US1836589A

US1836589A - Rural telephone system

Info

Publication number: US1836589A
Application number: US434244A
Authority: US
Inventors: Haigh Leslie Baines
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1929-03-13
Filing date: 1930-03-08
Publication date: 1931-12-15
Anticipated expiration: 1948-12-15
Also published as: GB330626A; FR692701A

Description

Dec. 15, 1931 1 BwHAIGH I 1,836,589

RURAL TELEPHONE SYSTEM Filed March 8, 1930 ll Sheets-Sheet 1- fie. /0 F/Gi 5 59.5 F/GJ/ 58.5 H615 59.5

INVENTD/F L.B.HA/GH 7 ATTORNEY MkHQ/VAL Dec. '15, 1931. B, HAIGH I 1,836,589

RURAL TELEPHONE SYSTEM Filed March 8, 1950 ll Sheets-Sheet 2 /NVEN7'UR L B HA/GH ATTU/PNEY Dec; 1931- B. HAIGH 1,836,589

RURAL TELEPHONE SYSTEM Filed March 8, 1930 11 Sheets-Sheet 3 unnnuuuu nuuuuun /N VE N TOE L. B. HA/GH BY @ae/M AT TORNEY.

Dec. 15, 1931. L, HAlGH 1,836,589

RURAL TELEPHONE S YS TEM Filed March 8, 1930 ll Sheets-Sheet 4 A TO/FNEY Dec. 15, 1931. 1.. B. HAlGH 1,836,589

I RURAL TELEPHONE SYSTEM Filed March 8, 1930 11 Sheets-Sheet 5 /NVEN7'0R L .flHA/GH BY 6916M ATTORNEY 11 Sheets-Sheet 6 Filed March 8, 1950 INVENTOR L..B.HA ICBH BY @P-M wmww A TTURNEY Dec. 15, 1931.

L. B HAIGHQ 7 1,836,589

RURAL TELEPHONE SYSTEM Filed March 8, 1950- 11 Shets-Sheet v L. B. HA/sH 0? 66 A TTURNEY Dec. 15, 1931.,

L. B. HAIGH RURAL TELEPHONE SYSTEM Filed March 8, 1950 11 Sheets-Sheet 8 INVENTOR .B.HA I6H ATTORNEY Dec. 15, 1931.

| B. HAIGH 1,836,589

RURAL TELEPHONE SYSTEM Filed March 8, 1930 11 Sheets-Sheet 9 //v VENTOR L. 5. HA G H A TTURNEY Dec. 15, 1931. L. B. HAlGH 1,836,589

RURAL TELEPHONE SYSTEM Filed March 8, 19150 11 Sheets-Sheet l0 m t A t w tw m A TTDRNEY v thmt L. B. HA/GH m ts t m t t m tm t 5 m m th t v t 5 m m t m m t tw t t Q t 96$ 1 m tm tm QA k m t m t \Bt m th t S t 1 Dec. 15, 1931.

L. B. HAIGH RURAL TELEPHONE SYSTEM 11 Sheets-Sheet 11 Filed March 8, 1930 INVENTDR L. 5. HA! GH A TTDRNEY Patented Dec. 15, 1931 UNITED STATES LESLIE IBAINES HAIGH, OF ALLDWYOH, LONDON, ENGLAND, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK RURAL TELEPHONE SYSTEM Application filed March 8, 1930,'Senia1 No.434,244, and in Great Britain March 13, 1929.

This invention relates to a telephone 'system of the type in which a number of semiautomatic ofiices are connected together and controlled from a main or urban ofiice. V

The invention is particularly adaptable to a network containing a large number of small outlying oflices and is therefore particularly applicable to those areas known as rural areas.

The offices in the network are arranged in tandem or tree formation so that the main or urban office has access to one or more rural ofiices each of which in turn has access to one or more rural ofiices, the arrangement being continued according to the requirements of the system.

The object of the invention is to provide an improved arrangement for connecting together two subscribers which may be located either in the same or in different offices in the area.

According to one feature of the invention a circuit arrangement is provided for establishing a connection from one subscriber to another under the control of an operator in a distant ofiice, the connection being extended automatically from the calling subscriber to the operator over a junction line, means being provided whereby the oflice containing the wanted subscriber is selected-by the oporator and a connection extended thereto over the same junction line whereupon an alternative path is automatically prepared between the two subscribers on the completion of which the common junction line is released.

More particularly the connection is ex tended automatically from the calling subscriber to the operator over one or more junctions and means is provided whereby the office containing the wanted subscriber is selected by the operator and the wanted subscriber is connected to such operator over at least one of the aforesaid junctions, whereupon an alternative path is automatically prepared between the two subscribers if necessary over one or more of the other unctions previously employed on the completion of which the common junctions may be released.

If the two subscribers should be located in the same office a direct alternative path may be prepared between them and the common junction line or lines over which the connection was set up may be automatically released as before. 7

According to a further feature of the invention the path from the operator to the wanted subscriber employs at each oflice en route, common apparatus, whereas the alternative path between the two subscribers is completed independently of such common apparatus.

The call is preferably routed from the calling subscriber to the operator over one or more junction switches, one of which is located at each ofiice en route after which the connection is routed from the operator to the wanted subscriber through one or more registering mechanisms, one of which may be located at each oflice en route. link circuits each having a plurality of finder switches may also be. provided at each ofiice, the arrangement being such that the switches ofone such link circuit in the office which is furthest from the main ofiiceand which also has access to the calling and wanted oflices set themselves in accordance with the setting of the junction switch and the registering mechanism respectively employed at that office, thereby preparing an alternative path between the calling and called subscribers.

ne or more junction circuits each having a finder switch may also be provided at each office, the arrangement being such that the switch of one such junction circuit in each of the ofiices between the ofiice which is furthest from the main oflice and which also has access to the calling and wanted ofiices,

sets itself in accordance with the jsetting of the registering mechanism in that oflice thereby further preparing an alternative path between the calling and wanted subscribers.

