US1943402A - Telephone system - Google Patents

Description

Jan. 16, 1934. B. WALLACE 1,943,402

' TELEPHONE SYSTEM Filed June 16, 1932 2'SheetsSheet l I H 757E775? BE JTHZ/Z/a/[ac'E' 2 Sheets-Sheet 2 w mm a am. R

B. A. WALLACE TELEPHONE SYSTEM Filed June16, 1932 Jan. 16, 1934.

W w n H ur'ne BET'THl/Z/H/[HE'E JZL I Patented Jan. 16, 1934 STATES PATENT FFi 1'1".

TELEPHONE SYSTEM Application June 16,1932. Serial No. 617,537

17 Claims.

My invention relates to telephone systems and has to do more particularly with systems for interconnecting telephone lines terminating at the same or different exchanges and has for its object a novel and improved circuit arrangement.

The circuit of my invention is equally eflicient in interconnecting two subscribers whose lines terminate at the same exchange or at diiierent exchanges associated with eachother by a 1g straightforward trunk. circuit as is well known in the art. Means are provided in the circuit which function upon the replacement of the subscribers receivers upon their switchhooks to instantaneously disconnect the respective lines is from the cord. circuit to permit an immediate re call evidenced. by the illumination of the line lamp associated with the line of the calling subscriber.

Another feature of my invention is the provision of means which place the control of a local 2; to trunk connection under the supervision or the local calling subscriber so that the trunk line is instantaneously released and ready for use in setting up another connection as soon as the local calling subscriber hangs up provided the called subscriber has not answered or has previously replaced his receiver.

A further feature is theprovision of means which function when the calling subscriber recalls on a local to trunk connection to switch from instantaneous disconnect with line lamp recall to a flashing recall appearing only before the original operator so that she may properly time and supervise the connection or attend the desires of the recalling subscriber.

Another feature of my invention is the provision of a listening key in association with the keyless listening and secret service means operable on a local to local connection. The listening key permits the operator to cut in only on local to 40 trunk connections for supervision purposes or to answer a recall on such a connection.

Further features of my circuit are selective party line machine ringing on local to local connections; dark keyshelf and double lamp discon- 5 nect supervision; non-ringing on trunk connections and an automatic peg count meter for answered calls.

Other features will become apparent upon a. further perusal of the specification and together I with the features above enumerated, will be explained fully hereinafter, reference being had to the accompanying drawings comprising Fig. 1 and Fig. 2 inclusive. When Fig. 2 is placed to the right of Fig. 1 they illustrate a complete circuit arrangement for extending a connection from a subscriber at one exchange to a subscriber at a. distant exchange.

Referring now particularly to Fig. l, I illustrate at the left of the drawing a calling common battery substation A terminating at a local exchange E in a line circuit L. The line circuit L comprises a line relay LR, a cut off relay CO and multiple answering jacks J associated with multiple line lamps S. The jacks J and lamps S appear before a plurality of operators and a call initiated at the substation A will appear before a plurality of operators at different positions of the switchboard as is well understood.

The link or cordcircuit C is but one of a plurality of similar cord circuits furnished each of the operators and may be used to interconnect a pair of lines local to the exchange E or one of such lines with a distant exchange. This circuit C comprises an answering plug AP and a calling plug CP connected by the heavily marked or talking conductors having condensers CD and CD interposed therein. The answering end of the link C consists of an answering sleeve relay ASL which is energized when the answering plug AP is inserted into a jack J of the calling line to connect the operators set C) to the cord conductors. An answering supervisory relay ASR controlled by the switchhook of the calling line in turn controls an answering supervisory lamp AS provided for the usual supervisory purposes. The 35 calling end of the link circuit C comprises calling sleeve relays CSL and CSL; the said sleeve relay CSL operating when connection is made with either a local line or with a trunk leading to a distant exchange. The sleeve relay CSL' is a marginal relay and energizes when connection is made with a trunk line but does not energize when the cord C is connected to a local line.

An operators disconnect relay ODR is provided and energizes upon the operation of the calling sleeve relay CSL to disconnect the operators set 0 from the cord conductors. A local disconnect relay LDR is provided to deenergize the answerdrawal of the calling plug from the associated jack.

A ringing control relay RCR, a ringing interrupter relay RI and a party line ringing key RK associated with the ringing generators G, G, G G and G provide means for signalling the desired subscriber on a local line. A calling superviscry relay CSR and a calling supervisory lamp CS are provided for the usual supervisory purposes. A flashing supervisory signal control relay FCR connects the answering lamp AS to a constantly rotating interrupter I to cause the lamp to flash to indicate a recall by a subscriber on a local to trunk connection. A listening key LK permits the operator at the local exchange E to connect her set to the cord conductors so that she may properly time and supervise a local to trunk connection and answer a recall in response to the flashing recall signal on such a connection. To the right of Fig. 1 I illustrate a called local substation B associated with a line terminating at the exchange E in a line circuit L' consisting of line relay LR, cut off relay CO, multiple line jacks J and multiple line signals S.

