US2268397A

US2268397A - Telephone system

Info

Publication number: US2268397A
Application number: US340073A
Authority: US
Inventors: Ralph E Hersey
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1940-06-12
Filing date: 1940-06-12
Publication date: 1941-12-30
Anticipated expiration: 1958-12-30

Description

Dec. 30, 1941. R. E. HERSEY TELEPHONE SYSTEM Filed June 12, 1940 11 Sheets-Sheet l /A/ VEA/TOR R. E. HERSE V A TTORN-V Dec. 30, 1941. R. E. HERsEY TELEPHONE SYSTEM Filed June l2,- 1940 ll Sheets-Sheet 2 A TTOR/VEV 11 Sheets-Sheet 3 R. E. HERSEY TELEPHONE SYSTEM Filed June 12, 1940 J vb@ h IWF. hl TIIH NR 3% @E Dec. 30, 1941.

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TELEPHONE SYSTEM Dec. 30, 1941.

Filed June l2, 1940 1l Sheets-Sheet 4 /NVENTOR Rf. HERSEY WW1/WK ATTORNEY Dec. 30, 1941.

R. E. HERsEY l TELEPHONE SYSTEM Filed June 12,y 1940 11 sheets-,sheet 5 .w MM m5% WHW. EHW.. Rim y, B

Dec. 30, 1941. R. E. HERsEY 2,268,397 -Y TELEPHONE SYSTEM Filed June 12, 1940 1l Sheets-Sheet 6 /NVEA/TOR R E. HERSEY Dec. 3o, 1941.

R. E. HERsEY TELEPHONE SYSTEM Filed June 12, 1940 11 Sheets-Sheet 7 /Nl/E/V TOR R. E. HERSEV WV? WWW ATTORNEY Deso, 1941. REHERSEY l v2,268,397'

TELEPHONE SYSTEM A TIGR/VFY Dec. 30, 1941.

R. E. H ERSEY TELEPHOM: SYSTEM Filed June l2, 1940 1l SheetS-Sheekl 9 y EFLILHI'Q,

NVEA/TOR R. E. HERSEV WW WW Dcc. 30, 1941. R. E. Hl-:RsEY

TELEPHONE SYSTEM Filed June 12, 1940 1l Sheets-Sheet 10 /NVE N TOR 'e E HERSEV R. E. HERSEY TELEPHONE SYSTEM Filed June 12, 1940 1l lSheets-Sheat 11 UWE/v70@ By R. E. HERSEV Patented Dec. 30, 1941 UNITED STATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation 'of New York Application June 12, 1940, Serial No. 340,073

20 Claims.

This invention relates to telephone systems and particularly to those in which automatic switching mechanism is used for establishing connections.

The objects of the invention are to improve the facilities for intercepting calls made to a particular subscribers line during his absence; to direct these calls automatically to a predetermined station, such as an operators position, without requiring any special effort on the part of the calling subscribers; and to make other improvements in systems 'of this character.

In one form of the system whereby the foregoing objects of the invention are realized one of the service operators in the central oiiice, having been called in the usual manner by a subscriber entitled to this special service and notified that he expects to be absent from his telephone, establishes a connection from her position over a special trunk circuit through the automatic switches to the subscribers line. To. establish this connection the operator transmits the impulses representing the subscribers designation, and the designation is registered in a register sender and also in a designation register associated with the special trunk used bythe operator. The register sender cooperates with a switch-controlling marker to operate incoming and nal selector switches, which may be of the cross-bar type, to complete the connection over 30 the special trunk to the subscribers line. In an alternative form of the system the subscriber unassisted by the operator sets up a connection over another special service trunk between the operators position and his own line. In either case the connection thus established is maintained during the subscribers absence, the subscribers number remains registered on the designation register, and a busy condition is impressed upon the subscribers line. Thereafter when the marker attempts to complete a call to a busy line, the designation of the busy called line registered in the marker is compared with the'designation of the absent subscribers line, which is registered in the designation register. Hence when the absent subscriber is called, the compared registrations match; whereupon the marker, being notied thereof, cancels the registration it has received pertaining to the called line and extends the calling line automatically to the particular special trunk used for intercepting the calls to said absent subscribers line. The calling party is now in telephonie connection with the operator, and she takes any message he wishes to leave and communicates it to the absent subscriber upon his return.

A feature of the invention, therefore, is a system in which the number of a subscribers line is registered during his absence and his line made busy; in which the numbers of all lines called thereafter and found busy are compared with the registered number; and in which any calling line is automatically routed to an operator as a result of the match that occurs when the calling subscriber attempts to call said absent subscribers line.

Another feature is a special intercept trunk which the operator uses to set up a conversational connection over the automatic switches to an absent subscribers line, and which also has an appearance'as a called circuit in said switches and is seized automatically to establish a conversational connection between a calling line and the operator whenever the calling subscriber attempts to call said absent subscribers line.

Another feature is a special trunk which the subscriber, who expects to be absent from his telephone, uses to set up a connection over the automatic switches between the operators position and his own line, and which also has an appearance as a called circuit in said switches and is seized automatically to establish a connection between a calling line and the operator Whenever the calling subscriber attempts to call the absent subscribers line.

Another feature of the invention is an arrangementin which ringing current is automatically applied to the absent subscribers line by way of the special trunk connection when a calling line is extended as above explained to the special trunk following the unsuccessful attempt to complete the desired connection to the absent subscribers line.

vA further feature of the invention is an arrangement in which the operator sends a momentary signal over the special trunk circuit to trip the ringing operation and thereby discontinue the application of ringing current to the absent Vsubscribers line. By arranging the system so that ringing current is always applied to the absent subscribers line whenever a call is intercepted the subscriber is given an opportunity 'to answer the call in case he returns to his telephone while the intercepting facilities are still in operation. On the other hand some provision must be made for tripping the ringing operation so that the operator may converse with the calling party in the event the called subscriber has not returned to his telephone. This is accomplished, as above noted by a special signal transmitted from the operators position.

The foregoing and other features of the invention will be described more fully in the following detailed speciication.

In the drawings accompanying this specification:

Figs. 1 and 2 constitute a general diagram of the system in which the invention is incorporated; Figs. 3 to 11, inclusive, disclose the details of the system; and Fig. 12 is a diagram showing the relative locations of Figs. 3 to 11.