Moreover the aforesaid junction circuit may be the same as those employed for extending a connection from a calling subscriber to an operator.

The arrangement may be such that when the alternative path between the two subscribers is completed, both the subscribers are automatically disconnected from the One or more a operator at the main oifice who is thus prevented from over-hearing any conversation between the two subscribers.

An arrangement is also provided whereby should a subscriber originate a. call and the operator not answer promptly, he may replace his receiver and await recall, the call being arranged to proceed until the operator answers.

An arrangement is also provided whereby should a subscriber originate a call and abandon it without replacing his receiver, means is provided whereby the operator can forcibly break down the connection- Arrangements are also provided for trunk offering.

The invention will be more completely understood from the following detailed description which is given in conjunction with the accompanying drawings in which Fig. 1 shows a link circuit for use at an end rural ofiice for completing an alternative path between two subscribers.

Fig. 2 shows a two-way junction circuit.

Figs. 3 and 4 show a register circuit for use at an end rural office.

Fig. 5 shows a tandem link circuit.

Fig. 6 shows a tandem junction circuit.

Figs. 7 and 8 show a register circuit for use at a tandem rural oflice.

Fig. 9 shows the termination of a tandem junction from a rural ofiice at the urban ofiice.

Fig. 10 shows a subscribers station and line circuit.

Fig. 11 shows a tandem line circuit.

Fig. 12 represents a layout of a number of the offices in the tandem formation with the various elements forming the offices shown diagrammatically.

Figs. 13 to 17 show the manner in which Figs. 1 to 11 are to be arranged in connection with each of the calls to be traced hereinafter.

It is thought that the invention will be best understood from first considering the layout shown in Figure 12.

In Figure 12 an urban or main ofiice is shown at D with one or more main junctions extending to a tandem rural office A. The tandem rural ofiice A has a number of outlets, some of which extend to the subscribers located on the oflice A others of which extend to a similar tandem rural office such as B while others extend to an end rural ofiice such as BB. Similarly exchange B has a number of outlets similar to those of A extending either to local subscribers or to another outlying end rural ofiice such as C and a group of tandem junctions connecting to the tandem rural ofiice A which corresponds with the group of main junctions connecting the exchange A to the urban ofiice D.

A brief description of the progress of a call between subscribers located on any of the four rural ofiices or on the main ofiice D will now be given.

In the case of a call from subscriber S2 on ofiice B to subscriber S1 on the urban office D the subscriber S2 initiates the call by turning the handle of his magneto, whereupon a line relay in the line circuit SLB responds and a free junction finder J SB sets itself on the calling line. A line relay in the tandem line circuit TLB in exchange A then 0 crates and a free junction finder switch SA sets itself on the line taken into use. A supervisory signal then operates in front of the operator at the main oflice D who then completes the connection manually to the wanted subscriber S1 in the usual way.

If subscriber S2 in ofiice B had wanted to extend the connection to subscriber S3 in the same office the connection to the operator in the main ofiice D would be established in the same way as previously described. The operator, however, on receiving the call connects by means of a set-up plug the junction circuit J A to the register RA of ofiice A. The operator then dials the digit corresponding to the group of tandem junctions JLB whereupon the line selector RSA of the register RA sets itself on the tandem line TLB taken into use and the junction circuit J B is connected to the register RB instead of to the junction finder switch J SB. The operator then dials through the register RA into the register RB the wanted subscribers number (two digits) whereupon the line selector RSB of the register BB is set on to the wanted line leading to the subscriber S3 and tests the line and signals to the operator at oflice D. At this stage the finder switch SBl of the link LB is positioned on terminals corresponding to those assumed by the switch J SB, that is to say, on the line of the subscriber S2. The switch SB2 of the link LB is positioned on the terminal corresponding to that assumed by the switch RSB, that is to say on the line leading to the subscriber S3. A link circuit is thus prepared between the subscribers over the link LB which is independent of the register and the lines extending back to the main ofiice. The operator the-n rings subscriber S3 through the registers RA and RB. When subscriber S3 responds the connection is established to subscriber S2 through the link LB and the switches SBl and SB2 and a signal is transmitted to the operator at office D who removes the set up plug whereupon the registers RA and RB release in turn. When the operator removes the regular plug the junction circuits J A and J B release in turn.

In the case of the extension of a call from a subscriber S2 in ofiice B to a subscriber S4.- in office BB the connection is set up to the operator in the oflice D in the same way as before. The operator inserts her set-up plug and dials into the register RA the digit corresponding to the group. of tandem junctions JLBB leading to the officeiBB. The opera tordials'through the register .RAinto the registerRBB the wanted subscribers number. The line selector RSBB of the register BBB is set on to the-line o'f subscriberS4 which is tested and a signal is transmitted to the operator. At this stage the finder switch J SB of the junction circuit is already positioned on the calling line. The switch SBB of the junction circuit of officeBB is positioned on the terminal corresponding to those assumed by the switch RSBB, that is to say on the wanted line leading to subscriber S4. The finder switch SAl of the link LA is positioned on a terminal corresponding to that assumed by the switch J SA, that is to say, on the line TLB while the switch SA2 is positioned on the terminals corresponding to those assumed by the switch RSA, that is to say on the line TLBB. The operator then rings subscriber S4 via the registers RA and BBB. \Vhen the subscriber S4 responds the register BBB is released and the junction circuit J BB is connected to the switch JSBB and a connection is established via the junction circuit JB, the link LA and'the junction circuit JBB whereupon a signal istransmitted to the operator. The operator takes out the set up-plug whereupon the register RA releases as before and when she removes the regular plug the junction circuit JA is released.

