US2386130A - Telephone system - Google Patents

Description

Oct. 2, 1945. H. P. MAHONEY TELEPHONE .SYSTEM Filed Jan. 8, 1944 5 Sheets-Sheet 1 oom OM LLDOWEO OKOO UW: M J.

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INVENTOR. HARRY R MAHONEY AT'LORNEYS Oct. 2, 1945.

H. P. MAHONEY TELEPHONE SYSTEM 5 Sheets-Sheet 2 Filed Jan. 8, 1944 INVENTOR HARRY P. MAHONEY BY I ATTORNEYS Oct. 2, 1945. H. P. MAFIONEY TELEPHONE SYSTEM Filed Jan. 8, 1944 5 Sheets-Sheet 3 -45 low M GE BY Z i, [H

ATT 'ORNEYS Oct. 2, 1945. H. P. MAHONEY TELEPHONE SYSTEM Filed Jan. 8, 1944 5 Sheets-Sheet 4 ATTORNEYS Patented Oct. 2, 1945 UNITED STATE s PATENT OFFICE TELEPHONE SYSTEM Harry P. Mahoney, Oak Park, 111., assignor to Antomatic Electric Laboratories, Inc., Chicago, 111., a corporation ot'Delaware Application January 8, 1944, Serial No. 517,538

11 Claims.

invention relates to telephone systems and any expensive or complicated temporary or auxiliary equipment.

The problem of converting a manual telephone system to an automatic system, while maintaining service in the entire system while it is partly manual and partly automatic, is complicated by the fact that an automatic system is commonly operated on a voltage much higher than that employed in a manual system and by the further fact that the polarities of the line conductors in an automatic system are reversed as compared with the usual manual system. These factors present substantial diificulties, particularly when theconversion from one system to the other extends over a considerable period of time during which both the manual and the automatic portions of the system are in operation and both types of lines are to be interconnected.

Heretofore, it has been the practice, where such a conversion became necessary, to install special and temporary auxiliary equipment including a call indicator switchboard comprising indicators adapted to notify the operators at that'posltion of the numbers being called by automatic lines,

thereby enabling the operator to extend the call manually to the called subscriber's line. Where the call originates on a manual line, the extension'of the call to the automatic lines has involved the provision of special operator positions at the'automatic ofllce for completing the connections extended thereto hy'the manual operators.

The present invention provides a solution for the above-mentioned difiiculties without the use of'substantial auxiliary or temporary additional equipment by furnishing a system according to which the manual telephone system is directly connected to the automatic-system as theautoinatic system is progressively installed and the two systems are coordinated for conjoint'oper ation by changes which are confined almost entirely to the manual equipment so that when the automatic system has been entirely completed and supplants the manual system, the automatic system requires only minor alterations to adapt it to the usual or, standard automatic operation,

and the automatic portions or the so that there is no impairment or interruption oi. service and no necessity for changing telephone numbers in any part or the system.

The primary object of the present invention is to provide an improved method of eflecting the gradual conversion from manual to automatic service according to which a system comprising manual equipment and automatic equipment is arranged for interconnection and the extension of calls 'in both directions between the manual systems by changes which consist, primarily, in reversing the polarity of the lines, of the manual system to agree with the polarity of the lines of the automatic equipment and, at the same time, making a minor change in the operating voltage of the automatic system to approximate or harmonize with the operating voltage of the manual system. A further object is to provide a manual telephone system comprising cord circuits of either the three. conductor type or the two conductor type, or both of these types, which is directly connected with an automatic telephone system and in which the polarity of the linesand the operating voltages of the diiferent parts of the composite system are altered so that, with 1 a minimum of additional equipment, telephone calls originating in any part or the system may bev extended to subscriber stations in the other parts of the system to provide satisfactory service without the attention of special operatorsr Other objects relate to various features of the improved system whereby a gradual and economic transition may be made from manual service to automatic service while providing a uniformly good service during the period of transition.

The nature of the invention will be understood from the following specification taken with the accompanying drawings in which a. telephone system embodying the present invention is illustrated. In the several figuresof the drawings, taken together, thereis illustrated, somewhat diagrammatically, a complete system which is partly of the manual type and partly of the automatic, the manual portion of the system being shown in Figs. land 4 and 'the automatic portion in Figs; 2, 3 and 5. It is assumed that in this illustrated system the conversion from manual to automatic service is in the process of transition and that the necessary changes have been made to permit the manual and the automatic portions of the system to be operated to permit calls to be extended in either direction between said portions of the system during the period when both portions of the system are operating.

2 During this period calls may, of course, be completed locally in each exchange or between different exchanges of the manualsystem and the plan of transition contemplates a gradual con- General description Before describing the operation of the system or the details of the method of conversion employed, some of the principal features embodied assaiso which the operator causes outgoing calls from the two-wire cord circuit 40 to be extended over the line In to a called subscriber line, such as the line L400.

The three-wire cord circuit 30 comprises the answering plug I02, the call plug I" and assoelated apparatus and circuit connections includin diflerent parts of the telephone system will be referred to.

, The manual portion of the telephone system comprises two divisions, shown in Figs. 1 and 4.

that portion of the system illustrated in Fig. 1 including three-wire cord circuits, such as the cord circuit 80, and that part of the system illustrated in Fig. 4 comprising two-wire cord circuits, such as the cord circuit ll. This manual system includes a plurality of subscribers sub-stations, such as the stations M and MA, which are connected by the subscriber lines LI and L4", respectively, with the contacts A of the main distributing frame MDF. These contacts A are adapted to be connected by jumpers with the associated contacts B of the main distributing frame and, in the portion of the circuit shown in Fig. 1, the contacts 3 are connected by the line lIla with the contacts D of the intermediate distributing frame IDF-I. Similarly, the contacts 3.

shown in Fig. 4 are connected by the line Illa with contacts D of the intermediate distributing frame lDF-I. Each subscribers line, such as the line LI00, has associated therewith an individual manual line circuit, such as the line circuit I05, and each subscriber's line of the other division of the manual system, such as the line L400, has associated therewith an individual manual line circuit, such as the line circuit 405. Each line circult I05 includes a cutoff relay RI III and a line relay RI I5. Similarly, each line circuit 405 includes a cutoff relay RIM and a line relay R4".

The contacts D of the intermediate distributing.

frame IDF-I, which are shown in Fig. 1, are

adapted to be connected by Jumpers with the contacts E which are connected by lines, such as the line I00b, with jacks, such as the Jack IOI, adapted to form a connection with the plug I02 terminating the three-wire cord circuit 30. Similarly, the contacts D of the intermediate distributing frame IDF-I, which are shown in Fig. 4, are adapted to be connected by jumpers with other contacts E connected by lines, such as line 4002;, withjacks, such as the Jack "I, adapted to form a connection with a plug 402 terminating the two-wire cord circuit 40. The terminals D of the intermediate distributing frame IDF-I,

shown in Fig. 1, are also connected by the line.

I00a with jacks, such as the jack I58, adapted to be connected with the plug I by which the operator causes outgoing calls from the threewire cor'd circuit 00 to be extended over the line Hills to a called subscriber's line, such as the line- LI00. In asimilar manner, the contacts D of the intermediate distributing frame IDF-I, which are shown in Fig. 4, are connected by the line 460a with the multiple jacks, such as lack 450, adapted to be engaged by the plug 455 by, 75 system were connected together without any rev ing the sleeve relays RI20 and RI, the supervisory relays RI20 and RI30, the ring relay RISII, a control relay RI, a ring cutoii relay RI", ringing generator I", the operator's headset IN and the talk key I00. A call originating in the manual system shown in Fig. 1 may be extended through the multiple Jack I50 and over the line 400! to subscriber stations of the division of the manual system shown in Fig. 4.

The two-wire cord circuit 40, shown in Fig. 4, comprises the answering plug I02 and the call plug I. together with associated apparatus and circuit connections including the sleeve relays R420 and R440, the supervisory relays R425 and R4", the operator's headset I and the talk key I. The portion of the manual circuit shown in Fig. 4 also includes the multiple Jack 458 by which a connection may be made with a plug 405 and through the line I000, a cordless B board 0, and a line I00! to subscribers lines, such as the line LI00, terminating at the switchboard shown in Fig. 1.

