US1217472A

US1217472A - Telephone-exchange system.

Info

Publication number: US1217472A
Application number: US31267306A
Authority: US
Inventors: James L Mcquarrie; Frederick H Loveridge
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1906-04-19
Filing date: 1906-04-19
Publication date: 1917-02-27
Anticipated expiration: 1934-02-27

Description

3. L. McQUARRiE 5;. F. H. LOVERIDGE.

TELEPHONE EXCHANGE SYSTEM.

APPLFCATION FILED APR. 19, I906.

Patented Feb. 27,1917.

2 SHEETS-SHEET 1.

WITNESSES: INVENTOR QM- g W W S ATTORNEY ZZ J. L. McQUARRIE (32 F. H. LOVERIDGE.

TELEPHONE EXCHANGE SYSTEM.

APPLICATEON FILED APR. 19, 1906.

I STATES PAIIENCI. OFFICE.

JAMES L. MCQUARRIE, OF OAK PARK, AND FREDERICK H. LOVERIDGE, OF CHICAGO,

ILLINOIS, ASSIGNORS, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

To all whom it may concern Be it known that we, JAMES L. McQUAnnrE,

Oak Park, in the county of Cook and State of Illinois, and FREDERICK H. Lovnarncn, a citizen of the United States, residing at Chicago, in'the county of Cook and State of Illinois, have invented certain new and use- I ful' Improvements in Telephon'e-Exchan e Systems, of which the following-is a speci cation. v

Our invention relates to a system for. the

interconnection of telephone lines, and has to do more particularly with a. system wherein certain of the acts incident to the establishment and disestablishment of connection between two telephone lines are accomplished by apparatus adapted to operate automatically, while other acts are performed manually through the agency of an operator.

The principal object of our invention is to provide a system which, by combining automatic and manual operation in such a way .that the advantageous features of both are retained, will reduce to a minimum the complication and cost of the interconnecting apparatus, both at the subscribers station and the central ofiice, which willIminimize the amount of labor required on the part of the subscriber in making a call and'on the part of the operator in completing the'cong nection, which will be capable of being"; adapted to the standard systems of'tele phonic operation with the least possible. change of equipment, and which will provide for the interposition of a human agency for handling the connection at these points where a machine'would be undesirable or inadequate. Other desirable features toward 1 which our invention is directed are, greater Iflexibility in the distribution of calls among the various operators, ready adaptability of r the number vof operators ositions in service v the effective supervisiongof connections; I

to the volumeof the tra c, and an arrangementof the connecting apparatus more favorable for prompt answering of calls and To this end we ,.'have' devised a system wherein the callsioriginating in the various lines of the exchange are distributed evenly among the various operators bymeans'of automatically operating switch mechanism which serves to extend the circuit of a call- Specificati'on of Letters Patent.

Patented Feb. 27, 1917.

Application filed April 19, 1906. Serial No, 312,673.

ing line to a connecting circuit under the control of an operator, the operator therea citizen of the United States, residing at upon taking charge of the call, completing and-supervising the-connection and disconnecting the calling and called lines upon the completion of the conversation.

In the particular embodiment. of our invention illustrated and described herein, the telephone lines extend to the central office and are theremultipled in groups to the star tionary contacts of a number of distributing or finder switches, the movablecontacts of which serve as terminals for the connecting cord circuits of the various operators positions. These switches operate to extend the circuit of a calling line to a particular. one of the connecting circuits, through the medium of which the connection with the called line is completed by the insertion of the other terminal of the connecting circuit in wassociated connecting circuit. This actuates a signal which apprises the operator, to

whoseposition the calling line has been extended, of. the call, and she thereupon attends to the establishment of connection with the called subscriber in the usual way. If the cord circuit associated with the switch which first reaches the calling line extends to a position where the operator is busy, the' switch is automatically prevented from completing connection with the calling line, and i one of j the other switches takes the call. Upon'the calling line being extended to a connecting-circuit by any of the switches, the condition. of the switch terminals of that line is changed so that the other switches --.jwhich reach it afterward are not stopped or affected... The various switches to which a group of'lines is multipled have their parts so related as to minimize the possibility of two'switches reaching a calling line at the same instant. When the call has been taken by the first switch that reaches the terminals of the calling line, the other switches continue their movement until they have moved through a cycle which brings them back to their normal position, where they are automatically brought to rest, ready for another call. The circuits that determine the operation of the finder switches are so arranged that as many of the switches as desired may be rendered inoperative, thus making it possible to concentrate the calls upon a small proportion of the whole number of positions and connecting circuits. The foregoing, and other features of our invention will be more particularly described hereinafter.

