US1566622A - William g - Google Patents

Description

Patented Dec. 22, 1925.

UNlTED STATES PATENT @FHCE.

WILLIAM G. SHULL, OF CHICAGO, ILLINOIS, ASSIGNOB T0 KELLOGG SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.-

Application filed September 28, 1921. Serial No. 503,777.

To all whom it may concern.

Be it known that I, WILLIAM G. SHULL, a, citizen of the United States of America, and a resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Telephone Systems, of which the following is a specification.

My invention relates to telephone systems in which manual link circuits are provided for interconnecting telephone lines, and has to do more particularly with so-called multiple line lamp systems in which instantaneous disconnect, automatic listening,'secret service and automatic ringing, etc., are provided, and has for its object a new and im-. proved system of the above character. D

A feature of my invention is the provision of a new and improved ringing circuit arrangement for applying ringing current to a called telephone subscribers substation, wherein only one four-party ringing key perposition is required to connect ringing generators of different frequencies to the called telephone line. In the present systems a ringing key is provided for each cord or link circuit at an operators position, whereas, in my invention I provide only one ringing key common to the cord circuits in an operator's position to connect the generators of different frequencies to the called subscribers telephone. lines, thus doing away with the large number of ringing keys as required in the old systems.

Another feature of my invention is the provision of a circuit arrangement whereby, it a cord or link circuit is connected to a busy line, the application of ringing current to the busy called line is prevented, even though the ringing key is operated.

For a more complete understanding of my invention, reference may be had to the accompanying drawing. in which I show a well-known common battery substation A, connected by the line limbs 1 and 2 to a line circuit L. Multiple jacks J are provided which are distributed among different operators, each jack having a line signal S associated therewith. The usual line relay LR for operating the line signals S and the usual cut-oil relay C0 are provided.

The cord circuit C comprises an answer ing plug AP and a calling plug GP, the two plugs being connected by the heavily marked conductors 3 and 4 which have condensers K and K inter osed. Associated with the answering end 0 the cord circuit C is the double-wound answering sleeve supervisory relay AS, which is energized through both its windings and in series with the cut-ofi' relay CO in the line circuit L when the plug AP is inserted into the jack J. Upon the energization of the answering sleeve relay AS, its upper winding is shunted out so that the first operator to answer the call seizes it to the exclusion of any other operator that attempts to answer the same call, that is, when the first plu AP is inserted into the jack J of the calling line the sleeve relay AS associated therewith has its low resistance winding directly connect ed to the sleeve conductor, and should a second operator attempt to seize the call, the sleeve relay associated with the cord circuit of the second operator will not operate, as suflicient current is prevented from flowing to energize it, due to the high resistance of its upper winding and due to the upper winding of the sleeve relay in the first operators cord circuit being shunted out. I also provide an operators listening relay OPR, which operates upon the energization of the sleeve relay AS to connect the operators telephone set to the talking strands 3 and 4 of the cord circuit An answering supervisory tip relay AT and an answering supervisory lamp AL are also provided, the sleeve relay AS and tip relay AT controlling the circuit of said supervisory lamp AL.- I also provide a link disconnect relay LD for disconnecting the calling line from the link circuit C upon the replacement of the receiver on its switchhook at the calling substation before the link circuit C is disconnected from the calling jack J, thus per mitting the calling party to initiate a new call or be called, as the case may be, before the operator has taken down the established connection. The functionofthe relay LD is to operatively disconnect theapparatus of the circuit from'the line at the will of the calling subscriber.

Associated with the calling end of the cord circuit C, I show a primary calling supervisory sleeve relay PCS which energizes when the calling plug CP is inserted into the jack J of the line circuit L]. l A secondary calling supervisory sleeve relay O k v SSR, a callin supervisory tip relay CT, ringing 'contro relay RC and a calling supervisory lamp signal CL are also shown, thev secondary calling sleeve relay SSR energizing upon the operation of ringing control relay RC and locking itself up through its upper alternate contest to ground in the line circuit L.