In Fig. 2 I show multiple trunk jacks TJ associated with multiple trunk busy lamps TBL and a trunk cut ofi relay TCO which operates when the trunk is busy to cause the illumination of the lamps TBL to inform the operators before whom they appear that this particular trunk is busy. The apparatus just mentioned is all located at the local exchange E and the dotted portion of the heavily marked conductors indicates the trunk line extending to a distant exchange F where it terminates in coils a and c of repeating coil RC.

-A condenser C is placed between the said coils a and 0 but a trunk bridging relay TAC is bridged across said condenser C and is actuated by current from the connected cord circuit C to cause the operation of a trunk signalling relay TSI which lights the trunk answering lamp TAL to indicate an incoming call to the trunk operator. The trunk operators set TO can be connected thru the contacts of a trunk listening key 'ILK to coils b and d of the repeating coil RC and condenser C connected in series therewith.

A trunk sleeve relay TSL operates when the trunk plug TP is inserted into a multiple jack J to interrupt the energizing circuit for the trunk answ g lamp TAL. A trunk. ringing key TRK and a ringing generator G are provided to signal the subscriber T whose line terminates at the exchange F in a line circuit L consisting of multiple jacks J and lamps S line relay LR and a cut on" relay 00 LR is operated by current flowing from grounded battery thru relay LR, normal closed contact 2 of CO over the line conductors and thru the closed contacts of the switchhook to ground at normal contact 3 of CO. The relay LR energizes.

and closes its alternate contact 4 to complete an obvious operating circuit for the line signals S. The lamps S appear before a plurality of operators and any one of these operators can seize the incoming call to the exclusion of the other operators. Assume that the operator associated with the cord circuit C seizes the call by inserting the answering plug AP of the cord circuit C into the answering jack J of the calling line. This insertion establishes an energizing circuit for the answering sleeve relay ASL which circuit can be traced from grounded battery thru windings 5 and 6 of ASL, conductor 7, normal closed contact 8 of line disconnect relay LDR, sleeve contacts of the connected plug AP and jack J, thru the winding of out off relay CO to ground. The sleeve relay ASL energizing closes its alternate contact 9 thereby shunting out its high resistance winding 6 and allowing the cut oil relay CO to be operated by current flowing over the previously described path with the exception of high resistance winding 6.

The relay CO upon energization opens its normal contacts 2 and 3 which interrupts the energizing circuit of the line relay LR and causes its restoration to efface the line signals S by opening contact 4. The relay ASL upon energizing closes its alternate contacts 10 and 11 to close the talking conductors and to connect the operators set 0 to the talking conductors over conductors 12 and 13, normal contacts 14 and 15 of operators disconnect relay ODR, conductors 16 and 1'7, alternate contacts 10 and 11 of ASL, to tip and ring conductors of the cord 0. The closure of contacts 10 and 11 of ASL establishes a circuit for the answering supervisory relay ASE which is operated for supervisory purposes by current flowing from grounded battery thru the lower winding of ASR, alternate contact 11, thru the subscribers loop, alternate contact 10, thru the upper winding of ASR to ground. If another operator attempts to seize the call subsequent to the seizure by the operator of the cord C, the

'insertion of the answering plug of the second cord into a multiple answering jack will have no effect upon the answering sleeve relay of the second cord as it cannot operate in shunt with the low resistance path thru the winding 5 of ASL of cord C as the high resistance winding of relay ASL of the second cord is included in the circuit. The relay ASL of the second cord does not operate and fails to connect the operators set to the calling line and the operator failing to receive a response to her inquiry withdraws her plug from the jack. The relay ASR establishes a circuit for the automatic answered call peg count meter which circuit may be traced from battery, normal contact 26 of CSL, conductor 59, normal contact of ODR, alternate contact 61 of ASR and the meter punching M which is connected to the metering apparatus (not shown) to register an answered call.

The operator of the cord C having been con-.

nected to the cord conductors as before described inquires the wants of the calling subscriber and learning that'a connection with the subscriber B is desired tests the jack J' leading to the subscriber B by touching the tip of the calling plug GP to the sleeve of the jack J. If the line is busy 2. battery potential will be present on the v sleeve of the jack J.

This current will flow thru the tip conductor of CP, conductor 23, normal contact 24 of ODR, conductor 25, thru the tertiary winding of the operators induction coil 010 to ground. This flow of current will cause a click in the operator's head set and thereby indicate the busy condition of the called line. Upon the transmission of this information to the subscriber A he replaces his receiver upon its switchhook and the operator will disconnect the answering plug AP from the line jack J and restore the circuits to normal.

If the called line is idle the operator inserts the calling plug CP into the jack J of the called line thereby closing an energizing circuit for the calling sleeve relay CSL and the cut-off relay C of the line circuit L. These relays are energized by current flowing from grounded battery at the disconnect sleeve relay DSL, normal contact 17 of said relay, normal contact 18 of the trunk disconnect relay TDR, normal contact 19 of the line disconnect relay LDR, conductors 20 and 21, the winding of the calling sleeve relay CSL', conductor 22, the winding of the .calling sleeve relay CSL, sleeve contacts of the connected plug CP and jack J through the winding of the cut on relay CO to ground. The calling sleeve relay CSL energizes and closes its alternate contact 26 to establish an energizing circuit for the operators disconnect relay ODR which is operated by current flowing from grounded battery, alternate contact 26 of CSL, conductor 27, winding of ODR to ground. The relay ODE opens its normal contacts at armatures l4, l5 and 24 to disconnect the conductors 12, 13 and 25 which lead to the operators set from the cord conductors.