We will describe our invention in connection with the accompanying drawings, wherein Figure 1 illustrates two subscribers lines extending to a central office, and there adapted for interconnection through the medium of circuits and apparatusarran ed in accordance with our invention, and ig. 2 is a view of a grouping arrangement whereby the incoming calls may be evenly distributed among all the positions, thus keeping the operators uniformly busy.

In Fig. 1 we have shown two metallic circuit subscribers lines 1, 2 and 6, 7 extending from the substations A and B, respectively,

' to the interconnecting apparatus at the central oiiice C. The equipment provided for each line at its substation may be of any desired character, and consists, in the present instance, of a telephone bell, a-condenser, a telephone receiver, a transmitter, and an induction coil, together with a telephone switch adapted to close the bridge of the line containing the telephone apparatus, when the telephone is taken from the hook in the act of initiating a call. We have shown but two lines, but it will be understood that a great many equi ped as shown may extend to the central 0 cc of the exchange, and there be adapted for interconnection. Each of the lines extends to a connection terminal or spring jack (1, a, b, b on each of a number of sections of switchboard where connection may be completed with the line through the medium of cooperating plugs or terminal devices.

The circuit of each line, the line 1, 2 extendin'g'to substation A being selected in the present instance as typical of all the lines, normally extendsto the poles of a central battery through a branch circuit 8, 9 controlled in the contacts f, f of a cut-off relay f. In accordance with the usual practice one pole of the battery, the positive pole in the present instance, is connected to earth or a return conductor. Although for the sake of convenience in illustration we have shown three central batteries marked 9, it will be understood that these may be, and in practice usually would be, one and the same.

Included in one of the conductors of the line between the branch extending to the cut-ofl relay and the substation, in the present instance in conductor 2 of the line, is the winding of a line relay (1 in whose contacts is controlled a circuit 10 extending between the poles of the central battery 9 and including the winding of a rela e, normally closed contacts f of the cut-o relay 7, and two resistances d and d'.- The winding of the relay 6 is preferably of low resistance, and is common to the conductors 10 of a' grcupsay one hundred-of the telephone lines extending to the exchange. The value of the resistance cl is preferably high, while that of resistance (i may be somewhat lower.

Leading from the circuit 10, from a point between the contacts of the relay (l and the resistance (Z', is a branch conductor 4 which extends,-together with the conductors 1, 2 and a conductor 3 leading from the frames or sleeve contacts of the multiple jacks a, a, associated with the line,to the contacts 11 2' of a number of automatic distributing or finder switches h and i. 7 Of these switches there may be as many as desired, and each may be adapted to accommodate upon its stationary terminals the conductors of a large number of subscribers lines. A convenient arrangement is to have each switch capable of accommodating one hundred lines, and to multiple each of the group of one hundred to, say, ten finder switches, so that each of the one hundred lines may be served by one or another of the switches to which it is extended.

The distributing or finder switches may be of any desired type, the switch comprising essentially a plurality of terminals upon which the telephone lines are terminated, cooperating terminals for extending the conductors of the lines to other circuits, and devices for producing and controlling a relative movement of the terminals of the switch. In the present instance we have illustrated these switches as being constructed in the form of a disk h of insulating material uponv which the stationary terminals 11?, which are connected with the telephone lines, are arranged in groups radially of the disk, the cooperating switch contacts 12.. being carried upon and insulated from an arm secured to a shaft It arranged centrally of the disk Ir, and adapted to be rotated to causethe arm with its contacts h to move over the contacts h by means of a motor it". As illustrated, the motor may be of the electrically operated type, having an energizing circuit supplied with current from the central battery g, and controlled by switch mechanism which will be described hereinafter.

Associated with the movable terminals h of each of the finder switches is a connecting circuit extending, as shown, in two

conductors

11, 19 and 12, 20, respectively, to the contacts of a terminal device or plug -p half of the connectin which is adapted to cooperate with the connection terminals or spring jacks a, b and a, b of the various telephone lines of the exchange. Included in the conductors of the 9 extending between the conductors of thecord circuit at a point between the windings of the repeating coil. The connecting circuit is provided with the usual ringing key a for applying ringing .currentyfrom the generator 41 to the plug 7), and thence to the line with which connection is made; and with the listening key u which controls the connection with the cord circuit of the usual operator's telephone apparatus 9. Supervisory relays 0, 0 are also included in the halves of the cord circuit leading to the calling and the called lines, respectively, being connected inthe present instance in the side of the circuit associated with the free pole of the central battery.

