jack of said trunk circuit, circuit connections 'tor coiiductively connecting said sections controlled by said relay, a supervisory relay connected in series with a winding ofsaid repeating coil, contacts on said supervisory i'ea cord circuit lay for opening the said sleeve relay circuit, and a local circuit for said sleeve relay also controlled by said supervisory relay.

19. In a jack ending trunk circuit comprising two sections, a repeating coil :tor inductively connecting said sections, a relay controlled over the sleeve of the jack of said trunk circuit, contacts on said relay for open ing and closing conductive connections between said sections, and a second relay controlled over one of said conductive connections tor controlling said tirst relay independent ot the sleeve of said jack.

20. In a jack ending trunk circuit comprising two sections, a repeating coil for inductively connecting said sections, a relay controlled over the sleeve of the jack of said trunk circuit, contacts on said relay Yfor open ing and closing conductive connections between said sections and for disconnecting said repeating coil whenever said conductive connections are closed, and a second relay controlled over one of said conductive convnectio'ns for controllingsaid first relay independent ot'tlie sleeve of said jack.

21. 1n combination` a* cord circuit, an operators telephone set adapted to be connected to said cord circuit, two retard coils connected in series across the talking leads oi' said telephone set, a battery connected to the june tion of said two retard coils, and a relay Jr'or disconnecting said two retard coils from the rtalking leads of said telephone set.

22. In combination, a'cord circuit, an operators telephone set, a listening key for conf necting said telephone set with said cord circuit, two retard coils connected in series across the talking leads of said telephone` set, a monitoring key for connecting the receiver ,of said telephone set to said cord circuit independent of the transmitter of said telephone set, and means controlled by said monitoring key for disconnecting said retard coils from said talking leads.

In witness whereof, I hereunto subscribe my naine tliis 12th day'of January, A. D.,

THOMAS F. ciiocKER. I