In the case of a connection being extended from subscriber S2 in office B to subscriber S5 in office C the connection is established in the same way as a connection from subscriber S2 to subscriber S3 until the junction circuit 'JB is connected to the register RB. The operator then dials through the register RA into RB a digit corresponding to the group of tandem junctions JLC leading to office C. The register RSB then hunts for a free junction in this group and the junction circuit JG is connected to the register circuit RC. The operator then dials through the registers RA and RB into the register R0 the wanted subscribers number. The line selector RSC in the register RC is set on to the wanted line (S5) which it tests and then signals to the operator at office D. The finder switch SBl of office B is set onto the terminals corresponding to those assumed by the junction switch J SB, that is to say, onthe calling line S2 and the finder switch S132 is set on to the terminals corresponding to those assumed by the line selector RSB, that isto say, on the line J LC leading to office C. The junction switch JSC is set on to the terminals of those assumed by the line selector RSC, that is to say on the wanted line S5. The operator then transmits ringing current to S5 via the registers RA, RB and RC. When the subscriber S5 responds the registerRC releases and the junction circuit J C is connected to the switchJSC instead of to the register RC whereupon a connection is established via the link LB and the junction circuit J C and a signal is transmitted to the operator. The operator removes her set-up plug whereupon the registers RA and RB re lease and when she removes the regular plug the junction circuits JA and J B release.

In the case of a: connection being extended from subscriber S1 in office D to the subscriber S4 in ofiiceBB, on the call arriving in front of the operator she inserts both plugs in thejacks of a-disengaged junction JLA leading to office A whereupon the junction circuit J A is connected to the register RA. The operator dials into the register RA a digit corresponding to the group of tandem junctions JLBB. The line selector RSA of the register RA hunts for a free jui'iction in this group and the junction circuit JBB is connected-to the register RBB. The operator dials through the register RA into the register RBB the wanted subscribers number whereupon the line selector RSBB of the register BBB is set on to the wanted line S4'which is tested and a. signal is transmitted to the operator. The junction switch JSA is set on to terminals corresponding to those as sumed by the line selector RSA that is to say, on the line JLBB while the junction. switch 'JSBB is set on to terminals corre sponding to those'assumed by the line selector RSBB, that is to say on to the wanted line S4. The operator then rings the wanted line S4 via'the registers RA and RBB. hen the called subscriber S4 responds the register BBB is released and the junction circuit JBB is connected to the junction switch JSBB. When the operator removes the set-up plug register RA is released and the junction circuit J A is connected to the switch J SA and a through connection is thus established.

Referring now to the circuits shown in Figs. 1 9, in order adequately to describe the operation of the system in the establishment of the various kinds of local calls, that is, calls between subscribers within the rural network, it will be convenient to consider operations involving the 4 rural offices diagrammatically shown in Fig. 12. These consist of an office A directly accessible to an n" an manual office D and'therefore having no effice code; twooffices Bl and B2, connected to A by groups of tandem junctions, and having the office codes 3 and 4 respectively; andan office C, connected by a group of tandem junctions to B1 and aving the oflice code 34. Since both offices A and B1 are bothtandem offices, only one showing has been made andFigs. 5' to 8 are repeated in the layout of Figs. 13 to 17. There are two groups of tandem lines on A so that relays 733 and 734. which identify these groups. are equipped but relay 7 32 is unnecessary. There is one group only on B1 so that relay 734 is assumed to be equippedin dialing with that oflice and relays 732 and 7 33 are unnecessary. Since offices B2 and G are both non-tandem otlices, they may both be considered to be wired according to Figs. 1 to 4.

Call I The establishment of a call from subscrlber 361 at office B1 to an urban subscrlber will first be described.

This call involves oihces B1, A and D, a tandem junction between B1 and A and a main junction between A and D. For this call Figs. 5 to 11 will be arranged as shown in Fig. 18. To originate a call the subscriber turns his hand generator 1001 and then removes the receiver from the switchhook. The generator 1001 isconnected across the line and the A. C. current operates the subscribers line relay 1002 at exchange B1. Relay 1002 locks through its middle and right winding, over its two contacts and conductor 504 in series with the common start relay 815 in the register (Figs. 7 and .8) which also operates. Battery potential from relay 815 is connected to conductor 503 and terminals such as terminal 604 individual to this line in the banks of all the junction finders in order to identify it. At the contact of relay 815, relay 802 being assumed normal, ground is connected to the start chain, and operates relay 619 in the first disengaged junction (Fig. 6). If a junction is busy or otherwise out of service, the start chain is extended over conductor 626 to the next junction via key 625, or contact 11 of relay 611, or contact 6 of relay 608, or contact 5 of relay 602. On operating relay 619 locks independently of contact 7 of relay 608 at con- 46 tact 4 of relay 619. Relay 619 closes a circuit for the magnet 624 of the junction switch 610, via its own interrupter contacts, at contact 1 of relay 619, and also a testing circuit through the lower winding of relay 608 at contact 2 of relay 619. The junction switch begins to hunt and when the calling line is found, relay 608 operates to the battery identifying the calling line on terminal 604. Relay 608 opens the drive at its 8th contact, locks over its third contact to ground at con- 8 of relay 620, and connects ground to the test wiper at its fifth contact, short circuiting relay 1002. Relay 608 extends the start chain to the next junction at its 6th contact and connects battery through the winding of relay 601 to the negative leg of the junction at its 4th contact. Relay 102 releases and opens the circuit of relay 815, which also releases, followed by relay 619.