The closing of alternate contact 49 of relay ODE establishes an energizing circuit for the flashing recall relay FOR which circuit can be traced from grounded battery, alternate contact 49, conductor 50, alternate contact 51 of relay ASE, the winding of relay FOR/to ground. The opening of normal contacts 28 and 29 of relay CSL prevents the operator from connecting her set 0 to the cord conductor should she actuate her listening key LK. The closing of alternate contact 30 of relay CSL closes a circuit for the calling supervisory lamp CS traced from battery, thru alternate contact 30, conductor 31, normal contact 32 of calling supervisory relay CSR, normal contact 33 of CSL, conductor 34, normally closed contact 35 of ringing control relay RCR, conductor 36, the lamp CS to ground. The calling supervisory lamp CS is lighted over this circuit and remains in such condition until the operator depresses the ringing key to signal the called subscriber at substation B.

The operator signals the subscriber at substation B by depressing one of the ringing key plungers of the party line ringing key RK to connect ringing current of the proper frequency to operate the call signal at the called substation B. Assuming that the generator G is of the proper frequency the key plunger associated with this generator is moved to its fully depressed position in which position the end spring contacts 38 and 39 of the ringing key RK are also closed. The closure of alternate contact 38 of the end spring contacts establishes an energizing circuit for the ringing interrupter relay RI which circuit may be traced from ground thru the winding of relay RI, conductor 37, alternate closed contact 38, conductor 34, normally closed contact 33 of calling sleeve relay CSL', normally closed contact 32 of calling supervisory relay CSR, conductor 31, and alternate contact 30 of calling sleeve relay CSL to grounded battery. The relay RI energizes and closes its alternate contact 42, thereby estabc lishing a circuit for the ringing current to give an initial ring at the called subscribers station. The circuit for the ringing current can be traced from grounded side of the generator G, alternate contact 40 of key RK, conductor 41, alternate contact 42 of relay RI, alternate contact 29 of CSL, the tip contacts of connected plug CP and jack J thru the call signal at the subscribers station B, the ring contacts of jack J and connecting plug CP, alternate contact 28 of relay CSL, conductor 43, alternate contact 44 of ringing interrupter relay RI to ground The ringing control relay RCR is also energized by current flowing over the circuit closed at contact 39 of the end springs which may be traced from ground thru the winding of ringing control relay RCR, conductor 40, alternate contact 39 of end springs, conductor 34, normally closed contact 33 of CSL', normally closed contact 32 of CSR, conductor 31 and alternate contact 30 of CSL to grounded battery to efiace the lamp CS and establish a locking circuit for itself which circuit can be traced from grounded battery, alternate contact 30 of CSL, conductor 31, normally closed contacts 32 and 33, conductor 34, alternate contact 35, thru the winding of relay RCR to ground. Relay RCR closes contact .46 thereby connecting a constantly rotating interrupter I in a series circuit with the ringing interrupter relay RI, thru the normally closed contact 38 of the end springs of key RK, which assumed its normal position when released by the operator, which causes the intermittent operation of ringing interrupter relay RI to alternately connect and disconnect ringing current to the called line. The breaking of normally closed contacts 62 and 63 by relay RCR opens the talking conductors and prevents the flow of ringing current back to the called subscriber A. However, a revertive ringing tone is transmitted to the calling subscriber to inform him that the operator is signalling the desired party. This revertive ringing tone can be traced from the punching RE which is connected to a ringing tone machine, not shown, alternate contact 64 of relay RI, to the heavily marked cord conductor which leads to the calling subscribers station A. The relay RI alternately opens and closes the make-before break contact 150 to form a shunt circuit across the called line to discharge any ringing current which may be charged thereon and thereby prevent the operation of relay CSR by this charge to signal a false completion of the call.

The subscriber at the substation B in response to his call signal removes his receiver from the switchhook and when the relay BI is in a deenergized position as it is during a silent period of the ringing cycle an energizing circuit is'established for the calling supervisory relay CSR. The relay CSR is operated by current flowing from grounded battery thru the upper winding of relay CSR, conductor 46, normally closed contact 44 and relay RI, conductor 43, alternate contact 28 of CSL, ring contacts of CP and J thru the closed switchhook contacts at substation B, the tip contacts of J and CP, alternate contact 29 of CSL, normal contact 42 of relay RI, thru the lower winding of relay CSR to ground. The opening of normally closed contact 32 of CSR opens the locking circuit of relay RCR which accordingly restores to normal to disconnect the interrupter I from the relay RI and prevent a further operation of ringing interrupter relay RI. The opening of contact 32 of CSR also breaks the operating circuit of the calling supervisory lamp OS to prevent its operation upon the closure of normal contact 35 of RCR. The calling subscriber at the substation A and the called subscriber at the substation B are now in a conversational circuit which may be traced over the heavily marked conductors and the interspersed condensers CD and CD.