Fig. 3 illustrates the service Operators position and shows the outgoing end of one of the special intercept trunks;

Fig. 4 shows the incoming end ofthe intercept trunk circuit;

Fig. 5 illustrates the incoming selector switch in which the intercept trunk terminates and a nal selector switch for extending the trunk through to the subscribers line entitled to the special service. This figure also illustrates the incoming and iinal selector switches for extending a calling line through to the special service trunk.

Fig. 6 shows a register individual to the intercept trunk for registering the telephone number of the absent subscriber. This figure also shows a connector for connecting the intercept trunk and the designation register to a register sender.

Fig. 7 illustrates the register sender;

Fig. 3 illustrates a switch-controlling marker and a marker connector by. means of which the sender is connected to an idle marker;

Fig. 9 shows a number comparing circuit for comparing numbers registered in the marker and the number of the absent subscriber; and

Figs. 10 and 11 show one of the special trunks by means of which the subscriber may set up a connection between the operator and his own line.

Although the invention is not so limited, it has been embodied for the purpose of the present disclosure in a system using switches of the crossbar type for establishing connections and register senders and markers for controlling the operation of these switches. Since the inventionis not particularly concerned with all of the detailed circuits and apparatus employed in systems of this type, many of these unessential details have been omitted in the present disclosure. For a full understanding of the operation of these systems reference may be had to Carpenter Patent 2,093,117 of September i4, 1937; Carpenter Patent 2,089,921 of August 10, 1937; Carpenter Patent 2,235,803 of March 18, 1941; and the application by R. E. Hersey, Serial No. 300,928, led October 24", 1939.

A general understanding oi the system may be had from the diagram shown in Figs. 1 and 2. These ngures disclose the incoming frames |00 and nal frames |0| of cross-bar switches comprising part of the terminating equipment of a local cross-bar cnice. The regular traflic through these frames to the called subscribers line is routed over incoming trunk circuits from the local originating unit and from the originating units in the distant oihces. One of these incoming trunks, trunk |02, is illustrated. Incoming register senders, such as the sender |03, are associated with the calling incoming trunk by means of the sender link circuits |04 and receive the designations of the called subscribers lines.

marker connectors |05 to idle switch-controlling markers, such as the marker |06. The marker receives the designation of the called line from the sender and connects itself to a number frame |01 for the purpose of testing the called subscribers line and for determining the location of the line in the iinal switch frames Having determined the location of the incoming trunk and the called line, the marker is connected to the proper incoming and final frames through frame connectors |03 and |09. Following this, the links interconnecting the switches in the frames are tested, an idle path through these frames is selected, and the magnets of the switches are operated to complete the 'desired coni nection.

The drawings also illustrate a special service or intercept operators position IIB. This operators position may be in the same oiiice containing the terminating equipment, or it may be in a distant oilice.` In either case special service trunks ||I and 2 extend from the operators position to the selectors on the incoming frame |00. These trunks are provided with relays and controlling equipments ||3 and ||4 at the incoming end, and each trunk also has an appearance, like a subscribers line, in the iinal switches on the frame |0|. The final switch appearance of trunk is represented by the line I5, and the final switch appearance of the trunk ||2 is represented by line IIG. special service'trunks is also provided with an individual designationregister whichserves to maintain a registration of the number of a. subscribers line`to which the special trunk isextended for intercept service. For example, the register ||1 is provided for the trunk andy a. similar register I I8 is provided for the trunk ||2. The trunk is selected by the operator for establishing an intercept connection to the line of a subscriber who has called her and requested the absentee service. The other trunk |I2 is under control of the subscriber and may be selected by him under control of his dial to set up the desired intercept connection between the operator and his line.

A special incoming register sender H9 is provided for registering the designation required for extending a connection over one of these special trunks to a subscribers line. Sender connectors |20 and |2| are provided for connecting the special sender ||9 to the intercept trunks and to their associated designation registers. The sender ||9 also has access through the marker connectors |05 to the common switch-controlling markers. A designation comparer |28, which is common to the markers, is connectable to any marker and is also associated with the designation registers I and I8 for the purpose of comparing the numbers of lines that are called and found busy with the numbers that are registered on the designation registers |I`| and IIB.

The district and office frames |22 and |23 of the originating office, located in the same oillce with the frames |00 and IUI of the terminating unit, are also illustrated. Calling subscribers lines in the oice are extended through the switches on the frame |0I, which serve as line switches as well as final switches, over district junctors, suchl as the junctor |26, to the district frame |22. 'I'he oilice frame has access to outgoing trunks to the same and other offices, to

These senders are connected through L".

special service trunks, such as trunk I2, and also to operators trunks, such as the trunk |24, to the Each of the service operators position which may be in the same or another oiiice.

Assume that the subscriber of line |25 wishes to have calls to his line intercepted during his absence. Before leaving his telephone he may call the special service operator in the usual manner by dialing the proper code to set the originating sender |32 and marker |33, which control the district and oii'ice switches |22 and |23 to extend his line over the district junctor |26 and over trunk |24 to the operators position. The operator responds, and the subscriber advises her that he is about to leave his home or oce and Wishes to have all calls to his line intercepted during his absence. 'Thereupon the operator seizes an idle one of the special service trunks, such as the trunk HI. Her act of seizing this trunk causes the connector |20 to operate and connect the sender H9 to the trunk ||I through the control mechanism H3 and also to connect the sender I I 9 to the designation register HI which is individual to the trunk II I. When the operator receives the dial tone, she manipulates her dial |2'I to transmit over the trunk ||I a series of impulses representing the number of the subscribers line |25. These impulses are registered in the sender I 9 in the usual manner, and at the same time they are registered in the designation register I I'I. The sender H9 seizes an idle marker |06 through the connector |05, and the marker proceeds to control the operation of the incoming and nal switches to extend the intercept trunk IH through to the absent subscribers line |25. Thereupon the marker |06, the sender H9 and the connector |20 are released. However, the established connections between the operators position and the subscribers line |25 and the registration in the designation register II'I are maintained during the subscribers absence, and the subscribers line |25 appears busy whenever a marker makes a test thereof during the time the special trunk connection is maintained.