At the office B1 we have, therefore, the following conditions :The wipers of the junction switch 610 are resting on the terminals of the calling line. Relay 608 is operated and locked, independently of any action on the part of the subscriber, to ground at contact 8 of relay 620 which is a back contact. The calling line is rendered busy to a testing selector by the ground connected to terminal 604 at contact 5 of relay 608. Battery is connected to the negative leg of the junction to extend the call to oflice A, and relays 617 and 618 are waiting in readiness to accept a battery from office A over the positive leg.

The junction appears at A as tandem line 1100, and relay 1102 operates to the battery on the negative leg. Relay 601 at ofhce B1 does not operate in this circuit owing to the high resistance of relay 1102. At contact 1 of relay 1102 a circuit is closed for relay 815 in the register at this ofiice. At contact 4 of relay 1102 battery is removed from the test wire 509 leading to the line selector 700 causing the line to test busy, and connected to the terminal 604 of this line to identify it. Relay 815 closes a circuit for relay 619 in the first disengaged junction as before, and relay 619 drives the junction switch 610 and closes a test circuit. When the calling tandem line is found, relay 608 operates, locks to ground at contact 3 of: relay 619, trips the switch, extends the start chain, connects'battery to the negative leg, and grounds the terminal 604, operating relay 1101. Relay 1101 locks over its 4th contact independently of relay 1102, to this ground, and disconnects relay 1102 from the line at its first contact. Relay 1102 releases, followed by relays 815 and 619. Relays 1102 and 619 are slow to release due to slugs. During the releasing time of relay 1102 ground is connected to the conductor 505 of the tandem line over contact 2 of relay 1102 and contact 2 of relay 1101, and until relay 619 has released, relay 620 is connected to terminal 605 over contact 5 of relay 619. Relay 620, therefore, operates during this fleeting condition and locks over contact 9 of relay 608 to ground at its second contact. Relay 603 then operates to this ground via contact 2 of relay 602 and contact 2 of relay 608. With relays 603 and 620 both operated, relay 608 locks independently of relay 619 to ground at contact 7 of relay 620.

At oifice A we have, therefore, the follow ing conditions :The wipers of the junction switch 610 are resting on the terminals of the calling tandem line which, in turn, has the wipers of its own switch at office B1 resting on the terminals of the calling subscribers line. Relay 608 is operated and locked to ground at contact 7 of relay 620. Relay 1101 is operated to ground at contact 5 of relay 608 which also busies the tandem line. Relays 620 and 603 are operated to ground at contact 2 of relay 620. Battery is connected to the negative leg of the junction through relay 601 to signal the call at the urban oiiice D.

At ofiice D relay 900 operates to the battery on the negative leg and closes a circuit for the calling lamp 901 at its second contact. 601 at .A does not, however, .operateowing to the high resistance of relay 900. To answer the call, the operator inserts a plug of one. of her regular cords inthe talk jackt902'and.

negative leg andrelay 900 releases. Relay,

617 operates relay602 which removes thecalling battery from. the negative legatits 8th contact, connecting the negative. leg OVGI 'ItS 7th contact also to the winding ofrelay 6:17

in order to balance the bridge and .reoperate extended to the tandem line. Relayz'603releases, but relay 608 is now held :byground at the4th contact ofrrelay 602..

positiveleg at contact 1 of relay 602 and opcrates relay 617 (but not relay618) at oflice As at A, relay 617at. B1 operates relay' 602, which removes battery from the negative leg of the junction, balances the bridge. and also holds relay 608. the talking connection from the: operator 'to the calling subscriber.

We now have the. following 'conditionsae \Veak battery connected at Dto. the'positive. legholds relay 617 at Awhich, in :turn, holds.

relay 602, which holds relay .608. Weak bat tery via the first contact is thus held under'the control of the operator;

If the receiver is stillon the switchhookat the sub-station, ground is connectedLtoltheJ negative leg through the sub-station ringer;

This ground operates relay 603 at B1; AtlltS: 5th contact (relay 620 being normal at B1). relay 603 removes ground from .the negative; leg of the tandem junction, and relay-.603 'atAi cannot operate. At A with relay 603 normal and relay 620 operated, ground is'kept'h-om;

the negative leg of the maln junction, .and-relay 900 at D is normal, lighting the supervisory lamp 901 at contact 10f relay 900. If.

on the other hand, the receiver is oil the resti.

relay 603 at B is normal, relay603 at A1 is operated, relay 900 at D is operated andzthe supervisory lamp is out. Positive supervise ion between the subscriber and the operator.

is, therefore provided.

Should the subscriber notremove hisxre. the operator; can' ring ceiver immediately, him. To do this, the revert-plug ofathe special operating cord 905 is insertedainthe opcrate jack 906, and the ring keywisthrown. Ground is thereby connected itolthe sleeveof:

Relay.-

third .contacts of: relay 602 the negative and positivelegs-are Weak battery through retard cord 616 is connected to the.

