US2021291A

US2021291A - Telephone system

Info

Publication number: US2021291A
Application number: US729772A
Authority: US
Inventors: Edgar H Clark; Frederick J Scudder
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1934-06-09
Filing date: 1934-06-09
Publication date: 1935-11-19
Anticipated expiration: 1952-11-19

Description

Nov. 19, 1935. E CLARK r AL 2,021,291

TELEPHONE SYSTEM Filed June 9, 1954 v Sheets-Shet 1 25 MA/PG/NAL FIGS F/G6 E hf CLARK INVENTORS. EJ. SCUDDER AT TORNEV Nov. 19, 1935. V E. H. CLARK ET AL 2,021,291

' TELEPHONE SYSTEM Filed June 9, 1934 '7 Sheets-Sheet 2 FIG. 2

EH cum/ WVENTOPS' F.J. scuoam ATTORNEY Nov. 19, 1935. E. H. CLARK ET AL TELEPHONE SYSTEM Filed June 9, 1934 7 Sheets-Sheet 5 mNm Il m o lllluj aoll. I'I q O- Qmd Qvm

EH cut/Pk INVENTOPS F. J.SCUDD/? ATTORNE NOV. 19, 1935. E H (:LARK AL I 2,021,291

TELEPHONE SYSTEM Filed June 9, 1934 7 Sheets-Sheet 4 ,5 H CLA RA WVENTORS E J 517/005 ATTORNEY Nov. 19, 1935, E H, CLARK ET AL 2,021,291

TELEPHONE SYSTEM Filed June 9, 1934 '7 Sheets-Sheet 5 mmm mmm m E. H. CLARK INVENTOPS- E SCUDDER ATTORNEY av. 19, 1935. E, H. CLARK ET AL TELEPHONE SYSTEM Filed June 9, 1954 7 Sheets-Sheet 6 E. H CLA PA R- EJ scuoom ATTORNEY 19, 1935. E. H. CLARK ET AL TELEPHONE SYSTEM Filed June 9, 1954 '7 Sheets-Sheet '7 EHCLA/PK ATTORNEY Patented Nov. 19, 1935 UNITED STATES PATENT OFFIQE TELEPHONE SYSTEM Edgar H. Clark, Forest Hills, and Frederick J. Scudder, Queens Village, N. Y., assignors to Bell Telephone Laboratories,

Incorporated, New

12 Claims.

This application relates to telephone systems and more particularly to telephone systems in which the establishment of connections involves more than one operator. 7

More specifically, the invention relates to an improvement on the operator's equipment disclosed in- Patent No. 1,753,348 granted to J. B. Newsom, April 8, 1930. The equipment of that patent is arranged for use Where the operators equipment and the automatic switches controlled thereby are located in the same office. Small offices in a territory serving a metropolitan area may very conveniently be served by dial equipment but the presence of one or two operators is usually necessary to assist in the completion of calls. That small groups of operators are uneconomical is well known and the circuits forming the subject matter of the present invention have been designed to permit the grouping of operators to control the completion of calls from manual to dial offices in one central office at which no switching takes place.

In the previous arrangement wherecontrol equipment was connected directly with-the incoming selector switch, the holding circuit for the switch is available throughout the establishment of the connection. In the present case, however, since the trunk conductors must be used in controlling the operation of the selector switches, the holding circuit can only be established after selections have been completed. A relay is therefore connected to the trunk at the selector switch following the completion of selections and the operation of this relay is necessary both to establish the talking condition and to permit the release of the connection. In the control equipment, therefore, means is provided to cause the preparation of a holding circuit by the trunk, but to reduce the interval before the completion of this holding circuit, a temporary holding circuit is provided in the control circuit which overlaps the closure of the holding circuit by the trunk circuit. Means is also provided to cause the closure of this temporaryholding circuit in case of trouble so that the selector may be released.

A clearer understanding of the invention will be obtained from a consideration of thefollow- 111g description in connection with the accompanying drawings in which:

Fig. 1 shows the relay equipment of a trunk circuit;

Figs/2 and 3 show the incoming selector in which the trunk of Fig. 1 terminates;

"Figs. 4 to 7 show the link circuit forconnecting the operatorsposition and sender with the trunk equipment; and

Fig. 8 shows the manner in which the remaining figures are to be arranged.

Equipment at four telephone offices is disclosed, 5 that is, equipment at a local oflice A, at a manual tandem office 0, a centralized office B and a terminating ofi'ice T. The centralized equipment at office B may be employed in the completion of calls, whichhave been extended from the call- 10 ing substation Illll to an operators position at the office O and by means of jack IGI, cord I92 and jack I93 to the trunk circuit at the centralized ofiice B. The establishment of a connection with the trunk circuit causes the link 15 circuit oiFigs. 4 to 7 to associate itself with the trunk and with a position circuit and a sender. The link circuit first connects the incoming end ofthe trunk with the position circuit so that the manual operator may give the wanted number 20 to the B operator. It then connects the position circuit with the sender to permit the registration of the number in the sender and finally connects the sender with the outgoing end of the trunk so that the sender may control the incoming se- 25 lector of Figs. 2 and 3 and the final selector 359 inthe selection of the wanted line 35b. The centralized equipment may also be usedfor the comence is made to the Dahl application for such details.

The subscriber at substation I98 inoriginating a call for a subscriber at substation 359 will'be 40 connected by jack IuI with the manual tandem A operators position having access through the 'centralized B ofiice with the office at 'which'substation 350 is located.

When the tandem operator inserts the calling 45 plug of her cord I92 in the jack I03 leading to the trunk circuit of Fig. 1, a circuit is closed from battery through the right winding of relay H9, inner left back contact of relay I IEI, upper left winding of repeating coil IM, over the tip con- 5 ductor of the incoming inter-ofiice trunk and through the repeating coil and supervisory relay (not shown) in the tandem operators cord, back over the ring conductor to the lower left winding of repeating-coil I0 1, right back contact of 5 relay II 8, to ground through the left winding of relay H8. Relay II9 closes a circuit for relay II4, from ground at the back contact of relay I 44. Relay II 4 connects ground over its front contact, upper normal contact of relay I06, outer left back contact of relay I2I, winding of relay I22 to battery at the right back contact of relay 425. Relay I22 locks over its inner upper front contact to its operating ground independent of relay I2I.

The operation of relay I22 initiates the association of the trunk circuit with the B operators equipment. It therefore connects ground over its outer upper contact and the inner left back contact of relay till to the start conductor I3I It also connects battery through resistance I34 over its middle lower front contact and the inner right back contact of relay I2! to conductor I32 which terminates in the test terminal of trunk finder 600. In addition, relay I22 closes a circuit from battery through the winding of relay I29 over the outer lower contact of relay I22, inner right back contact of relay I26 to conductor I33 which likewise terminates in the bank of finder 660.

