US1658829A

US1658829A - Telephone system

Info

Publication number: US1658829A
Application number: US132333A
Authority: US
Inventors: Clarence H Berry
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1926-08-30
Filing date: 1926-08-30
Publication date: 1928-02-14
Anticipated expiration: 1945-02-14

Description

Feb. 14, 1928. 1,658,829

- C. H. BERRY TELEPHONE SYSTEM- Filed Aug. 50. 1926 2 Sheets-Sheet 1 Feb. 14, 1928. 7 1,658,829

' c. H. BERRY TELEPHONE SYSTEM Filed Aug. 50, 1926 2 Sheets-Sheet Patented Feb. 14, 1928.

UNITE STATES ICE.

CLARENCE Iii. BERRY, or IsLrP, new YORK, AssIenoR T WESTERN nLnc'rRIoooM- PANY, INooRPORA'rEn, on NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed August so, iszeJserial' No. 132,333.

This invention relates to automatic telephone exchange systems, and more particularly to the cooperation between selective switches employed in the establishment of telephonic connections.

In telephone systems of the type employing central office senders for controlling the operation of selective switches andin which the control of one switch is placed-under 1o relays at a preceding switch, it has been found desirable toadvance the controlling sequence switch associated with the said I pre eding selective switch following the completion of certain functions at the succeedi5'ing switch. i

According to the present invention the sequence switch of such preceding switch is held in one position during selections by the succeedin switch, and is advanced under the control of the succeeding switch following the completion of selections at said lat ter switch. More particularly, two relays are provided in the circuit of the first switch, one to control the sender and one to control the sequence switch during the selective operations of the succeeding switch dependent on the succeeding selector. On the completion of connections these relays are simultaneously operated to advance the sequence switch to position for further operation. 7 During the completion of a call to a subscribers line, connections are completed to the incoming selector under the control of a sender. In the incoming selector one of the above mentioned relays is operated in the fundamental circuit includingthe stepping relay of the sender and operates the.

other relay to advance the incoming selec tor sequence switch. The revertiv'e impulses which control the setting of the switch hold the first relay operated in the usual manner. Following-the completion of incomingselections a circuit is prepared for the second relay which includeslafront contact of the first relay and extends to the tip conductor of the final selector. The first relay is again operated in the fundamental circuit and pulses sent back from the final selector over the ring conductor to release the stepping relay of the sender in the usual manner and determine the setting of the final selector. Following the completion of these final selections ground is simultaneously applied to the tip and ring conductors whereby bot-b.

selector which is shown in detail.

relays are operated and the incoming selector sequence switch is advanced to send back the usual signal initiating talkingselection and the dismissal of the sender.

In the drawings F 1 shows in diagrammatic form a subscribers line and switches for extending a connection to the incoming I Fig. 2 shows a final selector controlled through the cooperation of the incoming selector, and Fig.3 is a diagram showing the combination of Figs. 1 and'2 for a complete disclosure of thestructure of this invention.

. Assuming that the subscriber at substation 101 desires to converse-with a subscriber at substation 280, he will remove his receiver from the switchhook; Line finder 1.02will thereupon operate to find the line and extend it to a district selector 103 which is. associated by any suitable means with a sender 104:. When the sender is ready to receive dialing pulses a tone will be returned to the substation 101, after which the subscriber will dial the number of the wanted subscriber. District selector 103 and otlice selector 105 will be operated under the control of the sender to select an idle incoming selector. VVhenthe office selector has come to rest and the sender is advanced to position for controlling incoming selections, a circuit is established from battery through the winding of relay 106, lower right contact'of cam 107, upper left contact of cam 108, over the tip conductor of

selectors

105 and 103. through the stepping relay of the sender, back over the ring conductor of

selectors

103 and 105, upper right and lower,

left contacts of cam 109 to ground. Relay 106 closes a circuit from battery through the right winding of relay 110, upper left contact of cam 111, lower left contact of cam 112, front contact of relay 106 to ground at the lower right contact of cam 113; Relay 110 operates and locks in a fundamental circuit extending from battery,-througl1 its right winding, lower left contact of cam 115, right front contact of relay 110, upper right contact of cam 111, lower left contact of cam 112, front contact of relay 106 to ground at the lower right contact of cam 113. Relay 110, in turn, closes a circuit from battery through the winding of sequence switch magnet 100, lower left contact of cam 114, left front contact of relay 110, upper left contact of cum 113 to ground, advanc ing the sequence switch to position 2. With sequence switch in position 2, the cir cuitof updrive magnet 116 is closed and the incoming selector advanced in a brush selecting operation. The circuit for magnet 116 extends from battery, through the winding of magnet 116, lower contact 015021111 117, left front contact of relay 110, upper left contact of cam 113 to ground. As the selector moves upward brush 118 makes contact with commutator strip 119, intermittently closing a circuit from ground over the upper right contact of cam 12%, brush 118, conducting segments of strip 119, upper left and lower right contacts of cam 104 to the winding of relay 106. This circuit holds relay 106 operated while it shunts and deenergizes the stepping relay of the sender :in the usual manner to operate the counting relays. Then the condition set up in the sender has been satisfied, the fundamental circuit is opened by the sender and relay 106 releases, in turn, releasing relay 110' The release of relay 110 opens the circuit of magnet 116 and brings the selector .to