The supervisory relays o and 0 serve to control the operation of supervisory signals. 7, 1, respectively, which maybe the commonly employed miniature incandescent lamps as shown. The actuating circuit 23 for the lamp r associated with the calling cord circuit, extends from the free Pole 0 the battery through the winding of a relay t and the lamp 1* to the sleeve or body ofthe plug p, whence it is adapted to be completed to earth or the other pole of the battery, when the plug is inserted in ajack, by way of the conductor 3 of the associated jack and the winding of the corresponding cut-ofi' relay f. The contacts of the supervisory relay 0 control a conductor 24 which extends in a shunt about the lam) T and which ma include a re 'ulating resistance 8. The supervisory lamp 1" associated with the answering half of the connecting circuit'is included in a circuit 21 extending from the free pole of the central battery toearth and including the lamp, normally open contactst of the relay't, and a regulating resistance 25. The shunt conductor 22 about the lamp 1' which is controlled in the contacts of relay 0, is also con- 'trolled in normally open contacts t. of the relay t, and may include the regulating resistance 8.

Associated 'with the cord circuit is another signal'r -illustrated as a lamp in the present instance,which is included in a conductor 25 extending to earth by Way of v a conductor 27 from the normal or restmg contact of the switch t and consequently normally in connection with the conductor 22 described above as being adapted in the actuated position of the switch t to constitute a shunt about the su ervisory lamp 7*. With the switch t theret hre, in its normal or resting position, the closure of the contacts of relay 0 completes an actuating circuit for the lamp 7* by way of conductors 21, 22,v 25 and 27'; while with the switch contacts of the relay t in their actuated or alternative position the circuit for the lamp 1' is interrupted. Y

A relay w whose function will be more particularly described hereinafter, is included in the conductor 27, which forms a part of the actuating circuit of the signal 1*, and another branch 26 of conductor 27 extends to the free pole of the battery by way of the winding of relay t and is controlled in normally open contacts of the operators listening key u; the result being that whenever'the operators listening key is operated to connect her telephone apparatus with the cord circuit, or whenever the energizing circuit of the signal 0' is closed, the relay w is actuated.

' In order to maintain the connecting cirswitch, the normally open contactsk k a relay is are interposed in the conductors-- /12 and" 11 respectively, ,while other switch contacts k of the relay serve when the relay is actuated to close the circuit of conductor 13 to the free pole of the central battery, whence current flows by way of conductor 13 and the resistance is interposed therein to conductor 3 associated with the line withwhich the switch has made connection, and thence through the winding of the associated (mt-offrelay f, at the same time altering the potential of the sleeves or bodies of the associated multiple jacks (1, a to indicate that the line is engaged.

The operation of the motor h which effects the movement of the finder switch It, is governed, as hereinbefore stated, by a system of electrically controlled switches. The motor is provided with a switch which it itself operates, and which, in the present instance, is shown in the form of a grounded commutator h having an insulating portion It upon which is mounted a conduct-l ing stri or segment It on which two brushes 7 and it normally rest. The energizing circuit of the motor extends from the free pole of the central battery 9 through as witch 7', adapted for manual actuation,

completed to earth or the other pole of the battery by way of the grounded portion of the commutator It, on the operation of the motor, or by way of a conductor 5 extending to the normally open contacts of the common relay e, whose circuit is controlled by the line relay d. The relay e responds upon the actuation of the relay (1 to close the actuating circuit of the motor by way of conductor 5, and, upon the movement of the motor which ensues, the conductor 5 is dis connected, and the actuating circuit is closed independently by the withdrawal from beneath the brushes h, h of the strip or segment h, and the contacting of the brush k with the grounded commutator h, the circuit remaining closed at this point until the shaft h with its associated switch arm and commutator it have been caused to move through a complete cycle.

The stopping or controlling relay Z, whose normally closed contacts are interposed in the undivided portion of the actuating circuit of the motor, is included in a circuit 17 which extends between the poles of the battery 1, includes the winding of the above described relay is, is controlled in normally open contacts at of a relay m,'and is provided with a branch 18 which extends to earth by way of the normally open contacts t of the relay t. The relay m is preferably provided with two windings m m, as shown, the latter of which is preferably of high resistance, and is included in a conductor 14 extending from one of the movable contacts h of the finder switch to earth or the return conductor by way of a normally closed contact w of relay w, and the former m of vwhich is preferably of low resistance and is included in a branch 16 to earth of the conductor 14 controlled in normally open contacts m of the relay m.