The connection of ground to conductor I3l completes a circuit which extends over the normal contact of jack 5!", lower back contact of relay 505, lower back contact of relay 526 through the Winding of relay 5H6 to battery over the upper back contacts of relay 5I0. Relay 5I6 operates in this circuit, closing an obvious circuit for the trip magnet 64% of the trunk finder 600. It also closes a circuit from ground over its outer upper front contact, lower back contact of relay Slil, and thence over the lower contacts of cam 426 to the winding of relay H9 and battery to initiate the operation of the link circuit.

The start circuit of Fig. 5 closely resembles that disclosed in the above identified Newsom patent and serves to prevent interference between calls originating in close succession and acts in case of trouble to delay the handling of a call, to sound an alarm and automatically disable the group of link circuits on which the trouble occurred.

When relay 7 I9 is operated, it locks in a circuit from battery through its winding, over its inner left front contact, right contacts of cam 4I9, back contact of relay 424 to ground over commutator strip GI I and brush 6H]. Another holding circuit is also closed for relay H9 over the lower right and upper left contacts of cam 4I9 which extends to ground over the commutator strip 695 and brush 605 after the selector moves offnormal for the purpose of centering the brushes of the finder properly. With relay H9 operated, a circuit is closed from battery through the winding of sequence switch magnet 40!], lower right contact of cam 4G4, outer left front contact of relay II9, upper right and lower left contacts of cam M2 to ground, advancing sequence switch 400 from position I. With sequence switch 490 in position 2, a circuit is closed from battery through the winding of the updrive magnet 6I4, upper contacts of cam 4I2, outer left front contact of relay H9, over the lower right and upper left contacts of cam 408 to ground.

As the selector starts upward, ground is connected over brush 661 and commutator segment 608, left contacts of cam 4M to the winding of relay 5H] and battery. Relay 5Ill looks over its inner lower front contact, left back contact of relay 12! to ground over the upper left and lower right contacts of cam M5 and is therefore held operated until after the trunk has been found,

Relay 5H] in operating disconnects battery from the windings of relays 5I6 and 526, thereby rendering the start circuit unresponsive to calls over other trunks of this group. Calls over trunks of the groups served by relays 5I2 or 5I3 may be extended.

As the brushes of selector 600 move upward over the terminals leading to various trunk circuits, a test is made for the calling trunk which is marked by battery connected to conductor I32. When this is found, a circuit is completed from battery on conductor I32, brush 604, left back contact of relay IIO, through the winding of relay 424 to ground over the lower right contact of cam 407. Relay 424 in operating opens one holding circuit for relay H9 and that relay releases when the brushes are properly centered, as indicated by the position of brush 605 on commutator strip 5%. Relay H9 released, closes a circuit from battery, through the winding of sequence switch magnet 4%, upper left contact of cam 454, left back contact of relay H9 to ground over the lower right and upper left contacts of cam 45%, advancing sequence switch 400 to position 3. With sequence switch 400 in position 3 a circuit is closed from ground over the upper left contact of cam 409, right back contact of relay 123, winding of relay T22, over the inner right contact of relay II II to brush 603, conductor I33, right back contact of relay I28, outer lower contact of relay I22 to the winding of relay I20 and battery. Relays 1'22 and I2!) operate in this circuit.

The operation of relay I26 prepares the trunk circuit for the connection between the tandem:

right front contact of relay I20, left back contact of relay I26 to conductor I38 and brush 502.

Relay I20 also opens the circuit of supervisory relay H2 to prevent its premature operation, and furthermore closes an obvious circuit for relay I2! which prepares a locking circuit for itself from battery through its winding and the winding of relay I26, inner right front contact of relay 52!, to ground at either the front contact of relay I2! or the front contact of relay I23 depending upon which of these is operated, neither being operated at the present time. Relay !2I in oper ating, signalsthe link circuit that the operator's talking circuit has been established through the trunk circuit by transferring conductor I32 from battery through resistance I34, to ground through the winding of relay I21.

In the link circuit relay I22 which operates in series with relay I20 locks in a circuit from battery over conductor I33, brush 693, inner right back contact of relay H0, winding of relay 'I22,-

right back contact of relay I20, outer left front contact of relay I22 to ground over the upper right contact of cam 489. With sequence switch 4!!!! in position 3, conductor I32 is extended over brush 624, left back contact of relay H0, through 1 resistance 425 to ground at the lower right con tact of cam 42!! in parallel with the circuit previously traced through the winding of relay 424 to ground over the lower right contact of cam 401. Therefore, when relay IZI substitutes ground for battery on conductor I32, relay 424 releases quickly, closing a circuit from battery through the winding of relay H9, lower left and upper right contacts of cam 426, right contacts of cam M9, back contact of relay 424 to ground over commutator strip 5! l and brush 6W. Relay H9 looks over its inner left front contact, right contacts of cam M9, back contact of relay 424 to ground on commutator strip 6! I.

As soon as sequence switch we arrived at position 2, a circuit was closed from battery through the winding of relay M8, lower back contact of relay 64%, lower left contact of cam 469 to ground. Relay H8 in operating prepares the test circuit for the position finder by closing a circuit from battery through the middle winding of relay 54G, upper left and lower right contacts of cam Q93, lower winding of relay 54c, ieft front contact of relay H8, lower left contact of cam 309 to ground. At the same time a branch of this circuit is extended from ground through the lower winding of relay 548, as traced, and thence through the upper winding of relay 5 H! over the lower back contact of relay 635%, left back contact of relay 139, right back contact of relay 32!}, to brush 1c! of switch 580 which has access to the. operators positions. Relay 458 also causes the operation of the position finder tilt by closing a circuit from ground over the lower left contact of cam M32, outermost upper contact of relay 539, upper back contact of relay Bill, lower contact of jack I23, or the right back contact of relay T21, right front contact of relay M8, lower contacts of cam 485, back contact of stepping magnet "E if innerleft back contact of relay 5251, right back contact of relay 1 i l to the winding of relay 4i El battery. Relay are closes an operating circuit for magnet 761 which may be traced from battery through the winding of that magnet, over the right contacts of relay All] to the upper right contact of cam 485 and thence over the operating circuit for relay 4|!) to ground. Magnet it? opens the operating circuit for relay H8 which thereupon releases and in turn releases the magnet which advances position finder to the next position. On the release of magnet the circuit for relay illl is reclosed and the magnet and relay operate alternately until an idle position is found.