rest in position to trip the proper brush set. It also closes a circuit from battery through the winding of sequence switch magnet 100,

ooerated in a. circuit extendin to around w b in at the lower right contact of cam 124 throughout positions 3 to 5, inclusive, and is therefore operated at this time to cause the tripping of the selected set of brushes at the beginning of the group selecting movement. During this operation an intermittent circuit is completed from ground. at the upper .left contact of cam 113, left front contact of relay 110, upper right contact of cam 117, brush 122, commutator strip 123,

right contacts of cam 107, to the winding ofrelay 106. This circuit releases the stepping relay of the senderas above described.

When the sender is satisfied, relay, 106 releases, in turn, releasing relay 110, bringing the selector to rest. However, a circuit is provided, :from battery through the right winding of relay 110, upper left and lower right contacts of cam 125, and thence in parallel over the lower left and upper right contacts of cam 126, commutator strip 127,

to brush 128, and over strip 119 to brush 118, extending from

brushes

128 and 118 over the upper right contact of cain 117, left front contact of relay 110 to ground at the upper left contact of cam 113, which serves to the switch to position 3.

With the sequence switch 100 in position 5 a local circuit is closed for relay 110 extending from battery, through resistance 129, left winding of relay 110, lower left contact of earn 113 to ground. Relay 110 operates in this circuit and closes a circuit oin battery, through its right winding, lower left contact of 0am 115, right front contact of relay 110, upper right contact of cam 111, upper left contact of cam 112 to sleeve brush If the final selector connected to the first set of terminals of the selected group is .busy, ground will be connected to the sleeve terminal and relay 11.0 will be held operated in this circuit. The operation of relay 110 closes the previously traced cir cuit for sequence switch 100, advancing it to position 6, in which position the holding circuit of relay 110 to the sleeve brush 132 is n'iaintained.

I lVith the sequence switch 100 in position 6 the updrive magnet is again energized and the selector advanced in a trunk hunting movement. As soon as an idle trunk is found. the holding circuit of relay 110 is opened and that relay releases connecting ground over the lower contact of cani 133. right back contact of relay 110, upper right contact of earn 111, upper left contact of cam 112 to sleeve brush 132 to render the final selector busy to other incoming sclcrtors. With relay 110 released, the previously traced circuit is closed over the left back contact thereof, advancing sequence switch 100 to position 8. As soon as sequence switch 100 reaches position 6 direct ground is connected over the upper left coutact of cam 124 to sleeve brush 1 12 to hold the final selector busy. 127 functions at this time in the sauw uiain nor as it did in group selection to center the brush set.

\Vithsequence switch 100 in position 8 the fundamental circuit is reestablished to relay 106 and that relay operates. 'lVith relay 106 operated, a circuit is now closed from hat tery through the right winding' of relay 110. upper left contact of earn 111, lower left contact of cam 112, front contact of rclav 106. lower left contact of can". 131- to brush 130, tip conductor 201 of the. selected final selector, left contacts of cain 202. resistance 20 right contact of cam 20d, right winding; of relay .205 to ground over the right contacts of cam 207. At the same time a. circuit is closed in parallel with the right winding; of relay 110 from vbattery through resistance 129 over the lower left contact of earn 111 llu len'unutator strip to ground.

to the circuit'just traced. The effect of this circuit is to prevent the operation of relay 110 in series with relay 205, and to provide sufficient current to operate relay 205.