The movable contact of the finder switch to which the conductor 14 extends is adapted to engage the stationary terminals of the switch which are each connected by way of the conductor a of the associated line to the local circuit 10 controlled by the cut-off relay f and the line relay (Z. The result of this is that when line relay (1 is actuated by the taking of the telephone for use at the sub-station, the change of potential which is caused in circuit 10 by the closure of the contacts of relay (1 is communicated by way of conductor 4 to the corresponding stationary contact of the finder switch it, and

this, upon the cooperating movable contact? of the switch being brought into engagement therewith, causes current to flow through the high resistance winding -m of relay m, and, upon the relay closing its contacts, through the low resistance winding m thereof. As the actuating circuit 17 of relays k and Z is controlled in the contacts m of the relaym, both of these relays are actuated upon the operation of relay m, the relay is to extend the connecting circuit to the finder switch, and the relay Z to bring the finder switch to rest with its movable contacts in engagement with the stationary contacts of the calling line.

of the actuating circuits 14 of the relays m associated with the various connecting circuits, either directly, by being provided with a number of sets of switch contacts; as shown, one for each of such circuits, or indirectly by any of the methods which will readily suggest themselves. The result of this arrangement is that as long as current flows in the actuating circuit of any of the calling signals 1'? on the operators position. or as long as any of her listening-keys is thrown to connect her telephone with the corresponding circuit, the actuating circuits of the relays m of the various connecting cords will be open, and the relays consequently incapable of responding to the potential applied to the stationary terminals of the finder switches when the associated line is calling. As the response of the relay m determines the actuation of the stopping relay Z, and the arresting of the movement of the finder switch h when a calling line is found, the calls are thus diverted from the position as long as the operator is engaged in taking care of other calls.

The branch circuit 18 of the actuating circuit of relays k and Z, which has been heretofore referred to as being controlled in the contacts t of'the switch t, is provided for the purpose of making the actuation of the relays 7c and Z dependent upon the insertion in the jack of the calling or connecting plug 1), as well as upon the response of the relay m which is controlled by the calling'line, the operation of relay :5 which controlsthe branch 18 being governed by the position of the connecting plug.

The resistances of the apparatus associated with the conductors l and 14. through the medium of which the potential which determines the stopping of the finder switch 1s communicated to the switch terminal of the associated line, are so proportioned that while the potential is-sufliciently high to cause the energization of relay m when its high resistance winding is brought into communlcatlon with the terminal in the movement of the finder switch, the closure of the shunt aboutthe high resistance winding containing the low resistance winding m of the relay m reduces the potential to the point where 1t is no longer suflicient to energize the relays m associated with the other finder switches when they are subsequently brought into connection with the terminals I and stationary terminals of the various finder switches to which each groupof lines is multipled are preferably so arranged that their positions with relation to each other on the various switches are dissymmetrical. As illustrated in the present instance this result is attained by progressive'ly displacing the arms of the switches to which the group of lines is multipled so that the normal resting position of each switch arm with relation to'the stationary terminals is different from that of the others in the series, the consequence being that the terminals of none of the linesare separated by any great distance from the movable arms of one or another of the group of switches to which the lines extend. This not only insures a. prompt taking of the call by one or another of the switches, but it also tends to prevent the arrival of the movable arms of two or more switches at the terminals of the calling line at the same instant.

The finder switches,,upon which the telephone lines terminate, with their associated apparatus may be located at-any convenient point, and their circuits extended to connecting cords arrangedin the usual manner on sections of a telephone switch-board provided with the usual equipment of multiple spring jacks representing the various lines of the exchange. The connecting cords. of the finder switches towhich any particular group of lines is 'multipled are preferably distributed on different positions; or, in other words, the finder switch associated with the first cord at any given operators position may be connected with a particular group of lines, the finder switch associated with the second cord may be connected with another group of lines, and so on; Looking at it in another way, the connecting cords associated with the first switch in each series of finder switches serving a particular group of lines may be located at one operators position, the connecting cords associated with the second switch in each series may be connected with another operators position, and so on. In the drawing the finder switch It connected with the line 1, 2 extending from substation A, and with a number of other lines notxshown, is associated with acord terminating at one position on the switchboard. while the finder switch 2', to which thesame and other lines are multipled, is

associated with connecting,cordlocated upon another position.

The operation of the system of our invention is as follows: Assume that the subscriber at station A desires connection with some other line in the exchange. He removes his telephone receiver from its hook, and the closure of the line circuitwhich follows permits current from the central battery g to fiow through the line and the line relay (I included therein, by way of the branch conductors 8 and 9 controlled in the contacts 7, f of the cut-off relay 7". The line relay thereupon closes its contacts, thus completing the local circuit 10 and permitting current to flow through the common relay e, and at the same time altering the'condition of the outer one of the stationary contacts 71?, associated with the various finder switches to which the line [is multipled, by applying an electrical potential thereto. The actuation of relay ecloses the circuit of conductor 5 and permits current to flow through the motor of the finder switch I), and also through the motors of the other idle finder switches to which the line is multipled, by way of the energizing circuit 28 and the normally closed contact of the associated stopping or controlling relay Z. As soon as the motor starts its movement it withdraws the insulated segment of normally lies closest to the stationary ter--' minals of the calling line, the switch It is the first to bring its terminals into engagement with the terminals of that line. As soon as this occurs the

conductors

1, 2, 3 and 4 are connected to the conductors 11, 12, 13 and 1.4, respectively, and the potential which has been communicated to conductor 4 by the actuation of the line relay 0! causes current-to flow through the high resistance winding m of relay m to actuate that relay,-providing the contacts of the relay w are in their normal position. The operation of the relay m reduces the resistance to earth by way of conductor 14 by closing the shunt circuit through the low resistance winding m of the relay, thus reducing the potential upon the conductor 4 and restoring its associated terminals to substantially their normal condition.