As the manual system shown in Figs. 1 and 4 is organized, prior to any changes which are made in the connections for the purpose of conversion, the circuits are connected to battery by the lead I" and to ground by the lead I It by connections which are illustrated by dotted lines in Figs. .1 and 4. When the system operates with the dotted line connections, it customarily operates on a comparatively low voltage, such as a voltage of 24, which is common commercial practice. when the manual system is to be altered for operation in connection with a system of the automatic type, the connections to battery and ground are reversed, as indicated above. but the same operating voltage is retained in this manual portion of the system. As shown in Figs, 1 and 4, the connections have been reversed. as indicated by full system. with the sleeve of a busy called line connected to battery by way of the corresponding sleeve relay RI20 in the associated cord circuit and the tip of the calling. cord circuit connected to ground by way of its'associated supervisory relay R I 30, the test for a busy condition of such a line is made by momentarily connecting the tip of the associated calling plug with the sleeve I of the multiple call jack of the busy called line, the busy v condition being indicated by a busy click which is produced in the operator's headset as a result of opposite potentials on the sleeve and the connected tip. In the operation of an automatic system, on the other hand, the busy condition of a line is indicated by the presence of ground on the conductor corresponding to the sleeve conductor so that, if a manual and an automatic versal of polarity, the usual busy test procedure would bring "together two parts having ground connections or two parts having. battery connections, so that a false busy test would be made and no true indication of the busy condition given.

The automatic portion of the system shown in Figs. 2, 3 and 5 comprises a number of automatic subscriber stations, such as the station P, to which connections are made through automatic apparatus and lines including the link 200 comprising a finder Ill and a selector 220, together with a distributor 210, a connector 300, a trunk circuit 580, a selector 535, and a plurality of line circuits, such as the line circuit 306, and .a plurality of lines, such as the line 300i, connecting the line circuits with the finder banks by way of an intermediate distributing frame IDF2 through which connections are made with the finder 2I0. The automatic system also includes a plurality of lines, such as the connecting line I00d, for connecting the automatic system through the intermediate distributing frame IDF2 with the connecting line I00e which extends to the main distributing frame MDF of the manual system shown in Fig. 1. There is also included in the automatic system a plurality of lines, such as the connecting line 400d, extending from the connector bank of the connector 300 to contacts G of the intermediate distributor frame IDF-2 through which a connection is made with the connecting line 400e extending to the main distributing irame MDF of the manual exchange shown in Fig. 4.

All of the parts of the automatic system referred to above are installed as a part of the origautomatic system, referred to above, it is also necessary during the period of conversion-to alter the voltages of the busy relays of the connectors 800 and the cutoff relays of the line circuits such as the line circuits 20I, WI and 305 to cause them to agree with the voltages of the manual system.

- During the period of conversion, the battery consystem isautomathz, these battery connections are shifted, as shown at H0 in Figs. 3 and 5, to connect the terminals of these busy and cutoff relays to a high voltage battery, such as one having a voltage of 48, this being the standard voltage on which other parts of the automatic system operate throughout the period of conversion, as well as when the system has been entirely converted.

In the drawings, the low voltage battery con- I nections have been designated LV and the high inal automatic equipment and function as such throughout the time that the automatic system is being used in connection with the manual system for transmitting calls in both directions. In addition to these parts of the automatic system, other automatic apparatus and other lines are originally installed as a part of the automatic system but begin to function only as portions thereof are brought into use as the manual system is progressively converted into an automatic system. This additional equipment, which gradually comes into use as a part of the automatic system during the process of conversion, includes a plurality of line circuits, such as the line circuit "I,

and a plurality of line circuits 50 I.

When the automatic system is originally installed, for intended use in conjunction with the manual system, it also includes a plurality of temporary connecting lines 300a which extend from the jacks I59 of the manual system to terminals F of the intermediate distributing frame IDF-2 in the automatic system. Calls are extended over these lines 300a from the manual system to the automatic system during the period of conversion and when the conversion has been completed these lines 300a may be removed Also, during the period of conversion, the system comprises the jacks 459, adapted to be connected with the plugs 455 of the manual system, these jacks being connected by the lines 53I with the trunk circuit 530 from which lines 532 extend to the selector 535. When the conversion from manual to automatic service has been completed for the manual system shown in Fig. 4, the jacks 459, lines MI and 532, and trunk circuit 530 may be discontinued or removed.

In addition to the reversal of the polarities in the manual system which is eflected for purposes of conversion to agree with the polarities of the voltage battery connections have been designated HV. The tip, ring and sleeve conductors of the manual system have been marked T, R and S, respectively. The conductors of the automatic lines which correspond to the tip and ring conductors of the manual system have also been marked T and R, respectively, and the third or control'conductor has been marked C.

In order that the operation of the invention may be more fully understood, the manner of completing various telephqne connections, including the extension of calls from one manual station to another and of calls involving the use of both the manual and the automatic portions of the system, will now be described. All of these operations are described on the assumption that the above-described changes have been made for permitting the conjoint use of the manual and Assuming that the manual and the automatic systems have been interconnected as described and that the battery polarity alterations have been made in the manual system as indicated in full lines, a subscriber at the manual substation M, desiring to call the substation MA, lifts his telephone, which causes a loop, including the line conductors of the line LI00, to be completed at the substation M. The completion of the loop at the substation M causes the line relay RI I5' to operate over a circuit from ground at contacts III by way of the tip conductor of the lines I00c, I00a, and LI 00, through the loop at substation M, over the ring conductorsof the lines LI00, I00a, and I000, the contacts I I2 and through the winding of the line relay RI I5 to battery. The line relay RI I5 operates over this circuit to complete, at contacts IIB, an obvious circuit for operating the answer lamp signal I03. To answer the call, the operator inserts the answering plug of one of the cards. such as the plug I02 of the 'cord circuit 30, into the jack IOI which is associated with the signal I03. When the sleeve of the plug I02 contacts the sleeve of the jack IOI, a circuit is completed for energizing in series the sleeve relay RI20 and the cutoff relay RI I0. This circuit can be traced from ground at the lead II8, through the winding of the sleeve relay RI20, the sleeves of the plug I02 and jack IOI, and the winding of the cutoff relay RI I0 to LV battery on the con- V ductor II1. Inoperatins. the cutoi! relay RIII interrupts, at contacts III and 2, the circuit for energizing the line relay RIII which then restores to open, at the contacts IIO, the circuit for illuminating the answer lamp signal I 00. The sleeve relay I20, in operating, completes, at the contacts I22 and I20, an obvious circuit for connecting the operator's headset across the tip and ring conductors of the cord circuit, this circuit including the normally closed contacts I50 and I54. The supervisory relay RI25 is also operated over the line loop when the plug I02 is inserted into the jack IOI. This circuit may be traced from ground at the lead I I0, by way oi the upper winding of the supervisory relay RI25, the ring conductor and ring contacts of the plug I02 and Jack IOI, over the loop at the substation M by way 01' the line LI00, the tip conductors of the Jack IN and plug I02, and the lower winding of the supervisory relay RI25 to battery upon the lead II1. In operating, the supervisory relay RI25 opens, at the contacts I25, a circuit for energizing a supervisory lamp I04. With the operator's headset II connected across the tip and ring conductor of the cord circuit, which conductors are extended to the substation M through the associated capacitors I41 and I40 and the plug I02 and jack IN, the operator is in communication connection with the calling line LI00 and obtains the number of the desired line to be called. Also, when the plug I02 is inserted. into the jack IOI, the multiple jack I55 which is associated with the line LI00 is marked as bus by the ground potential which is applied to the sleeve conductor through the sleeve relay RI and over the line I00a. Ground upon the sleeve of the line I00a therefore marks all of the multiple jacks associated with the line LI00 as busy, In addition,

ground potential is also applied to the sleeve conductor of the connecting lines I00e and I00d from the sleeve of the jack IOI, which ground upon the sleeve conductor 310 marks the connecting line I00d associated with the line LI00 as busy in the The sleeve relay Rlll operates in series with the cutoi! relay mm and opens, at contacts m connector banks 0! the connectors, including the connector 300.