Relay 205 thereupon locks in a circuit which extends from the right winding of relay 205 over the left contacts of cam 206, right front contact of relay 205, left contact of cam 224, upper right contact of cam 225 The operation of relay 205 closes a circuit from battery through the winding; of relay 208, lower left and upper right contacts of cam 210, left front contact of relay 205 to ground. Rel y 208 looks in turn a circuit through its winding over the left contacts of cam 209, rightfront contact of relay 208, upper contacts of cam 211, contact 212 of jack 218, sleeve conductor 21%, brush 132, to ground at the upper left contact of cam 124. This locking circuit remains closed un til sequence switch 200 leaves position 6. The operation of relay 208 at this time closes a circuit from battery through the winding of final selector sequence switch magnet 200, lower contacts of cam 215, to ground at the left front contact of relay 208, advancing the sequence switch to position y With sequence switch 200 in position 2, a circuit is closed for high speed updrive magnet 216 extending from battery through the winding of magnet 216, upper left contact of cam 217 upper right contact of earn 210, left front contact of relay 205 to ground. Under the control of magnet 216 the final selector is driven upward in a brush selecting movement. As brush 221 passes over commutator strip 220, a circuit is intermittently closed from ground over the lower right contact of cam 222, brush 221, (3011111111: tator strip 220, left contacts of cam 219, ring conductor 218, brush 131, upper left and lower right contacts of cam 189, upper left contact of cam 1.08, lower left contact of cam 107 to the winding of relay 106. This circuit serves to hold relay 106 operated and shunt the stepping relay of the sender in the usual manner. when the sender is satisfied, it releases relay 106 opening the circuit of relays 110 and 205, releasing relay Belay 205 opens the circuit of magnet 216 and brings the selector brushes to rest in pos ion to trip the desired set of brushes. lVith relay 205 released, a circuit is closed from hattery through thewinding of sequence switch magnet 200, lower left contact of cam 223, to ground at the left back contact of relay 205, advancing the sequence switch 200 to position 8 operating trip magnet 226.

lVhen the fundamental circuit is again established by the sender, relay 106 operates, reclosing the circuit of relay 205. Relay 205 operates and locks, and advances sequence switch 200 to position 4, in a circuit extending over the upper contacts of cam 210 to ground at the left front cont-act of relay 205.

High speed magnet 216 is again operated and aliinterinittent circuit is completed for relay 106 over conduct-or 218, the lower left and upper right contacts of cam 219,"commutator strip 227, brush 228 from ground, the right contacts of cam 210 to ground at the left front contact of relay 205. Trip mag"- net 226 is operated in positions 3 to 5 of sequence switch 200, in a circuit from battery through its winding to groundat the lower left contact of cam 222, so that when the selector is moved upward under the control of magnet 216 in its group hunting movement, the selected set of brushes is tripped. lVhe-nthe sender is satisfied, relay 106 releases, in turnreleasing relay 205, whereupon the updrive is stopped, and sequence switch 200 is advanced to position 5.

When the fundamental circuit is estab lished for units selection with the final selector sequence switch in position 5, relays 106 and 205 are operated as before and relay 205 locked. The operation of relay 205' advances the sequence switch 200 to position 6 over cam 210 and left front contact of relay 205. In position 6 the holding circuit for 208 is transferred to a circuit through cam 209 and cam 242, back contact of relay 287, and left front contact of relay 208 to ground circuit is completed from battery through the winding of low speed upd *ive magnet 232, upper right contactsof cams 217 and 210 to ground at the left front contact of relay In position 6 the intermittent circuit connected to conductor 218 extends over the left contacts of cam 219, commutator strip 220, brush 221, lower right contact of cam 222 to ground. When the sender is satisfied, relays 106 and 205' release, relay 205 stopping the upward movement of the final selector and advancing the sequence switch 200 to position lover cam 223 and the left back contact of relay 205.

Sequence switch 200 is then immediately advanced from position 7 to position 0 in a circuit ext-ending from battery through the winding of magnet 200, upper left and lower right contacts of cam210, lower right contact of cam 222 to ground.

When sequence switch 200 passes through positions 6 10 8 inclusive, a circuit is closed from ground through winding of relay 23?). lower contacts of cam 21.1 to sleeve brush 234. If the called line is in normal condition. battery will be connected to the sleeve terminal through the cut-off relay 2% of the subscribers line, or if the line is busy, this relay will be shunted by ground. throuc'h a resistance. Relay 238 will operate uuh. thesleeve conductor is open or is grounder through a. low resistance such aswouldoccur if the sleeve were accidentally grounded. If either of these last two unnormal conditions exists, relay 238 would not operate, and the circuit for operating relay 205 which will be quence switch out of traced hereina ter is. open. "When sequence switch 200 reaches position 9, relay 205 would then be deenergi/ied and no circuit would be provided for advancing the sethat position. An alarm is theref re operated over cam 253 after a measured interval. The release of the selector is brought about manually after such a condition.

When relay 233 operates, indicating that the called line is normal, and switch 200 reaches position 7%, circuit is closed from battery through the left winding of relay 205, upper contact of cam 229, right winding of relay 205, the front contact of relay 233, upper contacts of cam 215, back contact of relay 237, left front contact of relay 208 to ground. it will be remembered that relay 208 was locked to the sleeve conductor 214 in positions 1 to 6 of the sequence switch 200.