Upon the termination of the conversation the subscribers at the substations A and B replace their receivers upon their respective switchhooks. The replacing of the receiver at the substation A opens the energizing circuit of the answering supervisory relay ASE at the switchhook contacts and the relay ASE upon deenergization closes its normal contact 51, to establish an energizing circuit for the local disconnect relay LDR which relay is energized by current flowing from grounded battery, alternate contact 49 of relay ODR, conductor 50, normal contact 51, alternate contact 52 of "PCB which is slow to release due to its construction, conductor 53, normally closed contact 54 of CSL, conductor 55, normally closed contact 56 of TDR, thru winding of LDR. to ground. Relay LDR operates and closes its alternate contact 58 thereby establishing a circuit for the answering supervisory signal AS which can be traced from grounded battery thru the lamp AS, alternate contact 58, to punching AP which is connected to ground thru a common pilot relay, not shown in the drawings. A locking circuit for relay LDR is also established at contact 57 traced from grounded battery, alternate contact 49 of relay 0BR, conductor 50, alternate contact 57 of relay LDR thru winding of LDR to ground.

The replacing of the receiver at the called substation 33 opens the energizing circuit of the calling supervisory relay CSR at the switchhook contacts and the closing of its normal contact 32 again establishes a circuit for the calling supervisory lamp CS thru alternate contact 30, conductor 31, normal contacts 32 and 33, conductor 34 and normal contact 35 of RCR. The restoration to normal of contact 48 of CSR interrupts the energizing circuit of the calling sleeve relay CSL which was held'up thru alternate contact 48 after the local disconnect relay LDR. had operated to attract its armature 19. The restoration of contact 30 of CSL interrupts the circuit for lamp CS but a substitute circuit is closed at normal contact 28 of CSL. The lamp CS is maintained in its operated condition by current flowing from battery, normal contact 25 of CSL, conductor 59, alternate contact of ODR, conductor 8'7, to ground at the lamp CS. The disconnect sleeve relay DSL is operated by current flowing from grounded battery thru the winding of DSL, conductor 21, resistance 65, sleeve contact of the plug CP and jack J to ground thru the winding of the cut on? relay CO. The winding of disconnect sleeve relay DSL is of high resistance and its series connection with the resistance causes the cut off relay CO and relay CSL to release and thereby condition the called line for a line lamp recall or another outgoing call.

The local disconnect relay LDR also attracts its normally closed contact 8 to interrupt the circuit of the answering sleeve relay ASL which restores and opens the talking conductors at contacts 10 and 11. The opening of contact 8 of LDR also causes the restoration of cut off relay CO so that the calling subscriber may initiate a recall by removing his receiver which will again bring about the energization of the line relay LR to light the line signals LS and the same operator who answered the original call may seize the recall or any one of a plurality of operators may seize it as is well understood from the previous description.

AS and CSInow removes the plugs and C? from the respective jacks J and J and the removal of the answering plug AP from the jack J disconnects the answering end of the cord 0 from the calling line. The removal of the calling plug CP from the jack J opens the energizing circuit of the disconnect sleeve relay DSL which opens its contact 17 to cause the restoration of relay ODR.

The opening of contact 49 of ODR disrupts the energizing circuits of the local disconnect relay LDR and the answering supervisory lamp AS both of which restore to normal. The restoration or" alternate contact 60 of ODR effaces the calling supervisory signal CS. The apparatus used in establishing the connection above described is now at normal and available for establishing other connections.

If the called subscriber at B does not respond to his call signal the calling subscriber at A can release the entire connection by replacing his receiver upon its switchhook. The relay ASR deenergizes and closes its normal contact 51 to close an energizing circuit for the local disconnect relay LDR which operates and interrupts the locking circuit of ASL and CO at contact 8 and closes an illuminating circuit for answering supervisory lamp AS at contact 58. The deenergization of relays ASL and CO sever the calling line from the cord and enable the subscriber at A to initiate a recall which will be evidenced by the lighting of the multiple line lamps S in the usual manner. The relay LDR interrupts the circuit of CSL at its contact 19 which restores its alternate contacts 26 and 30 to normal. The opening of alternate contact 30 interrupts the locking circuit of ringing control relay RCR which prevents the further application oi: ringing current to the called line. The calling supervisory lamp CS is illuminated by battery at normal contact 26 of CSL to signal for a disconnection. The relay DSL operates over a previously traced circuit to cause the deenergization oi the cut oiT relay CO which places the called line in its normal condition to permit the initiation of a new call in the usual manner. The operator upon noticing the lamps AS and CS will withdraw the plugs AP and CP from the jacks of the lines with the results above described.