At the same time by closing its contact m, the relay m eflects the actuation of the relays k and Z. The first mentioned relay in closing its contacts is, k closes the break that normally exists in conductors 11 and 12,

current from the central battery to flow by way of conductors 13 and 3 to the cut-off relay f, actuating it and also applying potential to the sleeves or frames of the associated multiple jacks to indicate that the line is busy. The current applied to the cut-off relay f causes it to open the branch conductors 8, 9 through which the battery 9 is normally connected with the limbs of the line, and to open the circuit 10 over which the current flows which energizes the motor starting relay e, leaving it free to respond to subsequent calls; the circuit 10 is at the same time reconnected to the free pole of the battery by way of the conductor 15 extendmg to the alternative contact of the switch f, in order to maintain the fiow of current through conductor 4 and the windingspf relay m as long as the line relay d remains actuated. The relayl is actuated through the agency of relay 172 immediately upon the engagement of the movable terminals of the switch it with the terminals of the calling line, and, by opening its normally closed switch contacts, breaks the'circuit through the motor it of-the finder switch, whereupon the motor immediately comes to rest with its movable switch contacts engaging theterminals of the calling line.

As soon as the conductors of the calling line are extended to the cord circuit, current flows through them by way of the bridge completed at the substation, and actuates the supervisory relay 0 in the answering half of the cord circuit. The actuation of this relay closes an energizing cirs cuit for the calling lamp 1' by way of

conductors

21, 22, 25 and 27, the normally closed contacts t of the relay t and the winding of the calling relay w. The operation of the relay w interrupts the circuits 14 of the relays m associated with all the cords on the position, the relay m of the cord which has answered the call, however, remaining energized by the current flowing through its low resistance winding'm It also, by illuminating the lamp 1' notifies the operator that a subscriber is waiting on the cord circuit associated with the lighted lamp. The operator thereupon comm-unicates with the calling subscriber by means of her telephone key it, the operation of which, by closing the conductor 26, effects the actuation of the relay t, and thus extinguishes the calling lamp 2" by opening its circuit in the switch contacts t of the relay, the relay at the same time operating to close the circuit of the supervisory lamp 7', and to complete the shunt circuit 22- about it subject to the control of the supervisory relay 0. The opening of the circuit through the calling lamp 1* does not result in the deenergization of the relay 'w, as the closure of the operators telephone key, which brings about the opening of the lamp circuit, also closes the conductor 26 over which current flows to the relay w to maintain its actuation.

Upon learning the number of the line with which the calling subscriber desires to be connected, the operator tests the line in the usual manner at its associated spring jackto ascertain if it is busy, and, if she finds it free, completes connection therewith and signals the substation by inserting the plug in the jack, and applying ringing current by means of the ringing key 1). The insertion of the plug completes the circuit which permits current to How through the supervisory lamp 1" by way of the relay t and through the cut-off relay f of the line with which connection is made. The operation of the associated cut-ofi relay of the called line prevents the possibility of the line relay d being operated to alter the condition of the switch terminals of the line such as would lead to its disturbance by the finder switches to which it is multipled. The supervisory lamp 1" is illuminated by the current which flows through it until the response of the called subscriber, when the resulting actuation of the supervisory relay 0 closes the shunt circuit 24 and extinguishes it.

\Vhen the connection has been established, the operator, by returning her listening key u to its normal position, cuts off the flow of current through the relay w, which permits its switches tofall back, and thus renders the position available for receiving other calls.

If during the continuance of the connection either subscriber replaces his telephone on its hook, the corresponding cord circuit supervisory signal will indicate this; but the stopping or controlling relay l will not be denergized to permit the movement of the finder switch to its normal position, as the stopping relay is under the independent control of both the calling subscriber and the terminal plug of the connecting circuit, it being necessary both for the calling subscriber to hang up and the operator to withdraw the connecting plug before'the relay 1 will become deenergized. lVhen, at the end of the conversation, this condition occurs, the closure of the switch contacts of the relay Zreestablishes the circuit through the motor h,- and the motor thereupon operates to cause the movable terminals of the finder switch to continue their movement until the circuit of the motor is opened by the arrival of the insulated segment of the commutator beneath the brushes It, h If the terminals of the switch engage the terminals of a calling line while they are returning to their normal position at the end of a connectlon they take the call in the same manner as they would if their movement had been occasioned as a result of the call.

