US1291766A - Telephone-exchange system. - Google Patents

Description

H. P. CLAUSEN.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED APR-24.1917. l9llfi66= Patented Jan. 21,1919. 2 SHEETS-SHEET //1 v/vfox- Hem y f. C/ause/v.

H. P. CLAUSEN. TELKPHONE EXCHANGE SYSTEM. APPLICATION mas APR.2-1, 2912.

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Pzaented Jan, 21,1919.

2 SHEETS-SHEET 2.

a F M.

UNITED STATES PATENT orrroa.

Heme? P. onausniv, 'oi 'ivroni'vrvnnnoiv, NEW YoRxgassieiv'oR 'ro' WESTERN ELECTRIC COMPANYQINCoRP'oRA'rED,or NEW YORK, N. Y., A CORPORATION or NEW YORK.

"'rniiiii iroivii nxcnlinen SYSTEM.

fifiecification of Letters Patent.

Patented Jan. 21, 1919.

hppncationnieu-Aprii 24, 1917. SerialNo. 164,232.

To all whom it may concern:

Be it knownth'atI, HEN Y P. Cngiuslm, a citizen of the United States', "res1d1ng--at "Mount Vernon, in the county ofjllfestchester and State of New York, hav'e' nvented'certain' new and useful" Improvements in Telephone-Exchange Systems, of which the fol- 'lowin 1s a *full "clear concise-and exact description.

This invention relates to 1 telephonefexchange systems, and' more particularly to such systems of the central'energy type, ts

' object being the provisionof improved" signahng means for systems of'tlns character. I

In accordance with a=featureofthisinvention, a telephonesystemcomprisi-ng telephone lines andlink" circuits is provided with asignal'commonto the link circuits which may be connected with an engaged link circuit and operated upon the opening and subsequent closing of the 'linecircuit connected with the engaged link circuit to furnish a recall-signal.

This invention is illustrated in the accompanying drawings, whereln Figure '1 shows a link circuit containing one embodiment of this invention; and Fig. 2 shows a link circuit containing another embodiment of this inventlon.

For convenience likeparts in the two figures will be designated by the same reference characters.

Fig. 1.

In Fig. 1 there are shown two ordinary telephone lines A and B, which extend from telephone stations to a central ofiice, at which is located a plurality of link circuits, one of which is shown at C. Located at the central oflice,'and common to the link circuits,*is' an automatic finder switch'comprising a stepby-step actuated ratchet wheel 6 carrying the contact brush 7 which, when the ratchet wheel is being rotated, is adapted to successively engage terminals which are severally connected to the different link circuitsto which the finder switch is common. A stepping niagnet 8 controls an armature 9 and pawl 10, which,when the stepping magnet is operated, causes the ratchet Wheel to make one-step advancements, moving its brush 7 from terminal to terminal. A start relay 11 is adapted, when energized, to close the stepping cirruit of stepping magnet 8, and a stop magnet 1.2 is-adapted, when enerthe following manner.

gized, to open the steppingcircuit. A'signaling'devi'ce' 13 is controlled bythe stop magnet 12 and operates as a flashing signal :uponthe operation of the stop magnet 12.

Referring now to the operation of the system shown in Fig. 1', it will be assumed that subscriber A initiates a call in the-usual manner. The operator then inserts answering plug 20 into line jack21, whereupon local circuit relay 22, cut-off relay 23' and supervisory relay 24 operate. The operator may now actuate listening key25 toconnect an operators telephone set to the talking strands of cord circuit C. Upon being advised that the subscriber A desires tobe connected with the line of subscriber B, the

operator restores the listening key 25 to normal position "and inserts calling plug 26 intoline jack 27 of line B, whereupon local circuit relay 28 and cut-off relay'29 operate. The operation of the local circuit relay 28 causes calling supervisory lamp 30 to be lighted. The operator may now actuate ringing key 35 to connect ringing current to the line of subscriber B for operating the call bell at that station. In response to the observing the disconnect signals removes the .plugs from the jacks, whereupon the apparatus is returned to normal position.