Generators G, G, G G of different frequencies and a four-party ringing key RK comprising the usual end spring E and manually operated buttons B, B, B and B corresponding respectively to the said 'gen-. erators are shown. To accomplish the results of my invention I further provide two generator selecting relays GR and GR, The operation of the generator selecting relays GR and GR is controlled by the buttons B, B, B and B? of the ringing key RK. When the operator has set up a connection between two telephone line circuits such as L and L by means of a cord circuit C, she depresses one of the ringing key buttons corresponding to the frequency generator required to signal the called substation. The ringing control relay RC will operate and relays GR and GR will either both operate or one will operate and the other will remain inert, or both relays GR and GR may remain inert, all depending on the button operated, to connect a certain one of said generators to the called line. The operation of these relays will be more fully explained in the ensuing specification.

I also provide a ringing interrupter relay IR and "an interrupter I for intermittently connecting ringing current to the called line.

1 A ringing trip relay RT is also shown which is energized to disconnect ringing current from the called line, should the called subscriber respond during aringing period; the calling tip relay CT disconnecting ringing current, should the called subscriber respond during a silent or non-ringing period, and link disconnect relay LD operating to'disconnectvringing current, should thecalling subscriber replace his receiver prior tothe response of the called subscriber. I also show a revertive ringing tone circuit including the resistance R and condenser N for giving the calling subscriber an audible tone indicating that the called party is being run". 7

Tb the right of the drawing I show a called substation'D connected by the line limbs 1 and 2"to a line circuit L similar to that of L and bearing the same reference characters but with the sufiix prime added. Connected to the line limbs 1' and 2' area numbar of conductors which lead to substations D", D and D which substations are the same in construction as substation D, except that .the call bells at D, D and D respond. to ringing current of a diti'erent frequency, so that when ringing current of one frequency is applied to line limbs 1' and 2', a call bell responsi e tothat frequency will operate while the other call bells will be non-responsive.

Having described in general the apparatus embodying my invention, I will now describe more in detail the operation of the system illustrated. I

Assuming that thesubscriberfiat the substation A initiates a call, the removal of the receiver thereat closes an energizing circuit for the line relay LR, traced from battery through the winding of the line relay LR, normal contact 5 of cut-off relay CO, line limb 1, through the substation A, line limb 2, normal contact 6 of cut-off relay CO to ground. The closing of alternate contact 7 upon the energization of line rela LR closes a circuit for the multiple line lamps S, traced from battery through the line signals S, alternate contact7 of line relay LR and to ground. An operator noting a lighted line signal S willinsert the answering plug AP of a cord circuit into the answering jack J of the calling line, thus closing a circuitfor the answering sleeve supervisory relay AS and cut-off relay CO, traced from bat- ,tery through both windings of relay AS, normal contact 8 of the link disconnect relay LD, sleeve contact of the plug AP and jack J, through the winding of the cut oii' relay to ground. Upon the energization of. cut-off relay CO, its normal contact 5 is opened,

which opens the circuit for the line relay LR and allows it to de-energize to-open alternate contact 7, thus eltacing the burning line signals S. WVhen the answering sleeve supervisory relay AS energized it closed its alternate contact 9, thus snunting out its upper high resistance winding 10, and locks itself up through said alternate contact and over the previously described circuit. The relay AS provides busy potential to the multiple jacks J of the calling line, thus making them busy against incoming calls. Upon the connection of the plug AP with the jack J a circuit was closed for the answering supervisory tip relay AT, traced from ground,- through the lower winding of relay AT, alternate contact- 9' of relay AS, strand 4 of cord circuit C, normal contact 11 of relay LD, tip contacts of the plug AP and jack J, line limb 2, through the substation A, .line limb 1, sleeve contacts of the plug AP and jack contact 12 of relay'LD, strand 3 of cord circuit.C,

line 13, through the upperjwinding of relay AT tobattery. RelayAT energizing;