If during the slack or quiet hours of the day it should be desired to concentratethe traffic upon certain positions, this may be accomplished by merely opening the switches j included in the energizing circuit of the motor of each finder switch. The result of this is that although upon the receipt of a call the energizing circuits of all of the finder switches of the group. are closed at the contacts of the relay 6, only those switches whose circuits are closed at the switches will respond to the call. We have illustrated only one simple way of rendering the distributing or finder switches irresponsive to calls in order to effect thedistribution of traffic; but it will be understood that other ways, which will readily suggest themselves may be employed for that purpose.

Referring now to Fig. 2, D, E, F, G each represent a group or division of lines multipled to a group of line finders h, 2', 7', In. Each group of lines may comprise as many lines as desired and each group of line find ers may comprise as many as may be necessary to take care of the maximum simultaneous number of calls from its group. In the present grouping scheme D, E, F, G each represent 100 telephone lines, each group being multipled to ten line finders although for simplicity but four, h, z', y, k,

are shown. The finder arms of each group.

of lines each terminate in plugs 29, 79 p", 72 before the banks of multiple jacks at different positions H, I, J, K. Thus assuming line A is multipled to the first terminal in each finder switch It, i, j, c, B to the second, and so on, it will be evident that an incoming call from line A finding the connecting circuit connected with the finder switch h of its group busy, said call-will thereupon ferred to finder switch 7' leading to a third position J, and so on. v

l1en both subscribers have hung up, the operator disconnects by .withdrawin the calling plug 9. This de'e'ne'rgizes re ay' t, and relay tin opening its contacts It opens the energizing circuit ofrelay 1. in deenergizing' closes the circuit of the motor It, as a result of which the switch brushes are moved off of the terminals of the calling line. But if the operator is listening in on the circuit when she withdrawsthe plug p, the energizing circuit of the relay t is maintained by way of the local contact of the listening key M and the winding of relay 1.0, and the deenergizationof relay Z and the accompanying release of th finder switch are prevented.

Although for the purpose of more clearly disclosingour invention we have illustrated it in connection with particular circuit arrangements and specific forms of apparatus,

Relay 1' and described. The distributing switch, for.

instance, and its associated actuating and controlling mechanism may assume a. variety of forms. It will also be understood that although we have illustrated our ins vention asemployed in connection with metallic circuit telephone lines, it is adapted for use in systems where only a single conductor is employed for each line.

We claim: a

1. In a telephone call distributing system, the combination with a finder switch and a telephone line extending to stationary terminals thereof, of electrically operated mechanism for causing the movement of the movable member of said switch, an actuating circuit for'said mechanism having an undivided portion and a divided portion, a manually operated switch and an automatically operatedswitch in the undivided portion of said circuit both of said switches being normally closed and the automatic switch being controlled from a distant point through the medium of a telephone line, a normally open switch under the control of the mechanism itself in one of the branches of saidcircuit, and an automatic switch controlled by said telephone line in the other branch thereof. V a

2. In a telephone call distributing system, the combination with aifinde'r switch having stationary and. movable terminals, of a connecting circuit associated with the movable terminals ofthe switches, a plu rality of telephone lines connectedwith the stationary terminals thereof, mechanism for causing said movable term nals 'totraverse the stationary terminals, means associated with each line and made operative in initiating a call therein for establishingan electrical, potential on one of the stationary finder'switch terminals associated with said line, a controlling relay associated with said finder switch, said relay having a high resistance winding and a low resistance winding, said highv resistance winding being in cluded in a conductor extending to a movable terminal of said switch adapted to 00-- operate with the stationary terminal upon which the electrical potential is established,

anda branch of said conductor including the low resistance winding ofsaid relay, said branch being normally open in contacts of said relay, and being adapted to be connected in shunt of the high resistance winding upon the operation of said relay to main-v ta in'the relay in its actuated reduce the potential of the a oresaid Sta-- osition and tionary terminal.