Relay 602 at B1 extends of relay; 602..atA l holds relay 617 at B1, which, in turn, holds ielay 602, which holds relay 608. The train:

the'plug, and relay .907 operates-, disconnect= ing the main junction from coil 904and relay- 900, and connecting-it to the: tip and ring-of the special cord.. The tip is connecte to strong battery, which holds-relay 617"at-A and in addition: operates-relay6l8. Atithesecondicontact offrelay 618 (relay 620 being operated) strong batteryis connected to the positive leg ofthe tandem junction, and this holds-relay6'17 at B1 and operatesrelay618; Contact 9- of relay 620 prevents a discontinuity. While relay 618 is changing over. At oflice B1 (relay 620 being unoperated) relay:- 618 joins the positiveand negative legs of the, subscribers line at contact 2.

Returning to A, relay 618 disconnects'relay 603fro1n the negative leg ofthe tandem line at contact 4. Ground through

relays

617 and 601 isalready disconnected at contact 4 of relay 603' (relay 620 being operated): from the negative leg of the main junction. l/Vehave, therefore, a directconnection, withoutnany branches, between the ring of the plug at D-and the negativeleg ofthe tandem junction. 'At-Bl, relay=6l8 disconnects relay 603 from the negative leg of the sub-=- scriber s line at its-4th contact, but relay 603- remains operated to ground at 5 contact 1- of relay 620. Relay 603 does not releaseduring the change-over owing to the damping-:efi'ect of theshunt over its third contact; Ground throughrela'ys 617 and601'is' al readyremoved from the negative leg aticontact 5 of'relay 603'(relay 620 being-unoperated) Herealso we have a direct connec tion without any branches, between the-negative leg 'of 'the tandem junction and the negative leg of the: subscribers line, but inthis case, the positive leg of the subscribers-line is also connected. is thrown, grounded ringing current is 'connectedto the ring of therevert plug; and

this current has a releases, followed By throwingtheespeak key in her regular cord 908, the operator. canconverse with: the. calling subscriber andwill complete his.

urban callin the usual manner.-

Atthe end. of the call, theoperator re-- ceives apositive clear signal, asalreadyex? plained. On the withdrawal of the plug, re lay-.903 at D releases, removing battery'.'from=. the: positive leg and ireleasing relays 6'17, 602,1

When the ring key at D- 7 direct path to ground. through the bell of the subset, which may be:

When the ring key is 608, 1101 and 620 at A and'relays 617, 602, 608 and 603 at B.

It should be noticed that if the operator withdraws the plug before the subscriber has replaced his receiver, the connection at A and B1 is not broken down for, at A, relay 608 is held via contact 2 of relay 603 and contact 7 of relay 620, both of which are operated independently of relay 602 and at B1, relay 608 is held over contact 1 of relay 603 and contact 8 of relay 620, both being unoperated On the release of relay 903 at D with relay 900 still operated, the, calling lamp again glows, informing the operator of her mistake. Thus it will be seen that the connection is normally held until the subscriber has replaced his receiver and the operator has withdrawn the plug in that order.

Should, however, the rural subscriber not replace his receiver within a reasonable time after the urban subscriber has cleared, the operator can forcibly release the connection. To do this, she removes the regular plug, inserts the release plug of the operating cord in the operate jack 906, and throws the release key. Ground is connected to the sleeve and operates relay 907, which disconnects the main j unctionvfrom coil 904: and relay 900 and connects it to the tip and ring of the cord. The tip is connected to strong battery which operates relay 617 erates relay 618. At contact 2 of relay 618 (relay 620 being operated), strong battery is connected to the positive leg of the tandem junction and this operates both relay 617 and relay 618 at B1. Relay 618 at A disconnects relay 603 from the negative leg of the tandem junction at contact 4 and relay 603 releases. At Bl relay 618 disconnects relay .603 from the negative leg of the subscribers line at contact 4, connects it to ground at contact 1 of relay 620, and relay 603 operates. At

A and B1 relay 608 is now holding to ground.

at contact 4 of relay 602, the alternative holding circuit'over contacts of relays 603 and 620 being open at both ofl ices. The operator then restores the release key and relay 907 releases,'removin battery from the positive leg of the main junction; relays 617 and 618 at'A release. Relay 617 releases relay 602, which releases relay 608, which releases relay 620. Either relay 602 or relay 618 removes battery from the positive leg of the tandem junction, releasing

relays

617 and 618 at B1. Relay 617 releases relay 602 which releases relay 608, relay 602 or relay 618 releases relay 603. Relay 603 at B1 is suflicient- 1y slow to release, due to the shunt over its third contact, to allow relay 608 to release before reclosing its alternative locking circuit. lVhen relay 603 at B1 has restored, a circuit is closed for relay 603 at A. Similarly relay 603 at A is sufficiently slow to operate to allow relay 608 to release before its alternative locking circuit is closed. The connec at A and in addition op tion at both ofiices has thus been forcibly released. Although the subscriber has not yet replaced his receiver, another call isnot originated, since his line relay at B1 requires generator current to operate it.

Gall II The establishment of a call from subscriber 361v to subscriber 352 at the same oflice Willnow be described.

' This call involves oflice B1 only, in the final connection, and after the establishment of this call the operator at D will releasethe junction between'D and A and between A and B1 which have been used. Figs. 5 to 11 will be used as shown in Fig. 1 1.

Subscriber 361 originates the call as already described by turning his generator and lifting his receiver. soon as junctions are available, via B1 and A to D and the calling lamp lights before the operator. 7

, The operator inserts the plug of one of her regular cords in the junction talk jack 902 and receives the subscribers requirements. The call is for subscriber 352, that is, for a subscriber within the same rural network, and is therefore established by the operator by means of her special operating cord.