If on the other hand the subscriber wishes to set up the intercept connection himself, he dials a code identifying the group including trunk H2 and also the number of his own line. The sender |32 and marker |33 control the district and office switches |22 and |23 to seize trunk H2, following which the number of the subscribers line is transferred from sender |32 to the incoming sender H9. The marker |06 then controls the incoming and final switches |00 and |0| to exi tend the trunk H2 to the subscribers line |25, omitting the busy test. At the same time the operator is signalled over trunk H2. She informs the subscriber the connection has been set up, and he then hangs up his receiver. The replacement of his receiver releases the connection from his line |25 through switches IOI, |22 and |23 to the trunk H2, leaving the established connection between the operator and line |25 by way of the special trunk H2.

Each time during the subscribers absence that the marker |06 or any of the other markers attempts to set up a connection to another called line and nds it busy, it operates the connector |29 to associate itself with the comparing device |28. The device |28 then proceeds to compare the number of the busy called line, which is still registered in the marker |05, with the number of the absent subscribers line, which is registered on the designation register H1 or H8 as the case may be and also with al1 other absent subscribers numbers which may be registered in other designation registers. The purpose of this comparison is to determine whether the busy called line is the line of an absent subscriber who has requested the intercept service. If, therefore, the subscriber of a calling line |30 attempts to call the absent subscribers line |25, the comparison shows that the number in the marker |06 is the s arne as the number registered in the register H'I, and the marker is notified of this fact. The marker then proceeds to operate the incoming and iinal switches to automatically route the calling incoming trunk |02 through these switches over the circuit H5 to the special intercept trunk which was used by the 0perator to set up the intercept connection to the line |25. When this connection is established from the calling line to the intercept trunk I, a signal is given the operator, and she responds and converses with the calling subscriber. When the calling subscriber is through conversing with the operator, his connection is released, but ther connection between the operator and the absent subscribers line remains established.

Referring now to Figs. 3 to 9, the -outgoing end of one of the intercept trunks 300 is shown terminating at the special service operators position in the contacts of a key 30|, by means of which the operator can associate her telephone and position dial with the trunk and can also hold the trunk while engaged on other calls. The trunk 300 is one that is used by the operator in setting up an intercept connection and co-rresponds to the trunk H in Figs. 1 and 2. The incoming end of the trunk 300 appears in the contacts 500 of an incoming selector switch 5H and also appears in the contacts of the senderconnector relay 600. The incoming end of the intercept trunk is also connected to a set of contacts 50| in one of the switches 5I8 on the final frame. -Moreoven the incoming trunk circuit is provided with a number of relays for applying ringing current, for controlling supervision, and for tripping the ringing operation either under control of the called subscriber or under the control of the service operator.

The register sender shown in Fig. 7 includes the usual controlling and impulse receiving relays and register means for registering the digits of a subscribers designation received in the form of impulse series. 'I'he register comprises a crossbar switch having Vertical rows of contacts for the usual thousands, hundreds, tens and units digits and for the incoming frame identiiication. Although some of the controlling relays and circuits are shown in detail, many of the relays and circuits that would ordinarily be included in the sender have been omitted and are illustrated in a general way by the rectangle '100.

The designation register shown in Fig. 6 also consists of a cross-bar switch having' four vertical rows of contacts, one for each of the four numerals of the subscribers designation. This register, which is individual to the incoming trunk shown in Fig. 4, is connected to the sender by the connector relay 600 at the same time the incoming trunk is associated with the sender.

The switch-controlling marker 800 includes registers 802, S03 and 804 for registering the thousands, hundreds, tens and units digits, respectively, of the subscribers number which it receives from the sender by way of the marker connector 805. The marker also contains a frame indication register 806 on which it records the frame identification of the trunk circuit 30,0,

The designation comparing circuit, which .is shown in Fig. 9, comprises four registers S00, 90|, 002 and 903 for the thousands, hundreds, tens and units digits of Va Subscribers number. This circuit also includes a group of four relays 904 for each one of the special intercept trunks appearing in the incoming frame. The windings of the relays of the registers 800,v 90|, 902 and 903 extend through the connector 801 to the marker, and the registers 80|, 802, 803 and 804 in the marker serve to operate these relays to duplicate in the comparing circuit the number registered in the marker. The contacts of the register relays in the comparing circuit are wired to the contacts of each of the cross-bar designation registers. Therefore, whenever the number registered in the marker is found to be the same as the number on the designation register associated with a particular intercept trunk, all four of the relays of the group 904 individual to that intercept trunk are operated. The relays of the group 904 when operated serve, as will be explained hereinafter, to notify the marker that the absent subscribers line has been called.

The operation of the system will now be described in detail. Assume for this purpose that the subscriber of line 502 is about to leave his residence or oflice and wishes to have all calls to his line intercepted by the operator. Having called and notied the operator of his intentions, the calling subscriber may leave immediately or he may wait to satisfy himself that the operator has successfully established the intercept connection to his line. In any event the operator proceeds to set up the connection by operating the two-way key from its normal position to the position for closing the contact springs 302, 303 and 304. The closure of these contacts associates the operators dial 305 with the trunk 300, and a circuit is closed from battery through the upper left Winding of repeating coil 306, closed Contact spring 302 Ythrough ini-` pulse contacts of the dial 305 thence through the closed spring contacts 303 and the lower left winding of coil 306 and winding of impulse relay 301 to ground. Relay 301 operates and closes a preliminary energizing circuit for relay 400 at distant end of the trunk. At the same time a e circuit is closed from battery through the winding of relay 308, contacts 304 and the normally closed contacts 309. associated with the dial 305. Relay 308 operates and disconnects the trunk conductors 3|0 and 3|| from the bridge through the contacts of relay 301 and connects these conductors through the right windings of the repeating coil 306 and the polarized supervisory relay 3|2. A circuit for relay 400 may now be traced from battery through the upper winding of relay 400, normal contacts of relay 40|, conductor 3|0, contacts of relay 308 through the repeating coil windings and polarized relay 3|2 through the lower contacts of relay 308, conductor 3| normal contacts of relay 40| to ground through the lowe': winding of relay 400. Relay 400 remains operated in this circuit; and the direction of the current iiow over the trunk is such that polarized relay 3|2 does not operate.