opens contact 14, which prevents the premature lighting of the answering supervisory lamp AL, and also closes normally open contact 15, vwhereupon a circuit isclosed for v the operator's listening relay OPR, traced from battery, through the winding of relay OPR, closed contact 15, alternate contact 16 of relay AS, line 17, normal contact 18 of relay SSR to ground. Relay OPR energizing closed a. locking circuit for itself through its alternate contact 19, contact 16 of relay AS, line 17, normal contact 18 of relay SSR to ground. A further result due to the energization of relay OPR is the connection of the operators telephonev set to the strands 3 and 4 of the cord circuit C through alternate contacts 20 and 21 of. relay OPR, and the operator now being in conversational circuit with the calling substation A over the heavil 1 marked lines, inquires the wants of the calling party A.

Assuming that a second operator inserts a plug AP into another jack J of this calling line, subsequent to the insertion of the first plug, this operators telephone will not be connected to the calling line due to the fact that the high resistance winding 10 of the sleeve relay AS of the second cord is connected in multiple with the sleeve relay AS of the first cord, which relay, having its high resistance .winding 10 shunted, shunts the sleeve relay AS of the second cord enough to prevent it from actuating, thereby preventing the operators set of the second cord from being connected to the cord circuit and calling line. The second operator not receiving any reply to her inquiry knows that the call has been seized by another operator.

Again taking the first connection, the operator, after learning the want of the calling subscriber, and assuming that he desires a connection with the subscriber D, tests the multiple jacks J in the usual manner, and assuming them idle, she will insert the calling plug CP into the jack J of the line circuit L leading to the called subscriber D. Upon the insertion, an energizing circuit is closed for the primary calling supervisory relay PCS and cut-off relay CO. traced from the battery, through the winding of relay PCS, normally closed contact 22, line 23, sleeve contacts of the plug CP and jack to ground through the winding of cut-off relay CO whereupon relay CO operating opens its normally closed contacts 5 and 6, thus preventing the energization of line relay LR and the lighting of multiple line signals S when the called subscriber responds. The circuit just traced also provides a busy potential for the multiple jacks J, rendering them busy against incoming calls. Relay PCS energizing closes contacts 24, 25, 26 and 27 and lamp CL will light to notify the operator that ringing current has not as yet been connected to the called line and nothing more happens until the operator depresses one of the buttons B, B, B and B of the ringing key RK. Assuming that button B is the one to be operated, the operator having actuated button B, ringing control relay RC will energize over a circuit traced from battery, through the winding of relay RC, make-before-break contact 28 of relay RC, alternate contact- 24: of relay PCS, alternate contact 29 of ringing key RK (which always closes and remains closed as long as any of the buttons B, B, B and B are in their fully depressed positions) to ground. Ringing control relay RC energizing opens contact 31, thus opening the circuit of lamp CL, which burns as long as relay RC is in its normal position and relay PCS is energized, to indicate to the operator that she has not operated her ringing key. Alternate contacts 30, 32 and make-before break contact 28 close, the last one providing a locking circuit for the relay, traced frombattery, winding of relay RC, makebefore-break contact 28, line 33, normal contact 34 of relay LD, line 35, to ground at alternate contact 27 of relay PCS. A fui ther operation due to the closure of alternate contact 32 of relay RC is the energization of secondary supervisory sleeve relay i SR, which operates to open its normal contact 18 and to open the circuit of relay OPR to cause said relay OPR to de-energize to disconnect the operators telephone set 0 from the strands 3 and 4 of the cord circuit C. The circuit for relay SSR may be traced from battery, winding of relay SSR, line 36, alternate contact 32, line 23, sleeve contacts of the plug CP and jack J to ground through the winding of cut-ofi' relay CO; relay SSR energizing closes a locking circuit for itself from battery and contact 22 and over the previously described circuit, these last two traced circuits also providing busy potential to the multiple jacks now that relay PCS is de-energized'due to the opening'of its circuit at contact 22 of relay SSR. When the operator depressed the button B, a circuit was closed for both generator selectin relays GR and GR. the circuit for relay lR being traced from battery through the winding of relay GR, alternate contact 25 of relay PCS, alternate con tact 37 of ringing key RK to ground, whereupon relay GR energizing 'locks itself up through its alternate contact 38, line 39, alternate contact 18 of relay SSR to ground. The circuit for relay GRistraced from battery, through winding of. relay GR, alternate c0ntact25 of relay PCS,'alternate contact 37 to ground, whereupon relay GR locks up over a circuit traced from battery, winding of said relay GR, alternate contact 40, line, 39 to ground through alternatecontact 18 of relay SSR; the energization of relays GR and GR being prior to the de-energization of relay PCS, as will be readily understood. Ringing control relay RC does not de-energize when its locking circuit hereinbefore traced is opened at contact 27, but is held locked u over a newly closed looking circuit trace from battery, winding and lll) make-before-break contact 28 of relay RC, .line 33, normal contact 34 of relay LD, line 35, normal contact 41, of relay CT, line 42, normally closed contact 43 of relay RT to ground at alternate contact 18 of relay SSR. Interrupter relay IR is now energized and de-energized by the interrupter I over a circuit traced from battery, winding of relay IR, line 44, alternate contact 30 of relay RC to ground through the conducting segments of interrupter I. Interrupter relay IR, intermittently energizing, connects ringing current to the called line, operating the signal of the called substation D, circuit being traced from battery 51, alternate contact 48 of interrupter relay IR, ring contacts of plug CP and jack J, line limb 2, through the call bell of the substation D, line limb tip contacts of plug CP and jack J, alternate contact 50 of relay IR, winding of ringing trip relay RT, alternate contact 47 of relay GR, alternate contact 45 of relay GR, generator G to ground and back to ground at battery. does not energize over this circuit due to the combined high resistance of the call bell and condenser at the substation D, which prevents sufiicient flow of .current to energize said relay RT. During the time in 30 which ringing current is being supplied to the called substation, an audible ringing tone is received by the calling subscriber at substation A, indicating to him that the desired party is bein rung, this circuit being traced from groun generator G resistance R, condenser N, alternate contact 49 of relay IR, tip conductor of the cord circuit C, tip contacts of plug AP and jack J, line limb 2, through the substation A and back to battery in the cord circuit C.