The operator inserts the set-up plug of this cord in the operate jack 906 of the junctionover which the call has arrived. Ground on the sleeve operates relay 907 which at contact 6 disconnects the calling lamp 901 and lights a guard lamp 909. At contacts 1 and 4. the positive and negative legs of the junctionare disconnected fram the talk jack 902 and coil 904 and relay 900 and at contacts 2 and 3 are connected instead to the tip and ring of the operate'jack and thence to the operating cord. The tip of this cord is connected to weak battery which is kept on the positive leg and holds relay 617 at A operated. The ring of this cord is connected to strong battery which causes relay 601 at A to operate. At contact 2 of relay 601 a circuit is closed for the impulse accepting relay 701 in the register (Fig. 7) providing the register switch is in its home position. the register is oil normal, due to theoperator reinserting the plug immediately after releasing a previous call, relay 701 will not operate and a supervisory signal will be given to the operator. This delay in the operation of relay 7 01 will not normally occur'and will in any case be of short duration unless the register is out of order. Relay 701 operates and closes a circuit for relay 802 at its second contact. At contact 3 of relay 802 ground is removed from the contact of relay 815 so that no junction finder can operate while the register is in the use, and ground is connected over contact 1 of relay 601 in thejunction taken into use to relay 611, which operates. Relay 611 looks The call proceeds as.

at its 13th contact independently of relay 601. At the 7th and 8th contacts of relay 611 the holding circuit of relay 608 is transferred from relay 602 to relay 706. At contacts 3 and 4 of relay 611 the negative leg of the junction is disconnected from relay 601, which releases, and is connected to relay 7 01, which now holds over this circuit independently of relay 601. At contact 1 of relay 611, the positive leg is disconnected from relay 617 which releases, followed .by relay 602. Relay 602 at contact 1 disconnects the battery which is holding relay 617 at B1 and relay 617 releases, followed by relay 602 at B1, but the junction circuit is not released because relay 617 has restored before the subscriber has hung up, as already explained. At contact 1 of relay 802 at A, an alternative ground is provided for relay 701 so that relay 701 will not release when the selector leaves its home position. The positive leg is now disconnected, so that the supervisory lamp goes out.

lVe now have the following conditions At B1, relay 608 is looked over its third contact, contact 8 of rela I 611, contact 1 of relay 603 and contact 8 o relay 620. The junction is busied by contact 6 of relay608. The

calling subscribers line is busied by contact 5 of relay 608. At A, relay 608 is locked over contact 3 of relay 608, contact 7 of relay 611, contact 3 of relay 706. The calling tandem line is busied, and relay 1101 is held, by contact 5 of relay 608. The junction is busied by contact 11 of relay 611'.

Relay 620 is held by contact 9 of relay 608. The operator is no longer connected to the calling party. Since she is now concerned in establishing connection with the called party and. is using the same junction, this is a desirable condition. The supervisory lamp and calling lamp are both out, but the guard lamp warns the operator that a register is being held. Battery over the dial springs in the cord holds relay 701 which holds relay 802, which holds relay 611.

The operator then proceeds to dial the digits of the wanted number. Relay 701 responds to the impulses of the first digit, and at each break closes a circuit for

relays

822 and 703 over contact 3 of relay 701, contact 5 of relay 802, contact 8 of relay 725, contact 1 of relay 710, contact 1 of relay 805 and contact 4 of relay 701. Relay 822 repeats the im ulscs to the drivin magnet 702 of .the selector. Relay 7 03 being slow-to-release remains operated until the end of the digit and-operates relay 827 at contact 1.

If one of the digits 1, 2, 8, 9 or O has been dialed in error, no connection can result. (It is assumed that relay 732 is not equipped and that contact 2- of relay 814 is connected to terminal 72). If 2 has been dialed, the selector 700 is resting on the terminals of line 72 and when relay 7 03 releases a circuit is. closed for relay 805 over contact 2 of relay 703, contact 13 of relay 724, wiper 716, contact of relay 814, contact 2 and lower winding of relay 805, contact 8 of relay 706, contact 4 of relay 802. If 1, 8, 9 or 0 has been dialed, a circuit for relay 822 is closed at contact 3 of relay 827 as soon as relay 827 releases and the selector drives until line 72 or 61 has been reached, when relay 805 operates in a similar circuit. Relay 805 locks out in either case over its third contact and opens the drive at its first contact. The opening 01 contact 1 of relay 805 also renders further dialing ineffective. Relay 805 closes'a circuit for relay 712 over contact 4 of relay 805, contact 7 of relay 8.09, winding of relay 701, and contact of relay 712, and as relay 712 interrupts its own circuit a tone is produced. This is induced into the line winding of relay 701 and transmitted over the junction to the operator, who then removes the set-up plug. Strong battery is disconnected from the neg; ative leg and on the release of relay 907', weak battery is replaced on both legs. Relay 701a't A releases, followed after'an interval by relay 802, which in turn releases relay 805 and relay 611 and closes a homing circuit or the selectorv 700, controlled by relay 822, over wiper 7'15, interrupter con tact of magnet 702, contact 6 of relay 802, contact 8 of relay 7 25, contact 1 of relay 710, and contact 1 of relay 805. Relay 703 also operates over contact 4 of relay 701, operates relay 827 and relay 827 prevents any other finder from stepping at its 6th contact. Then the selector 700 is again in its home position the register has been completely re leased. The operator will then reinsert the set up plug and dial the number again.