Relay 400 closes a circuit from ground through its armature and front contact, normal contacts of slow-release relay 402 through the winding of slow-release relay 403 to battery. Relay 403 operates and closes a circuit from ground through its contacts over the start conductor 404 through 75' the winding of preference relay to battery; Relay operates and opens the battery Supply for any other preference relay that may have operated at this time` A circuit is now closed from ground through the back contacts of, prei.'- erence relays 602 and 603. front Contact of relay 60| t0 ground through the winding of relay- 600. Relay 600 operates and extends aJ number' of leads from the trunk. 300 through to the register sender and also extends the. operating conduce tors for the select and hold magnets of; the, desig? nation. register S04 through to the resister sender. The operation of relay 600 closes a holding circuit for relay 60| traceable from battery through the winding of relay 60|, @Ontacts ci relay 600, Conductor 605 to ground at the. back Contact of the sender release relay 10|., Relay 600 also closes circuits for the scndcrot-normal relay 102 and relay 105. The circuit f0.1. relay 102 is traceable from battery through lthe wind* ing of said relay, normal contacts of relay 103, conductor 104 through contacts of the relay 000 to ground. The circuit for relay 105 may be traced from battery through the winding of said relay, conductor 106, normal contacts of the hold magnet 101, conductor 108 to ground through the contacts of relay 600. Relay 103 also operates in a circuit from battery through its wind--` ing, frcnt contacts of relay 102 to the grounded conductor 605.. Relay 102 is now held energized in a circuit from battery through its Winding and front contacts to the grounded conductor 605.

The identity of the incoming frame in which the trunk 300 appears is now registered on the fourth vertical row of contacts in the register switch 109 of the sender. To this end the relay 105 in operating extends the operating circuits for the ten select magnets 1|0, 1||, 1|2, etc., through the connector 600 to the terminal block 405 associated with the trunk v300. Assuming that the terminal associated with conductor 406 is grounded, a circuit is completed over this conductor through the contacts of relay 600, conductor 028, contacts of relay 105, conductcr 1|3 through the winding of select magnet 1|4 to battery. Magnet 1|4 operates and prepares the contacts in the horizontal row associated thereF with. Following the operation of magnet 1|4 a circuit is closed over the conductor 1|5 and through the winding of the hold magnet 101 to battery. Magnet 101 operates and closes the cross-point contacts to register the frame identication. Magnet 101 locks in a circuit from battery through its winding and contact, conductor 1I0 to ground at the front contacts of relay 102. Magnet 101 in operating opens the circuit of relay 105, and this relay releases, opening in turn the circuit of the select magnet `1|4. The magnet 1|4 releases, and the crossfpoint contacts are held closed by the continued ener, gization of the hold magnet 101.

When relay 105 releases following the registration of the frame identification, a circuit is closed for operating relay 40| in the trunk, circuit may be traced from battery through the Winding of relay 40|, conductor 4 01, contacts of relay 600, conductor 606, contacts o f relay 1|1, closed contacts of relay 103 to ground at the back contacts of relay 105. Relay 40| disconnects the windings of relay 400 from the trunk 300, and relay 400 releases. Relay 400 opens the original circuit of relay 403, but this relay is now held in a circuit from battery through its winding and contacts to ground at the contacts of relay 40|. Meanwhilethe pulsing circuit has been completed from the trunk 300 to the impulse relay 1|8 in the sender. 'Ihis circuit may be traced from battery through the winding of relay 1|8, front contacts of relay 102, back contacts of relay 1|1, conductor 1| 9, contacts of relay 600, conductor 601 to the tip conductor 3|0 of the trunk and thence as previously traced through the repeating coil windings 306 and returning over the ring conductor 3| I, conductor 608, contacts of relay 000, conductor 609, contacts of relays 1|1 and 102 through the secondary winding of the tone coil 120. The direction of current iiow over the trunk is the same as before; consequently the polarized relay 3|2 remains deenergized. At the proper time tone current is applied to the coil 120, and the operator, hearing the tone in her receiver, proceeds to dial the number of the subscribers line 502.

Assuming the number of line 502 is 2345, the operator transmits with her dial 305 four corresponding series of impulses. As the dial moves away from normal preparatory to the transmission of each series, the oil-normal contacts 309 open and relay 308 releases, closing the trunk 300 through the contacts of the pulse relay 301. At each interruption of the circuit of relay 301 the relay releases and opens the circuit of pulse relay 1|8. The pulse relay 'H8 operates the pulse and sequence mechanism 100, and at the end of each series of impulses a circuit is closed for operating the proper one of the select magnets of the register switch-109. Since the thousands digit is 2, ground potential is applied to conductor 12| by the impulse circuit 100. Parallel circuits may now be traced for operating the No. 2` select magnet 122 of the sender register 109 and the No. 2 select magnet 6|0 of the designation register 604. The circuit for magnet 122 eX- tends from battery through the winding of said magnet to the grounded conductor 12|; and the rcircuit for magnet |0 extends from battery through its winding over conductor 6|| through contacts of relay 600 thence over conductor 14| to the grounded conductor 12|'.l Thereupon ground potential is applied to conductor 123 and parallel circuits are closed through the thousands hold magnet 124 of register 109 and the thousands hold magnet 6|2 of register 604. Magnet 124 locks through its own contact to the holding conductor 125; and magnet 6| 2 locks through its own contact over conductor 6|3 to ground at the closed contacts of relay 403l Following the operation of

hold magnets

124 and 6|2

the'select magnets

122 and 5|0 are released, preparing the switches for registering the next digit. In like manner the hundreds, tens and units digits are received and cause the operation of

select magnets

126, 121 and 128, respectively, of switch 109, and select magnets 6|4, SI5 and 6|6, respectively, of switch G04. The successive operations of these select magnets are followed by the operations of the

corresponding hold magnets

129, 130 and 13| of switch 109 and hold magnets 6|1, 6|8 and 6|9 of switch 604. The select magnets are released, and the hold magnets are held over obvious locking circuits.