. Should the called subscriber at the substation D remove his receiver during a ringing'period, the combined generator and battery current from the generator G and that of battery 51 brings about the energization of the relay RT over a circuit traced from the generator relay GR, alternate contact 47 of relay GR, through'the winding of relay RT, alternate contact 50 of rela IR, plug CP and tip contacts of the jac J, line limb 2, closed contacts of the now raised switchhook at substation D. line limb 1, ring contacts of plug CP, and jack J, of relay IR to battery and ground.- The combined generator and battery flow through the relay RT brings about the operation of the said relay RT, causing it to open its normal contact 43; the opening of said contact 43 opens the -locking circuit of the ringing control relay to normal prevents-further a plication of ringing current to the calle subscribers linel fShould the subscriber at substation D remove his receiver during a silent or'non- Ringing trip relay RT- G, alternate contact 45 of alternate contact 48 RC, and relay RC restoring r nging period, an energizing circuit for the relay CT is established from battery, upper winding of relay CT, alternate contact 52, line 53, normal contact 50 of relay IR, which is in normal positioii' fduring a non-ringing period, tip contacts of plug CP and jack J, through the closed contacts of the raised switchhook of the called substation D, ring contacts of plug CP and jack J, normal contact 48, ring conductor of cord circuit C, lower winding of relay CT to ground. Relay CT energizing opens its normal contact 41, and the opening of said contact 41 opens the circuit of relay RC, causing relay RC to restore to normal, preventing the application of ringing current to the called substation 1). Thus, I provide a method by which ringing current is instantly disconnected should the callcd subscriber remove his receiver during a ringing or nonringing period.

The subscribers at substations A and B are now in conversational circuit, which may be traced over the heavily marked lines.