Assuming that 3 has been correctly dialed, the selector has now taken 3 steps and its wipers are standing on the terminals of line 73. At'the end of the digit, when relay 703 releases, a circuit is closed for relay 733 over contact 2 of relay 703, contact 13 of relay 724, wiper 716, contact 7 of relay 724, upper winding of relay 733, contact 6- of relay 814, and contact 4 of relay 802. Relay 733 locks over its second contact and operates relay 724 at its third contact. At its 4th contact, relay 708 is connected to the terminals of brush 716 belonging to the tandem lines in the 3 group that is, with typical wiring as shown, lines 54, and 56'. Relay 724 operates relay 731 over contact 6 of relay 7 24, contact 7 of relay 726 and contact 7 of relay 7 08, and relay 731 at its 2nd contact connects the steer wires of all the tandem lines to contacts of relays 733 or 734.- Relay 733 only is operated and at its first contact extends the steer wires of the lines in the3 group to the lower winding of relay 726. Over contact 6 of relay 7 24, contact 1 of relay 731 and contact 6 ofrelay 611, battery is connected to terminal 605 and wire 505 of the calling tandem line, which is in the3 group since the calling subscribers number is 361, and this battery is extended over conductor 506 contact 2 of relay 731, contact 1 of relay 733, Winding of relay 726, contact 9 of relay 611, contact 3 of relay 608, contact 7 of relay 611, to ground at contact 3 of relay 706, so that relay 726 operates. Relay 726 looks at its first contact, disconnects relay 731 at its 7th contact and relay 731 releases. hen relay 703 has restored, relay 827 releases. Relay 724 also closes a driving circuit for the selector 700 controlled by relay 822 over wiper 715, interrupter contact of magnet 702, contact 4 of relay 724, contact 10 of relay 708, contact 1 of relay 710, and contact 1 of relay 805. The selector is now searching for the calling tandem line and when this has been reached a circuit is closed for the tripping relay 7 08 over contact 4 of relay 802, lower winding and 4th contact of relay 708, contact 4 of relay 733, wiper 716 and its associated contact, contact 12 of relay 724, contact 2 of relay 726, wiper 705 of selector 700, steer wire 506, terminal 605 and its associated wiper of finder 610, contact 6 of relay 6'11,

contact 7 of relay 726 and contact 6 of relay 724. At its 7th, 14th, 8th and 3rd contacts relay 724 disconnects relays 733, 734, 708 and 813 and 814 respectively, from terminals over which wiper 716 passes during this search. Relay 708 opens the drive at its 10th contact and 7 looks out at its 5th contact. It also closes a circuit for relay 725 over contact 5 of relay 805, contact 3 of relay 7 08, contact 9 of relay 724. and contact 5 of relay 717, and for relay 804 over contact 6 of relay 725. Relay 725 holds over contact 6 of relay 726. At contact 7 of relay 725 ground is placed on wiper 704 to hold relay 1101 of the calling tandem line1100. Over contact 2 of relay 804, contact 5 and 2 of relay 725 weak battery is connected to the positive leg of the tandem line through the non-inductive winding of relay 823 and operates relay 617 at B1. Relay 617 operates relay 602 which connects relay 617 and ground also to the negative leg at its 7th contact. Over contact 9 of relay 725, contact 2 of relay 809 and contact 1 of relay 7 01, strong battery is connected to the negative leg and this operates relay 601 at B1 and associates the register with the tandem junction in precisely the same manner as the register at A was associated with the main junction. Relay 725 operates slowly thus giving relay 804 a soak before it opens its circuit at its 6th contact. Relay 801 is slow to release and keeps the operative windings of relay 823 off the positive leg at its first contact until relay 611 has operated at B1. On

the release of relay 804, relay 823 is connected to the positive leg and awaits a ground signal from B1.

- The operator then dials the second digit 5. 7 Relay 701 at A responds but does not step the register because the energizing circuit of relay 822 is open at the 8th contact of relay 725, nor does relay 703 operate. The im- I pulses are repeated to B1 over contact 1 of relay 7 01, which is shunted by a spark quench consisting of a 2 mt. condenser in series with 100w, by opening the circuit in which relay 7 01 is holding at B1. Relay 7 01 responds and steps the selector at this exchange. Relays 703 and 827 operate during the train of impulses. The selector has now taken 5 steps and is resting on the terminals of line 75. WVhen relay 827 releases a circuit is closed for relay 7 08 over contact 2 of relay 7 03, contact 13 of relay 724, wiper 716, contact 8 of relay 724, contact 5 of relay 827, contact 4 and the lower winding of relay 7 08, and contact 4 of relay 802, and relay 708 operates and locks over its 5th contact. At contact 10 of relay 7 08 the drive circuit for the selector 700 is kept open so that the selector remains on the terminals of line 75, that is, at the beginning of the 50s group. At contact 1 of relay 708 a circuit is closed for relay 816 over contact 9 of relay 816, contact 1 of relay 708, contact 8 of relay 726, contact 2 of relay 717, contact 9 of relay 611, contact 3 of relay 608, contact 7 of relay 611, contact 3 of relay 706. Relay 16 operates and locks over its 10th contact.

At contact 13 of relay 816 a test is made to determine whether there is at B1 a disengaged link. If the first choice link (Fig. 5) is engaged or out of service, the chain is closed over contact 3 of relay 508 or key 510, and relay 807 receives a circuit over contact 4 of relay 802, contact 8 of relay 706, contact 13 of relay 816, contact 3 of relay 508 or key 510, and contact 2 of relay 807. Relay 807 operates, locks out over its first contact and at its remaining arinatures changes over to the second choice link. If this also is engaged, the chain is further extended over the contact of relay 508 or key 510 of the second link to relay 805 and this relay operates, locking out over its 3rd contact. Belay 805 closes a toneproducing circuit at its 4th contact and the operator is informed either that she has dialed incorrectly or that there is no link available. and she will release the registers by removing the set-up plu If she is satisfied that the number has so far been correctly dialed, she will inform the calling party, who has been reconnected toher by the operation of relay 617, and relay 602 at A and B1, that there is no outlet available. Otherwise, she will dial again.