As soon as the units digit is registered, a circuit is closed from ground through the front contact of the units hold magnet 13|, conductor 132 through the winding of relay 1|1 to battery. This relay operates and closes an operating circuit for slow release relay 402 in the trunk. This circuit may be traced from battery through the vwinding of relay 402, conductor 408, contact of relay 000, conductor 620, closed contacts of relay 1I1. to ground at the front contacts of relay 103.v At the same time relay 1|1 opens the pre- Viously traced circuit for relay 40|, and the latter relay releases. Relay 400 is again connected to the trunk 300, the direction of current flow over the trunk being the same as before. Hence the lpolarized supervisory relay 3|2 at the outgoing end of the trunk remains deenergized. Relay 1| 1 in the sender also opens the impulse circuit, disconnecting the impulse relay 1|8 from the trunk 300, Relay 402 in the trunk circuit is held in a locking circuit from battery through its winding and front contact to ground at the front contact of relay 400. After an interval slow-release relay 403 releases and opens the energizing circuit of preference relay 60|. Relay 60|, however, remains locked through the contacts of relay 600 until the sender releases. Relay 403 opensits grounded connection to the conductor 6|3, but ground is maintained on this conductor by relay 402 to hold the select magnets of the designation register 604.

Following the registration of the number in thel sender the start circuit 133 is closed through the front contacts of magnet 13| thence over conductor 134 to the start relay 823 of the marker connector 805, and the marker connector operates to connect the sender to an idle marker 800. sender by the closure of the selected cross-points in the vertical rows of contacts of the cross-bar switch 109 is transferred over the groups of conductors 135, 136, 131 and 138 to the thousands, hundreds, tens and

units registers

802, 803 and 804 in the marker. Similarly the registration of the frame identification is transferred vfrom the register sender over the group of conductors 139 to the frame register 806 in the marker. The marker proceeds in the usual manner to test vthe called line 502 and to operate the switch magnets for closing the incoming primary and

secondary cross-points

500 and 503 and the nal primary and secondary cross-points 504 and 505 to extend the trunk circuit 300 through to the subscribers line 502. The

hold magnets

506 and 501 of the incoming switch and the hold magnets 508 and 509 of the iinal switch are held to maintain the connection in a circuit over the sleeve conductor 5|0 through the contacts of relay 409, conductor 4|| to ground at the front contacts of relay 402.

During the operations of the marker a circuit Iis closed over conductor 808 through the conf nector 805, conductor 809, contacts of relay 600,

conductor 62| to operate the relay 409 in the trunk circuit. Relay 409 serves to extend a number of control conductors 4|0 through to the marker 800. Having successfully established the connection the marker proceeds to release, but before'doing so it closes a release circuit for the sender traceable over conductor 322 through connector 805, conductor 8|0 through the winding of relay 10| to battery. Relay 10| operates and causes the release of the sender including the operated hold magnets of the register 109. Relay 10| also removes ground potential from conductor 605, and relays 600 and 60| release, disconnecting the sender from the trunk. The register 604, however, remains in its operated condition, the hold magnets being held by the grounded conductor 6 3.

While the trunk 300 is connected to the marker by way of conductors 4|0, the proper control relays in the trunk are operated to control the Thereupon the number registered in the application of ringing current to the called line. Assume, for example, that it is desired to apply ringing current to the tip conductor of the sb-y scribers line 502. This being the case, the marker causesl the operation of relay 412 over a circuit from battery through the winding of said relay, contacts of relay 409, the latter relay be ing operated while the trunk is connected to the marker, thence over conductor 413 to ground in the marker. Relay 412 operates and locks in a circuit from battery through its winding and front Contact, back contact of the .tripping relay 414, conductor 415 to ground at the front contact of relay 402. At the same time the marker closes a circuit from ground over conductor 416 through the contacts of relay 409 and the wind; ing 411 to battery. Relay 41'1 also operates and locks through its winding and contact and the back contact of relay 414 to the grounded conducto'r 415. When thereafter the marker, having completed the connection through to' the called line 502 as above described, releases the relay 409 and disconnects itself from the trunk, ringing current is applied through the incoming and

final selectors

511 and 512 to the line 502. The ringing circuit may be traced from the source 418, front contact of relay 411-, winding of the tripping relay 414, normal contact of relay 419, front contacts of relay 412, front contacts of relay 411, normal contacts of relays 409 and 420, tip conductor 521 thence through the

switches

511 and 512 over the loop of the line 502 and returning through the switches to the ring conductor 422, normal contacts of relays 420 and 409, front contacts of relays 41'1 and 412 to ground.

If the subscriber of line 502 is waiting to verify the establishment of the intercepted connection before he leaves his telephone, he now replies by removing the receiver from the switch-hook. The closure of the subscribers loop operates the ringing trip relay 414 in the well-known manner, and this relay causes the release of relays 412 and 41'1. Relay 41'1 disconnects the ringing source and icloses the called subscribers line through to the windings of the supervisory relay 423. Relay 423 operates and closes a circuit from ground through its front Contact, front contacts of relay 402, conductor 434, resistance 442, through the winding of relay 401 and battery. Relay 401 operates and reverses the con-- nections of relay 400 to the tip and ring conductors of trunk 300 extending toward the operators position. Relay 400 remains energized, and the reversal of current over the line causes relay 312 to operate. In the meantime the operator, having completed the dialing operation, throws the key 301 to the hold position, opening the contact springs 302 and 303 and closing springs 313 and 314. Relay 308 is now held in a circuit closed to ground at thespring 314. When, therefore, the called subscriber answers and current is reversed to release the relay 312 as described, the signal lamp 315 is lighted in a circuit closed from battery through the lamputo ground at the closed contact of relay 312 The operator, seeing the light 315knows that the subscriber has answered. She then throws the key 301 back to the talking position, closing springs 302 and 303 and connecting her telephone set to the trunk. She then speaks to the subscriber and notifies him that the intercept condition has been established for receiving calls to his line during his absence. Thereupon the subscriber replaces his receiver and leaves his CIM release of relay 400.-

telephone. Replacement of the receiver opens the loop and causes the releasev of relay 423. Relay' 423 releases relay 401, and the currentflo'vl7 over the trunk is restored to its former directicri.l Relay 312 again releases and opens the circuit for l-ighting the lamp 315. The key isinow restored to the holding position where it is left until a call to the absent subscribers line is intercepted.