In the establishment of a local to trunk connection such as is necessary when subscriber A at exchange E desires to communicate with the subscriber T at the exchange F the operation of the circuit arrangement shown in Fig. 1 is the same as previously described up to and including the connection of the operators set 0 to the cord conductors of the cord circuit C. The operator inquires the wants of the calling subscriber at the substation A and is informed that the subscriber at T is wanted. The operator inserts the calling plug CP into a multiple jack TJ of an idle trunk line terminating at her position and extending to the distant exchange F. This causes the operation of calling sleeve relays CSL and CSL and trunk out oii? relay TCO by current flowing from battery, normal contact 17 of DSL, normal contact 18 of TDR, normal contact 19 of LDR, conductors 20 and 21, winding of CSL', conductor 22, Winding of CSL, sleeve contacts of CP and trunk jack TJ, winding of trunk cut off relay TCO to ground. Relay TOO closes its alternate contact 55 to establish an obvious energizing circuit for the multiple trunk lamps TBL which light to inform the operators at the other posi- The operator noting the two lighted signals tions that this particular trunk is busy. The operation of sleeve relay CSL establishes an energizing circuit for the operators disconnect relay ODR which is operated by current flowing from grounded battery, alternate contact 26 of CSL, conductor 2'7, winding of ODR to ground. ODR operates to disconnect the operators set 0 from the cord conductors. The operation of calling sleeve relay CSL' establishes a circuit for the calling supervisory signal CS which is accordingly actuated by current flowing from grounded battery, alternate contact 30 of CSL, conductor 31, normal contact 32 of CSR, alternate contact 33 of CSL, conductor 87, lamp CS to ground. The calling lamp CS remains lighted until the subscriber at substation T answers the call.

The closure of contacts 28 and 29 of CSL establishes an energizing circuit for trunk relay TAC the circuit for which can be traced from grounded battery, thru the lower winding of CSR, conductor 4'7, normal contact 42 of RI, alternate contact 29 of CSL, tip contacts of CP and TJ, conductor 67, winding a of repeating coil RC, upper and lower windings of relay TAC, winding 0 of RC, conductor 63, ring contacts of TJ and CP, alternate contact 28 of CSL, conductor 43, normal contact 44 of RI, conductor 46, upper winding of CSR to battery. The relay CSR does not operate due to the high resistance of the windings of relay TAC. The operator throws her listening key LK to connect her operators set 0 to the cord conductors thru alternate contacts '75 and '78 of CSL.

The bridging relay TAC is operated by the flow of current and closes its alternate contact 69 to establish an energizing circuit for the trunk signalling relay TSI which is operated by current flowing from grounded battery thru the winding of TSI, conductor '70, to ground at alternate contact 69 of TAC. The relay TSI closes its alternate contact '71 thereby establishing an energizing circuit for the trunk answering lamp TAL which is operated by current flowing from grounded battery, thru lamp TAL, alternate contact '71 of TSI, normal contact '72 of trunk sleeve relay TSL to ground. The lighting of lamp TAL informs the operator attending the position at which the trunk line terminates that a call has been placed and she thereupon throws her listening key TLK to connect her operators set TO to the talking conductors of the trunk circuit which places her in a conversational circuit with the operator at the exchange E. This circuit may be traced from the trunk operators set TO, alternate contact '73 of TLK, winding 13 of RC, condenser C winding (1, alternate contact '74 of TLK to the trunk operators set TO.

The other side of the circuit can be traced from operators set 0 at the exchange E, conductor 12, alternate contact '76 of LK, alternate contact '75 of CSL, normal contact 42 of RI, alternate contact 29 of CSL, tip contacts or" the plug CP and trunk jack TJ, conductor 67, winding a of RC, condenser C winding 0, conductor 68, ring contacts of trunk jack TJ and plug CP, alternate contact 28 of CSL, conductor 43, normal contact 44 of RI, conductor 46, alternate contact '78 of CSL, alternate contact '77 of LK, conductor 13, to operators set 0. The operator at O informs the operator at T0 that the subscriber T is desired.

After testing the called line and finding it idle the trunk operator inserts the trunk plug TP into the jack J associated with the called line T. This causes the operation of trunk sleeve relay TSL and out 01f relay CEO by current flowing from grounded battery thru the winding of TSL, sleeve contact of trunk plug TP and jack J the winding of cut off relay CO to ground. The relay TSL operates and opens its normal contact '72 thereby elfacing the trunk answering lamp TAL. The operator next actuates her trunk ringing key TRK to signal the called subscriber T. The circuit for the ringing current can be traced from the grounded side of the generator G thru generator G alternate contact '79 of TRK, normal contact 83 of TDA, tip contacts of plug TP and jack J 2 thru the call bell at the substation T, ring contacts of jack J 2 and trunk plug TP, normal contact '81 of TDA, alternate contact 30 of key TRK to ground. The subscriber T removes his receiver from its switchhook in response to the call signal and as soon as the trunk ringing key TRK is restored to normal the trunk supervisory relay TSR is operated by current flowing from battery thru the lower winding of TSR, winding d of RC, normal contact of key TRK, thru the now closed switchhook contacts at substation T over the circuit previously traced for ringing current, back thru normal contact '79 of key TRK,