To extend the call to the substation MA, the plug I is inserted into the multiple jack I50, which is connected by the lines 400! and LI00 to th substation MA. In inserting the plug I55 into the jack I58, ground potential is applied through the winding of the sleeve relay RI 50 to the sleeve of the jack I58 and to the sleeve conductor of the line 400}. Ground upon the sleeve conductor of the line 4001 marks the line L400 as busy in all the multiple jacks associated with this line in-both the sw'itchboards, and the multiple jack 455 has its sleeve grounded also by connection with the sleeve conductor of the line 400! through the line 400a. In addition to marking the line L400 "as busy at the manual switchboards, the line L400 is also marked as busy in the banks of the connectors, such as the connector 300, over the sleeve conductors of the associated connecting lines 400e and 400d. The connecting line 4008 is connected in multiple with the line 400! at the A contacts of the main distributing frame MDF and is crossconnected to the connecting line 400d through the F and G terminals of the intermediate distributing frame IDF-2. The cutoff relay RAM is operated from the ground potential upon the sleeve conductor of the line 400a to battery upon the lead I I1, and, in operating, this cutoif relay disconnects, at the contacts 4I2, the line relay R4I5 from the line conductors of the line 400k and I54,- the connections to the'operators headset IOI. The relay RI50, upon operating, also completes, at the contacts I52, a circuit .102 illuminating the supervisory lamp I51 which indicates to the operator that the call has not yet been answered. The automatic ringing oi the substation MA is initiated by the operation oi'the ring relay RIII, this relay being operated over a circuit including the contacts III and I42 when the relay RI50 operates. In operating, the ring relay RI" completes, at the contacts I00 and III, a path for projecting ringing current over the lines 400! and L400 In the substation MA.- This circuit may be traced from battery upon the lead II1, through the ringins generator I15 and the ring cutofl' relay RI45 in series, through contacts I05 to the tip of the plug I55; and from ground upon the lead III through the resistor I15 and contacts I05 to the ring oi the plug I55. The tip and ring of the plug I55 are connected by way of the tip and ring of the lack I50 and the tip and ring conductors, respectively, oi the lines 400! and L400 to the ringer at the substation MA. The ringers respond to this ringing current, thereby notifying the subscriber at substation MA that a call is to be answered.

To answer the call at the substation MA, the telephone is lifted from its hook to complete a loop circuit over the tip and ring conductors of the lines L400 and 400i. These tip and ring conductors of the line 400! terminate upon the tip and ring of the jack I50 which has been connected to the tip and ring of the plug I55, and the ring cutofl' relay RI45, being connected in series relation with the'loop and with the ground connected resistor I16 and being connected to battery through the generator I15, is then operated over this loop.

The ring cutofl relay RI 45, in responding to the completion of the loop circuit at the substation MA, operates to complete, at the contacts I45, an obvious circuit for energizing the relay RI40. The relay RI40 operates and completes, at the contacts I, a locking circuit for itself, this circuit including the grounded contacts I5I which have been closed by the previous operation of the relay RI50. At the contacts I42, the relay RI40, upon operating, interrupts the circuit for. energizing the ring relay RI35. The ring relay RI35 then restores to open, at the contacts I38 and I30, the circuit for projecting ringing current over the lines 400! and L400 extending to the substation MA. Also, the ring relay RI35, in restoring, completes, at the contacts I01 and I39, connections between the tip and ring conductors of the calling end of the cord circuit with the tip and ring conductors oi the called end of the cord. Further, when the call at substation MA is answered to complete'the loop circuit at that station, the supervisory relay RI30 is operated, over substantially the same loop circuit as that described above, and interrupts, at contacts I3I, the circuit for illuminating the supervisory lamp I51. The operator at the switchboard is thereby advised that the called party at the substation MA has answered the call.

with the switchboard apparatus in this condition, the call from substation M is extended by way of lines LI00, I00a, b, answering jack IN, the cord circuit 30, the multiple jack I50, and the lines 400! and L400 to the called station aaepnao V 5 MA. It is noted that the sleeve relays RI20 and RI50, the supervisory relays RI! and RI30 and the relay RI40 remain operated while the connection remains established between the calling and called substations and untilthe connection is released. When the called party at the sub station MA hangs up, the loop circuit extending over the lines L400 and 400 is interrupted, thereby causing the supervisory relay RI30 to restore. Upon restoration of the supervisory relay RI30, the circuit for illuminating the supervisory lamp I51 is completed at the contacts I3I. The operator is thus advised that the called party has disconnected and the operator may withdraw the plug I55 from the jack I58. When the calling party at substation M disconnects, the circuit extending over the lines LI00, [a and 1001) is interrupted to cause restoration of the supervisory relay RI25 which completes, at the contacts I26, a circuit for illuminating the supervisory lamp I04. The operator is thereby advised that the calling party at the substation M- has disconnected and the plug I02 may be withsleeve relay RI50, over the above-traced circuit to disconnect, at its contacts 33I and 332, the

line relay R395 from the subscriber's line L300.

The sleeve relay RI50, in operating, completes,

5 at its contacts I5I, a circuit including the condrawn from the jack IOI. When the plugs I02 and I55 are Withdrawn from their respective jacks, the ground potential applied to thesleeve conductors through their respective sleeve relays is removed, thereby causing the busy markings to the associated jacks in the manual switchboards to be removed and also the busy 'markings to the associated contacts in the connector banks in the automatic system. Upon removal of the plug I55 and the restoration of the sleevefirelay RI50, the contacts I5I are opened to interrupt the circuit for the relay RI40. Also, when the plug I02 is removed from the jack IOI, the circuit for energizing the cutoif relay RI I0 in series with the sleeve relay RI20 is interrupted to cause these relays to restore. Likewise, when the plug I55 is removed from the jack I58, the relays R4I0 and RI50 are restored to normal. The equipment of the manual system has now been restored to normal andmay be used to extend other calls.

Call extended from manual substation M to automatic substation P In explaining the connection from the manual substation M to the automatic substation P, it is assumed that the cord circuit has been used to answer an incoming call from the substation M over the lines LI00, I00a and M01), and that the plug I02 has been inserted into the jack IOI. It is also assumed that the supervisory relay RI25, the sleeve relay RI20, and the cutoff relay RI I 0 have been operated, as heretofore described. To extend this call to the substation P, the plug I55 is inserted into thejack I which terminates the line 300a extending to the F terminals of the intermediate distributing frame IDF-Z. When the plug I is inserted in the jack I59, the sleeve elements thereof are grounded through the sleeve relay RI50, and this ground extends over the sleeve conductor of the line 300a to a G terminal of the intermediate distributing frame IDF2 where the circuit divides, one branch xtending to the control conductor 302 in the connector switch bank, and the other branch extending through the contacts 391 of the line relay R395 to the winding of the cutoff relay R390, and then to battery LV. Ground potential thus placed upon the control contact of; the connector bank by the conductor 382 marks the line 30012 as busy to the connector 300. The cutoff relay R390 then operates, in series with the tacts I42 for operating the ring relay RI35 and thereby closes the contacts I36 and-I33 to cause ringing current to be projected over the line 300a. This circuit for projecting ringing current over the line 300a may be traced from battery upon the lead I I1 by way of the ringing generator I15, the winding of the ring cutoff relay RI45, the contacts I36 connected to the tip elements oi the plug I55, and the jack I59 and from ground upon the lead II8 by way of the resistor I16, the contacts I38 connected to the ring elements or the plug I55, and jack I59. The ringing current is thus conducted over the tip and ring conductors of the line 300a to the G terminals of the,IDF2, which terminals are cross-connected to the F terminals of the IDF--2. Since the line L300 extends from the F terminals of the IDF2 to the automatic substation P, the ringing current is thus transmitted to the substation P. The subscriber at the automatic substation P, in answering the call, lifts the telephone from the switchhook to complete a loopcircuit which includes .the tip and ring conductors of the lines L300,

300a, the tip and ring elements or the Jack I53 and the plug I 55, the contacts I36, the ring outoff relay RI45, the generator I15, and battery, and the contacts I38 and the resistor I13 to ground. 1 e;

Asa result of completing the loop circuit at the substation P, the ring cutoff relay RI45 is operated to complete, at its contacts I45, an obvious circuit for the relay RI40. The relay Rl40'operates and completes, at its contacts I, a holding circuit for itself, this circuit including the ground connected contacts I5I which have been closed by the operation of the relay RI 50. Also, in operating, the relay R interrupts, at its contacts I42, the circuit for energizing the ring relay RI35, thus causing this relay to restore and interrupt, at its contacts I 36 and I38, the circuit for projecting ringing current to the substation P. When the relay RI35 restores, a circuit is completed, at the contacts I31 and I39, between the answering plug I02 and the call plug I55. The connection is now complete between the calling manual subscriber substation M and the automatic subscriber substation P through the associated lines embodied in the connection, and-these linesare appropriately marked as busy by ground potential which has been applied to the sleeve conductors of each of the lines associated with the calling and called substations.