Should the subscriber of line 502 leave 'his telephone immediately without waiting for the op erator to s'et up the intercept connection, it then becomes necessary for the operator to discon', tinue the ringing of his line. If, therefore, he does not answer his bell, the operator momentarily throws the key 301 to the neutral position and then returns it to the hold position. Inthe neutral position of the key both relay 301 and 308 release; therefore, thel circuit of relay 400 is opened. Relay 400 releases and closes a circuit f'rom ground through its back contact, winding of relay 424 to battery at the frontl contact of relay 402. Relay 424 operates and closes a new locking circuit for slow-release relay 402 to replace the holding circuit just opened by the The new locking circuit may be traced from battery through the winding and front contact of relay 402, frontcontact of relay 424, back contact of relay 400 to ground at the back contact of relay 423. Relay 424, also closes an obvious operating circuit for slowrelease relay 4 25. Relay 425 closes a bridge across the trunk circuit to trip the ringing operation. This bridge may be traced from the tip conductor 421, conductor 426, resistance 421, contacts of relay 425, conductor 428 to the ring conducter 422. This bridge causes the operation of the tripping relay 414, and relays 412 and 411 are released to discontinue the ringing operation as above described. In the meanwhile, the operator has restoredthe key 301 to the hold position and relay 308 reoperates to close the trunk circuit through the winding of relay 312. Relay 400 thereupon reoperates, reclosing the hold circuit of relay 40 2 and opening the circuit of relay 424.. Relay 4 24 releases and in turn causes the release of relay 4725. I

During the subscribers absence the numbers of all lines that' are called and found busy are compared with the registered number of the absent subscriber in order that all calls intended for his line may be intercepted and extended to the lservice operator. The comparison is made by the comparing mechanism shown in 9 which is common to the markers. ach time a marker, such as the marker 800, receives and registers the number of a called line and finds the line busy on making a test thereof, it seizes the comparing mechanism and connects itself thereto through the connector 0011. Thereupon the number of the busy called line is transferred from the marker to the

registers

900, 901, 902 and 903 of the comparing mechanism. The comparing mechanism then determines whether the number it has received from the marker is the same as the number registered on the designation register 604 pertaining to the absent subscribers line. If the compared numbers are not identical, the usual busy tone isreturned to the calling subscriber; however, 'if they are identical, the marker proceeds to extend the calling line to the operators position. When, therefore, a calling line is extended to an incoming trunk circuit 515 on a call intended for the absent subscribers line 502, the number 2345 is registered on the

registers

001, 802, 803 and 804 in the marker. The marker, having tested the sleeve conductor |3 of the line, appearing in the number frame 5|4 and having found the line busy, seizes the comparing mechanism and applies ground potential over conductor 8|| through the connector 801, conductor 8|2, causing the operation of certain relays (not shown) in the comparing circuit and resulting nally in the operation of relay 909. The thousands digit 2 is now transferred from the register 80| through the connector 801 and conductors 8|3 causing the operation of relay 906, the remaining

relays

905, 901 and 908 remaining deenergized. In like manner the hundreds, tens and units digits 345 are transferred over conductor groups 8|4, 8|5vand 8| 6 causing the operation of relays 9I0 and 9|| of the hundreds register 90|, relay 9| 2 of the tens register 902, and relay 9|3 of the units register 903, the other register relays remaining deenergized.

Circuits are now extended through the contacts of the registers 900, 90|, 902 and 903 to the corresponding rows of contacts in the crossbar designation register 604 to determine whether the operated relays match with the operated cross-point contacts in the switch. The matching circuit for the thousands register may be traced from the grounded conductor 8I2, through the contacts of relay 909, conductor 9|4, back contacts of relay 905, front contacts of relay 905, back contacts of relay 901, conductor 9| 5, through the cross-point contacts which were closed by the conjoint operation of select magnet 6I0 and hold magnet SI2 when the thousands digit 2 was registered, and which are maintained closed by the continued energization of the hold magnet 6I2, thence over conductor 622 through the winding of relay 9|6 to battery. The matching circuit for the hundreds digit may be traced from the grounded conductor 9|4 through the front contacts of register relays 9|0 and 9|I, back contacts of relay SI1, conductor 9|8 through the closed cross-point contacts in the vertical row controlled by the hold magnet 6|1 and returning over conductor 623 through the winding of relay 9I9 to battery. In like manner the matching circuits for the tens and units digits are traceable from grounded conductor 9| 4 through t-he contacts of the tens register 902 to conductor 920 and through the contacts of the units register 903 to the `conductor 92|. Conductors 920 and 92| are further traceable through the closed cross-point contacts in the tens and units rows of the switch 604 and returning over conductors 624 and B25, respectively, through the windings of

relays

922 and 923, respectively, to battery. Thus all of the relays of the group 904 are operated indicating a match between the registered numbers. For a more complete disclosure and description of the number comparing circuit and its cooperative relation with the marker, reference is made to the copending application by R. E. Hersey, Serial No. 300,928, led October 24, 1939.

With all of the relays of the group 904 operated a circuit is closed as follows for the relay 924: Battery through the winding of said relay, front contacts of

