Patent GB-286659-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M19/00
Filed: 1928-03-07
Abstract: 286,659. Associated Telephone & Telegraph Co., (Assignees of Wicks, J.).' March 7, 1927, [Convention date]. Automatic and semi-automatic exchange systems.-A systern includes an exchange X in which current is fed to both parties from the connector, and an exchange Y of the kind described in Specification 191,003, in which current is fed to the calling party from the first selector and to the called party from the connector. impulses being repeated at the first selector over the a-wire, and the b-wire serving for the control of change over at the succeeding switches and for the transmission of supervisory signals. Arrangements are described for dealing with calls between the exchanges X, Y, and with incoming toll calls from a manual position, impulsing and supervision being effected over the junction wires in parallel. The general arrangement of the switches is shown in Fig. 1. Local call in exchange Y. On seizure of an idle first selector repeater SR2, switching relay 201 of the line switch energizes in series with relay 211. and line relays 207. 208 energize over the calling loop and connect up release relay 209. Impulses are repeated to the vertical magnet, and when change-over relay 210 falls back, the rotary magnet rotates the wipers until an idle trunk is found. Switching relay 212 energizes in series with release relay 231 of the selector S5. Impulses are now repeated over the a-wire bv line relay 208 to energize impulse relay 232, relay 210 being energized at the first impulse to operate change-over relay 233 by the connection of battery to the b-wire. The relapse of relay 233 at the end of the vertical movement initiates the rotary operation. The next selector S6 operates in a similar manner to make connection with the connector C2, in which release relay 324 energizes over the incoming test wire. Impulse relay 326 responds to impulses over the a-wire, while relay 327 is energized over the b-wire during each train, and on falling back advances the side switch 329, 330 to the next position. If the wanted line is idle, ringing takes place, and on the reply of the called party, the talking circuit is completed and relays 326, 327 energize thereover, and the side switch moves into the 4th position, in which the incoming b-wire is cannected to battery through low-resistance relay 325. A small current flows in the talking wires during conversation through resistances 205, 206 at the first selector repeater SR2, the battery connection to the a-wire being through resistance 328 at the connector C2. The opening of offnormal contacts such as 213, 230 reduces the holding current in the test wires. When the calling party hangs up, line relays 207, 208 relapse and connect up relay 210. Relays 209, 210 fall back in turn, and metering relay 217 operates momentarily over the b-wire and connects direct ground to the test wire to actuate the meter M. The holding ground of switching relay 212 is removed, and release relay 231 of the selector S5 falls back, opening the holding circuit of the selector S6. The connector C2 is released in a similar manner. Call from exchange X to exchange Y. Connection is made over the first selector S1 and repeater R1 to the second selector repeater SR3 at the exchange Y. Line relay 404 and release relays 405, 409 energize, and the vertical and rotary magnets 415. 413 operate to seize a trunk 419 - - 421 leading to the selector S6, changeover being effected by relay 406. Switching relay 410 energizes, and further impulses are repeated by line relay 404 over the a-wire, battery being connected to the b-wire during each train by relay 406. The selector S6 and connector C2 operate as described in the last paragraph. When the called party replies, the side switch 329, 330 moves into the 4th position, and relay 407 energizes over the b-wire in series with relay 325, and connects up reversing relay 403, which controls metering or supervision at the exchange X in the usual manner. When the calling party hangs up, relays 404, 405, 409 fall back and initiate the release of the succeeding switch. Call from exchange Y to exchange X. Connection is made over the first selector repeater SR2 and repeater R2 to the second selector S3 at the exchange X. In the repeater R2 release relay 601 energizes and closes the bridge across the outgoing junction, which includes the upper winding of polarized relay 604. Impulses received over the a-wire are repeated over the outgoing loop by impulse relay 602, while relay 606 is energized during each train by battery applied to the b-wire and short-circuits relav 604. When the called party replies, the line current is reversed at the connector, and relav 604 responds and connects up relay 603, which locks, inserts a resistance in series with impulse relay 602, and connects battery through relay 606 to the b-wire in preparation for metering when the calling party hangs up. Release relay 601 on falling back frees the outgoing junction and disconnects relays 603, 604. Toll call from a manual position to exchange Y. On plugging into the jack J of the junction terminating in the selector repeater SR1, release relay 553 energizes, operating relay 552 and connecting the wires of the junction in parallel to supervisory relay 554, so that this relay energizes in series with line relav 505 and lights lamp L. Release relays 506, 511 energize. The operator throws the dialling kev K and operates her dial CD and the vertical and rotary magnets 517 515 operate to seize a trunk 217 - - 219 leading to the selector S5, chance-over being effected by relav 507. Switching relay 512 energizes, and further Impulses are repeated by line relay 505 over the a-wire, battery being connected to the b-wire during each train by relay 507. The succeeding switches operate as already described. When the called party replies, relay 508 energizes over the b-wire and connects up relay 504, which closes a local circuit for relay 505 and connects the junction wires to ground through relay 503. thereby releasing relay 554 and extinguishing lamp L. When the plug is removed from the jack J, relay 553 falls back, connecting the junction wires to battery through relay 551, which energizes and disconnects relay 552. Relay 503 energizes, disconnecting line relay 505 and release relay 506 and closing a fresh circuit for relay 508. Relay 552 on relapse disconnects battery from the junction wires, so that relays 503, 508, 504, 505 fall back and the selector repeater SR1 releases. In the case of an unsuccessful call, relays 508, 504 are not operated, and when the operator clears down, line relay 505 remains energized over relav 551 due to the difference in potential of the batteries at the automatic exchange and at the toll position until relay 552 falls back. Modified toll call arrangement. The use of special selector repeaters SRI for incoming toll calls may be avoided by providing a repeater R3, Fig. 8, between each junction and a regular selector repeater SR2'. When the junction its seized, line relay 801 energizes over the junction wires in parallel, and repeats dialled impulses over the loop to the selector repeater SR2<1>. On the reply of the called party, relay 804 energizes over the b-wire, closing a local circuit for line relay 801 and connecting the junction wires to relay 802 to give supervision to the toll operator. Release takes place substantially as described in the last paragraph.