3. In a telephone call distributing system, the combination with groups of finder switches having stationary and movable terminals, of a plurality of telephone lines connected with the stationary terminals of each switch, a connecting circuit associated with the movable terminals of each switch, means associated with each line and made operative in initiating a call therein to establish a potential upon one of the stationary switch terminals associated with such line, mechanism adapted to cause the movable terminals of each switch to traverse the stationary terminals thereof, an electrically actuated device associated with each switch and adapted to arrest the movement of the movable terminals thereof, an actuating circuit for each of said devices extending to a movable terminal of the associated switch adapted to engage the stationary terminal having the potential thereon, an electromagnetic switch adapted to control said actuating circuits and to maintain the same normally closed an oierators tele )hone keV associated with each connecting circuit, and an actuating circuit for said electro-magnetic switch adapted to be closed when any of the telephone keys at said position is operated, whereby said switches are rendered incapable of completing connection with a calling line while a telephone key is in its operated position. x

i. In a telephone call distributing system,

the combination with groups of finder switches having stationary and movable terminals, of a plurality of telephone lines connected with the stationary terminals of each switch, a connecting circuit associated with the movable terminals of each switch, means associated with each line and made operative in initiating a call therein to establish a potential upon one of the stationary switch terminals associated with such line, mechanism adapted to cause the movable terminals of each switch to traverse the stationary terminals thereof, an electrically actuated de-' vice associated with each switch and adapted to arrest the movement of the movable terminals thereof, an actuating circuit for each of said devices extending to a movable terminal of the associated switch adapted to engage the stationary terminal havlng the potential thereon, an electro-magnetic switch adapted to control said actuating circuits and to maintain the same normally closed, and

a calling signal circuit associated with each connecting circuit and adapted to be energized as long as a calling line connected with said cn'cult remains unanswered, the winding of the electro-magnetic switch being included in all the calling circuits of said position, whereby said switches are rendered incapable of completing connection with a calling line as long as a call on any of the connecting circuits of said position remains unanswered.

5. In a telephone call distributing system,

the combination with a plurality of telephone lines'extending to connection terminals at a central ofiice, of a group of connecting circuits adapted to make connection with said lines at the connection terminals thereof, each of said connecting circuits being provided with a signal circuit actuated while a call upon thev associated connecting circuit remains unanswered, means associated with each of said connecting circuits for extending the connection of any of said lines thereto, electrically actuated mechanism adapted to prevent the operation of said connecting means, and an actuating circuit for said preventing mechanism made operative in the actuation of any of the aforesaid signal circuits.

6. In a telephone call distributing system, the combination with a plurality of telephone lines extending to connection terminals at a central office, of a group of connecting circuits adapted to make connection with said lines at the connection terminals thereof, each of said connecting circuits being provided with an operators listening key, means associated with each of said connecting circuits for extending the connection of any of said lines thereto, electrically actuated mechanism adapted to prevent the operation of said connecting means, and an actuating circuit for said preventing mechanism made operative in the actuation of any of the aforesaid listening keys 7. In a telephone call distributing system, the combination with a plurality of finder I switches having stationary and movable ter minals, of a plurality of telephone lines multipled to the stationary terminals of the said switches, mechanism associated with each switch to cause the movable terminals to traverse the stationary terminals, a plurality of connecting circuits located at different operators positions connected to the movable terminals of individual switches, an electrically operated circuit closing device associated with each switch the normally open contacts of which are included in the associated connecting circuit, means associated with each'telephoneline and actuated in the initiation of a call therein for causing the movement of all the finder switches to find the calling line, and means whereby one of the finder switches having found the said line the associated circuit closing device will operate to extend the said calling line to the associated connecting circuit.

a 8. The combination with a group of telephone liues, a plurality of switches associated therewith, a. plurality of operators positions, and groups of connecting circuits for each position terminating thereat, the other ends of the individual members of each group being associated with different ones of said switches, whereby calls from said lines may be distributed among the various posiventing a second calling line from being connected with a connecting circuit leading to the same position while said first call remains unanswered.

9. The combination with groups of telephone lines, groups of switches corresponding thereto to which the said groups of lines are respectively multipled, a plurality of operators positions, and agroup of connecting circuits terminating at each position, the members of each group of said connecting of link-circuits extendingto diflt'erent operators positions at the exchange, automatic switching means for establishing connection between a calling line and an idle one of said link-circuits, and means responsive to the establishment of such connection to render all other link-circuits at the particular opprising-a, plurality of telephone lines, a pluralityof link-circuits extending to different o erators ositions at.the exchan e automatic' switching means for establishing connection between a calling line and an idle one of said link-circuits, and automatic .means for rendering allother link-circuits at the particular operators position artificially busy. T 7 4 '13. A telephone exchange system comprising a plurality of telephone lines, a plurality of link-circuits extending to different operators positions at the. exchange, automatic switching means for establishing .con-

nection between a calling line and an idle one of said link-circuits, automatic means 'for'rendering all other link-circuits at the particular o'perators position artificially busy, and .means under the control of the operator for removing said busy condition.

14'. A telephone exchange system comprising a plurality of telephone lines, a group of signal indicators therefor, means operated over the lines for variously. amociating said lines and indicators and cansing the display of the latter, and means operated during the display of any one indicator to prevent. the display of any other indicator in the group.

15. A telephone exchange system comprising a plurality of telephone lines, a group of signal indicators therefor, means operated over the lines for variously associating said lines and indicators and causing the display of the latter, and connections rendering the other indicators inoperable while one is displayed.