The release of the calling line is effected as described hereinbefore. The release of the called substation P is initiated when the subscriber at that station hangs up to interrupt the loop circuit which extends over the lines L300 and 300a to the cord circuit 30 and, more particularly, to the windings of the supervisory relay RI30. The supervisory relay RI30 is restored when the loop circuit is interrupted and completes, at the contacts I3I, a circuit including the contacts I52, to

illuminate the supervisory lamp I51; Upon ob-.

serving the lighted condition of the supervisory lamp I51, the operator withdraws the plug I55 from the jack I59 to remove the ground potential from the sleeve conductors of the lines 300a and 300d. Removal of ground from the sleeve conductors of these lines removes the busy marking to the equipment having access to these lines.

I Also, upon removal of-the plug I00. the sleeve Call from manual substation MA to manual substation M e In making a connection from the manual sub station MA to the manual substation M by way of the manual switchboard shown in Fig. 4, the

subscriber at the substation MA lifts his telephone to complete a loop circuit which includes the line relay R4I5. This circuit may be traced from ground, at the contacts H I, by way of the tip conductors oi the lines 400e, 400a and L400, through the closed loop at the substation MA, the ring conductor of the lines L400, 400a and 400e, the contacts H2 01 the cutoil' relay R4I0, and the winding of the line relay R4I0 to battery. The line relay R4I operates and closes, at its contacts '4 I 0, an obvious circuit for illuminating the answer lamp 400 which lamp notifies the operator that relay R400 and through contacts 440 and 410 to the tip oi the plug 400, the placing of the tip in contactwith a jack sleeve which is marked as busy with ground potential produces a busy click in the receiver of the operator's headphone, due to the potential dii'ierencebetween the grounded jack sleeve and the plug tip. Idle lines have negative battery potential on the lack sleeve, and

when tested by applying the plug tip thereto no difference in potential is encountered so no click is produced, which indicates that the associated line is idle.

When the operator moves .the switch 400 to a closed position, the headset 40I is connected across the tip andgring conductors of the cord circuit 40 and a communication connection is thereby completed between the calling substation MA and the operator's headset I, which connection includes the lines L400, 400a, 400b,

a call is to be answered upon the line L400. To V answer this call, 'a plug such as the plug 402 is inserted into the lack 40I, It is noted that the plugs of the cord circuit 40-are of the type which have but two elements, including a tip element which is arranged to make contact with the tip spring of the iack 40l and a combination ring and sleeve element which makes contact with both the ring. spring and the sleeve of the jack 40I. When the plug 402 is inserted into the Jack 40I, the cutoi! relay R4I0 is. operated'in series I with the sleeve relay R420 of the cord circuit 40 over a circuit which may be traced from ground upon the lead IIO, through the winding oi the sleeve relay R420, the ring-sleeve element of the plug 402 the sleeve of the jack 40I, and through the winding of the cutoi! relay R'4I0 to battery upon the lead I". Upon operating, the cutoii relay R4I0 opens, at its contacts 4 and H2, the

circuit or the line relay R4I0. The supervisory relay R420 also operates in series with the sleeve relay R420 over a circuit from ground upon the lead I I 0, throughthe sleeve relay R420, the ringsleeve element of the plug 402, the ring spring of the jack 40I, the ring conductors of the lines 400?), 400a and L400, through the loop at substation MA, the tip conductors oi. the lines L400, 400a and 40011, the tips of the jack '40I and the plug 402, and

' through the supervisory relay R420 to battery on the lead, I IT. The supervisory relay R420, in operating, opens, at its contacts 420, the circuit to the supervisory lamp 404. Ground potential, as supplied to the sleeve conductor through the sleeve relay R420, is effective to markthe multiple jacks 400 of the line 400a as busy. Also, the jack I00 is marked as busy by the ground potential which is applied to its sleeve by way ot the sleeve conductors of the lines 400b, 4004: and 400i. The con-'- trol contact in the connector bank or the connector 000, which is associated with the lines L400, 400a and 400d, .is also marked as busy by the ground potential which is applied from the sleeve "relay R420 through the sleeve conductors of these lines.

The usual busy test upon linesin manual telephone systems is made by bringing the tip of a cord circuit into contact with the sleeve of the jack which is associated with the line to be tested. With battery potential on the tip 01' the. cord circuit, as, for example, in the cord circuit 40, shown in Fig. 4, which has battery potential applied through the winding of the supervisory the jack 40I, the plug 402, the'capacitors 44'! and 440, and talking conductors of the cord 40 and the switch 460. The operator may then obtain the number of the desired line to be called and extend the call by inserting the call plug 400 into theiack 400, which lack terminates the line I00a extending to the cordless B board 440. The operator at the cordlessB board 440 then extends the call over the lines I00! and LI00 to the substation M in the usual manner.

Upon inserting the plug 400 into the lack 400. the sleeve relay R440 is operated in series with a relay in the cordless B board 440 which is similar to the usual .cutoil' relay in a line circuit.

4006. More particularly, the supervisory relay R400 operates by a circuit which extends from ground at the lead IIO to the sleeve relay R440 and then through the contacts 440 and4l4, the ring-sleeve element of the plug 400, the ring spring of the jack 400, a loop in the cordless B board, the tip conductor of the cord circuit, the tips or the jack 400 and the plug 400, the contacts 410 and 440, and the supervisory relay R400 to battery on the lead III. In operating, the supervisory relay R400 opens, at its contacts 400, the circuit for lighting the supervisory lamp 401, causing this lamp to'be extinguished and thereby giving an indication to the operator attending the cord circuit 40 that the operator at the cordless B board has answered the call. Alter ascertaining the number 'of the called line from the manual operator, the operator at the cordless B board 440 tests the busy condition of the called line and it it is found to be idle completes the connection in a well known manner. In completing the call to the substation M over the line mu, ground potential is applied to the sleeve conductor of this line by the equipment at the cordless B board 440. The sleeve conductor of the line I00! is connected, at the A terminals of the main distributing frame MDF, to the sleeve conductors of the lines I00a and I00e. The sleeve conductors of the lines I00a and I00a are effective to extend the busy ground marking to the jacks I M and I 00, and also to the control Contact in the connector banks of the connector 900 by way of the line'l00d associated with called line L100.

Theanswering of the call at the substation M causes apparatus in the cordless B board 440 to respond, whereby the operator at this board is notified that the call has been answered. When the plug 455 was inserted in the jack 459, the sleeve of the jack 458 was grounded from the ground which was applied through the winding of the sleeve relay R440 and the contacts 449 and 414 to the ring-sleeve element of the plug 455. The grounding of the sleeve of the jack 459 marks the line 1009 as busy to any operators who may test this line at any multiple connected jacks at the switchboard.

When the subscriber at the manual substation MA hangs up the receiver, the loop circuit extending over the line L400 is opened and this causes the supervisory relay R425 to restore and close, at its contacts 426, a circuit, including'the contacts 42L for illuminating the supervisory lamp 404. The operator, upon observing the lighted condition of the supervisory lamp 404,

the

is advised that the calling party at substation- MA has hung up and that the plug 402 may be withdrawn from the jack.40l. In withdrawing the plug 402, the circuit for energizing in series the sleeve relay R420 and the cutoff relay R4l0 is interrupted, causing these two relays to restore. In restoring, the sleeve relay R420 opens, at its contacts 42l, the circuit for illuminating the supervisory lamp 404. The cutoff relay R4l0, in restoring, prepares, at its contacts 4 and 412, the circuit for energizing the line relay R415, Also, when the plug 402 is'removed from the jack 401, ground potential is removed from the sleeve conductors of the lines 400b, 400a, 4001, and the connecting lines 400e and 400d. The absence of ground from the sleeve conductors of these lines removes the busy marking which was previously applied to these lines and battery potential now extends from the lead H1 through the winding oi! the cutofl relay R4I0 to the sleeve conductors of the above-mentioned lines, whereby these lines are now marked as idle.