An idle operators position is indicated by the connection of battery through a resistance to conductor 14!. When the idle position is found, the battery connected over conductor Ml to the terminal of brush ltl operates relay 548 which opens the operating circuits of relay 4H] and magnet I01, bringing the position finder Hill to rest. Relay [343 looks in a circuit from battery on brush llll through its upper winding as previously traced and thence over its upper front contact and the upper normal contact of relay 639 to ground at the lower left contact of earn 492. The operation of relay M l opens the circuit of relay 4H3 which releases after an interval. When relay M8 closes its back contact, a circuit is completed from battery through the winding of relay Ill, outer left back contact of relay 129, right contacts of earn- 414, left back contact of relay 8, lower front contact of relay Mil to ground at the lower left contact of cam 4539. Rolay ll'l locks in a circuit'which extends through its winding over the left back contact of relay I29, outer left front contact of relay ill, over the lower contacts of cam M l, outer left front contact of relay 722 to ground at the upper right contact of cam 409. Relay 'H'l also closes a circuit from battery through the winding of relay H4, inner left front contact of relay 1 H, to ground over the upper right contact of cam 409. With relay H4 operated, a circuit is closed from battery through the winding of sequence switch magnet 400, lower right contact of cam Q94, outer left front contact of relay 'HQ, outer right front contact of relay H4 to ground over the upper contacts of cam 498 advancing sequence switch 460 to position 4.

.As soon as the sequence switch reaches position 3%, battery through resistance H3 is also connected to brush 694 over the left contacts of cam M4 and the left back contact of relay H0, and when sequence switch tilt leaves position 3, relay 424 is disconnected from brush 50 3, although ground through resistance 6'25 remains connected thereto. This potentiometer arrangement operates relay I27 and holds the terminal on which brush 634 is resting at such a potential that no other trunk selector will pick this trunk. Relay l2! completes the locking circuit for relays l2l and I26, previously traced. The advance of sequence switch 466 from position 3 also opens the locking circuit of relay 5! and permits the further extension of calls in this group.

With relay TM operated, the tip and ring brushes of the trunk finder are connected through to the tip and ring brushes of the position finder. The circuits may be traced from the tip brush 59 I, middle right back contact of relay l l6, left winding of relay H l, inner left front contact of re lay "H4 to brush H35 and from ring brush 662, outer right back contact of relay Ht, left contacts of cam M8, right front contact of relay 122,

resistance 5'53, outer left front contact of relay 'H l, right winding of relay H 5, middle eft contact of relay H4 to brush li ii. Condenser H2 is bridged across resistance i it and the contacts of cam 4H5.

In the operators position, tins circuit extends from brush 105 through the winding of a relay (not shown) to brush let. Since battery and ground are supplied to brushes to! and 6532, as previously described, a circuit is completed in which this relay operates but the windings of relay HI are differentially arranged so that it does not operate at this time. position circuit relay in operating establishes the order tone circuit from the trunk to the position, starts the generation of the tones and prepares the keyset for pulsing. Thereafter, battery is disconnected from brush 'Hll thereby releasing relay 6%.

The release of relay 6&6 closes a circui from battery through the winding of sequence switch magnet upper right and lower left contacts of cam 4&3, lower contact of jack 123, upper back contact of relay 6M, outer upper back contact of relay 639, to ground over the lower left contact of cam 6G2 advancing sequence switch to position 5. In this position, a circuit is closed from battery through the winding of relay ltd, upper right contact of cam on to 64d, left front contact of relay 558, outer right front contact of relay I30 to ground at the upper right contact of cam 406. A circuit also extends from ground through the lower winding of relay 36 as traced and from there through the upper winding of relay lower back contact of relay 63%, outer left front contact of relay 730 to brush 523 of the sender selector. An idle sender is characterized by the connection of battery through a resistance to conductor 653 and the terminal to which brush 523 has access. If the sender selector 6% is resting on the terminal of a busy sender when the circuits for relay 640 are closed, relay 5% will remain unoperated and a circuit will closed from battery through the left winding of relay H8, upper left and lower right contacts of cam right front contact of relay 4H3, lower contact of jack 123, upper back contact of relay can, upper back contact of relay 330 to ground at the lower left contact of cam Relay H8 is made slow-to-operate by its short-circuited right winding to prevent its operating prematurely when an idle sender is encountered. When relay H8 closes its right contact, a circuit closed from ground over that contact to the winding of relay M8 to hold that relay energized. A circuit is also closed from battery through the winding of updrive magnet 636 of the sender selector, outer left front contact of relay no, upper back contact of relay 639 to ground at the lower left contact of cam 6G2, causing the sender selector to move upward in search of an idle sender. Relay H8 is held operated over its inner left front contact to ground over commutator strip 628 and brush E2? to insure that the brushes will be centered.

When an idle sender is found, relay E540 operates and when the brushes of the sender selector are centered, relay H8 releases, in turn releasing the updrive magnet 53% and bringing the selector to rest. With relay H8 released and relay 640 operated, the circuit of relay H8 is opened and that relay releases after an interval. When relay 4&8 closes its back contact, a circuit is closed from battery through the winding of relay 54L inner left front contact of relay 130, left back contact of relay 4H3, lower front contact of relay E li outer right front contact of relay 130 to ground at the upper right contact of cam 406. Relay 64! looks over its inner lower front contact and the inner right front contact of relay I30, back contact of relay ll I5 to brush 622 which is connected over conductor 652 to ground in the sender. Relay E li closes a circuit from battery through the winding of sequence switch magnet 48%, outer upper front contact of relay MI to ground over the left contacts of cam 4%, advancing sequence switch 405? to position Ii. Relay fi il, in operating, closes a new holding circuit for relay H1 which extends as previously traced to the outer left contact of relay l I! and thence over the middle upper front contact of relay 5M, outer left front contact of relay I22, upper right contact of cam 435 to ground.

With sequence switch 40th in position 6, a circuit is closed from ground over the lower right Contact of cam 6% through resistance E38 to brush 625 to mark the sender busy. In the sender this circuit extends through the winding of a relay which, in operating, disconnects battery from the terminal of brush 623 thereby releasing relay fi lfl. It also closes an off-normal ground to provide locking circuits for the sender relays.

With both sender and position circuits connected to the link circuit, a circuit is established sender relays causes the operation of the transfer relays to prepare the sender for registration.

With the transfer relays operated, a signal is transmitted to the position to indicate that the sender is ready to receive the wanted number by closing a circuit from battery over the contacts of the transfer relays to conductor 65I, brush 62 I, lower front contact of relay 64I, inner right front contact of relay H4, brush I02, conductor I42 through the winding of a relay in the position.

This relay causes the removal of battery from conductors E43 and I44, releasing the sender relays and completing the preparation for registration after which battery is removed from conductor 65L scribed in detail in the Dahl application hereinbefore referred to.

At the completion of registration, ground is disconnected from conductor 652, opening the locking circuit of relay GM and releasing that relay. Conductors 554 and 655 are disconnected from the recording relays and are connected together thereby preparing the fundamental circuit for selections. At this time battery is also connected to the fundamental circuit in the sender.