Assuming that the subscribers at substations A and D have finished conversation, the subscriber at the substation A inreplacing his receiver uponthe switchhook opens the energizing circuit of the relay AT at the switchhook contacts. The relay AT restoring to normal, closes its normal contact14, which closes an energizing circuit for the link disconnect relay LD, traced from battery, through the winding of said relay LD, normal contact 14 of relay AT, alternate contact 55 of'relay AS, line 56, alternate contact 18 of relay SSR to ground. The closure of normal contact 14 of relay AT also causes the burning of the answering lamp AL, over a circuit traced from battery, through the lamp AL, AT and over the circuit just previously described to ground at relay SSR. Relay LD energizing opens its normally closed contacts 11, 12, 8 and 34, thus removing the'busy potential from the multiple jacks J and freecontact 14 of relay' loo ing the hue circuit L from the cord circuit C, which enables the calling subscriber at the substation A to initiate a new call or be called by another subscriber. Upon the replacement of the receiver on the switchhook by the subscriber at the substation D, the

circuit for the relay CT is interrupted at the switchhook contacts, and relay CT reervisory lamp storing causes the calling su to burn over a circuit trace from battery; through the lamp CL, normal contact ,31

of relay RC, line 35, normal contact 41 of relay CT,line 42, normal contact 43 of relay RT, alternate contact 18'of relay SSR to ground. The operator noting the burning of I the two lamps AL and CL will know that the conversation between subscribers A and D has terminated and will withdraw the plugs AP and CP from the multiple jacks J and J, which. will restore the apparatus of the cord circuit C to normal.

Should the calling subscriber at the substation A'initiate a new call before the plug AP is withdrawn from the jack J, and should the same operator upon noting the burning line signal S desire to answer the call, she may do so by withdrawing the plug GP from the jack J, it being understood that relay AS is slow-acting and does not deenergize when normal contact 8 is opened, but remains operated and is again locked up through alternate contact 8 of relay LD, alternate contact of relay AS, line 56, alternate contact 18 of relay SSR to ground' Upon the removal of the plug CP from the jack J alternate contact 18 of relay SSR' is opened, which opens the circuit of relay LD; relay LD restoring closes its contacts 11, 12, 8 and 34, whereupon relay AS is locked up over the same circuit as traced in the beginning of this specification, and relay AT again energizes to eliace the lamp AL and to close a circuit for the relay OPR, which'operates to connect the operators telephone set to thepcord circuit, the remaining part of the connection being the same as described in the foregoing specification.

Assuming that the calling subscriber at the substation A replaces his receiver be' fore the subscriber at the called substation removes his receiver during the application of ringing current, relay LD will operate as before described, and the opening of its normal contact 34 opens the circuit of relay RC, which restores to normal, thus disconnecting ringing current from the called line.

Furthermore, assuming that the operator finds the multiple jack J busy when making the usual test, but nevertheless inserts the plug CP into the jack J and depresses the button B as before described, ringing current will not be connected to the called line due to the fact that when the plug OP is inserted into the jack J, relay CT energizes over a circuit as previously traced, but through the busy substation on the same line. Relay PCS also operates upon the insertion of the plug CP into the jack J but does not remain operated long enough to cause relay RC to operate due to the operation of relay SSR, which energizes and opens its normal contact 22. causing the de-energization of relay PCS before relay RC has a chance to operate, the energizing circuit for relay SSR being traced from battery, through its winding, line 36, alternate contact 54. line 23, to ground through cut-oil relay CO. Relay SSR then locks itself over the locking circuit hereinbefore traced. Relay RC failing to operate, it is obvious that ringing current will not be applied to the called subscribers substation. Thus, it will be readily understood that I have provided a system wherein an operator is prevented from interfering with a busy line when she fails to hear or attempts to disregard the busy signal and to connect ringing current to a called busy line. 1

To give a further description of the different operations of relays GR and GR to connect the other generators G, G and G to the called line, I will describe the operations for connecting these generators to the called line in connection with the cord circuit C and called substation D.