When the sequence switch reached position 6, this holding circuit was transferred to the lower right contact of cam 242, back contact of relay 237 and ground at the left front contact of relay 208, which holding circuit is effective until the sequence switch leaves position 10 or until relay 237 is operated. Relay 205 operates in the circuit above traced and locks ina circuit through its two windings, left contacts of cam 200, right front contact of relay 205, left contact of cam upper right contact of cam 225 to ground, until the sequence switch leaves position 9 From the time that relay 205 released with the sequence switch 200 in position 6 following units selection until the sequence switch leaves position 8%, ground is connected to conductor 218 over the lower contacts of cum 219, right back contact of relay 205, upper left contact of cam 224, from the upper right contact of cam 225. and, as soon as position 7 is reached. ground is connected to conductor 218 over the lower contacts of cam 219 from the upper right contact of cam 222. This circuit extends as previously traced to the winding of relay 106, operating that relay independently of the sender.

When the sequence switch 200 passes through position 8+ 8 ,4 direct ground is conneotcd to conductor 201 over the lower left and upper right contacts of cam 202, right contacts of cam 210, and the lower right con tact of cam It will be remembered that the circuit of relay 111.0 ealended to conductor 201, over the front contact of relay 106, but this relay 110 could not operate, due to the shunt around its winding, in series with the resistance of relay 205.- However, the current through relay 110, when connected to direct ground as above described is sufficient to operate this relay. The operation of relay 110 advances sequence switch 100 to position 9, in which position a signal is transmesses mitted to the sender as will be described here inafter.

With relay 205 operated, a circuit is closed as soon as sequence switch 200 reaches position 9, for advancing to position 10, extending from battery through the winding of magnet 200, upper contacts of cam 210, left front contact of relay 205 to ground.

While the sequence switch 200 is moving through positions 8 to 10, a circuit is closed from sleeve brush 23%, lower right and upper left contacts of cam 211, right front contact of relay 208, right contact of cam 238, winding of relay 237, lower contact of cam 225 to ground.

If brush 23% is resting on the terminal of a busy line in a group leading to a private branch exchange, battery will be connected to the terminal through a high resistance and ground will also be connected thereto through a low resistance. Relay 237 is marginal. so that it will not operate through so high a resistance in parallel with the busy ound or in parallel with another P. B. X. test relay. In consequence, relay 208 remains operated in its previously traced looking circuit. Relay 205 also remains operated in position. 10 in a circuit which extends as previously traced to the upper left contact of earn 206, and is completed in this position over the lower right contact of cam 206 to ground at the left front contact of relay 205. lVith relay 208 operated, the sequence switch remains in position 10 and a circuit is completed from battery through the winding of low speed updrive magnet 232, upper right and lower left contacts of cam 217 to ground at the left front contact of relay 208.

hen an idle line is encountered no ground will be connected to the sleeve terminal and the current will be sufiicient to operate relay 23'7. Relay 237 also operates through the lower resistances connected to the sleeve terminals of individual lines and last lines of P. B. X. groups whether busy or not. The operation of relay 237 opens the holding circuit of relay 208 which in turn opens the circuit of magnet 232 bringing the selector to rest. An additional holding circuit for relay 208 exists at this time from ground at the left front contact of relay 208. lower left contact of cam 217, lower right contact of cam 210, brush 240, commutator strip 239, upper right and lower left contacts of cam 209 to the winding of relay 208 which insures that relay 208 will remain energized until the brush set is properly centered. The release of relay 208 also closes a circuit from battery through the winding of magnet 200, upper left contact of cam 223, to ground at the left back contact of relay 208 advancing the sequence switch to position 12. As soon as relay 208 releases, ground is connected to sleeve brush 234i, extending from ground at the left front contact of relay 205, lower contacts of earn 200, right front contact of relay 205, left contact of cam 224, through resist ance 246, upper contacts of earn 241, right bacl: contact of relay208, upper left and lower right contacts of earn 211, to the sleeve brush 234, as a tenuiorary busy condition.

lVhile sequence switch 200 is passing from position 10 to position 10 with sequence switch at position 9, the holding circuit of relay 205 is extended from the upper left cuit for relay 205 would then be closed over the upper left and lower right contacts of cam 206 to ground at the left front contact I of relay 205 imposition 11 and the two circuits' overlap sufiiciently to prevent the release of relay 205. The operations following connection with a busy line will be described later.