The release of relay 64I opens the locking circuit for relay 1|! which also releases, in turn releasing relay H4. With relay 1 I4 released, the position circuit is restored to normal. With relay II1 released, the tip conductor ofthe fundamental circuit is opened at the inner right contact of that relay but the ring conductor is extended from conductor 655, brush 625, right back contact of relay H1, upper contacts of cam M6, outer right back contact of relay H0, brush 602 to conductor I38. Since relay I is still operated, a circuit is closed from ground over the next to inner right front contact of relay I20, lower right winding of repeating coil I04, outer right front contact of relay I20, outer left back contact of relay I26 to conductor I38, over the ring conductor of the fundamental circuit as above traced to conductor 655 and through the winding of a sender relay to battery. This relay causes the connection of ground over conductor 65I, brush 62L lower back contact of relay 64I, left contacts of cam 426, to the winding of relay H9 and battery. Relay H9, in operating, closes a circuit from battery through the winding of relay H5, inner left front contact of relay I22, middle right contact of relay 1 I9, lower left contact of cam 461 to ground. Relay H5 locks over its inner right front contact directly to this same ground and closes a circuit from ground over its outerright front contact, upper right contact of cam 404 to the winding of sequence switch magnet 400 and battery, advancing the sequence switch to position 1 from which position it is advanced to position 8 over its local cam. Relay H5 also connects battery through resistance H6 over the middle right contact of relay H5, upper right and lower left contacts of cam 43I, inner right back contact of relay Registration takes place as de- I H0, brush 603, conductor I33, inner right back contact of relay I26, outer lower contact of relay I22 to the winding of relay I 20 and battery. This releases relay I20, permitting relay I26 to operate in the locking circuit of relay I2I. The release of relay I20 disconnects battery and ground from the right windings of repeating coil I04,

opensthe talking conductors extending from the repeating coil to the link circuit and reconnects relay I12 to the right windings of repeating coil I04. The disconnection of ground from the repeating coil permits the closure of the fundamental circuit in the sender.

Relay I26, in operating, disconnects the incoming end of the trunk from the link circuit and connects the link circuit with the outgoing trunk, transferring conductor I31 from association with the repeating coil I04 into direct con nection with the tip conductor I4I of the outgoing trunk and conductor I38 from the connection with the repeating coil I04 into connection with the ring conductor I42 of the outgoing trunk through resistance I30. Relay I23 disconnects relay I20 from conductor I33 and connects that conductor to ground through the left winding of relay E25 and the winding of relay I23. Since battery is connected to conductor I33 through resistance I I6 over the circuit previously traced, relay I23 operates but relay I25 which is marginal does not. The operation of relay I23 closes a circuit from ground over the right contact of relay I23 to the locking circuit of relays I2% and I26 in parallel with the front contact of relay I21.

With relay I20 operated and sequence switch 400 in position 8, the fundamental circuit may be traced from battery through the winding of relay 3I5 of the incoming selector circuit, upper right contact of cam 221, upper left contact of cam 2I6, over the tip conductor I4I of the outgoing trunk, outer right front contact of relay 126, conductor I31, brush 60I, middle right back contact of relay 1 I0, inner right front contact of relay 1I5, lower contacts of cam 423, brush 020, conductor 654 through the polarized relay and stepping relay (not shown) of the sender, conductor 655, brush 625, right back contact of relay 1I1, upper contacts of cam 4I6, outer right back contact of relay 1I0, brush 602, conductor I38, outer left front contact of relay I20, resistance I30, over the ring conductor I42 extending between the two offices to ground Over the left contacts of cam 2|4 and resistance 229 at the incoming selector. Relay 3I5 operates in the fundamental circuit, closing a circuit from battery through the right winding of relay 304, lower right contact of cam 2I1, lower left contact of cam 2| I, front contact of relay 315, upper left contacts of cams 2I0 and H0, upper right contact of cam 222 to ground. Relay 304 looks in a circuit which may be traced over its operating circuit as far as the upper left contact of cam 2H! and thence over the lower left contact of cam 2I9, right front contact of relay 304 to ground over the lower left contact of earn 233. Relay 304, in operating, closes a circuit from battery through the winding of sequence switch magnet 200, upper left contact of cam 220, upper contact of cam 2I8, left front contact of relay 304, to ground over the lower right contact of cam .233 advancing sequence switch 200 to position 2. When sequence switch 200 reaches position 2, a circuit is closed from battery through the winding of updrive magnet 3| 9 over the lower contacts of cam 2l9, right front contact of relay 304 to ground over the lower left contact of cam 233, advancing the incoming selector in its brush selecting movement. As the selector moves upward a circuit is closed intermittently from ground over the lower right contact of cam 233, left front contact of relay 304, right contacts of cam 2 I3, brush 32 3, commutator strip 321, lower left contact of cam 22l to the fundamental circuit, holding relay 3 I 5 and shunting the stepping relay of the sender. When the sender is satisfied it opens the fundamental circuit causing relay 3I5 to release. A series of operations are performed by the sender as described in the above mentioned Dahl application after which the fundamental circuit is reestablished.

In the incoming selector, the release of relay 3 i 5 at the termination of brush selection also releases relay 304 which opens the circuit for the updrive magnet 3I9, bringing the selector to rest in position to trip the proper set of brushes. The release of relay 304 also closes a circuit from battery through the winding of sequence switch magnet 200 over the upper left contact of cam 224, right back contact of relay 304 to ground over the lower left contact of cam 233. When sequence switch 2 00 advances to position 3 and the fundamental circuit is reestablished in the sender, relay 3I5 again operates, in turn operating relay 304 over the circuit previously traced to the front contact of relay 3I5 thence over the lower right contacts of cams 220 and ZIB, the upper right contact of cam 222 to ground. In position 3 of sequence switch 200, the locking circuit of relay 304 extends as previously traced to the front contact of relay 3I5 and from thence over the lower right contact of cam 220, upper right contact of cam 2I0, left front contact of relay 304 to ground over the lower right contact of cam 233. Relay 304, in operating, advances sequence switch 200 to position 4 in a circuit over the upper right contact of cam 224, right front contact of relay 304 to ground at the lower left contact of cam 233. In position 4, the updrive magnet 319 is reenergized and the selector advances in a group selecting operation. When sequence switch 200 reached position 3, a circuit was closed for trip magnet 320 extending from battery through the winding of that magnet over the lower right contact of cam 222 to ground and this circuit is maintained through position 4 so that the proper brush set is tripped as the selector moves upward. For group selection, ground is connected to the commutator brushes over the front contact of relay 304 the same as for brush selection and ground is intermittently connected over brush 324, commutator strip 328, the lower right contact of cam 221 to the tip conductor in shunt of the winding of the stepping relay.

The stepping relay functions in the usual manner and when the condition set up on the counting relays by the registers is satisfied, the fundamental circuit is opened for a measured interval after which it is reclosed.

At the incoming selector, the opening of the fundamental circuit releases relay 3I5 which, in turn, releases relay 304. Relay 304 advances sequence switch 200 to position 5 in a circuit over the upper left contact of cam 224, right back contact of relay 304 to ground as previously traced. In position 5, a circuit is closed from battery through resistance 305, left winding of relay 304, back contact of relay 3I1, lower left contact of cam 2I0, upper left contact of cam 2I9, upper right contact of cam 222 to ground. Relay 304 idle final selector.