If the operator hears no tone at this stage, she dials the third digit 2. Relay 701 at A responds and repeats the impulses to relay 701 at B1 and the latter steps the selector. Relays 703 and 827 at B1 are energized during the train of impulses Relay 827 closes a circuit for relay 804 over contact 2 of relay .out over its and contact 5 of relay 805.

transmitted to the operator.

827, contact 10 of relay 724, contact 3 of re lay 708 and contact 5 of relay 805.

It Will be observed that with typical Wiring as shown (and relay 732 not equipped), 51, 52 and 53 are the only lines available in the 's, and accordi y contact 8 of relay 708 W1 oe connected to the terninal of line 54. If 54 or alcove been di'aled in error, relay 805 operates, as soon as line 54 is over 00.: 3t 9 of relay 708, contact a P er 7 16, contact 8 of relay 708, on -0 t 5 of relay 724, Contact 2 and. Winding of relay 805, contact 8 o and contact 4 of? relay 80 reached.

I tops the selector and renders ctr 1 first contact and closes a tone pronuc cuit at its 4th conta t. Tone at corrolease the registers and dial ana ASSllII'llHgr that 2 has been correctly dialed, at the end of the digit the Wipers are resting on the terminals of line 52, that is, of the Wanted line, and relays 703, 827 and 804 release in turn. During the rel .ing period of relay 804 a circuit is closed for relay 811 over contact 4 of relay 804, contact 1 of relay 827, contact 10 of relay 724, contact 3 of relay 708, Relay 811 operates relay 710 over contact 4 of relay 811 and contact 4 of relay 802. At contact 1 of relay 710 the stepping circuit for the selector is opened so that subsequent dialing is ineffective. At contact 7 of relay 710 ground is connccted through the Winding of relay 809 to the positive leg of the tandem junction, operating relay 823 at A. Relay 823 operates relay 710. Relay 710 operates relay 706 over 1 its 5th contact and contact 7 of relay 811 and relay 7 06 locks over its 7th contact; also relay 710 connects ground through the Winding of relay 809 to the positive leg of the main unction and this operates a relay in the setup cord at D, lighting the supervisory lamp to inform the operator that dialing and testing of the Wanted line are complete. hen relay 804 releases, relay 811 is connected over contact 5 of relay 804, contact 2 of relay 708 and contact 6 of relay 811 to brush 704.

If the wanted line is busy, there is ground on the test terminal from the associated link or iunction and relay 811 remains operated.

1 Relay 811 closes a tone producing circuit over she can offer the call. To do this she connects low resistance battery direct to the tip, and the strong battery operates relay 809 at A. At contact 5 of relay 809, relay 701 is removed from the negative leg and is connected to a holding battery. The tone circuit is opened the 7th contact of relay 809. At contact 8 of relay 809 the low resistance Winding cl? relay 823 is connected to the positive leg of the tandem'junction and operates relay 809 at B1. Relay 809 at B1 removes relay 01 from the negative leg as at A, and at contacts 1 and 3 connects the tandem junction to b e Wanted line. The operator can then offer the call to the Wanted subscriber and, should he accept, Will instruct him to replace his receiver. She Will then restore the key, releasing relay 809 at both exchanges, and Will again hear tone. When the Wanted subscriber hangs up, his existing connection is broken down and ground is removed from his test terminal and his line is now free.

It the Wanted line is free, relay 811 is deprived of its circuit and releases, disconnec ing the tone at its 5th contact and connecting relay 710 over contact 3 of relay 8.11, contact 2 of the relay 710, and contact 7 of relay 717' to ground at contact 4 of relay 802. Relay 703 then operates over contact5 of relay 710 and contact 7 of relay 811 and looks over its 7th contact. Relay 706 opens the circuit of relay 608 at its third contact but relay 608 is held to ground at contact 6 of relay 710. Over contact 2 of relay 816, contact 9 of re lay 706, and contact 6 of relay 611, and the Wiper of the junction finder, groundis connected to terminal 605 and Wire 505 of'the calling line. Over contact 6 of relay 818, contact 6 of relay 816, contact 6 of relay 706 and contact 8 of relay 807, relay 818 is connected to Wiper 523 of finder 520. Over contact 4 of relay 706, contact 4 of relay 7126, contact 9 of relay 717, contact 11 of relay 816, contact 1 of relay 818 and contact 4 ofrelay 807 a driving circuit is closed for magnet 525 of finder 520. V] hen its Wipers are resting on the terminals of the calling line, relay 818 operates and opens the drive at its first contact, closing also a driving circuit for magnet 535 of finder 530 over its second contact and contact 6 of relay 807. Over contact 5 of relay 706 and Wiper 705 of the selector 700, battery is connected to the steer Wire 506 of the called line. Over contact 4 of relay 717, contact 3 of relay 818, contact 10 of relay 807, relay 717 is connected to Wiper of finder 530 and When the Wipers of this finder are resting on the terminals of the called line, relay 717 operates. Relay 7 17 opens the drive at its 9th contact, locks at its 3rd contact and connects relay 710 to the negative leg of the called line over contact 3 of relay 811, contact 2 of relay 710, contact 6 of relay 717, contact 10 of relay 725, and contact 2 of relay 809. Relay 710 remains held to ground at the subset.