Assumingthat the line is idle, as soon as the sequence switch leaves position 10, relay 205 will release and connect ground from the upper right contact of ca1n222 over its right back contact, left contact of cam 224 through resistance 246 to sleeve brush 234 over the path previously described to make the line busy.

l'Fhen the sequence switch reaches position 12, with relay 205 released, relay 208 is operated in a circuit through its winding, lower left contact of 0am 209, upper right contact of can] 242, to ground at the left back contact of relay 205. Relay 208- in operating closes a circuit from battery through. the winding of sequence switch magnet 200, lower contacts of cam 215, left front contact of relay 208 to ground, advancing the sequence switch to the talking position 13.

As soon as the sequence switch 200 reaches talking position 13, ground is connected over the upper right contact of cam 225, through resistance 246, the left contacts of 01111241,

to the sleeve brush to hold it busy throughout conversation. Relay 208 when operated in position 12, locks over the left contacts of cam 209,.right front contact of relay 208, uppercontacts of 0am 211, contact 212 of jack 213, sleeve conductor 214, brush 132, to ground at the upper left contact of earn 124. In talking position, tip conductor 201 is extended over the lower contacts of cam 202 to the tipbrush 254 and the tip of the called line. The ring conductor 218 is extended over the upper contacts of cam 252 to ring brush 255 and the ring of the called line} 7 that relay releases.

In the meantime the advance of the incoming selector sequence switch 100 to position 9 has taken placeat position 8 the sequence switch 200 as above described and the incon1- ing selector has functioned as follows.

The advance of sequence switch 100 from position 8 opens the circuit of relay and With sequence switch 100 in position 9, relay 106 is connected over the upper contacts of earn 109 to the ring conductor, and ground is connected over the lower left contact of cain 107 and the upper left contact'of earn 108 to the tip conductor, a

reversing the direction of currentin the fundamental circuit, indicating to the sender that selections have been completed and that the district selector inay be advanced to talking position, following which operation the sender is released. Relay 106 operates in this circuit and closes the circuit through the right winding of relay 110. Relay 110 operates and advances sequence switch 100 out of position 9. The circuit of relay 106 is maintained through position 10, in turn holding relay 110 operated, but as soon as sequence switch 100 leaves position 10, relay 106 releases, in turn releasingr'elay 110 and bringing the sequence switch to rest in'position 11. '3

-In position 11, relay 135 is connected to the incoming tip and ring conductors, the

circuit being traceable from battery, through the right winding of relay 135, upper windleft contacts of cam 141, back contact of relay 106, lower right contact of cam 113 to ground, Relay 135 operates, closing the circuitthrough the right winding of relay 110. Relay 110 operates and closes the previously traced circuit for magnet 100 advancing the sequence switch to position 12. Relay 110 looks as beforevthrough its right .ing of retard coil 136, left contacts of cam V winding, making the advance from position 11 independent of the continued operation of relay 135, and releases in position 11.

The testing operations of the final selector above described take place quickly and that selector will now be in talking position 13.

Therefore, when sequence switch 100 is in

positions

12 and 13 ringing current is connected over the left contact of earn 142, through the winding of relay 143, right back contact ofrelay 110,'right contacts of cam 149 to the ring brush 131, and it will be transmitted over the ring conductor 218 of the final selector, upper contacts of cam ing from position to position 13.

In position 13, a circuit is prepared for relay 110 through its left winding and the lower left contact of cam 113, but the operation of relay 110 is prevented by shunt around its left winding extending through resistance 129, lower right and upper left contacts of cam 120, back contact of relay 1 13, left back contact of relay 110 toground at theupper left contact of cam 113. This shunt is present in position 12 but is ineffective on the right windingof relay 110.

The closure of its lower contact by interrupter 1 15 completes a circuit over the upper left and lower right contacts of cam 116, lower left contact of cam 11 1, winding of sequence switch magnet 100 to battery, advancing the sequence switch to position 1 1.

In position 14, ringing current is connected through interrupter 147 and the right contact of cam 14-2, to the circuit previously raced. Ringing current tone is transmitted to the calling subscriber by means of a circuit, extending from the ringing circuit just traced, through condenser 14A, pper right contact of cam 115, winding of supervisory relay 1 18, lower right winding of repeating coil 138 to battery. The current in the winding of the repeating coi is induc-- tively transmitted to the calling subscribers station informing him that ringing is taking place.