6 roman right contact of earn 224, right front contact of relay 304 to ground over cam 233 to advance the sequence switch 200 to position 6. In this position, the operating circuit of relay 304 is opened, but the holding circuit is maintained if the final selector is busy. Assuming that it is busy, a circuit will be closed from battery through the winding of updrive magnet 3 I 9, over the lower contacts of cam 2| 9, right front contact of relay 304 to ground, advancing the selector in search of an During trunk hunting, ground is connected to the commutator brushes over the front contact of relay 304 as previously traced and commutator strip 328 is connected over the right contacts of cam 226 to the left winding of relay 384. When an idle finder selector is found, the circuit over brush 342 for relay 304 is opened and when the brushes are properly centered the circuit over the commutator strip 326 is also opened and relay 304 releases, releasing magnet M9 and bringing the selector to rest with its brushes engaging an idle final selector. As soon as relay 304 releases, ground is connected to the sleeve brush 342 to mark the final selector busy to other incoming selectors. This circuit may be traced from ground over the lower contacts of cam 233, left back Contact of relay 304, upper right and lower left contacts of cam 2||, to brush 342. With relay 304 released, a circuit is closed from battery through the winding of sequence switch magnet 200, upper left contact of cam 224, right back contact of relay 304 to ground over cam 233, advancing sequence switch 200 to position I from which position the sequence switch is advanced to position 8 over its local cam. When sequence switch 200 reaches position 5%, ground is connected to brush 342 over the lower left contact of cam 222.

During trunk hunting, relay 3|5 is held operated over the fundamental circuit and when sequence switch 200 reaches position 8, closes a circuit from battery through the right winding of relay 304, lower right contact of cam 2|'|, lower left contact of cam 2| l, front contact of relay 3|5, lower left and upper right contacts of cam 206 to brush 340 and thence over the tip conductor to the final selector. A circuit is also closed from battery through resistance 305 and the left contacts of cam 2 over the front con-' tact of relay M5 and the contacts of cam 206 to brush 340. Under these conditions, relay 304 does not operate but a relay in the final selector does operate to prepare that circuit for functioning. During final selections, commutator pulses are connected over brush MI and the upper right contact of cam 2|6 to the winding of relay 3|5 in shunt of the winding of the stepping relay and relay 3| 5 is held operated.

When the final selector completes the selection of the wanted line, it connects ground to both brushes 340 and 34L The connection of ground to brush 34| holds relay 3 5 operated which holds closed the previously traced circuit for relay 304 to brush 340. The connection of ground to that brush therefore operates relay 304. Relay 304 closes a locking circuit for itself from battery through resistance 305, left winding of relay 304, back contact of relay 3H, lower left contacts of cams 2| and 2 l 9, right front contact of relay 304 to ground over the lower left contact of cam 233. It also closes a circuit from battery through the winding of sequence switch magnet 200, upper left contact of cam 220, upper right contact of cam 2 l8, left front contact of relay 304 to ground over the lower right contact of cam 233, advancing sequence switch 200 to position 9 in which 10' position relay 304 releases. While sequence switch 200 is in position 8+8 A,, a circuit is closed from ground over the right contacts of

cams

233 and 225 to the winding of relay 309. When the sequence switch leaves position 6%; this circuit is opened but relay 309 which is slow-to-release is held operated in a circuit over the right contacts of cam 225, left back contact of relay 304 which releases quickly, lower contacts of cam 230 to ground. In this position reverse battery is connected to the fundamental circuit which extends from the tip conductor |4| of the interoflice trunk over the upper left and lower right contacts of cam 2|6,

lower right contacts of cams 220 and H8, upper I right contact of cam 222 to ground, and from the ring conductor I42 of the interoffice trunk over the upper left and lower right contacts of cam 2 l4 to battery through the winding of relay After the completion of final selections, the fundamental circuit is reestablished in the sender and the connection of reverse battery to the circuit is a signal for the sender dismissal.

When relay 3|5 operates in the reverse battery battery closure and a circuit is closed from battery through the winding of sequence switch magnet 200 over the contacts of cam 2|3, left normal contact of relay 309 to ground, advancing sequence switch 230 to position l0 and thence to position over its normal cam. When sequence switch 200 leaves position 9, relays 3|5 and 304 release.

When sequence switch 200 passes through positions |0+|0 A battery through the resistance 305 is connected over the contacts of cam 20| to the upper left winding of repeating coil 203 and the upper terminal of condenser 240 while the lower terminal of the condenser and the lower left winding of repeating coil 203 are connected to ground over the upper contacts of cam 225 and the lower right contact of cam 233.

When sequence switch 200 reaches position I battery through the right winding of relay 308 is extended through the upper winding of retard coil 335, right contacts of cam 232, upper left winding of repeating coil 203 over the upper contacts of cam 20| to the tip conductor |4| of the interoffice trunk. As the sequence switch 200 leaves position 9, the ground above traced is disconnected and when the sequence switch ing of retard coil 335, left winding of relay 308 to ground over the upper contacts of cam 233. The incoming selector now awaits trunk closure by the link or trunk circuit.

In the sender when the reverse battery circuit is opened, ground is disconnected from conductor BSI indicating that the sender has completed its functions and opening the circuit of relay H8 which now releases closing a circuit from battery through the winding of sequence switch magnet 469, upper left contact of cam 884, left back contact of relay I l9 to ground over the lower right contact of cam 4B8, advancing sequence switch to position 9 from whence it is advanced to position I? over its local cam. As soon as sequence switch till) leaves position 8% ground is disconnected from conductor 656 causing the disconnection of off-normal ground in the sender thereby releasing all sender relays and putting the sender in condition to control another call.

As sequence switch tell passes through positions I2 to I 4 a circuit is closed from the tipconductor It! of the interoflice. trunk which was connected as previously traced to battery through the right winding of relay 398 over the right alternate contact of relay E26, conductor I31, brush BilI, middle right contact of relay HQ, inner right front contact of relay H5, through resistance Ml, lower right and upper left contacts of cam 4H5, outer right back contact of relay lib, brush 6G2, conductor 538 over the outer left front contact of relay I25, through resistance I30 to the ring conductor I42 and thence to ground through the left winding of relay 398 as above traced.

When sequence switch 4M3 reaches position I3 battery through resistance M3 is removed from conductor I32 thereby releasing relay I2? but since relay I23 is still operated, the locking circuit of relays I 2! and i26 is maintained and a circuit is closed from ground over the back contact of relay I21, inner left front contact of relay !26, inner lower front contact of relay I22, through the winding of relay the, right back contact of relay I25 to battery. Relay I86, in operating, closes a locking circuit for itself from battery over the back contact of relay I25, winding of relay I 06, inner upper front contact of relay I06 to ground at the front contact of relay H4. Relay I06 disconnects ground from the holding circuit of relay I22 which now releases. Relay I06 also connects the tip conductor I II of the interoffice trunk over its outer upper front contact, upper right winding of repeating coil lil l, back con-- tact of relay I26, winding of relay H2, lower right winding of repeating coil ltd, outer lower front contact of relay 9% to the ring conductor I42 of the interoflice trunk and thereby making a second trunk closure which overlaps the trunk closure made by the link circuit. Since relay H2 is polarized it does not operate in series with relay 3&8 at this time.