When the called party at the substation M restores the telephone, the operator at the cordless B board 440 is advised by the usual supervisory signal that the connection may be taken down and, in turn, extends the supervision over the line 100g to the operator attending the cord circuit 40. The loop circuit, including the tip and ring conductors extending to the Jack '450, is thereupon interrupted and that causes the supervisory relay R430 to restore. In restoring, the relay R490 completes, at its contacts 495, a circuit including the contacts 44! for illuminating the supervisory lamp 451. The operator attending the cord circuit 40 is thus advised to remove the plug 455 from thejack 459, and, when that is done, it removes-the ground potential from the and the cutofl relay R4I0 have been operated. It will also be assumed that the operator at the cord circuit has received the number of the desired line in the automatic telephone system. To extend this call, the plug 455 is inserted into the jack 459 and ground potential at the lead I" is thereby appliedto the sleeve conductor of the line 59l extending to the trunk circuit 590, shown diagrammatically in Fig. 5. This ground potential upon the sleeve conductor marks the Jacks associated with the line 591, including the Jack 959, as busy. This ground potential is applied through the sleeve relay R440 to the contacts 449 01' the ring key 442 and the contacts 419 of the switch 410, to the sleeve-ring element of the plug 455 and to the sleeve of theiack 459. .When the ring-sleeve element of the plug 455 engages the sleeve of the Jack 459, the sleeve relay R440 is operated. This circuit may be traced from ground upon the'lead I I! through the sleeve relay R440, the contacts 445 and 419, the sleeve of the plug 455 and the sleeve of the jack 459 to battery potential, which is not shown, in the trunk circuit 590. Upon operating, the sleeve relay R440 completes, at its contacts 44!, a circuit including the grounded contacts 499 for illuminating the supervisory lamp 451.

The trunk circuit 590 and the selector 595 are of conventional type and tunction to extend the call to the line 599 and to maintain a busy ground potential on the sleeve of the jack 459. More particularly, the selector 595 responds to impulses which are sent from the dial 449 in the cord circult 40, this dial 449 being connected by way of the contacts "I and 412 of the switch 410, to the tip and ring conductors which are connected to the plug 455. This connection extends through the jack 459 to the selector-595 by way of the line sleeve of the jack 459 and so removes the busy marking from the sleeve conductor of the line i00g. Also, upon removal of the plug 455 from the jack 459, the sleeve relay R440 is restored and opens, atits contacts I, the circuit for illuminating the supervisory lamp 451.

Call from manual, substation MA to automatic substation P In completing a call from the manual substation MA, it will be assumed that the cord circuit 40 has been used to answer the call on the lines 591, the trunk circuit 590, and the line 592. The selector 595 responds to the'impulses sent by the dial-445 to position its wipersupon the contacts terminating the line 599. More particularly, the impulses produced by the dial 449 are conducted -by way oi the contacts "I and 412 of the switch 410, the tip and ring contacts of the plug 455, the jack 459, the lines 591 and 592, and the trunk circuit 590, to the selector 595. The selector 595 responds to the impulses of the first digit transmitted to elevate the wipers thereof to a position adjacent the row or level of contacts terminating the line 599 which extends to the connector 900. The selector 595 selects automatically an idle line which extends to one of the connectors, and, assuming that the connector 900 is the first idle connector terminated in the row of contacts selected, the line 599, comprising the conductors 214, 215 and 219, is selected to extend the connec tion to the connector 900.

The connector 900 is preferably of the wellknown Strowger type, and operates, in the usual way, to raise the wipers 911", 912 and 919 in response to the second digit dialed, to a position adjacent the level in the connector bank corresponding to the digit dialed. In response to the third digit dialed upon the calling device 440, the wipers 911, 912 and 919 are rotated into engagement with the contacts in the connector bank terminating the line which extends to the called party, and in the present example the wipers 911, 912 and 919 are rotated into engagement with the contacts terminating the conductors 990, "I and 992 of the line 900d. If it be assumed that the tor 323, for transmitting busy toneover the established connection which extends to the calling substation after the operator has restored the switch 410, in a well-known manner. The original circuit for operating the busy relay R333 passed through the contacts 352 of the slow-torelease relay R350, which relay restores after a short interval to close, at the contacts 353, a holding circuit for the busy relay R330. This circuit extends from ground upon the contacts 322, by way of the contacts 332, 353 and 333, through the busy relay R330 to LV battery upon the conductor !!1. It will be noted that the busy relay R333 is connected to the LV battery source which corresponds to the battery voltage which is applied to the windings of the cutofi relays in the line circuits associated with the lines extending to the connector bank. With the busy relay R330 connected to the same battery potential as the cutoir relay windings, there is no possibility of any false operation of the busy relay R330 or the cutoff relays of idle lines which terminate in the level associated with the line 300d, when the control wiper 313 comes into contact with the terminal connected in circuit with the windings of their cutoff relays when the wipers are being rotated to the contacts of a called line.

Upon hearing the busy tone, the subscriber at the manual substation MA replaces the telephone upon the hook to open the loop circuit extending to the cord circuit 40. Thereupon, the supervisory relay R425 restores to complete, at the contacts 426, a circuit including the contacts 42! for illuminating the supervisory lamp 404 which indicates to the operator at that position that the calling subscriber has disconnected and that the plug 402 may be withdrawn from the jack 40!. The operator also removes the plug 455 from the jack 453, thereby opening the loop circuit which extends through the trunk circuit 530 and the selector 435 to the connector 300, causing the trunk circuit 530, the selector 535 and the connector 300 to be restored.

If it be assumed that the called line L303 is idle when called, LV battery will be connected through the cutofl relay R330 to the control terminal in the connector bank by way ofthe contacts 331 and through control conductor 332. The LV battery potential upon the control terminal of the line 300d short-circuits the'winding of thebusy relay which has one terminal connected to the same source of LV battery potential. After the slow-to-release relay-R350 restores, the switching relay R360 is operated over a circuit extending from ground at contarts 322 by way of the contacts 33!, the upper winding of relay R360, the contacts 35!, and

the wiper 313, the control terminal and conductor 332, contacts 331 and through the winding of the cutofi relay R330 to LV battery. The cutoff relay R330 is thus operated to open, at its contacts 33! and'332, .the circuit of the line relay R335. In operating, the switching relay R330 completes, at its contacts 35! and 352, acircuit for conducting ringing potential to the called line L300 and for preparing the talking circuit to the called substation P. At the contacts 365, the switching relay R330 connects ground potential to the control conductor 332 to mark the line 333d as busy to any other connectors attempting to call this line. The re- -lease relay R3|0 is operated by the line relay,

which is not shown, and completes at the contacts 32! a holding ground'which extends back over the control conductor 213 to maintain the connector marked as busy to the link 203 and to the selectors in the group which'includes the selector 533.

The release and restoration of the manual lease relay R3l0, upon restoring, removes the holding ground potential at the contacts 32! from conductor 216, thus causing the selector 535 to restore its wipers to normal in a well known manner and rendering thetrunk circuit 530 available for other calls.

Connection from the automatic substation P to the manual substation M When a call is-initiated at the automatic substation P, a loop circuit is completed over the line L303 which causes operation of the line relay R335. This circuit extends from ground by way of the contacts 33!, the conductor 333, the closed loop at the substation P, conductor 33!, contacts 332 and the winding 01' the line relay R335 to HV battery. The line relay R335 operates to close, at its contacts 333, a circuit for applying ground potential to the sleeve conductors of the line 300a extending to jacks at the operators positions in the switchboard of Fig. 1, including the jack I53, for marking the line 330a and the associated line L300 as busy to incoming calls from the manual switchboard. The control conductor 332 is also grounded by the closure or the contacts 333, which marks the lines L300 and 303d as, busy inthe banks of the connectors. The operation of the line relay R335 also closes the contacts 333 to apply LV battery potential by way of the winding of the cutoil relay R333 to the control conductor of the line 3031 which extends to the banks of the finder 2!0. Also, the operation of the line relay R335 closes the contacts 333 to apply ground potential to the start conductor 30! which extends through its associated resistor 302 to the distributor 210 to cause the distributor to choose an idle link for the use of the calling line L330. The ground upon the start conductor 30! also marks the level in the vertical bank 253 in which the calling line is located. Assuming that the link 200 is the first idle link encountered by the distributor 210, the finder 2l0 is first caused to search for the level in which the calling line is located. The vertical wiper 255 is raised step by step into engagement successively with the contacts of the vertical bank 253, until ground potential is encountered upon one of the contacts of the bank 253. In the present example, ground potential will be encountered upon the second contact which terminates the grounded conductor 33!. The distributor then controls the finder 2!0 to search in the selected level for the contacts terminating the calling line, this line being marked with LV battery. When the'wipers of the finder 2l0 reach the contacts corresponding to the calling line, the control wiperC will encounter LV battery potential upon the contact terminating the C conductor 326 of the line 3001i, which causes the finder to select the calling line and extend the connection to the selector 220 of the link 200. The finder 2I0, which is preferably of the well-known Strowger type, in extending the connection to the selector 220, causes the switching relay R230 to be operated and close the contacts 23!, 232, 233 and .234.