,lVhen the called subscriber answers,'relay 1 13 operates removing the shunt around the winding of relay 110 and that relay operates, cutting the ringing current and adrancing sequence switch 100 to position 15. The operation of relay 110 temporaril supplies talking battery through position 14 of the sequence switch to the called subscriber over the lower right winding of repeating coil 138, winding of supervisory relay 148, upper right contact of cam 115, right front contact of relay 110, right con tacts of cam 1 19, to the ring conductor, the tip conductor being grounded over the lower rightcontact of cam 13%. l Vhen sequence switch 100 leaves position 14 relay 110 releases, opening these temporary circuits but circuits are closed in position 1 1% which overlap, the temporary circuits sufficiently to preventthe release of relay 148. These circuits remain closed through position 16 and may be traced as follows from the outgoing ring conductor over the upper contact-of cam 134 and the upper right winding of repeating coil 138 to ground and from the outgoing ring conductor over the upper contacts of cam 1 19, winding of relay 148 and the lower right winding of repeating coil 138 to battery, respectively, operating relay 1 18.

Sequence switch 100 is immediately advanced to position 16 in a circuit over the upper contacts of cam 112, upper left contact of cam124i to ground. .l/Vith sequence switch 100 in positions 14 to 16, relay 110 is released. The circuits from the windings of relay 135 in positions 15 to 16 of sequence switch 100 to the tip and ring conductors of the incoming trunk circuit may be traced as follows: battery, through the right winding of relay 135, upper winding of retardcoil 136, upper left contact of cam 115, upper right andlower left contacts of cam 125, left back contact of relay 110, lower right and upper left contacts of cam 137 to the upper left winding of repeating coil 138; from ground over the lower right contact of cam 113, back contact of relay 10G, lower left and upper right contacts of cam, 141, left winding of relay 135, lower winding of coil 136, upper right and lower left contacts of cam 1 16, right back contact of relay 110, right contacts of cam 1 10 to the lower winding of repeating coil 138. These circuits supply battery and ground to the district selector in thereverse direc tion from that previously traced, for the purpose of operating a supervisory signal, controlling coin collecting apparatus or any other desired operation.

As soon as switch 100 reaches position 16 relay 110 is reoperated in a circuit from battery through resistance 129, left winding of relay 110, frontcontact of relay 1 18, upper right contact of cam 108, lower left contact of cam 107 to ground. Sequence switch 100 remains in position 16 throughout conversation and relay 110 remains operated under the control of the called subscriber. lVith relay 110 operated the circuits of relay 135 are from battery through the right winding of relay 135, upper winding of coil 136, upper left contactof cam 115, right front contact of relay 110, right contacts of cam 14:0, lower left winding of repeat coil 138; from ground over the lower right contact of cam 113, back contacts of relay 106, lower left and upper right contacts of cam 141, left winding of relay 135, lower winding of coil 136, left contact of cam 117, left'front contact'of relay 110, lower right and upper 1 left contacts of cam 13?, to the upper left winding of repeat ,coill138 and over the calling line and to battery over the circuit above traced.

When the calling subscriber restores his llll) relay 106 to ground at the lower left contactof cam 113, In this circuit the sequence.

switch is advanced to position 18, as soon as the sequence switch leaves position 17, the circuit of relay 148 is opened, in turn opening the circuit of relay 110, if these relays have not been released by the disconnection of the called party.

lVhen the sequence switch arrives in position 18, a circuit is closed from battery, winding of. downdrive magnet i150, lower right contact of cam 108 t6 ground at the j lower. left contact of cam 107. Theselector switch is restored to normal'position under the control of the downdrive magnet 150. As soon as it reaches normal a circuit is closed from battery, through the winding of sequence switch magnet 100, lower right contact of cam 114,v normal commutator segment 151, brush '128 to ground at the upper right contact of cam 124, advancing the sequence switch to position 1, li hile the sequence switch remains in position 18,

ground is connected to the tip and ring terminals appearing. in the bank of-the district or oilice selector, to prevent false operation of the sender if this incoming selector is. taken for use during itsrestoration. These circuits may be traced from the ti w conductor, over the upper left Contact of cam 108 to ground at the lower left contact 107 and from the ring conductor over .he.

upper right and lower left contacts ofcani 109 to ground.

When sequence switch 100 leaves position 17% ground is removed from sleeve brush 132, permitting relay 208 to release.- The release of relay 208 advances sequence switch 200 to position 16 in a circuit from battery through the winding of magnet 200, upper leftcontact of cam 223, to ground at the left back contact of relay 208.