Assuming that the call bell of the substation D is one which will operate upon the application of ringing current from the generator G, the operator will depress push button B of the ringing key RK, which will cause the energization of ringing control relay RC, the operation of the system up to the application of ringing current and the operation of relays PCS and SSR being the same as described in the first instance. Ringing control relay RC will energize and close a locking circuit for itself over the same circuit as hereinbefore traced. When the button B was de ressed, an energizing circuit was closed $01 the relay GR, traced from battery, winding of relay GR, alternate contact 25 of relay PCS, alternate contact of button B to ground, whereupon relay GR energizing locks itself up from battery through its winding and alternate contact 40, alternate contact 18 of relay SSR to ground. Relay GR remains inert and relay GR energizing connects ringing current to the called substation D, traced from ground, through the generator G, normal contact 45, alternate contact 47, ringing trip relay RT. alternate contact 50 of the interrupter relay IR, which operates as before described, and over the same path as before described to battery.

Again assuming that the operator depresses button B of ringing key RK, ringmg control relay RC will operate and lock up as before described. Relay GR will encr gize over a circuit traced from battery, winding of relay GR, alternate contact 25' of relay PCS, alternate contact 61 of button B to ground. Relay GR energizing will close a locking circuit for itself from battery, through its winding and alternate contact 38, line 39, alternate contact 18 of relay SSR to ground. Relay GR remaining now in its normal position, relay GR will connect ringing current to the called line, traced from generator G, alternate contact 46 of relay GR, normal contact 47 of relay GR, winding of relay TR, alternate contact 50 of relay IR and over the before-described circuit to battery.

Should the operator depress the button B, relay RC will operate as before exof relay IR and over 1o,

ton B to be closed, as is obvious from an inspection of the drawing to close an energizing circuit for either of these relays. Ringing current will now be applied from generator G traced from ground through the generator G normal contact 46 of relay GR, normal contact 47 of relay GR, winding of relay RT, alternate contact 50 the same path to battery 51, as before described.

It is to be understood that ringing current from any one of the generators G, G, Gr and G to the called line will be discontinued, when the subscriber at the called substation D responds, in the same manner as was described in the foregoing specification.

In a general way, it will be observed that the two relays GR and GR give four distinct selections of generator current by their discriminative energizations and de-energizations under the control of the common ringing key BK. Also, that the relay PCS serves as a relay to temporarily associate I GR and GR with the ringing key. Instantly upon the o erators actuating a. button of RK, the end spring E energizes RC, which in turn energizes SSR, and the latter opens the circuit of PCS, whereupon BK is wholly dissociated from GR and GR of the cord circuit, and in condition to be connected to any other cord circuit of the operators position. v 4

From the foregoing specification, it is seen that. I have provided a system wherein only one four-party ringing key is required before each operators position for applying ringing current of different frequencies to the called line, instead of having a ringing key for each cord circuit in an operators' position. It will be further seen that I have provided a system wherein it is made impossible to connect ringing current to a busy Although I have shown a preferred embodiment of my invention for the purpose of illustrating and describing my invention, I am aware that the features of my invention are applicable to other systems than that shown, and many modifications and changes may be made by those skilled in the art, and I, therefore, do not wish to be limited to the'exact structure as shown, but aim to cover all such changes and modifications as come within the spirit and scope of the appended claims.

' Having described my invention, what I claim as new and desire to secure by United Statets Letters Patent, is:

1. Atelephone system including a calling and a called telephone line and a cord circuit for interconnecting them, a ringing key for applyin ringing current to said cord, means eflective' automatically on the operation of said key to disassociate it from-said matically disassociating said cord circuit from said calling line when the subscriber on said calling line replaces his receiver.

2. A telephone system including a calling line and a called inulti-party line, a cord circuit for interconnecting said lines, relays for said cord circuit less in number than the parties on the-line to selectively signal any one of said parties, a party-line keyto control said relays, interrupter means for automatically and'intermittently applying ringing current to said called line, said interrupter means also controlling contacts in the talking conductors of said cord circuit, control means in said cord circuit for disconnecting applied ringing current from said cord circuit when the subscriber on said called line answers during a ringing or silent period, and automatic disconnect means for said cord circuit controlled over said calling line to operatively disassociate said calling line and said cord circuit and also to prevent further signaling of any one of said parties while said cord circuit remains connected to said lines.