The talking connection now extends through the T and R'wipers of the finder 2 I and through the contacts 23! and 232 of the switching relay R230 to the selector 220. At the contacts 233, ground potential is put upon the control wiper C, to operate the cutofi relay R390 and to mark this line as busy to incoming calls. The relay R24!) is also operated to app y, at contacts 24!, ground potential to the control conductor 242, thereby holding the switching relay R230 operated by way of the contacts 234.

The selector 220, which is also preferably of the well-known Strowger type, responds to the first digit dialed at the calling station MA, to position, the wipers 21!, 212 and 213 adjacent the level of contacts corresponding to the number dialed. During the interval between the first and second digits dialed, the selector 220 operates automatically to select an idle line in the selected group of lines extending to the group of connectors in which the connector 300 is included. Assuming that the connector 300 is selected, the connection is extended thereto by way of the selector wipers 21!, 212 and 213 and the conductors 214, 215 and 216 of the line 533 and the connector 300 is prepared for the second and the final digits. When the selector 220 is seized, the release relay R250 is operated to complete, at the contacts 25!, a circuit for extending multiple ground potential over the control conductor 242 to maintain the switching relay R230 operated, and, at contacts 252, the control conductors 242 and 213 are connected together. Upon receiving the second digit, the connector 300 responds to select the level or group of lines in which the called line is located. The final digit causes the wipers 31!, 312 and 313 to select the contacts in the connector bank which terminate the desired line, which, in the present example, is the line I000! and. the connected line L|00. The functions of the connector 300 with respect to encountering a busy condition upon the line !00d, and with respect to switching through to the line L! 00 if the line is idle, need not be described as they are the same as those described in connection with making a call from the substation MA and through the cord 40 to the substation P. The train of switches including the finder 2! 0, the selector 220, and the connector 300, is held operated by the ground which is applied to the control conductors 216, 325 and 242 at the contacts 32! and 322 upon the operation of relay R3l0 in the connector 300.

When the connector 300 has selected the line l00d by moving the wipers 31!, 312 and 313 into contact with the terminals which terminate the conductors 311, 318 and 319 of the connecting lin l00d, a busy test is made to determine if the associated line L|00 is in a busy condition. If the line L|00 is busy, ground potential will be found upon the conductor 319 of the line l00d. This ground potential will be applied to conductor 319 through the winding of the sleeve relay Rl20, the associated plug I02 and the jack !0! if the line L|00 is the calling line; or through the winding of the sleeve relay RI50, the associated plug I55 and the Jack I56 if the line L|00 is the called line in a manual connection; or by way of the cordless B board if the operator thereat extended a call to the line L|00; or through the associated contacts 365 and the wiper 313 of another connector 300 if the line L|00 is called by another automatic subscriber. The busy relay R330 is operated from ground on the conductor 319 over the control wiper 313 and connects, at the contacts 324, busy tone to the talk conductor which extends through the selector 220and the finder M0 to the calling line L300 and thesubstation P. Assuming, however,

that the connecting line l00d is idle when called, the control wiper 313 encounters LV battery upon the control conductor319, which battery shunts the winding of the busy relay R330 which therefore does not operate. When the switching relay R360 operates shortly after the busy test to close the contacts 36! and 362 and connect the line conductors 311 and 318 to the ringing leads through the contacts 34! and 343, this switching relay also applies, at the contacts 365, ground potential to the control conductor 319. The ground upon the control conductor 319 marks the line L|00 as busy to the connectors having access to the line !00d.' Also, the ground upon the conductor 319 is cross-connected at the intermediate distributing frame IDF-Z to the sleeve conductor of the line I00e which conductor terminates upon an A terminal of the main distributing frame MDF. The sleeve conductors of the lines 00a and l00f are also connected to the sleeve terminals of the main distributing frame MIDF and the ground upon the sleeve of the jack I56 thus marks the line !00a as busy to the operators at the switchboard shown in Fig. l, and the line l00f is marked as busy by the ground placed upon the sleeve conductor which cooperates with the cordless B board 440 to mark this line busy to the operators at this board. When the switching relay R360 operates and connects the line conductors 311 and 8'18 to the ringing leads by way of the contacts 34! and 343, ringing current is transmitted to signal the subscriber at substation M from battery, the interrupted ringing generator GEN, the upper winding of the ring cutoff relay R340, the contacts 34! and 36!, the wiper 31!, the tip conductor 31! of the line l00d, the line I 00s, the line L|00, the ringer at the substation M, and returning by way of the ring conductor of the line L|00, the line I00e,

the line l00d, the ring conductor 318, the wiper 312, and the contacts 362 and 363, to ground. When the subscriber at substation M answers the call, a direct current loop circuit is completed and causes the ring cutoff relay R340 to operate and open its contacts 34! and 343 to terminate the ringing signal. The relay R340 also completes a locking circuit for its lower winding (not shown) and, at its contacts 342 and 344, it

completes a'talking circuit from the calling sub- Method of converting a manual subscribers line to automatic operation The operations thus far described are those which are based on the assumption that the manual systems illustrated in Figs. 1 and 4 are still entirely manual in operation and that they have been connected with the automatic system shown in Figs. 2, 3 and which may have replaced an old manual system or be merely an addition to the manual system disclosed, appropriate changes in polarity in the manual system and changes in voltage in the automatic system having been made, according to the present invention, to permit the two types of systems to be interconnected and to allow the extension of calls from one portion of the composite system to another.

Consideration will now be given to the operation of the composite system disclosed when a manual portion of the system is gradually converted to automaticoperation. It will be assumed that the manual system shown in Fig. 4 is to be thus converted to automatic operation while maintaining its operative connections with the manual system of Fig. 1 and the automatic system of Figs. 2, 3 and 5.

In converting a manual line such as the line L400 to full automatic operation, the manual sub station instrument 'at the substation MA is replaced with an automatic type instrument which includes an impulse transmitting dial. At the manual switchboard, the answering jack 40l, the line 400b, the manual line circuit 405, and the line 4000 are disassociated from the line L400, by disconnecting the line 40011 from the E terminals of the intermediate distributing frame IDF-l, and by disconnecting the line 4000 from the D terminals of that intermediate distributing frame. In the automatic switchboard the line circuit 50! is associated with the line L000 by connecting the previously installed line 400h which extends from the line circuit 50! to the F terminals of the intermediate distributing frame IDF-Z, and by connecting to the F terminals of the intermediate distributing frame IDF2 the previously installed line 0007' which then extends from the terminals of the IDF-Z to the bank terminals of the line finder 2 I 0.

The above changes are of minor nature and involve no alterations or-additions of equipment and are quickly and easily made without interruption of telephone service longer than the time required to replace the manual telephone instrument with the automatic instrument at the substation MA and the brief interval required to remove the lines 4001: and 0000 and to connect the lines 4001 and 40070.

Completing connection from the converted substation MA to the automatic substation P In initiating a call at the converted substation MA, just referred to, the telephone is removed from the hook switch, which completes a loop circuit extending over the lines L400, 400a and 400k to cause operation of the line relay R520. This circuit may be traced from ground, upon the contacts 5| I, by way of the, tip conductor of the line 400h, over the tip conductor of the lines 400e and L400, through the completed loop at the substation MA, over the ring conductors of the lines L400, 400e and 400h, through contacts in and the winding of the line relay R520 to H'v" battery. In operating, the line relay R520 completes, at its contacts 52L a circuit for applying ground potential to the sleeve or control MDF.

conductors of the lines 400h, 400e, 400i. and 400a, the sleeve or control conductors of these lines being connected together at the distributing frames as shown. The ground upon the sleeve of the line 400! marks the line L400 as busy to operators in the switchboard of Fig. 1 having access thereto by way of the jack H0, and ground upon the sleeve of the line 400a marks the line L400 busy to the operators in the switchboard shown in Fig. 4, having access thereto by way of the jack 456.