Suppose, however, that before the plugs are withdrawn from the jacks subscriber A wishes to initiate another connection. In

'so doing, the receiver is removed from the switchhook, whereupon the answering supervisory lamp 37 is lighted continuously and the common lamp 13 is lighted intermittently to furnish a characteristic signal to the operator. This is accomplished in When subscriber A originally restored the receiver to the switchhook, the release of thesupervisory relay 24. caused the operation of startrelay .11 and relay 38 over a circuit from battery through the winding oi start relay 11-, co1n+ pletes a locking circuit for itself through its left-hand alternate contact, which removes this relay from under control of the answering supervisory relay 24. The operation of the start relay 11 completes an operating circuit for the lamp 13, whereupon this lamp operates continuously, and

also completes the stepping circuit of stepping magnet 8. This stepping circuit includes an interrupter'41 so that in the rotation of the interrupter 41, the stepping magnet 8 is intermittently energized, causing the one step advancement of the brush 7 from terminal to terminal. After the automatic finder switch has been started in operation, the removal of the receiver from the switchhook by the subscriber A causes the operation of answering supervisory relay 24, whereupon, when the brush 7 of the automatic finder'switch comes into engagement with terminal 2 connected to the cord circuit C, stop magnet 12 is operated and answering supervisory lamp 37 is lighted over a circuit from battery through the lamp .37, alternate contact of the supervisory re- 7 lay 24, right-hand alternate contact of relay 38, terminal 2 and brush? of the automatic finder switch, contact 42 of a key 43 (which is common to the link circuits) and the winding of stop magnet 12 to ground. The operation of the stop magnet 12 opens the stepping circuit of the stepping magnet 8. The brush 7 remains in engagement with terminal 2. The energization of the stop magnet 12 also includes an interrupter 44 in circuit with the lamp 13, whereupon this lamp is intermittently lighted.

It will be observed that the answering supervisory lamp 37 is lighted continuously when relay 24'is deenergized to serve as a disconnect signal and is also lighted continuously when the connected calling subscriber has initiated asecond call before the cord circuit C has been disconnected from the line. The operator observing the flashing of the common lamp 13 knows that one of the calling subscribers connected with the various cord circuits, which may be plugged up into the lines, has made a recall. If only one answering supervisory lamp'is glowing the operator will know that thecalling subscriber connected with the cord c1rcu1t, wlth which that answering supervisory lamp 1s assoclated, has made the recall and may, therefore, actuate the listening key to connect the telephone set to the cord circuit. In actuating the listening key, contact 40 in the locking circuit of locking relay 38 and start relay 11 is thereupon opened, releasing these-relays. Relay 38,

in releasing, opens the circuit of the answering supervisory lamp 37 and the stop magnet 12. The lamp 13 is then extinguished. Start relay 11, in releasing, opens the step ping circuit of stepping magnet 8, whereupon the finder switch is free to be connected with another cord circuit on which a recall is being made. Upon being advised of the connection desired, the operator may withdraw the calling plug from the jack of line B and after restoring a listening key to normal, may insert the calling plug into the jackof any line desired. The connection will then be completed in the manner heretofore described. It will be observed that when the listening key is restored to normal, the contact 40 closes.- This. does not cause the operation of the locking relay 38 and the start relay 11 or the stepping and stop magnets 8 and 12 for the answering supervisory relay 24 is nowenergized.

Suppose, however, that when the opera tor observed the flashing of the common lamp 13 she had also observed more than one answeringv supervisory lamp glowing. It would not then be possible to determine which of the several calling subscribers had made the recall. The operator would, therefore, actuate key 43, which would close contact 45, thereby establishing a maintaining circuit for the stop magnet 12 and would open contact 42 in the operating circuit of the answering supervisory lamp 37. This lamp would then be effaced and would thereby serve as an indication to the operator that calling subscriber A, connected with the cord circuit shown, had made the recall. After determining the cord circuit on which the recall had been made, the operator would restore key 45 to normal position and actuate the listening keyof the proper cord circuit to connect thereto the operators telephone set.

The operations following the actuation of the listening key of this cord circuit would take place in the order hereinbefore mentioned.

Fig. 2.