relays

923, 922, 9|9 and 9I6 to ground. Relay 924 locks in a circuit from battery through its winding and contact, conductor 925, ground at the back contact of relay 429. Relay 924 also closes an operating circuit for relay 429 traceable from battery through the winding of relay 429, conductor 430 to ground at the front contact of relay 924. Relay 429 operates and opens the temporary locking circuit cf relay 924, but the latter is held over its original operating circuit under control of the marker. The marker 800 is now notified that the absent subscribers line has been called and that the calling line should be automatically routed to the service operators trunk 300. The notifying signal is sent to the marker by the relay 924, which operated as a result of the matched designations. The signal circuit may be traced from ground through the front contacts of relay 924, conductor 921 through connector 801, conductor 8I8 through the winding of a route relay 8I1 in the marker. In the well-known manner the operation of the route relay in the marker causes the marker to associate itself through a connector 8|9 and over a group of test conductors 820 with the number frame 5|4 containing the group of intercept trunks extending from the service operators position. Having connected itself to the number frame, the marker proceeds to test the group of intercept trunks in the same manner that a marker ordinarily tests a private branch exchange group. Normally each one oi these intercept trunks appears busy at the number frame 5I4. For example, the test conductor 5I5 of the intercept trunk 300 is normally grounded at the back contact of relay 429, so that the trunk will appear busy to a marker testing the group at the number frame 5|4. Since, however, a call is about to be intercepted by this trunk, ground potential is removed from the test conductor 5|5 by relay 429 which has just operated as above described. Therefore, when the marker tests the group containing the intercept trunk 300, it will find this trunk idle and all others busy. Consequently the marker selects this trunk and also selects an idle set of links for extending the incoming trunk 5I0, to which the calling line has already been extended, through the incoming and final switches 5I1 and 5|8 to the intercept trunk 300. Having tested the conductor 5|5 and found it idle, the marker 800 applies ground potential over conductor 820 to conductor 5I5, resulting in the operation of relay 420 over a circuit traceable from battery through the winding of said relay, ront contacts of relay 429 to the grounded conductor 5I5. Relay 420 closes a circuit for holding relay 429, traceable from` battery through the winding and front contacts of relay 429 to ground at the front contact of relay 420. Relay 420 also extends the grounded conductor 5| 5 through its front contacts thence over conductor 432 through the winding of the hold magnet 5I9 to battery. Magnet 5I9 closes and holds the contacts 50| of the nal secondary switch, and in the well-known manner, the marker also operates the hold magnets 520, 52| and 522 to close the iiaining cross-points in the switches 5I1 and The marker releases, and the connection through the incoming and nal switches 5I1 and 5I8 is maintained by the hold magnets 520, 52|, 522 and 5I9 which are h'eld in holding circuits extending through the closed contacts of the switches to ground applied on the holding conductor 523 of the incoming trunk 5I5. Relay 420 is also held in a circuit from battery through its winding and front contact, conductor 432 thence through the closed contacts of switches 5|8 and 5|1 to the grounded conductor 523. Ringing current is also applied to th'e subscribers line 502 from the incoming trunk 5|6. The ringing circuit extends frorn the source 521, over the tip conductor 524, through the contacts ci switches A511 and 518, conductor 525, through front 'contracts of relay 420, 'thence over tip conductor 421, through the

switches

511 and 512 over the loop of the line 520, returning through switches 51'2 and 51 I, conductor 422, front contacts of relay 420, conductor 433 through the

switches

518 and 511 to ring conductor 526. Since the called subscriber is absent and does not answer his telephone, it is necessary to signal the operator in order 'that she may trip the ringing operation. At the time the calling line is being extended to the intercept trunk, a circuit is closed from ground through th'e front contacts of relay 420, conductor 434, through the winding of relay 401 to battery. Relay 401 operates and reverses the connection of the windings of relay 400 to the `trunk 300. This reversal causes the operation of relay 312 at the originating end of the trunk, and this relay closes an obvious circuit for lighting the lamp 315. The operator, seeing the lamp lighted, throws the key 301 to the talking position and challenges. Receiving no reply she knows that a call is being intercepted and that she should trip the ringing operation. To do this |she throws the key momentarily to the midposition to open the trunk circuit 300. Relay 400 releases and operates relay 424 as above described. Relay 424 holds relay 402 and operates slow-release relay 425. Relay 425 closes a bridge for tripping Jthe ringing operation. The tripping circuit may be traced from the ringing source in the incoming trunk 516 thence over conductor contact of relay 435 to ground at th'e contacts of relay 420. After a moment the operator throws the key 301 from the mid-position to the talking position, and relay 308 operates to reclose the trunk 300 through the winding of polarized relay 312. YThereupon relay 400 reoperates and releases relay 424. After an interval relay re leases and a circuit is closed from ground to the back contact of said relay, front contact of relay 435, winding of relay 43B to battery. Relay 435 operates and completes the talking circuit between the operators position and the calling subscribers line. Talking current is supplied toward the originating end of the trunk 300 through the windings of relay 400. Th'e talking circuit from the incoming end of the trunk 300 toward the calling subscribers line may be traced from battery through the lower winding of relay 423, conductor 431, conductor 43B, front contacts of relay 435, conductor 428, front contacts of relay 421i,

conductor 433 and thence through the switches extend through the windings of a batterysupply relay similar to the relay 423 of the intercept trunk 300. The windings of the relay in trunk 515 may be connected in either direction. 1f they are connected in the same direction as the windings of relay 423, no current flows and neither the relay 423 nor the relay in the incoming trunk 516 will operate. The operator now |speaks to the calling subscriber, advises him that the called party is absent, and offers to take'any message that the calling subscriber may Wish to leave for subsequent communication to the absent subscriber.

After the operator and the calling subscriber have nni'shed their conversation the'callingsubscriber replaces his receiver and releases the connection he has established from his line through' the

switches

511 and 518. The release of this connection removes ground potential Vfrom conductor 432, and relay 420 releases to open the tip and ring conductors of the trunk 300 which appear in the cross-point contacts 501 of the final switch 518. Relay 420 in turn releases relay 429, which restores the normal busy potential-to 'th'e conductor 515 of the intercept trunk 300. 'Relay 420 also releases relays 435 and 401 and relay 435 releases relay 436. Relay 401 reverses the direction of the current over the 'trunk 300, and relay 312 releases. TheV operator restores' her key to the `hold position and notes that the lamp 315 is dark, indicating that the calling subscriber has replaced his receiver. The equipment is now in the same condition that existed prior tothe call to the absent subscribers line; `that is to say, the intercept trunk 30'0 remains connected to the absent subscribers line through the switches 51 1 and 512, and the absent subscribers number remains registered on ythe designation register 604 in readiness for interceptng thenext call made to the line 502;