16. A telephone exchange system comprising a plurality of telephone lines, a group of electrically operated indicators therefor, means controlled over the lines for closing the operating circuits of said indicators to cause their display, and means 0perated during the display of any one indicator to prevent'the closing of the operating circuit of any other-indicator in the group.

17. The combination with an operators position, of a plurality of connecting circuits each including an automatic switch for extending calling lines to said position, a listening-switch for each connecting circuit, and means for rendering said call-extending means inoperative to extend calls to said position while any of said listening switches is operated.

18. The combinationiwith an operators position, of a. connecting circuit including an automatic switch forextending calling lines to said position, operators telephone apparatus, a switch for connecting the same with said connecting circuit, and means made active in operating said switch for preventing the extending of calls to said position.

19. The combination with an operators position, of means including an automatic swltch for extending calls thereto. and a device at the position actuated in the extend ing of a call thereto for preventing the extending of another call to the position.

20. The combination with an operators position, of meansincluding an automatic switch for extending calls thereto, a circuit controlling the operation of said call extending means, a switch 'at said operators' positlon for controlling said circuit to render said call extending means inoperative to extend calls to said position, and means for operating said switch upon the extension of a call to said position.

21. The combination with an operators position, of means for extending calls thereto, a device for rendering said position inaccessible to calls, means for operating said device in the extending of a call to said position, and means for restoring said device to its normal condition to render said position again accessible.

22. The combination with an operators position, of a plurality of connecting circuits at said position, means for extending calls to said connecting circuits, and a switch automatically operated in extending a call to one of said circuits for rendering the others of said circuits inaccessible to calls.

23. The combination with a plurality of telephone lines and a plurality of operators positions, of a group of connecting circuits at each operator-Is position, means for extending calls from said telephone lines to the connecting circuits of the said positions, and means actuated upon the extension of a calling line to the connecting circuit of any group for preventing a second calling line from being connected with another connecting circuit of the same group until the call from the first line has been answered.

' 24. A telephone exchange system comprising a plurality of telephone lines, a plurality of connecting circuits extending to different operators positions at the exchange, automatic switching means for establishing connection between a calling line and an idle one of said connecting circuits, and means responsive to the establishment of such connection for preventing the establishment of a connection between another calling line and another one of the connecting circuits at that particular operators position.

25. The combination with an operators position having a plurality of connecting circuits, of means for extending calls to said circuits, means actuated'in extending a call to any of said connecting circuits for preventing the extension of calls to the other circuits, and means actuated in completing the connection over the connecting. circuit to which the call has been extended for rendering the other connecting circuits again accessible to calls.

26. In a telephone system. the combination with a connecting circuit, of a calling line and a called line united thereby, means for automatically disconnecting the connecting circuit from the calling line made operative in disconnecting the connecting circuit from the called line, and an operators key for preventing the operation of said automatic disconnecting means.

27. In a telephone system, the combination with a connecting circuit, of two lines united thereby, means for automatically disconnecting the connecting circuit from one of the lines made operative indisconnecting said circuit from the other line, operators telephone apparatus, and a switch acting to connect said telephone apparatus with the connecting circuit and at the same time render inoperable said automatic disconnecting means.

28. In a telephone system, the combination with a cord circuit terminating at each end in a connecting switch, of operators telephone apparatus, a switch for connecting the same with said connecting circuit, means made operative in actuating one of said connecting switches to break its circuit for causing the actuation of the other of said connecting switches to break its circuit, and means made operative in the actuation of said telephone apparatus connecting switch for rendering inoperable said first mentioned means.

29. In a telephone system. the combination with a connecting s-Quit, of a calling line and a called line united thereby, means for automatically disconnecting the connecting circuit from the calling line made operative in disconnecting the connecting circuit from the called line, and an operators key for preventing the operation of said automatic disconnecting means.

30. In a telephone system, the combina tion with a connecting circuit, of two lines united thereby, means for automatically disconnecting the connecting circuit from one of the lines made operative in disconnecting said circuit from 'the other line, operators telephone apparatus, and a switch acting to connect said telephone apparatus with the connecting circuit and at the same time render inoperable said automatic disconnecting means.

31. In a telephone system, the combination with a cord circuit terminating at each end in a connecting switch, of o'perators telephone apparatus, a switch for connecting the same with said cord circuit, 'means made operative in actuating one. of said connecting switches to break its circuit, and means made operative in the actuation of said telephone apparatus connecting switch for rendering inoperable said first mentioned means.

JAMES L. McQUAR-RIE. FREDERICK H. LOVERIDGE.

lVitnesses:

ROY T. ALLOWAY, R. W. INGERSOLL.