The system shown in Fig. 2 is provided with apparatus by means of which there may be coiiperation between operators at adjacent positions, whereby greater efficiency in the handling of both original calls and recalls is obtained. This result is accomplished by providing at the operators position at which cord circuit C is located, designated as operator No. 2, and at the operators positions to the left and right thereof, designated respectively as operators No. 1 and No. 3, non-locking keys 50, 60 and common to the respective operators positions. By the actuation of the common listening key at the position, any one of the'three operators may determine the cord circuit on which a recall hasb'een made; In this F ig; 2, the automatic finder switch diiiers slightly from that shown in Fig. l,in that its rotatable arm 7 is equipped with three brushes 81, 82 and 83 adapted-to successively engage sets of three terminals to which are connected circuit leads of the different cord circuits of the position, there being one set of terminals for each cord circuit. The brush 81-is for the same purpose as the simple contact arm 7 of Fig. 1, while the two brushes 82and 83' are connected by leads to normally open contacts of common listening keys 51, 61 and 71 at the operators positions No. 1, No. 2 and No; 3, respectively. The normally open contacts are connected in multiple, so that any one of the three operators, when the finder switch is connected with a cord circuit on which there is'a recall, may, by the actuation of the common listeningkey of the position, connect thehasso'ciated, telephone set with the particular cord circuit.

Referring now tothe operation of the system disclosed in Fig. 2, it will be assumed that subscribers A and Bare connected together by means of the cord circuit C and that the receivers are removed from the switchhooks and the subscribers-are in conversation. ,Cut ofi relays 23 and 29, as well as theloc'al circuit relays 22mid 28 and the supervisory relays 24 and 36 are therefore operated; At the{con'c1usion of the conversation the subscribers restore the receivers to the switchhooks, releasing the supervisory' relays 24 and'36, whereupon the supervisory lamps 37 and 30 are lighted to fur nish disconnect signals.