thru the upper winding of TSR to the other side of battery. The operator restores her listening kcyTLK to disconnect her operators set TO from the talking conductors of the trunk circuit. The closure of alternate contact 84 of relay TSR provides an .energizing circuit for the calling supervisory relay .CSR of the cord circuit C. This relay is operated by current flowing from grounded batterythru the upper winding of CSR, conductor 46, normal contact 44 of RI, conductor 43, alternate contact 28 of CSL, ring contacts of plug Cl and trunk jack TJ, winding 0 of RC, lower winding of relay TAC, conductor 85, alternate contact 84 of TSR, conductor 86, winding a of RC, conductor 67, tip contacts of trunk jack TJ and plug CP, alternate contact 29 of CSL, normal contact 42 of RI, lower winding of CSR to ground. Prior to the closure of alternate contact 84 the relay TAC was held energized by the flow of current over this circuit thru both windings of the relay TACw but the shunting of the upper winding of relay TAC by the closure of alternate contact 84 of TSR provides a low resistance path for the flow or" current which allows the calling supervisory relay CSR to operate. CSR opens its normally closed contact 32 to efface the calling supervisory lamp CS which informs the operator that the subscribers are now in a conversational circuit.

Upon the termination of conversation the subscribers replace their receivers upon their respective switchhooks and the replacing of the receiver at the called substation T at the distant exchange causes the restoration of the trunk supervisory relay TSR which restores its contact 84 thereby opening the energizing circuit of the calling supervisory relay CSR which closes its normal contact 32 to establish a circuit for the calling supervisory signal CS which circuit may be traced from grounded battery, alternate contact 30 of CSL, conductor 31, normal contact 32, alternate contact 33 of CSL', conductor 8'7, lamp CS to ground. The lighted lamp informs the operator that the trunk subscriber has restored his receiver to its switchhook.

The restoration of the receiver at substation A causes the deenergization of answering supervisory relay ASR which restores its contact 51 to its normal position to interrupt the energizing circuit of the flashing recall relay FCR. The relay FCR is provided with a copper sleeve to make it slow in releasing and the energizing circuit for the trunk disconnect relay TDR is established and the relay TDR is operated by current flowing from grounded battery, alternatecontact 49 or" ODE, conductor 50, normal contact 51, alternate contact 52 of FCR, conductor 53, alternate contact 5% of CSL, conductor 88, thru the winding of trunk disconnect relay TDR. The relay TDR closes alternate contact 89 to close a circuit for the lighting of answering supervisory relay AS which circuit can be traced from grounded battery thru the lamp AS, alternate contact 89 of TDR, conductor 90, normal contact 91 of FCR to ground, not shown, on the answering pilot punching AP. The lighted lamp AS informs the operator that the subscriber A has replaced his receiver.

The closure of alternate contact 92 of TDR provides a locking circuit for itself which may be traced from battery, alternate contact 49 of 0BR, conductor 93, normal contact 94 of listening key LK, conductors 95 and 9S, alternate contact 92 of TDR, the winding of TDR to ground. The opening of normal contact 18 of TDR opens the energizing circuit of relays CSL and CSL which restore to normal. The contacts 28 and 29 of CSL restore to normal and interrupt the circuit for trunk relay TAC which deenergizes and restores its contact 69 to cause the restoration of trunk signalling relay TSI which closes its normal contact 101 to form an operating circuit for trunk d sconnect relay TDA. Current flowing from grounded battery thru the relay TDA, normal contact 101 of T31, and alternate contact of TSL to ground operates relay TDA which thereupon closes its alternate contact 102 to close a locking circuit for itself and closes alternate contact 103 to light the trunk disconnect lamp TDL. The lighting or" TDL informs the trunk operator that the subscribers are ready to be disconnected. The withdrawal of TP from J causes the deenergization of TSL which restores its contact 72 to open the locking circuit of TDA which restores and eifaces the lamp TDL. It is evident from the above that the trunk is instantaneously released upon the replacement of the calling subscribers receiver. The restoration of relays CSL and CSL allows the disconnect sleeve relay DSL to be operated by current flowing from grounded battery thru the winding of DSL, conductor 21,

resistance 65, sleeve contacts of plug CP andtrunk jack TJ, the winding of trunk cut off relay TCO to ground. The resistance of the winding of relay DSL is so high that the trunk cut off relay TCO will restore to normal and open its contact 66 thereby efiacing the trunk busy lamps TBL. The relay DSL in operating establishes a substitute circuit thru its alternate contact 17 for the operators disconnect relay ODR, the original. circuit for ODR having been broken at contact 26 of CSL when the said relay CSL restored. The restoration to normal of contact 26 of CSL established a substitute circuit for the calling supervisory signal CS which circuit may be traced from grounded battery, normal con-' tact 26 of CSL, conductor 59, alternate contact 60 of ODR, conductor 8'7 thru the lamp CS to ground. The operator noting the display of both the disconnect lamps removes the plugs AP and CP from their respective jacks. The removal of the answering plug AP from the jack J causes the deenergization of relay ASL and cut off relay CO. The removal of the calling plug CP from the trunk jack TJ causes the deenergization of relay DSL and the relay ODR which restores its contact 60 to normal to interrupt the energizing circuit of the lamp CS. The opening of alternate contact 49 by the restoration of ODR breaks the locking circuit for the trunk disconnect relay TDR which restores its contact 89 to normal to eiface the lamp AS. The apparatus used in establishing the connection between the subscriber A and the trunk subscriber T is all at normal.