Should the absent subscriber return while his bell is being rung on a call that is about to be intercepted he may answer inthe usual manner by removing his receiver. The removal of .his receiver trips the ringing mechanism in the calling incoming trunk 516, the tripping circuit being traceable from conductor 524, through

switches

511 and 518, .conductor 525, front contacts of relay 420, conductor 421,

lswitches

511 and 512, over the closed loop of the line 502 and returning through

switches

512 and 511, conductor 422, front contacts of relay 420, conductor 433 through the

switches

518 and 511 to'conductor 5215. The called subscriber may now speak to the calling party. In `the meantime the 0perator, having observed the lighted lamp 315, throws the key 301 to the intermediate position, causing the release Aof relay 400 and the operation of

relays

424, 425 and 435 as above described. Relay 43'5 locks in a circuit from battery through the front contacts of relay 402, winding and front contacts of relay 435 to ground at the front contact of relay 420. When the operator subsequently moves thevk'ey to the talking position, relay 400 reoperates, and relaysw424 and 425 release and relay 435 operatesv to extend the talking connection from the trunk 300 to a called subscribers line 502. The operator now challenges and discovers that the absent -subscriber has returned to his telephone and has `answered the calling party. While the trunk 300 is extended through relay 4311` to the established connection between the calling and called parties, supervisory relay `423 is operated in a circuit inducing the loop of the called une 502, and the same is true of the corresponding supervisory relay in the incoming trunk 5| 6. After learning that the called party has answered, the operator throws the key 30| to the hold position and the energizing circuit of relay 400 is maintained, and relay 402 is held by relay 400. As soon as the supervisory relay 423 is operated, relay 40| is operated, and relay 3|2 is operated at the originating end of a trunk to light the supervisory lamp 3|0 as a signal to the operator that the called subscriber has his receiver oli the switchhook. i When the calling subscriber replaces his receiver, the connection to the called partys line 502 is released, and relays 420 and 429 are deenergized. If the called subscriber 502 still has his receiver oiT the switchhook the circuit of relay 423 is reclosed and relay 435 is now held in a circuit from battery through the front contact of relay 402, winding and front contact of relay 435, conductor 434, front Contact of relay 402 to ground at the front contact of relay 423. When the subscriber of line 502 iinally restores his receiver, relay 423 releases, and relays 435 and 435 release. The release of relay 423 opens the circuit of relay 40| and relay 3|2 releases to eX- tinguish the lamp 3|5.

Should the absent subscriber return and wish to discontinue the intercept service, he may do so by merely removing his receiver from the switchhook. The removal of the receiver closes the circuit of relay 423, and this relay in turn closes the circuit for relay 40|. Relay 40| reverses the current direction, and the lamp 3| 5 is lighted at the operators position. The operator responds by throwing the key 30| immediately to the talking position. Relay 400 remains energized and holds the relay 402 operated, and the operator now speaks to the subscriber over the intercept trunk connection. He informs her that he does not wish the service any longer, and she instructs him to hold his receiver E the switchhook for a moment, in order that she may release the connection. While the subscriber is holding his receiver oi the switchhook and relay 423 is energized, she throws the key 30| to the intermediate position and leaves it there. Relay 400 immediately releases, and after an interval the slow-release relay 402 releases, since relay 423 is now operated. Relay 402 removes ground potential from conductor 4||, and the incoming and nal switches 5| l and 5|2 are restored to normal. Relay 402 also removes ground potential from conductor 6|3, allowing the hold magnets 6|2, SI1, 6|8 and 6|9 to release and restore the designation register 604 to its normal condition. The subscriber of line 502 now replaces his receiver on the switchhook, and his line is available for incoming and outgoing calls as usual.

A description will now be given of the operations involved When the subscriber establishes the intercept connection to his own line without the assistance of the operator. In this case the special intercept trunk |000 shown in Figs. 10 and-11 is used; accordingly, these figures should be substituted for Figs. 3 and 4 in the drawings.

When the subscriber of line 502 wishes to set up the intercept connection, he removes his receiver, resulting in the automatic extension of his line through the line switches to a district junctor |00| terminating in the district frame |002. An originating sender is associated with the subscribers line, and he dials a code designation representing the group of intercept trunks, including the trunk |000, following which he dials the numerical designation of his own line. The originating sender and marker control the operation of the district and office switches |002 and |003 to seize the idle intercept trunk i000. A circuit is now closed from battery through the upper Winding of relay ||00 thence over conductor |0| through the contacts of relay H02, conductor |03 through the oice and district selectors |003 and |002, thence through the supervisory relay (not shown) in the district junctor l 00| and returning through the district and oiiice switches |002 and |003, over conductor |004, contacts of relay |02, through the lower winding of relay H00 to ground. Relay |I00 closes a circuit from ground through its front contact, normal contact of relay |04 through the winding of slow-release relay ||05 to battery. Relay H05 closes a circuit from ground over conductor ||06 and 404 to operate the relay 60| in the manner previously described for the purpose of connecting the intercept trunk |000 to the idle register sender of Fig. 7. Relay ||05 also closes a circuit from ground over conductor |01 and thence over the sleeve conductor ||08 to guard the trunk |000 against seizure by other oice selector switches |003.

As soon as the incoming sender yof Fig. 'l is associated with the trunk |000, the numerical designation is transferred in the well-known manner from the originating sender to the incoming sender. If the transfer of the designation is made by the usual revertive impulse method the pulse and sequence circuit |00 of the incoming sender may be arranged to transmit these revertive impulses back over the established connection to satisfy the registrations in the originating sender. As these numerical designations are received in the terminating sender they cause the operation of the cross-bar registers '|09 and 604 in the manner already described. 'I'hus the number of the subscribers own line 502, which he has dialed into the originating sender, is registered in the terminating sender of Fig. 7 and also on the register mechanism 604 individual to the special service trunk |000.

Since the connection being established is one that reverts to the calling line, which is, therefore, in a busy condition, it is necessary to apprise the sender and marker of this fact in order that the usual busy test may be omitted. This class information is sent to the sender by means of a circuit traceable from ground through the back contact of relay H04, conductor H09 thence over conductor 62| through contacts of the relay 600, conductor 809 to the sender control circuit '|00 where appropriate relays may be operated to record the information.

After the numerical designation has been registered in the sender and in the register mechanism 604, an idle marker is associated with the sender in the manner described, and the numerical registration is transferred to the marker together with the necessary class information for notifying the marker that the called line is one that should be seized Without regard to its busy condition and. that the usual ringing operation may be omitted. The marker sets up the connection in a manner previously described, causing the operation of switches 5|| and 5|2 to extend the intercept trunk |000 through to the subscribers line 502. When the sender reaches the stage at which relay 'H1 is operated, relay H02, which was previously operated in the