When the sleeve or control conductor of the line 400h is grounded, the sleeve conductor of the line 400d is also grounded through the crossconnections at the intermediate distributing frame IDF-2, extending between the F and G terminals. The grounding of the sleeve or control conductor 316 of the line 400d marks the connecting line 400:; as busy to the connector switches in the automatic system. The lines 400d and 400a are cross-connected between the F and G terminals of the intermediate distributing frame IDF-2-, which connection eifectlvely marks the line L400 as busy to the connectors as stated above. Upon the operation of the line relay R520, the contacts 522 are opened, thereby removing LV battery potential through the relay R5l0 from the sleeve conductors of the lines 400h, 000e, 400a, 400 and 40011; this battery, prior to its removal at the contacts 522, marked the above'lines as idle to their respective points of access, as described. At the same time, the contacts 523 are closed to apply LV battery potential through the cutoff relay R510 to the control conductor 426 of the line 4001, which extends to the finder bank contacts of the finder 2l0 corresponding to the calling line L400. It will be noted that the talking conductors of the lines 0001' and 000e are connected together at the F terminals of the intermediate distributing frame IDF--2 and that the talking conductors of the lines 800e and L400 are connected together at the A terminals of the main distributing frame The application of LV battery potential to the conductor 426 of the line 400 marks the line L400 as the calling line in the finder banks, whereby the finder is caused to select the line 4007' which is associated with the line L400.

The contacts 524, upon closing, in response to the operation of the line relay R520, complete a circuit over the conductor 403 for starting the distributor 210, which selects an idle link for the use of the calling line. The operation of the distributor 210 and the finder M0 to select the calling line 4001 appearing in the finder bank is well known and briefly described in explaining the extension of a call irom the substation P to the converted substation M, so that it need not be described in detail. Also, the progress of the call through the finder M0, the selector 220 and 'the connector 300 to select the connecting line 300d which is associated with the line L300 will not be described in view of the previous description given of a call through these switches.

In making calls through the automatic system and, more specifically, when the wipers of the connectors are rotated over the contacts of a level in search for the contacts of the called line, the wipers may pass over a number of contacts which are associated with idle lines. The control wiper of the connector, in passing over the control contacts of idle lines, applies LV battery poassociated with the lines.

tential to these contacts as these contacts are passed over by way of LV battery which is fed from the conductor II'I through the busy relay R330 and by way of the contacts 363 and 352 to the control wiper 313 and to the control contacts being contacted. As stated above, the control conductors are connected through the various distributing frames and lines to the cutofi relays With the busy relay R330 connected to LV battery, it will be seen that there will be no potential diiference between the battery connected to the busy relay R330 and the battery-connected cutoif relays in the line circuits. Therefore, as the connector control wiper successively makes contact with the control contacts of lines in passing over, the busy relay R330 and the cutoff relays of the lines will not be falsely operated.

However, if the busy relay R330 were connected to HV battery potential while a cutoff relay, for example, such as the manual cutofi relay RI I 0, is connected to LV battery potential, then, upon movement of the control wiper 313 into contact with the bank contact which terminates the conductor 319 (assuming these contacts are on the same.level and precede the contacts 382), there would be a potential diilerence between the LV battery upon the cutoff relay RI l and the HV battery upon the busy relay R330. This circuit extends from the LV battery potential upon the relay RIIO, from the conductor I I1, by way of the winding of the 'relay RI I0, the sleeve conductors of the lines I000, I00c, I00e and I00d, the conductor 319, wiper 313, contacts 352, 363 and the winding of the busy relay R330 to HV battery potential. From the foregoing, it will be seen that with both the relays R330 and the cutoff relays of the line circuit connected to the same battery potential, these relays are prevented from false operation when the control wiper 313 encounters the control conductors of line circuits.

The release of the connection between the converted substation MA and the automatic substation P need not be described in detail since it is effected in the manner usual to the release of connections of lines in an automatic telephone system. With respect to the release of the switch train, however, it is noted that the control conductors 216 and 325 are disconnected at the contacts 32! and 322 when the release relay R3I0 is restored and, likewise, that the control conductors 242 and 216 are disconnected at the contacts 25I and 252 when the release relay R250 is restored. This arrangement whereby the control conductors 216 and 325 are disconnected acts, upon release of the connector 300, to prevent ground potential from being conducted over these control conductors in series to the control wiper 313 during its return to normal position. Ground potential upon the conductor 325 during the period of release of the connector might cause improper operation of certain apparatus, such as the. switching relay R360 and the cutoff relays in line circuits which may be momentarily connected upon restoration of the connector 300.

From the foregoing description of how a manual line is converted to a line of the automatic typ as applied to the line L400, it will be seen that the line LI 00 may also beconverted to automatic operation by replacing the substation instrument at the substation M with a substation of the automatic type, by disconnecting the lines I00c and I00b from the intermediate distributing frame IDF-I and by connectingthe lines I001, I007 to the F terminals of the intermediate distributlng frame IDF-2 in a manner similar to that by which the line L400 and its associated lines are connected when the line L400 is converted to automatic operation.

Connection from the automatic substation P to the converted substation MA In completing a connection from the substation P to the substation MA, after theisubstation MA has been converted to automatic operation, the operation of the switching apparatus is similar to that described in connection with a call from the substation P to the substation M. However, in making a call to the substation MA, the manual line circuit 405 (Fig. 4) is disconnected and the line circuit 50I (Fig. 5) is connected to the lines 40011 and 400e in accordance with the conversion plan described above. When the wipers of the connector 300 come into engagement with the contacts terminating the conductors 314, 315 and 316 of the line 400d, and the switching relay R360 operates, ground is applied by way of the contacts 365 and the wiper 313 to the sleeve conductor 316 of the connecting line 400d. Ground potential on the conductor 316 is extended through the cross-connections at the intermediate distributing frame IDF-2 to the sleeve conductors and ground is thereby extended through the contacts 522 and the winding of the cutofi relay R5I0 to LV battery. The cutofi. relay R510 operates to interrupt, at .its contacts 5H and 5I2, the circuit for energizing the line relay R520. The ground potential on the control conductor 316 of the line 400d is extended to the sleeve conductor of the line 400e by way of the intermediate distributing frame IDF.-2 and this sleeve conductor is connected to an A terminal of the main distributing frame MDF which also terminates the sleeve conductors of the lines 400) and 400a. Thus, the line L400 is marked busy at the jack I58 and 456 to the operators at the switchboards shown in Figs. 1 and 4. The method of releasing the above connection is the same as that conventionally practiced in automatic telephone systems, and the apparatus for restoring the switches used in making the connection has not been shown for this reason.

Although one embodiment of the improved telephone system and certain examples of the improved method of conversion from manual to automatic operation have been shown and described by way of illustration, it will be understood that the improved system is capable of other embodiments and that the improved method may be practiced in various ways without departing from the scope of the appended claims.

I claim:

1. In a communication system, a manual telephone system including manual lines terminating in jacks at operator controlled switchboards, said jacks each including a sleeve element whereon the busy condition of the associated line may be marked by the presence of a characteristic potential, cord circuits at said switchboards having plugs for engagement with said jacks, means in said cord circuits including said plugs for applying said characteristic potential to a sleeve element of said jacks, an automatic telephone system including line selecting switches having sets of contacts for terminating lines of both said automatic and said manual systems, said sets of contacts each including a control contact whereon the busy condition of the associated line may be marked by the presence of a characteristic potential which is substantially different from the first-mentioned characteristic potential, means in one of the telephonesystems for altering its busy characteristic potential to render' it substantially the same as the busy characteristic potential of the other system, and means a for interconnecting the two telephone systems.