Should the trunk circuit be seized by another cord before the trunk plug T? is removed from the jack J an operating circuit for relay TSI will be completed as above described and T31 will close alternate contact 71 to light lamp TAL. The circuit for TAL can be traced from grounded battery, lamp TAL, alternate contact 71 of TSI, alternate contact 175 of relay TSL which is still energized by reason of TP being in jack J and alternate contact 103 of TDA to ground. The trunk operator noting the lighted signal will answer the call in the usual manner.

If the called subscriber at T fails to answer the call signal the calling subscriber at A replaces his receiver to give the operator a disconnect signal. The relay ASR restores to energize relay TDR which attracts contact 89 to illuminate disconnect signal AS and opens the contact 18 to cause the deenergization of relays CSL and CSL. The restoration of contacts 28 and 29 of CSL cause the restoration of trunk relays TAC and T81 and the subsequent energization of TDA and the illumination of trunk disconnect lamp TDL. The relay DSL operates and restores trunk cut off relay TCO which efiaces the trunk busy lamps TBL. The lamp CS remains operated and as both lamps CS and A6 are lighted the operator knows that the call been abandoned and removes the plugs AP and CP from the jacks.

If the calling subscriber wishes information relative to the trunk connection as to the charges, wrong number, or any inquiry of a similar nature prior to the disconnection of the plugs AP and CP from the respective associated jacks, the removal of the receiver at the substation A causes the energization of the answering supervisory relay ASR which attracts its armature 51 to close an energizing circuit for the flashing recall relay FCR which circuit can be traced from grounded battery thru the alternate contact 49 of ODR, conductor 50, alternate contact 51 of ASR, the winding of PCB to ground. The relay FCR energizes and attracts its alternate contact 91 thereby establishing a circuit for the answering lamp AS which is intermittently operated or flashed. This circuit can be traced from grounded battery thru the lamp AS, alternate contact 89 of TDR, alternate contact 91 of FOR, thru the constantly rotating interrupter I, to ground. The operator at the cord C is the only one that receives this flashing recall signal and she operates her listening key LK to connect her operatcrs set 0 to the cord conductors thru normal contacts 28 and 29 of CSL. The operation of the listening key LK breaks the locking circuit of the relay TDR at alternate contact 94 of LK and the relay TDR and lamp AS restore to normal. If another party is wanted by the calling subscriber A the operator will remove the plug 0? from the trunk jack TJ and insert the same into the jack associated with the desired new party and proceed as previously described to complete the connection.

The operator upon noticing the flashing signal can also answer the recall by removing the calling plug CP from its connected jack instead of throwing her listening key as above explained, The withdrawal of plug CP causes the deenergization of relay DSL which interrupts at contact 17 the circuit for relay ODE which restores its contacts 14 and 15 to connect the operators set 0 to the cord conductors. The opening of contact 49 restores the relay TDR which extinguishes the flashing signal AS by breaking the circuit therefor at contact 89 and the apparatus of the link circuit is ready to complete the new connection.

While I have shown and described a preferred embodiment of my invention, it is to be understood that changes and modifications will readily suggest themselves to those skilled in the art, and I desire to be limited only by the scope of the appended claims. 7

Having described my invention, what I claim is new and desire to secure by United States Lctters Patent is:

1. A telephone system comprising local calling lines and called local and trunk lines, an operators link circuit having a pair of terminals for connecting said calling line to a called local line or a trunk line, means in said link circuit controlled by said calling local line on a local to local connection for operatively disassociating said calling line from said link circuit, a supervisory signal in said link circuit lighted upon the operation or" said means, means in said link circuit for rendering ineiiective the said first means when said local line is connected to a trunk line, and subscriber controlled means for operatively disassociating said link circuit from said trunk line.

2. A telephone system comprising local calling lines and called local trun 1 s, an operators link circuit having a pair terminals for connecting said calling line to a called local line or a trunk line, means in said link circuit controlled by said calling local line on a local to local connection for operativeiy disassociating said calling line from the said link circuit, a supervisory signal in said link circuit lighted upon the operation of said means, means in said link circuit for rendering ineffective tie said first means on a local to trunk connection and for closing another circuit for said supervisory signal to cause said signal to be intermittently operated, and subscriber controlled means for operatively disassociating said link circuit from said trunk line.

3. A telephone system comprising local calling lines and called local and trunk lines, an operators link circuit havin a pair of connecting terminals for connecting said calling line to a called local line or a trunk line, a relay in said link circuit responsive to the connection of a terminal of said link circuit to a called local line, means in said link circuit controlled by said calling line on a local to local connection and said relay for disassociating said calling line from a terminal of said link circuit, said relay being ineffective when a terminal of said link circuit is connected with a trunk line to render ineifective the calling lines control of said means, and subscriber controlled means operative upon a local to trunk connection to disassociate said link circuit from said trunk line.

4. A telephone system including a calling subscribers line, called local and trunk lines, a signal individual to said calling line, a link circuit for connectin said calling line to said called lines, a signal individual to said link circuit, subscriber controlled means operative on a recall for operating said first signal if said link circuit is used to connect said calling line to a called local line, and for operating the second of said signals if said link circuit is connected to a called trunk line to denote a recall, and other subscriber controlled means for operatively disassociating said link circuit from a trunk line on a local to trunk connection.