Suppose, now, that before the plugs are withdrawn from the jacks the calling subscriber initiates another call. In so doing the answering supervisory lamp 37will be lighted continuouslyand the common lamp '13 will be lighted intermittently to furnish to the operator a characteristic signal. The manner in which this is accomplished is as follows; Upon the'restoration of the receiver to theflswitchhook by subscriber A, answering supervisory relay 2% releases, as before described. The release of this relay causes the operation of start relay 11 and lock-up relay 38 over a circuit from battery through the left-hand normal contact of stop magnet 12, the winding of start relay 11, contact 40 of listening key 25, winding-of relay 38 and normal contact thereof, normal contact of answering supervisory relay 24:, and the contact local circuit relay to ground. Lock-up relay 38, in operating, completes a locking circuit for itself which removes 'this relay from under control of the answering supervisory relay 24. This locking circuit may be traced from battery through contact 7-1 of common listening key 70, contact 64 of common listening key 60, contact 54: of common listening key 50, winding of start relay 11, contact 410 of listening key 25, winding and left-hand alternate contact of lock-up relay 38, and contact of relay 22 to ground. The operation of start relay l1 completes a circuit for the lamp 13 to cause the continuous operation thereof and also closes the stepping circuit of the stepping magnet 8. This stepping circuit may be traced from battery, contact 52 of common listening key 51, contact 62 of common listening key 61, contact 72 of common listening key 71, normal right-hand contact of stop magnet 12, right-hand contact of start relay 11, the winding of stepping magnet 8, and interrupter -11 to ground. The rotation of the interrupter -11 causes the stepping magnet 8 to be intermittently energized to rotate the ratchet wheel 6 and consequently move the brushes 81,82 and 83 over the sets of terminals. In themeantime the subscriber A has removed the receiverfrom the switchh'ook, again causing the operation of the answeriii'g'supcrvisory relay 24. After the operation of answering supervisory relay 24-, brush 81 of the automatic findei' switch comes into engagement with terminal 90, connected with the cord circuit C, and as a resultstop magnet 12 is' -immedia-tely energized and the answering supervisory lamp 37 lighted over a circuit from battery through the lamp 37, alternate contact of answering supervisory relay 24:, right-hand alternate contact of the lock-up relay 38, terminal 90, brush 81, winding of stop magnet 12, contact 53 of key 50, contact 63 of key (50, and contact 73 of key to ground. The energization of stop magnet 12 opens the stepping circuit of the stepping magnet 8, and connects interrupter 44L in circuit with the common lamp 13, whereupon the lamp 13 is intermittently lighted while the answering supervisory lamp 37 is continuously lighted. Upon the opening of the stepping circuit, the stepping net 8 remains deenergized and the brushes remain. in engagement with the set of contacts associated with the cord circuit C. The continuous glowing of the answering supervisory lamp 37 and intermittent glowing of the common lamp 13 serve as a characteristic signal to the three operators, indicating that one of the subscribers connected with the various cord circuits in the position at which cord circuit C and the automatic finder switch are located has made a recall. If, at this time the cord circuit C, only, is inuse and operator No. 2 is at theposition and not busy, this operator will know that the recall has been made by subscriber A and will actuate the listening key 25, thereby connecting this operators telephone set to the cord circuit Cir C and causing the release of the lock-up relay 38 and start relay 11, and the efiacement of answering supervisory lamp 37 and the common lamp 13. The connection with the desired line may be com leted in the manner hereinbefore describe Suppose, however, that when the common lamp 13 was glowing intermittently several cord circuits were in use and several of the answering supervisory lamps were glowing continuously in which case, the operators would not know which calling subscriber had made the recall. Operator No. 2 now actuates key 60, causing the answering supervisory lamp 37 to be intermittently lighted thereby indicating the cord circuit on which the recall was made. While the key 60 is actuated, stop magnet 12 which is of the slow release type, remains energized over a circuit from battery through the lamp 37, alternate contact of answering supervisory relay 24., right-hand alternate contact of lock-up relay 38, terminal 90, brush 81, winding of stop magnet 12, contact 53 of key 50, contact of key 60 and interrupter 4A to ground. The lamp '37 is intermittently lighted over this circuit. This operator may restore the common key 60 to normal position and actuate either the individual listening key 25 associated with cord circuit C, or the common listening key 61, to connect the telephone set of operator No. 2 with the cord circuit C. Should the common listening key 61 be operated, the operators telephone set would be connected to the cord circuit through the upper and lower alternate contacts of the common listening key 61 and the brushes 82 and 83 of the automatic finder switch. The actuation of the common listening key 61 would open the contact 64 in the looking circuit of the lock-up relay 38 and contact 62 in the stepping circuit of stepping magnet 8. Lock-up relay 38, start relay 11 and stop magnet 12 are now de'cinergized and both lamps 37 and 13 extinguished. Should another calling subscriber make a recall while the common listening key 61 is actuated, start relay 11 would be operated to light the common lamp 13 but the stepping magnet 8 would not be energized, for the stepping circuit is open at contact 62 of key 61.

manner operator No. 35 by first actuating key to determine the cord circuit on which the recall is being made, then restoring this key to normal position and actuating the common listening key 71, could take up the recall. 7

The common keys at each position may, of course, be located so that by moving a common lever in one direction, one key would be actuated and by moving the lever in the opposite direction the other key would be actuated. The keys 50, 60 and 70 are preferably of the non-locking type, while the keys 51, 61 and 71 are preferably of the locking type.

The lock-up relay 38 individual .to a cord circuit is normally deenergized and may be considered as an individualizing device which, when rendered efiective as by en ergization, cooperates with the supervisory relay 24 to appropriate and connect the common automatic finder switch with the cord circuit with which the effective individualizing device is associated. The automatic finder switch may be considered as electromagnetic signal control mechanism rendered operative for signaling purposes when connected with a cord circuit.

What is claimed is;

' 1. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, a signaling device individual to each link circuit, a signaling device common to the link circuits, a supervisory relay for each link circuit controlled over a connected telephone'line, an operating circuit for each individual signaling device for causing the continuous operation thereof completed when the associated link circuit is connected with one of the lines and the supervisory relay thereof is energized, and interrupter mechanism brought into circuit with the common signaling device upon the completion of the operating circuit of theindividual signaling device 2. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, oneofthe link circuits being connected with one of the lines, a. relay for the engaged link circuit controlled over a connected line, an automatic finder switch common to the link circuits started 7 upon the deenergization of the relay and appropriated by and connected with the engaged link circuit when the relay thereof is subsequently energized, a signaling device, and interrupter mechanism connected in circuit with the signaling device upon the appropriation and connection of the automatic finder switchv with the'engaged link circuit.