, tomatic lines and said manual lines, said contact sets each comprising a pair of line contacts and a control contact, means in each of said line selecting switches and including said control contacts for marking said automatic lines as busy by applying a second characteristic potential upon said control contacts, said first characteristic potential being of opposite polarity to said second characteristic potential, .means in one of,

the systems for changing the polarity of the characteristic potential of that system to agree with the polarity of the other system, and means for interconnecting the two systems together,

3. In a communication system, a manual telephone exchange having manual lines terminating in jacks, cord circuits at said exchange having plugs for engagement with said jacks, a group of manual line circuits each associated with one of said manual lines, a first power source connected to said manual exchange, an automatic exchange having line selecting switches terminating automatic lines, a group of automatic line circuits each associated with one of said automatic lines, a second power source connected to said automatic exchange, means for interconnecting said exchanges to permit calls to be completed between said exchanges, sai first power source being normally connected to said manual exchange with its polarity in opposed relation to that in which said second power source is connected to said automatic exchange, and means for altering certain connections of said first power source to said manual exchange to cause the polarity of corresponding lines in the two exchanges to agree.

4. In a communication system, a manual telephone exchange having manual lines terminating in jacks, cord circuits at said exchange having plugs for engagement with said jacks, a group of manual line circuits each associated with one of said manual lines, a first power source connected to said manual exchange, an automatic exchange having line selecting switches terminating automatic lines, a group of automatic line-circuits each associated with one ofsaid automatic lines, a

5. In a communication system, a manual telephone exchange including a plurality of manual lines terminating in Jacks, a group of manual line circuits each associated with one of said manual lines, cord circuits at said exchange provided with plugs for engagement with said jacks, control apparatus in said cord circuits including relays for controlling supervisory devices, a first power source at said exchange connected to said line circuits and to said control apparatus including said relays, an automatic exchange comprising automatic lines and switches for completing connections to said automatic lines, a group of automatic line circuits each associated with one of said automatic lines, a second power source connected to said switches and to said automatic line circuits, the polarity of said second power source being normally connected in opposite relation to that in which said first power source is connected, means for interconnecting the two exchanges comprising connecting lines corresponding to said manual lines and said automatic lines of the two systems to permit the lines in each exchange to call the lines in the other exchange, said connecting lines being associated with said jacks and with said automatic switches and comprising two line conductors and a control conductor, and means in said manual exchange for altering the polarity of the connections of said first power source to said relays and to certain parts of said manual line circuits, thereby causing corresponding connected lines in the two exchanges to have the same polarity.

6. In a communication system, a manual telephone exchange, a plurality of manual lines terminating in jacks, cord circuits at said exchange provided with plugs for engagement with said jacks, said jacks each comprising two line elements and one control element, line and control apparatus in said cord circuits, a manual line circuit associated with each manual line, a first power source connected to said control apparatus in each of said cord circuits and each of said manual line circuits, an automatic telephone exchange comprising a plurality of automatic lines and automatic line selecting switches terminating said automatic lines, said automatic switches each including a set of line terminating contacts each associated with one of said automatic lines, each set of said contacts comprising two line contacts and one control contact for each automatic line, a second source of power different in potential and opposite in polarity from said first power source and connected to apparatus in said line selecting switches, an automatic line circuit associated with each of said automatic lines, means for interconsecond power source connected to said automatic necting said two exchanges comprising connecting lines corresponding tothe manual lines and to the automatic lines in the two systems through which the lines in each exchange have access to the lines in the other exchange, said connecting lines each including two line conductors and a control conductor which are adapted 'to be connected with said jack elements in said manual exchange and said line terminating contacts in the automatic exchange, means in said manual exchange for reversing the polarity of said first power source connected to points in said line and control apparatus in said cord circuits and to said manual-line circuits, and means in said line selecting switches in the automatic exchange for altering the potential applied to apparatus therein and to said automatic line circuit.

7. In a communication system, a manual teleeach terminating upon a set of manual line terminating contacts and a jack, cord circuits at said manual exchange each provided with plugs for engagement with said jacks, each plug including two line elements and one control element, line and control apparatus in each cord circuit, a manual line circuit associated with each manual line, a power source connected to said line and control apparatus in said cord circuit and to each of said manual line circuits, an automatic exchange having a plurality of automatic lines, a

plurality of automatic line selecting switches having contacts upon which said automatic lines terminate, an automatic line circuit associated with each of said automatic lines, a second source of power connected to said automatic switches and to said automatic line circuits, said second source of power being different in potential and opposite in polarity from said first source of power, a plurality of first connecting lines each associated with contacts in said automatic switches and with a corresponding one of said manual line terminating contacts, an automatic jack inthe manual exchange for each automatic line, a plurality of second connecting lines each associated with one of said automatic jacks and with one of said automatic lines, means in said manual exchange for reversely connecting the polarity of said first power source to said line and control apparatus in said cord circuits and to each of said manual line circuits to agree with the polarity of the connections of said second power source, and means in said line selecting switches for altering the potential of said second power source connected to apparatus in said switches and to said.

automatic line circuits to agree with the potential of said first power source.

8. In a communication system, a manual exchange including a plurality of lines terminating in three-element jacks, a two-conductor cord circuit comprising two element plugs together with supervisory equipment and control equipment, said plugs being adapted to eengage with said jacks to answer and extend calls, aimanual line circuit for each of said lines, a first power source connected to said supervisory equipment and control equipment and to said manual line circuits. an automatic exchange including a plurality of automatic lines terminating in contact sets of automatic switches, an automatic line circuit for each of said automatic lines, a second power ,power source connected to power source connected to'said supervisory and control equipment and to said manual line circuits, an automatic exchange comprising automatic switches having contact sets at which a plurality of automatic lines terminate, an automatic line circuit for each of said automatic lines, a second power source connected to said automatic switches and to said automatic line circuits, an automatic three-element jack at said manual exchange for each of said automatic lines, means including three-conductor connecting lines for connecting together said line terminating contacts of said manual lines with corresponding contacts of said automatic switches, other connecting lines for connecting said contacts of said automatic switches with corresponding elements of said automatic jacks in said manual exchange, said first power source being normally connected to said equipment in the manual exchange with its.polarity in opposition to that of said second said automatic switches and said automatic line circuits, and means in said manual exchange for reversing said first power source connections to said equipment in said manual exchange to agree with the polarity of said power source connected to said automatic switches and said automatic line circuits.

10. In a telephone system comprising a manual exchange, an automatic exchange, and connecting lines for interconnecting apparatus in the manual exchange with related apparatus in the automatic exchange, said manual exchange comprising a plurality of manual lines, a manual line circuit for each manual line, an operator switchboard, and a first. power source in said manual exchange for operating said manual line circuits and apparatus in said operator switchboard, said automatic exchange comprising a plurality of automatic lines, an automatic line circuit for each automatic line, and an automatic switchboard, said automatic switchboard including apparatus operable in connection with related apparatus in said manual exchange over said connecting lines, and a second power source for operating apparatus in said automatic switchboard-which is of substantially the same voltage as that of said first power source.

11. In a telephone system'comprising a manual exchange, an automatic exchange, and connect source connected to said automatic switches and I to said automatic line circuits, and means including three-conductor connecting lines for connecting together said two exchanges by connecting .said manual lines with contacts of said automatic switches and by connecting saidautomatic lines to corresponding elements of said jacks in said manual exchange, said first power source being connected to said manual line circuits and to said supervisory and control equipment in said manualexchange with its polarity in agreement with the polarity of said second power source connected to said automatic switches and said automatic line circuits.

9. In a communication system, a ma nual exchange including a plurality of manual lines terminating in line terminating contacts and in three-element Jacks, a three-conductor cord circuit comprising three-element plugs connected with supervisory equipment and control equinment, said plugs being adapted to engage with said jacks to answer and extend calls, a. manual line circuit for each or said manual lines, a. first ing lines for interconnecting apparatus in the manual exchange with related apparatus in the automatic exchange, said manual exchange com-' prising a plurality of manual lines, a manual line circuit for each manual line. an operator switchboard, and a first power source in said manual exchange for operating said manual line circuits and apparatus in said operator switchboard, said automatic exchange comprising a plurality of automatic lines. an automatic line circuit for each automatic line, and an automatic switchboard, said automatic switchboard including cooperating apparatus operable in connection with related apparatus in said manual exchange over said connecting lines, and a second power source for operating apparatus in said automatic switchboard which is of substantially the same voltage as said first power source, additional apparatus in said automatic exchange, a second power sourceof substantially the same voltage as that of said first power source for operating said cooperating apparatus insaid automatic exchange, and an additional power source for operating said additional apparatus.

HARRY P; MAHONEY.

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