5. A telephone system including a calling subcribers line, called lines of different character, an operators link circuit having a pair of terminals for interconnecting said calling and called lines, an operators telephone set, relay means in said link circuit for connecting said operators telephone set to said link circuit, other relay means for disconnecting said telephone set from said link circuit, an operators listening key for connecting said telephone set and said link circuit, relay means in said link circuit responsive to the connection of a terminal of said link circuit to a called line of one character to render said listening key ineiiective to connect said operators telephone set and said link circuit, and subscriber controlled means for operatively disassociating said link circuit from said called lines of diiferent character.

6. A telephone system comprising local calling lines and called local lines and trunk lines, an operators link circuit having a pair of connecting terminals for connecting said callin line to called lines, an operators telephone set, relay means in said link circuit for automatically connecting said operators telephone set to said link circuit, said means responsive to the connection of a connecting terminal of said link cicuit to said calling line, relay means in said link circuit responsive to the connection of a connecting terminal of said link circuit to a called line for automatically disassociating said operators telephone set from said link circuit, means in said link circuit for connecting said operators telephone set to said link circuit subsequently to the operation of said secondrelay means, said means being rendered ineffective when said connecting terminal is connected to a called local line and subscriber controlled means for automatically operatively disassociating said trunk line from said link circuit.

'7. A telephone system comprising local calling lines and called local lines and trunk lines, an operators link circuit having a pair of terminals for connecting a calling local line to a called local line or to a trunk line, an operators telephone set, relay means in said link circuit for automatically connecting said operators telephone set to said link circuit, relay means in said link circuit for automatically disassociating said operators telephone set from said link circuit, an operators listening key for connecting said operators set and said link circuit subsequently to the operation of said second relay means, means in said link circuit responsive to the connection of a con necting terminal to a called local line whereby the said listening key is rendered ineffective to connect said operators telephone set to said link circuit, and subscriber controlled means for operatively disassociating said trunk line from said link circuit.

8. A telephone system comprising a calling line terminating at a local exchange, a called line terminating at a distant exchange, a cord circuit and a trunk circuit cooperating to interconnect said lines, indicating means in said trunk circuit at said local exchange operable upon the connection of said cord circuit and said trunk circuit to indicate the busy condition of said trunk circuit, and subscriber controlled means for releasing said indicating means.

9. A telephone system comprising a local calling line and a called line, an operators link circuit and a trunk circuit for interconnecting said lines, means in said link circuit controlled over said lines for operatively disassociating said trunk circuit from said link circuit, and means in said trunk for indicating the associated or disassociated condition of said circuits.

10. A telephone system comprising a calling line and a called line, a trunk circuit associated with said called line, an operators link circuit and a pair of terminals for interconnecting said called line and said trunk circuit, means in said link circuit for holding said trunk circuit, and subscriber controlled means for rendering said holding means ineifective.

11. A telephone system comprising a calling line and a called trunk line, an operators link circuit having a pair of terminals for interconnecting said calling line and said trunk line, means in said link circuit for holding said trunk line, and means controlled over said calling line for rendering said holding means ineffective.

12. A telephone system comprising a calling line and a called trunk line, an operators link circuit having a pair of terminals for interconnecting said calling line and said trunk line, means in said link circuit for holding said trunk line, and means controlled over said calling line prior to the completion of a trunk call for rendering said means ineffective.

13. A telephone system comprising a calling line terminating at a local exchange, a called line terminating at a distant exchange, a trunk line associated with said called line and terminating in a jack at said local exchange, an operators link circuit having a pair of plugs one of said plugs adapted to be inserted into said trunk jack to interconnect said calling line and said trunk line, and means controlled over said calling line for operatively disassociating said trunk line from said link circuit.

14. A telephone system comprising a calling line terminating at a local exchange, a called line terminating at a distant exchange, a trunk line associated with said called line and terminating in a jack at said local xchange, an operators cord circuit having a pair of plugs, one of said plugs adapted to be inserted into said trunk jack to interconnect said calling line and said trunk line, and means controlled over said calling line for operatively disassociating said trunk line from said link circuit prior to the Withdrawal of said plug from said jack.

15. A telephone system comprising local calling lines, and called local lines and trunk lines, an operators link circuit having a pair of connection terminals for interconnecting said calling local and called local or trunk lines, means in said link circuit controlled by said calling local line on a local to local connection for operatively disassociating said calling line from a connection terminal of said link circuit, said means being rendered ineffective when said local line is connected to a trunk line, and subscriber controlled means operable on a local to trunk connection for operatively disassociating said trunk line from said link circuit.

16. A telephone system comprising local calling lines and called local and trunk lines, an operators link circuit having a pair of connec tion terminals for interconnecting said calling local and called local or trunk lines, means in said link circuit controlled over said lines for operatively disassociating said called lines from said link circuit.

17. A telephone system comprising a local calling line and a called trunk line, an operators link circuit having a pair of connection terminals for interconnecting said lines, means in said link circuit controlled over said lines for operatively disassociating said trunk line from said link circuit.

BERT A. WALLACE.

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