In positions 15 to 15 4 of sequence switch 200 a circuit is closed from battery through the left winding of relay 205, upper contact of cam 229, right winding of relay 205, upper contacts of cam 207, back contact of relay 237, lower left contact of cam 217, lower right contact of cam 210, to ground at the lower right contact of cam 222. called subscriber has not restored his receiver to the switchhook, relay 205 locks in a circuit extending through its two windings, as: previously traced, left contacts of 351111 206, right front contact of relay 205, upperright contactof earn 224, over the If the called subscribers loop, back to the right contacts of cam 202, left front contact of relay 205 to ground. It the called subscriber still fails to hang up his receiver, interrupter 243 will close its upper contact, after an interva completing a circuit there over, over the upper eft contact cf cam and lower left contact of cam 209 through the winding of relay 208110 battery. 'Rclay 208 operates and completes a circuit through the winding of sequence swit 'h magnet 200, upper left contact of cam 210, lower left contact of i 217, to ground at the let front contact of relay 208sadvancing the sequence switch to position 17, releasing relay 208. After a predetermined interval, interrupter 243 closes its lower contact and extends a circuit thereover the lef Contact of. cam 242 and thence as traced through the winding of relay 208. Relay 208 again advances the sequenceswitclnthis time to position 18, and releases. When the sequence SWll-ill leaves position 17, the

holding circuit of relay 205 epened an that relay releases.

If thecalic subscriber hangs up promptly the locking circuit above described for relay 205 will be open and. that relay will release in position 10. Sequence switch'200 is then advanced to position 18 in a circuit over the lower left contact of cam 223 to ground at the left back contact of relay 205.

In positionlS a circuit is closed for downdrive magnet 24%, extending over the lower right contacts of cams 217, 210 and 222 to ground. The selector switch is restored to normal under the control of magnet 24%;, trip magnet 226 being operated. W hen the selector reaches its normal position, a circuit is closed from battery through the winding of sequence switch magnet 200, lower right contact of cam 223, normal commutator ment 2415, brush 228. to ground atthe lower right contact of cam 222, advancing the sequence switch to position 1.

The release of relay 208 when sequence switch 100 leaves position 17 connects ground to sleeve conductor 21%, :trei'n the'lower contact of cam 22*, through the winding of relay 287, lower left contact of earn 238, right baclr contact of relay 208, and the upper contacts of care 211. This ground serves to marl: the final selector busy to other incoming selectors. lVhen sequence switch 200 arrives in position 16, ground over the left contact of cum 225 is substituted for ground.- through the messes closed in position 12 through the winding of downdrive magnet 2-14 lower right contact of cam 217, upper right contact of cam 210 to ground at the left front contact of relay 205. The final selector is restored to nor mal under the control of magnet 2-141, the trip magnet 226 also being operated at this time. lVhen the final selector reaches normal, a circuit is closed from battery through the winding 01 relay 20S, lower contacts oi cam 209, normal commutator brush 228 to ground at the lower right contact ot cam The operation of relay 208 advances sequence switch 200 to position 13 as previou ly described. With the tinal V ector 4 a circuit closed from battery through the winding of magnet 200, lower right contact of cam 223, normal segment 245, brush 228 to ground at the lower right contact of earn 222, advancing the sequence switch 200 to position 1%.

When the sequence switch 200 leaves position 12, the holding circuit relay 205 opened and relay 205 relei V 205 released and sequence s :h 200 in position 14, a circuit is closed from ground through interrupter 247, lover left contact oi earn 229, left winding of relay 2% to battery causing relay 205 to oper 'e intermittently. On each operation of relay 205 a circuit is closed from ground through the secondary wi1 of tone '1- il upper contact oi cam 20%, resistance 203, upper right and lower left contacts of cam 206, V1113 front contact of relay 205, lower contact of cam 22 1, to ring cnductor'218, and thence through relay 143 to the ringing source sequence switch 100 being at the time in position 12. Belay 1 13 operates, ausing the advance of switch 100 from position 12 to talking pos tion 16, in which position the tone is transmitted to the lower ri ht winding of repeating coil 138 from whence it is inductively transmitted to the calling subscriber, indicating the fact that the line busy. lVhcn the calling subscriber resrorcs his receiver in response to this signal, sequence switch 100 is advanced from positibn 16 to position 18, releasing relay 208 and advancing sequence switch 200 to position 16, as previously described. Since the final se ector is normal at this time, a circuit will be closed from battery through the sequence switch magnet 200, lower right contact of earn 223, normal segment 2 15, brush 228, to ground at the lower right contact of earn 222, advancing the sequence switch 200 to position 1 and restoring the final selector completely to normal.