3. In a telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines,

AQA telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines,

a signaling device individual to each link circuit, a relay forthe engaged link circuit controlled over the connected line, an automatic finder switch common to the link circuits started upon the deenergization of the relay and appropriated by and connected with the engaged link circuit when the relay thereof is subsequently energized, a signaling device common to'the link circuits, and operating circuits for the signaling device individual to the engaged link circuit and for the common signalin device completed upon the connection of t 'e switch with the engaged link circuit.

5. A telephone exchangesystein comprising telephone lines, link circuits fora'nt'erconnecting the lines, one of the link-circu ts being connectedwith' one of the lines, a relay for the engaged link circuit controlled over a connected line, an automatic finder switch common to the link circuits, a second relay for the engaged link circuit operating .upon the de'elnergization of the first relay to start the finderswitch in operation, the finder switch being appropriated by and connected with the enga ed link circuit upon the subsequent energizatlon of the first mentioned relay, and a signaling device operated upon the connection of the switch with the engaged link circuit.

' 6. A telephone exchange system comprising telephonelines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines, a relay for the engaged link circuit controlled over the connected line, an automatic finder switch common to the link circuits started upon'the de'e'nergization of the relay and appropriated by and connected with the engaged link circuit whenthe relay thereof is subsequently energized, a signaling device operating upon the connection of the switch withthe engaged link circuit, and an operator controlled switch for disconnecting the switch from the engaged link circuit.

7. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines, a supervisory relay for the engaged link circuit, an automatic finder switch commonto the latenci e fase ee relw he-en a ed link circuit operating upon the denergization of the supervisory relay for starting the finder switch in operation, the finder switch being appropriated by and connected with the engaged link circuit upon the subsequent energization of the supervisory relay, and a smnaling device operating upon connection 0 the finder switch withthe engaged link circuit.

8. A telephone exchange system comprisingtele'phone'lines, link circuits for interconnecting the lines, one of the link circuits being connected with one ofthe lines, a signaling device individual to each link circuit, a supervisory relay for the engaged link circuit, a step-by-step finder switch common to the linkcircuits, a second relay for the engag'ed link circuit operating upon the deenergiz'ation of the supervisory relay to start the switch in operation, the switch being appropriated by and connected with the engaged link circuit upon the subsequent energization of the supervisory relay, a signaling device common to the link circuits, and operating circuits for the signaling device individual to theengaged link circuit and for'the common signaling device completed ,upont'he connection of the switch with the engaged link circuit. 1

9. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines, a signaling device individual to each link circuit, a supervisory relay for the engaged link circuit, an automatic finder switch common to the link circuits, a second relay for the engaged link circuit operating upon the deenergia'ation of the supervisory relay to start the swltch in operation, the'switch beingappropriated by and connected with the engaged link clrcuit upon the subsequent energiz'ation of the supervisory relay, an operating circuit for the signaling device individual to the engaged link circuit completed upon the connection of the switch to the engaged link circuit, and an operator controlled switch common to the link circuit for opening the operating circuit.

10. A telephone exchange system comprising telephone lines', link circuits for inter connecting the lines, one of the link circuits being connected with one of the lines, a signaling device individualto each link circuit, a supervisory relay for the engaged link circuit, a step-by-step finder switch common to the link circuits, stepping and stopping magnets therefor, an operating circuit for the stepping magnet, a second relay for the engaged link circuit operating upon the deenergization of the supervisory relay for completing the operating circuit of the stepping-magnet, and a circuit for the stopping magnet including the signaling device of the eea scd link: c necomp t p the gagemcnt of the switch brush with a terminal conne;ted with the engaged link circuit when the supervisory relay thereof is ener- 'zed. 11. A telephone exchange system comprising telephone lines, link circuits for in terconnecting the lines, a normally inefi'ective individualizing device for each link circuit, an electromagnetic signal control mechanism common to the link circuits, and means common to the link circuits and cooperating with the individualizing device of an engaged link circuit when rendered eflective by the restoration to and the subsequent rcnoval from the switchhock of the receiver of the engaged line to connect'the signal control mechanism with the engaged link circuit and to prevent the connection thereof with any other link circuit.