'3. A selectlve party-line ringing system having a link circuit and including more than two kinds of ringing current for impression upon said link circuit, a pair of relays having cooperative action to produce distinctive circuit connections from such current to said line, one for each kind of current, a party line ringing key for discriminatively controlling said relays, a relay operable to associate said ringing key with said pair of relays, means including a single relay for causing the restoration of said second relay to disassociate said key from said pair of relays and also for continuing said relays in operative conditions as determined by said key after said key is dissociated from said relays, and calling subscriber controlled means for automatically disconnecting ringing current from the called subscribers line.

4. In a telephone system, a cord circuit, a cord circuit relay 0 erable on connection made to a line, a locking cord circuit relay operable after said first relay and serving to relay when said locking circuit relay operates.

5. A telephone system including a partyline and a party-line ringing-key having an end spring common to a number of cords, a relay for operatively associating said key and said line. another relay for causing the restoration of said first, relay to effect the dissociation of said key and said line, said last relay controlled by the end spring of said key.

6. A telephone system including a partyline, a pair of relays, means responsive to the energization of both relays to signal a station on said line, means responsive to the de-energization of the one and the energization of the other to signal another station on the line, means, responsive to the'energization of the one and de-energization of the other to signal a third station on the line, means responsive to the de-energization of both to signal a fourth station, a fourparty line ringing key to control said relays,

- a relay for operatively associating said key with said pair of relays, another relay for causing the restoration of said last relay to disassociate said key from said pair of relays and also for maintaining said pair of relays operated as determined by said key, and calling subscriber controlled means for automatically disconnecting ringing current from said line regardless of the substation being signaled-on said line.

7. In a telephone system a selective partyline key common to a plurality of cords and arranged for automatic association with any cord by the operation of a-relay in such cord, and another relay responsive to any use of saidkey to cause said first relay to operate to dissociate said 8. A telephone system Including a partyline and selective party-line ringing ap-. para'tus, relay means operable to automatically associate said ringing apparatus with said line, other relay means operable to restore said first relay means to disassociate said ringing apparatus from said line, re-

lays less in number than the number of parties on said line and sensitive to said apparatus to selectively signal any selected one of said stations after sa-idapparatus is dissociated from said line.

9. A telephone systein including a line with a plurality of stations connected to it and a party-line key with members to be manually actuated to selectively signal said stations one member for each station, relay contacts actuated on connect-ion made to said line. to operatively associate said .key and line,- autoniatic' means including a single relay efi'ective on the actuation of any memkey and such cord."

her to restore said relaycontacts to dismeans for automatically and intermittently applying ringing current to said called line, said interrupter means also controlling contacts in the talking conductors of said link circuit, control means in said cord circuit for disconnecting applied ringing current from said cord circuit when the subscriber on said called line answers during a ringing or silent period, and automatic disconnect means for preventing thefurther signaling of a signaled station when the subscriber on the calling line replaces his receiver,

and means also effective to disassociate said link circuit from said calling line.

'11, A telephone system including calling I and called telephone lines, a link circuit for use in interconnecting them, a plurality of stations connected to one of said lines, a 9

manually operated ringing key havingactuating members associated with said circuit, one for signaling each one of said stations, relays associated with said members and less in number than said stations and arranged for discriminative energization and de-energization to selectively signal any one. ofsaid stations whlle said key is dis- ,associated from said circuit, interrupter and intermittently means for automatically applying ringing current to said called line, said interrupter means also controlling contacts in the talking conductors of'sa-id link circuit, control means in said cord for-"disconnecting applied ringin from said cord circuit when thes on said called line answers during: or silent. period, and automatic,disconnect means for preventing the further signaling of the signaled station when the subscriber on the calling line, replaces his receiver and also to disassociate said link circuit from said calling line;

Signed b me at Chica C ok and September, 1921.

WILLIAM G. SHULL.

go, in the county of tate of Illinois, this 26th .day of

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