If the linal selector should fail to operate correctly and advance sequence 100 out of position 8 within a predetermined time, a circuit is closed by means of interrupter 15? extending from battery, through the right winding relay 135, retard coil 136, lower contact of interrupter 157, upper left contact of cam 133 to ground. lhe operation of relay 135 in this circuit closes a circuit for supervisory relay 148 extending from but tci through the lower right winding 01' re 1 ml 138, winding of relay 1&8, left contacts of can lei-9, frontcontact ot relay 135, lelt contacts of cam 1 10, n ding of retard coil 136, lelt winding of i-el- 135, right contacts of cam 1&1 to ground. This circuit serves to hold relay 135 operated as well as to operate relay 14S. .Vith relay 118 operated, as soon as interrupter 157 closes its upper contact, a circuit is completed from ground over the upper contact oifjcam 133, upper contact of interrupter157, frontxcontactoi, relay 1&8, left winding" of relay 110, resistai'ice 129 to battery. .Helay 110 operates in this circuit and advances the sequence switch to position 9 as previously described.

ions

9 and 10 relay 106 is connected erse direction to the incomin line c ed, operating relay 110and ad- \ancin the sequence switch. to position 11. is connected to the incoming line crates relay 110 asbefore, advancseauence switch to position 12.

p on v described by operation of interrupter 1 and operation o1 relay 110. The sender responds to the premature reverse battery signal to cause the district selector to connect a tone to the calling line to indicate that the call could not be completed. when the'calling subscriber restores hisreceiver in response to this tone, relay 135 releases, operating-relay 106 which closes the circuitof relay 110 and thus advances switch to position 15. Switch 100 is then advanced to position 16 over upper right and lower left contacts of cum 122, left front contact of relay 106 to groundat cam 115. Since relay let-8 is not operated'when the sequence switch arrives in position 16, relay 110 is not operated and the selector proceeds to restore as above described.

Although the present invention has been disclosed in connection with panel type switches it may be applied to other kinds of switches.

Vhat is claimed is:

1. In a telephone system, a called line, selector switches extending a connection to said line, a sender for controlling said switches, a plurality of control circuits ex tending between said switches, means in one of said switches under control of said sender for controlling the selecting functions of a succeeding switch, means in said first switch for controlling said sender, and means at said second stage for simultaneously establishing said control circuits to control said last means.

2. In a telephone system, a called line,

ee to position 141 is the sameas to said line, a sender for controlling said switches, a plurality of control circuits ex-- tending between said switches, a pair of relays in one of said switches, a fundamental circuit connecting said sender with one of said relays, means for operating said relay to control the selecting functions of a succeeding switch, means in said first'switch to reverse the connection of said relay to said fundamental circuit to control said sender,

and means for rendering said reversing means effective controlled by the simultaneous operation ofboth said relays over said control circuits established by said second switch. v

4. In a telephone system, a called line, selector switches for extending a connection to said line, a sender for controlling said switches, a plurality of control circuits extending between said switches, means in one of said switches under control of said sender for controlling the selecting functions of a succeeding switch, means in said first switch 7 for controlling said sender, said means controllable from said second switch over said control circuits simultaneously established at said second switch, and independent means effective if said circuits are not established within a predetermined time interval to control said sender controlling means. 7

5. In a telephone system, a called line,-

selector switches for extending a connection to said line, a sender for controlling said switches, a pluralityof control circuits extending between said switches, a pair of relays in one of said switches, one of said relays controlled by said sender to control the selecting functions of a succeeding switch,

means in said first switch for controlling said sender, said means controllable by the simultaneous operation of both said relays over said control circuits established by said second switch,and independent means effective if said circuits are'not established within a a predetermined time interval to control said sender controlling means.

6. In a telephone system, a called line,

selectorswitches for extending a connection to said line, a sender for cont-rollin said switches, a pair of relays inlone of said switches, a plurality of control circuits extending between said switches, a fundamental circuit connecting said sender with one of said relays, means for operating said relay to control the selecting functions of a succeeding switch, means in said first switch to reverse the connection of said relay to said fundamental circuit to control said sender, means for. rendering said reversing means effective controlled by the simultaneous operation of both said relays over said control circuits established by said second switch, and independent means effective if said cir cuits are not established within a predetermined time interval to render said reversing means effective.

7. In a telephone system-,a called line, selectorswitches for extending a connection to said line, a sender for controlling said switches, a pair of relays in one of said switches, a sequence switch associatedwith said switch, a fundamental circuit connecting said sender with oneof said relays, means for operating said relay to control the select-.

ing operations of said switch, means under the control'of said relay to operate said sequence switch following each of said selecting operations, means for operating said relay to control the selecting operations of a succeeding switch, and means for again operating said sequenceswitch operating means only after all of the selecting functions of said succeeding switch have been completed.

8. In a telephone system, a called line, selector switches for extending a connection to said line, a sender for controlling said switches, a pair of relays in one of said switches, a sequence switch associated with said switch, a fundamental circuit connecting said sender with oneof said relays,

means for operating said relay to control the selecting operations of said switch, means under the control of said relay to operate said sequence switch following eachof said selecting operations, means for operating said relay to control the selecting operations of a succeeding switch, and means for again 4 operating said sequence ,switch operating means only after all of the selecting functions of said succeeding'switch have been com- CLARENCE H. BERRY.