When sequence switch 4% leaves position I6, battery through resistance H2 is disconnected from conductor I33 thereby releasing relay I23 which, in turn, releases relays I2I and I25. The link circuit is the completely disconnected from the trunk circuit.

When sequence switch dill) reaches position I6, a circuit is closed from battery through the winding of relay ilo, upper contacts of cam M I, commutator strip Bit, brush EH2 to ground. When sequence switch dill] reaches position Ii, relay illi closes a circuit from battery through the winding of downdrive magnet 6I5 of the trunk finder 800, left front contact of relay 4M, right contacts of cam M5 toground, restoring the runk finder to normal. When the trunk finder reaches the bottom of its bank, brush 6l2 leaves commutator strip Gill and relay 3H] releases, in 5 turn releasing downdrive magnet tilt.

With sequence switch ltil in position iii, a test is made t determine the location of the sender selector by means of a circuit from ground over brush 529, commutator strip 63L upper contacts 10 of cam 422, winding of relay 8%, resistance 139 i to battery. If the selector is not engaging one of the predetermined top relay 839 is not operated and when relay H5] releases sequence switch is advanced to position I8 over the upper right contact of cam an, inner lower i normal contact of jack i inner upper back contact of relay 639 to ground over the back contact of relay ilt and the contacts of cam H5. If the selector is engaging a sender in such a top group, relay will operate and look over its inner lower front contact and the left contacts of cam 6253. en relay till releases with sequence switch 4&5 in position H, a circuit is closed from battery through the winding of downdrive magnet till, inner upper front contact of relay Eli-iii, back contact of relay :iIt to ground over the right contacts of cam ME. The sender selector 62! is restored to the bottom of its bank in this circuit and when it reaches this position, a circuit is closed from ground over brush E329, commutator strip upper left and lower right contacts of cam ill to resistance and battery in shunt of the winding of relay E33 which new releases. With relay released, the circuit 35 above traced is closed through the winding of sequence switch magnet and sequence switch is advanced to position in which position it remains until it is assigned for use by the advance of the next link to position 2.

Relay 3538 operates in response to the trunk closures by the link and trunk circuits, coinpleting a circuit from ground over the front contact of relay 323, upper contacts of cam 2H3, through the winding of relay see to battery. Relay 3E9 closes a substitute ground to the left winding of relay 388 from the upper left and lower right contacts of cam It also connects around over its left front contact, upper right and lower left contacts of cam back contact of relay leit winding of relay resistance 3% to battery, operating relay 33:3. Relay 38 5 looks in a circuit from battery, resistance 3&5, left winding of relay 3M, back contact of relay 35?, lower left contacts of cams E 5 and 2 I 9, right front contact of relay $64 to ground at the lower left contact of cam Relay also closes a circuit from ground over the right contacts of cam 233, left front contact of relay 3%, upper right contact of cam 2I8 and upper l ft contact 69 of cam 229 to battery through the winding of sequence switch magnet 28 3 advancing the sequence switch to position It. In this position ringing takes place.

The polarity of the ringing current to be used in signaling a called line is determined by the group of final selectors having access to that line. As sequence switch passes through positions 8 to II, a circuit is prepared from battery through the left winding of relay 3M, lower completed to ground over the upper right contact of cam 222. Relay 3% looks in positions I! and I2 over its right winding and inner right contact, lower left contact of cam Ziil, lower left contact of cam fit}, right front contact of relay 7554 to ground at the lower left contact of cam 233.

With relay Sill operated, the ringing circuit is closed in position I2 from positive superimposed ringing current applied to conductor 332, outer right front and left front contacts of relay 32!, upper contacts of cam 298, winding of relay 3, left front contact of relay 324, lower left and upper right contacts of cam 261, brush through the final selector and over called 1 line 359 to brush right contacts of cam 286 to ground.

This ringing continues intermittently until the called subscriber answers. When the called subscriber answers, relay Ell operates over the sub- :scribers line thereby opening the circuit of relay Relay 32% connects battery through the lower right winding of repeating coil 223 winding of relay 2E5, left contacts of cam 238, left back contact of relay lower left and upper right :contacts of cam 22? to ring brush 34! to supply tact of relay 324 to ground over the lower left contact of cam 233. Sequence switch 222 advances to position it in which talking may take piace. Relay 2I5 operates over the called subscribers line and closes a circuit from battery through resistance 325, left winding of relay 324,

front contact of relay 235, upper contacts of cam 229 to ground. With relay 324 operated and sequence switch 22% in position It, the circuit of relay 353 may be traced from battery through right winding, upper winding of retard coil upper right contacts of cams 222 and H8, left front contact of relay 3B4, upper contacts of cam lower left winding of repeating coil 2' 3, upper contacts of cam 2M and thence as traced through the winding of relay H2 back to the upper contacts of cam 2m, upper left winding of repeating coil upper right and lower is t contacts of cam 232, right front contact of relay 3%, lower left and upper right contacts of cam 2H3, lower winding of retard coil 335, left winding of relay 326 to ground over the right front contact of relay 3% and the lower right and upper left contacts of can The reversal of battery and ground over the tip and ring interofiice leads, operates relay H2. Relay H2 closes a circuit from battery, winding of relay Iii front contact of relay H2, left back contact of relay i if front contact of relay Hi! to ground at the back contact of relay I44. Relay I It reverses the connection of battery and ground through the winding of relay H9 to the incoming trunk as a signal to the operator at office 0 that the called subscriber has answered. Relay H2 at its outer left contact closes a looking circuit for itself under the control of relay H2. It also closes an obvious circuit for relay E44 which opens the operating circuit of relay I I4 but closes a holding circuit for that relay to ground over the front contacts of relays H9, I44 and I I4.

When the called subscriber restores his receiver to the switchhook, relay 2I5 releases, in turn releasing relay 32 1 and restoring the connection. of battery and ground through relay 398 to the interofiice trunk, releasing relay H2 which reverses the connection of battery and ground to the trunk conductors leading to the manual office and causing the lamp at that office to light as a disconnect signal. Relay H2 also releases relays H9 and I44 in turn. When the tandem operator removes the plug of cord I02 from jack I23, relay H9 releases, in turn releasing relay I I4. Relay H4 in releasing disconnects ground from the locking circuit of relay I06, thereby causing the release of relay I06. 10 The release of relay I96 disconnects relay H2 from the windings of relay 358 and that relay, in turn, releases, releasing relay 309. With relay 369 released, relay 308 can not reoperate.