' 12. A telephone excha ge system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines, a normally ineli'ective individualizing device for each link circuit, an automatic finder switch common to the link circuits, means controlled bv the restoration to and the subsequent removal from the switchhook of the receiver at the connected station to render the individualizing device of the engaged link circuit effective to connect there with the finder switch, and a s gnaling device actuated upon connection of the finder switch with the engaged link circuit.

13. A telephone exchange system comprising telephone lines, link circuits for in terconnecting the lines, one of the link circuits being connected withone of the lines, a supervisory relay for each link circuit,

a second relay for the engaged link circuit.

operating upon the deenergization of the supervisory relay, and an electromagnetic signal control mechanism common to the link circuits rendered individual to and connected with the engaged link circuit upon the operation of the second relay followed by the energization of the supervisory relay. 1 A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines, a supervisory relay for each link circuit, a second relay for the engaged link circuit operating upon the decnergization of the supervisory relay. an automatic finder switch common to the link circuits rendered individual to and connected with the engaged link circuit uponthe subsequent energization of the supervisory relay, and a signaling device actuated upon connection of the finder switch with the engaged link circuit.

15. A telephone exchange system comprising teleph ne lines, link circuits for interconnecting lines, an electromagnetic signal control mechanism common to the link circuits, an individualizing device for each link circuit for rendering the common signal control mechanism individual to any one of several engaged link circuits, and means responsive to the closure and subsequent opening of an engaged telephone line and cooperating with the individualizing device of the corresponding engaged link circuit to connect the signal control mechanism thereto to the exclusion of other engaged link circuits. I

16. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines, a normally ineflective individualizing device for each link circuit, an automatic finder switch common to the link circuits, means responsive to the opening and subsequent closure of the connected linecircuit for rendering the individualizing device of the engaged link circuit effective to connect therewith the automatic finder switch, and a signaling device actuated upon connection of the finder switch with the engaged link circuit. v v

17. A telephone exchange system comprising telephone lines,link circuits for in terconnecting ,the lines, a signal common to the link circuits, apparatus for connecting the signal to any one of several engaged link circuits to the exclusion of other engaged link circuits, means responsive to the opening and subsequent closure of an eligaged telephone line and cooperating with the apparatus to connect the signal with the corresponding engaged link circuit 7 and means responsive upon such connection for operating the signal. V 18. A telephone exchange system comprising telephone lines, link circuitsfor in' terconnecting the lines, a signaling device commoi'i to the linkcircuits, switching ap 'paratus for connefting the signaling device to one of severalengaged link circuits to the exclusion of other engaged link circuits, electromagnetic mechanism responsive to the opening and subsequent closure of an engaged telephone line for causing the switching apparatus to connect the signaling device with the corresponding engaged link circuit, and an. operating circuit forthe signaling device completed upon connection thereoi with the engaged link circuit.

19. A telephone exchange system com prising telephone lines, link circuits for interconnecting the lines, a signaling device common to the link circuits, switching appav ratus for connecting the signaling device to one of several engaged link circuits to the exclusion of other engagedlink circuits, a supervisory relay for each engaged link circuit, a second relay therefor operating upon the dee'nergization of the supervisory relay and cooperating with the supervisory relay when subsequently energized to cause the swltching apparatus to connect the slgnahng device with the correspondlng engaged link ,circuit, and an operating circuit forthe signaling device completed upon connection thereof with thecorresponding engaged link circuit.

20. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, asignaling device individual to each link circuit, a signaling d'evice common to the link circuits, switching apparatus for connecting the common sig naling device to one of several engaged link circuits to the exclusion of other engaged link circuits, a supervisory relay for each engaged link circuit, a second relay therefor operating upon the deenergization of the supervisoryrelay and cooperating with the supervisoryrelay (when "subsequently energized to cause the switching apparatus to connect the common signaling device with the corresponding engaged link oircuit,'and

" operating circuits for. the signaling device individual to the link circuit and for the common signaling device-completed upon connection of the common signaling device with the corresponding engaged link circuit.

21. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, a signal common to the link circuits, switching apparatus for connecting the signal to any of the link circuits, means responsive to the opening and subsequent closure of a connected telephone line and cooperating with the switching apparatus to connect the signal with the corresponding engaged link circuit and operate the signal, an operators telephone set, and an operator-controlled key common to the link circuits and upon actuation cooperating with the switching apparatus for connecting the operators telephone set with the engaged link circuit.

- 22. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, a signal common to the link circuits, switching apparatus for connecting the signal to any of the link circuits, means responsive to the opening and subsequent closure of a connected telephone line and cotiperating with the switching apparatus to connect the signal with the corresponding engaged link circuit and operate the signal, a plurality of operators positions, an operators telephone set for each position, and an operator-controlled key at each position for connecting the operators telephone set thereof with the engaged link circuit when the signal is connected therewith.

23. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, a signal individual to each link circuit, a signal common to the link circuits, switching apparatus for connecting the connnon signal to one of several engaged link circuits to the exclusion of other engaged link circuits, and means responsive to the opening and subsequent closureof a connected telephone line and cooperating with "the switching apparatus to conncctthe common signal with the corresponding engaged link circuit and operate both the 'con'nnon signal and the signal individual to "the corresponding engaged link circuit.

A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits bci'ng'connected with one of the lines, a signal in'dividual to each link circuit, a signalcommon to the link circuits, switching apparatus for connecting the common signal ing'telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines, a signal individual to each link circuit. a signal common to the link circuits, switching apparatus for connecting the common signal to any of the link circuits, means responsive to the opening and subsequent closure of the connected line circuit and cooperating withthe switching apparatus to connect the common signal with the engaged link circuit and operate both the common signal and the signal individual to the engaged link circuit, a plurality of operators positions. and an operator-controlled key at each position for stopping the operation of the individual signal of the engaged link circuit.

26. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines, a signal individual to each link circuit. a signal common to the link circuits, switching apparatus for connecting the common signal to any of the link circuits, means responsive to the opening and subsequent closure of the connected line circuit and cooperating with the switching apparatus to connect the common signal with the engaged link circuit and operate both the common signal and the signal individual to the engaged link circuit, a plurality of operators positions, an operator-controlled key at each position for stopping the operation of the individual signal of the engaged link circuit, an operators telephone set for each position, and an op orator-controlled key at each position for connecting the operators telephone set thereof with the engaged link circuit.

27. A telephone exchange system compris ing telephone lines, link circuits for interconnecting the lines, one of the link circuits being connected with one of the lines a signaling device individual toeach link circuit, an automatic finder switch common to the link circuits means responsive to the opening and subsequent closure of the connected line circuit for connecting the'finder switch with the engaged link circuit an operating circuit for the signaling device ofthe engaged link circuit completed upon connection of the finder switch 'therewi'tl1,'and an operator-controlled key common to the link circuits for stopping the operation of the signaling device.

28. A telephone exchange system compris ing telephone lines, link circuits for interconnecting the lines, a signaling device in dividual to each link circuit, a signal comanon to the link circuits, apparatus for connecting the signal to one of several engaged link circuits to the exclusion of other engaged link circuits, means responsive to Gopies of this patent may be obtained for Y 29. A telephone exchange system comprisin'g telephone lines, link circuits for interconnecting the lines, a signaling device common to and connectible to any one of several engaged link circuits to the exclusion of other engaged link circuits, means common to the link circuits for connecting the signaling device to any one of the engaged link circuits, and means individual to each link circuit and controlled from the respec tive connected telephone lines for determining the engaged link circuit with which the signaling device is to be connected.

In witness whereof, I hereunto subscribe my name this 20th day of April, A. D. 1917.

HENRY r. CLAUSEN.

Washington, D. G.

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