A circuit is closed from battery through the 15' winding of sequence switch magnet 200, left contacts of cam 213 over the normal contact of relay 399 to ground, advancing sequence switch 220 to position I5. In position I6 a circuit is closed from battery through the winding of 20,

ground, advancing sequence switch 200 to posi- 301' tion Il. Sequence switch 200 is advanced to position I8 over the upper right and lower left contacts of cam 22I and the normal contact of relay 329 and to position I over the upper left contact of cam 224, right back contact of relay 35 a 324, and the lower left contact of cam 233. The

advance of sequence switch 200 from position I5 4 removes ground from the sleeve brush 342 thereby permitting the final selector to restore to normal. 40

Trouble conditions Relay I21 controls the release of the link circuit in case of trouble and is operated under a variety of conditions.

The link circuit is provided with a time alarm 45 arrangement under the control of interrupters I25 and I25. With sequence switch 400 in

positions

3, 6 and 8, ground is connected to interrupter I24 which has a comparatively slow period, While in

positions

2, 4, 5, i and 9 to I6, inclusive, ground is connected to interrupter I25 which has a period of somewhat less than half that of interrupter I24. It may be noted that the right and left contacts of these interrupters are connected in parallel so that the effect of the operation of the interrupters is the same except for the speed at which they operate. The first closure of the left contact of either interrupter completes the circuit for relay I26 which looks in a circuit from battery through its right winding and inner right contact to ground at the upper left contact of cam 426, this locking circuit being closed irrespective of which interrupter is functioning and opened as the sequence switch passes from position to position. If relay I26 remains operated until the right contact of the same interrupter closes, a circuit is completed over the left contact of relay 126 through the left winding of relay I21 to battery. 7

The position circuit is normally disconnected from the link circuit by the advance of the link circuit. However, if the position is held because connect key or reorder key. Before the trunk is connected through to the position, the operation of the position disconnect key will connect ground to conductor I44, operating relay 121 to bring about the forced release of the link.

After the trunk and position have been connected the operation of the disconnect key connects ground to conductors I45 and I46. This ground shunts the left winding of relay II I while maintaining the circuit through the right winding. Since relay III is differentially wound, it now operates and closes an obvious circuit for relay 127.

If the operator removes her headset from the position jack just as the position has been seized by a link, a circuit is closed from ground to conductors I45 and I46 operating relays II I and 127.

If relay I2I operates in

positions

2 or 3 of sequence switch 400, it looks in a circuit from battery through its right winding and inner left front contact to ground over the lower left contact of cam 406. Relay 'I2I also extends this locking ground through the winding of relay I29 to battery. In addition it closes a circuit from battery through lamp I28 to ground at its middle right contact. It also closes a circuit from ground over its inner right contact, lower normal contact of jack I3I, to conductor 645 which extends through the winding of relay 523 which controls the time alarm circuit. Furthermore, it opens the locking circuit of relay 5I0. Relay I29 opens the circuit of relay M and also opens the circuit by which the position finder tests for an idle position.

Relay I29 closes a circuit from battery through the winding of relay H0, inner left contact of relay I29 to ground over the lower right contact of cam 402. Relay II 0 locks over its outer left front contact to ground at the lower left contact of cam 406 and disconnects brushes GM to 604, inclusive, from the link equipment, thereby releasing trunk relays such as relays I20 and I2I which may be operated under the control of the link. Since the wanted number has not been given to the B operator, the connection is maintained at the originating office and, with relay I0 released, another link may be assigned to handle the call. Relay IIO also closes a circuit from ground over its locking circuit and its inner left contact, middle normal contact of jack I23, upper left contact of cam 404 to battery through the winding of sequence switch magnet 400, advancing the sequence switch to position 5 Where the sender finder hunts for an idle sender, after which the sequence switch is advanced to position 6. Relay 'IIO advances the sequence switch from position 6 to position 9 after which it advances to position I'I under the control of its local cam and restores to normal in the usual manner.

If relay 121 is operated in position 4 to 0 of sequence switch 400, it operates relay I29 as above. Relay I29 also opens the circuit by which relays H4 and III are held if these relays have been operated, and relay I I4 permits the position circuit to restore to normal. It also closes a circuit from battery through the left winding of relay I20, right front contact of relay I29 to ground over the lower left contact of cam 40I. Relay I20 locks in a circuit from battery through its left winding and the inner left front contact to this ground, independent of relay I29 and opens thelocking circuit of relay I22 and that relay releases. In addition, relay I20 closes a circuit from battery through resistance 12 l, inner right front contact of relay I20, inner right back contact of relay H0, brush 603, conductor I33, inner right front contact of relay I26, through the windings of relays I23 and I25 to ground. Relay I23 operates in this circuit and relay I25 also operates due to the low value of resistance I2 I.

Relay I25 in operating closes a locking circuit for itself from battery over its right front contact and right winding to ground at the frcnt contact of relay I I4. Relay I25 in operating disconnects battery from the winding of relay I22 and that relay releases. It also disconnects battery from the operating circuit of relay I05 to prevent its premature operation and to disconnect relay I ill from the outgoing trunk conductors. It also closes a circuit from battery through resistance I34 over the outer left front contact of relay I25 through the winding of relay I I2, left back contact of relay I20, inner left front contact of relay I25 to ground through interrupter I35 thereby causing relay I I2 to intermittently operate and release, these interruptions causing the cord supervisory lamp at the tandem office to flash. Relay I20 in operating also closes a circuit from battery through the winding of sequence switch magnet 400, upper left contact of cam 404, middle contact of jack I23, middle right front contact of relay I20 to ground, advancing sequence switch 400 to position 5 from which position the selection of a sender advances it to position 6, relay I20 advances it to position 9 and the local cam advances it to position. 11. The restoration of the trunk finder and advance to position I8 take place in the usual manner.

If during selection, the incoming selector 300 finds all of the trunks in the selected group busy, the selector is driven to the overflow terminal to the sleeve of which no ground is connected. Therefore, relay 304 releases when this terminal is reached in turn releasing the updrive magnet 3I9 and advancing sequence switch 200 to position 8. A circuit is thereupon closed from battery through the winding of sequence switch magnet 200, lower left contacts of cams 2 I3 and 226, commutator strip 321, brush 323, upper right contact of cam 222 to ground, advancing sequence switch 200 to position 9. In this position reverse battery is connected to the interofiice trunk in the manner previously described. Reverse battery is also supplied to the interofiice trunk if, in making any selection, the selector goes to the top of the bank, in which case a circuit is closed from battery through the winding of sequence switch magnet 200, lower right contact of cam 224, commutator segment 329, brush 323 and thence to ground as just traced.

Premature reverse battery is also closed to the sender if the incoming selector is not in its normal position when the fundamental circuit is first established. This is apparent since it will take fewer than the normal number of selections to advance the incoming selector sequence switch to the reverse battery position.

When the sender receives premature reverse battery a circuit is closed from battery to conductor 652 over brush 622, left front contact of relay I I5, right winding of relay I20, to ground over the upper contacts of cam 408. Relay I20 in operating connects battery through resistance I2 I to brush 503 as previously described to give a reorder signal to the trunk circuit. Relay I20 also advances sequence switch 400 to position 9 whence it is advanced to position I'I over its local 16, relay 120 releases.

When sequence switch 460 passes through positions fil to l the trunk closure previously described, is completed in order to operate relay Slit? if the sequence switch 2% is standing in position I l. The operation of relay 398 operates relay 339 which in turn operates relay 304 which locks under the control of relay 3l'l'and advances sequence switch 200 to position l2.

As soon as the trunk closure 1s removed by the link circuit relay 368 releases since no closure is made by the trunk circuit. The release of relay SE38 releases relay 3139 which closes a circuit from ground at its left normal contact, lower contacts of cam 22!, resistance 228, left front contact of relay 3B4, winding of relay Bil, upper contacts of cam 208 to the ringing machine over

conductor

338 or 339 depending on the operative condition of relay 3M. Relay 3H operates in this circuit, releasing relay 304. Relay 304 advances sequence switch 259 to position M as previously described. Since relay 309 is released, the sequence switch is immediately advanced to position it where the selector switch is restored to normal, after which the sequence switch is restored to position I.

What is claimed is:

1. In a telephone system, an originating ofiice, an intermediate office, a terminating ofiice, a trunk circuit extending from a manual terminal at said originating ofiice through said intermediate ofiice to an automatic switch at said terminating office, and means at said intermediate oflice for recording wanted line numbers and for controlling said automatic switch.

2. In a telephone system, a trunk circuit extending from an originating office through an intermediate oifice to switching equipment at a terminating office, and means in said intermediate office for receiving line designations from said originating office and for controlling the switching equipment in said terminating ofilce, no switching operations being performed at said intermediate ofl'ice.

' 3. In a telephone system, an originating oflice;

an intermediate office, a terminating ofiice, a trunk circuit extending from said originating office through said intermediate ofiice to switching equipment at said terminating oliice, control equipment at said intermediate ofiice,'means for successively connecting said control equipment with the originating ofiice and with the terminating oihce over said trunk circuit to control the completion of a connection thereover, and means responsive to the completion of said connection to render said trunk circuit independent of said control equipment.

4. In a telephone system, a trunk circuit connecting an originating and a terminating ofiice, an intermediate oflice through which said trunk circuit passes, an operators equipment at said intermediate ofiice for controlling the completion of connections over said trunk circuit at said distant office, no switching operationbeing performed at said intermediate oifice.

5. In a telephone system, a plurality of originating ofiices, a plurality of terminating oi'iices, trunk circuits connecting said originating offices and said terminating offices, an intermediate ofiice through which said trunk circuits pass, but in which no switching takes place, and an operators equipment at said intermediate ofiice for controlling the completion of connections over said trunk circuits.

6. In a telephone system, a first plurality of oflices, a second plurality of offices, trunk circuits connecting said first oilices with said second oiiices terminating in switches in said second offices, an intermediate non-switching ofiice through which said trunk circuits pass, and an 5 operators equipment at said intermediate ofiice for receiving instructions from said first ofiices and for controlling the operation of said switches;

7. In a telephone system, an originating ofiice, an intermediate oflice, a terminating office, a 10 trunk circuit extending from said originating oflice through said intermediate ofiice to switching equipment at said terminating oflice, control equipment at said intermediate ofiice, means associated with said trunk circuit to connect said 15 control equipment with said originating oflice to receive a wanted line designation, means responsive to the completed recording of said designation to transfer the connection'of said control equipment at said trunk circuit to said terminating oflice to control said switching equipment to complete a connection to said wanted line, and means responsive to the completion of said connection to disconnect said trunk circuit from said control equipment. 26

8. In a telephone system, a selector switch, a. trunk circuit terminating in said selector switch,

a link circuit, control equipment, means including said link circuit for connecting said control equipment with said selector switch over said 30 trunk circuit, a relay associated with said selector switch, means responsive to the operation and release of said relay for causing the release of said switch, means effective after said selector switch has been operated for connecting said relay with said trunk circuit, means in said trunk circuit normally effective for operating said relay, and means in said link circuit effective in case of trouble to operate said relay.

9. In a telephone system, a selector switch, a trunk circuit terminating in said selector switch,

a link circuit, control equipment, means including said link circuit for connecting said control equipment with said selector switch over said trunk circuit, a relay associated with said selector i5 switch, means responsive to the operation and release of said relay for causing the release of said switch, means effective after said selector switch has been operated for connecting said relay with said trunk circuit, means in said trunk circuit normally effective for operating said relay, means in said link circuit eifective in case of trouble to prevent said trunk circuit from operating said relay, and means in said link circuit for closing a substitute circuit for operating said relay.

10. In a telephone system, a trunk circuit terminating in an automatic selector switch at one oflice, a link circuit and a register sender at a second office, means to cause said link circuit to connect said sender with said'trunk circuit at said second office, means in said sender to control 'the operation of said selector switch, a holding relay associated with said selector switch, means to connect said holding relay with said trunk circuit, means in said sender responsive to the completion of selections to initiate the release of said link circuit, means in said link circuit for causing said trunk circuit to prepare a holding circuit at said second oflice for said holding relay, and means in said link circuit for establishing an overlapping holding circuit for said holding relay.

11. In a telephone system, a trunk circuit extending from a first oflice and terminatingin an 16 automatic selector switch at a second office, a link circuit having an associated sequence switch, and a register sender at said first office, means to cause said link circuit to connect said sender with said trunk circuit, means in said sender to control the operation of said selector switch, a holding relay associated with said selector switch, means effective following the completion of selections to connect said holding relay with said trunk circuit, means in said sender responsive to the completion of selections to initiate the release of said link circuit by advancing said sequence switch, means controlled by said sequence switch in its advance to sequentially establish a holding circuit for said holding relay in said link circuit, to cause the closure of a holding circuit for said holding relay by said trunk circuit and to disconnect said link circuit from said trunk circuit.

12. In a telephone system, a trunk circuit terminating in an automatic selector switch at one office, a link circuit and a register sender at a second oifice, means to cause said link circuit to connect said sender with said trunk circuit at said second ofiice, means in said sender to control the operation of said selector switch, a holding relay associated with said selector switch, means to connect said holding relay with said trunk circuit, means in said sender to initiate the release of said link circuit, means in said link circuit for causing said trunk circuit to prepare a holding circuit at said second ofiice for said holding relay, means in said link circuit for establishing a holding circuit for said holding relay, means to prevent the completion of the holding circuit by said trunk circuit, and means to establish the holding circuit in said link circuit whether or not the holding circuit in said trunk circuit is completed.