Patent GB-316931-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1929-05-22
Abstract: 316,931. Associated Telephone & Telegraph Co., (Assignees of Wicks, J.). Aug. 6, 1928, [Convention date]. Automatic and semi-automatic exchange systems; metering.-A differential relay common to the battery feeding circuits of both calling and called parties is adapted to be energized in response to ground placed on both speaking wires by a toll operator in order to break down an established local or inter-exchange automatic connection. The invention is described in connection with a forward-loop impulsing system having group selector feed. A local call is set up over a first selector-repeater S1, Fig. 3, intermediate selectors S, S3, Fig. 4, and a rotary connector RC, Fig. 5, which may either hunt for an idle line in a group or be set on to a particular line thereof. Talking battery is fed over the windings of differential relay 224 at S1 and over relays 221, 223 respectively to the calling and called parties, and the energization of 224 by the toll operator operates relay 228 which opens the metering circuit and disconnects 221, 223 to effect the release of the connection. Normally, metering occurs during release. When a rotary connector is taken into use over a toll selectorrepeater TTS, Fig. 2, the direction of current flow over the forward loop is reversed, and a differential relay 403 at the connector energizes to change the busy marking of the called line to prevent breaking in on a line which is toll-busy. The rotary connector has a combined change-over and release relay 401 and a line relay 402 which acts also as a stepping relay during rotary hunting. A call to a distant exchange is set up over selector-repeater S1 and an incoming selector repeater ISR, Fig. 6, and each outgoing trunk has an individual relay group TMR which sends a predetermined number of impulses to operate the called subscriber's meter. Local call; first selector repeater S1, Fig. 3. When a calling party A is connected by line switch LS to selector S1, a. circuit is completed for the windings of differential relay 224 and line relay 221 in series, relay 224 remaining inert. Release relay 222, normally short-circuited at 241, pulls up over parallel circuits including relay 226 and vertical magnet which do not operate, and relays 223, 227 energize over their upper windings in series with 224 (upper) which still remains unoperated. Relay 227 prepares, at 266, a holding circuit for 223 during impulsing, locks up over 270, and connects up dialling tone from DT over 268. Each relapse of relay 221 during dialling connects direct ground from 247 to the vertical magnet short circuits 222 to make it slow to release, and energizes relay 226 which also holds during the impulse train since it releases slowly due to current flow over relay 222 when the short-circuit around this relay is opened. Relay 226 also operates during subsequent impulse trains and improves the impulse circuit by connecting direct ground from 264 to the lower conductor. When relav 226 falls back at the end of the train, a self-interrupting circuit (245, 255, 278, 262, 252) is completed for the magnet 231 which rotates the selector until its circuit is opened by switching relay 229 which operates in a circuit from ground at 246, 269, 302 to battery over resistance 345 at an idle second group selector S2. Relay 229 locks overs its lower winding in series with magnet 231, short-circuits 226 (lower), holds 222 over 226 (upper), and connects the ground over the upper low resistance winding of 228 to test terminal. If the call is to an operator over a tenth level, the resistance in the first circuit is such that 228 operates and opens the metering circuit. Battery and ground over the upper and lower windings of relays 224, 223 is now extended forward to line relay 304 of the second group selector S2, relay 223 remaining operated in the circuit. Second and third group seelctors, Fig. 4. Line relay 304 opens at 310, the short circuit about relay 305 so that this relay operates in a circuit Jrom battery over 345, vertical off-normal springs 312, eleventh rotary step springs 317 to ground at 302, and shunts the springs 312 at 316. The second digit is repeated by line relay 221 to line relay 304 which operates the vertical magnet 307 and intermittently shunts relay 305. At the end of the train the shunt persists and 305 falls back to complete a self-interrupting circuit for the rotary magnet 308. When the test wiper picks up battery potential, switching relay 306 operates over its lowest winding, locks to the release wire over its upper winding, disconnects 305 from the release wire, and extends the loop to the line relay of S3 which operates in the same manner as S2. Line relay 304 falls back and opens the circuit of the rotary magnet 308. Rotary connector RC, Fig. 5. Battery potential at an idle connector is fed in parallel over resistance 442 and winding cut-off relay 405 (upper), off-normal springs 443, to the test terminal of the preceding selector, and relay 405 operates when the switching relay thereat cuts out its lower windings. The impulsing loop now extends over the upper windings of relays 402, 403 in series. Relay 403 is differential and does not energize. Relay 405 is slow to pull up and energizes shortly after 402, opens the ringing circuit at 434, 438, disconnects resistance 442, and locks itself to the release wire. The next digit is repeated to line relay 402 which operates the vertical magnet 410 over 416, 430, 448, 419, 435, and during the train slow-torelease relay 406 is energized in a parallel circuit. After the first vertical step, the circuit of slowto-release relay 408 is completed over off-normal springs 420 when relay 402 is energized, and at the end of the train, 406 falls back to complete a circuit (457, 445, 433) for 401 which locks to the release wire and disconnects relay 405 therefrom so that this relay falls back to prepare the ringing circuit. Relay 401 also connects up the rotary magnet 411. The ground at 435 is replaced by ground at 414. It will now be assured that connection is required with one of a group of lines having the same number, for example the lines connected to the first five terminals shown in Fig. 5A. In response to the digit 1, relay 402 completes the circuit (414, 418, 419, 448, 430, 416) of the rotary magnet 411, and group test-wiper 464 is stepped on to terminal 480 which is connected to battery over resistance 481. If this line is busy, test-wiper 469 picks up ground and busy relay 404 operates before 406 falls back. When relay 406 falls back, relay 404 locks over 441, 431, 450, 418, line relay 402 de-energizes since its circuit is open at 432 and 444, and relay 409 (lower) operates in a circuit from ground over 457, 445, 433 to battery on the first group test-terminal. Relay 409 holds over its upper winding to busy ground over test-wiper 465, opens the circuit of 406, and completes a circuit for line relay 402 (lower) extending from battery over 460 to ground over springs 413 of the rotary magnet, so that the line relay and magnet interact to step the connector m search of an idle line in the group. Relay 408 has remained energized up to the present. The setting of a connector on to a particular line of a group will be described later in connection with a toll call. Busy signal. If all the lines are busy, the connector stops on the last contact of the group since ground from 483 over 464 short-circuits the line relay 402, and busy tone is sent back from BT over 429, 447. At the selector-repeater, Fig. 3, relay 223 falls back since the forward loop is open at 432, Fig. 5, and relay 227 de-energizes to complete the circuit for busy tone over the upper conductor. Ringing; completion of connection. When an idle line is found, relay 409 falls' back to stop the hunting, and switching relay 407 (upper) energizes over the switching relay and magnet of the line switch of the idle line, completes the ringing circuit over 405 (lower), connects direct ground from 424 to the test multiple, unlocks busy relay 404, completes a ring-back circuit at 452, and locks over its upper winding in series with the vertical magnet 410. When the called party replies, ringing cut-off relay 405 completes the speaking circuit at the connector and locks to ground at 435 or 414. At the first selectorrepeater, relay 223 fell back when the loop at the connector was opened by the switching relay 407, and was followed by 227 which at 268 completed the talking connection and at 269 connected direct ground to the test terminal. Talking current is fed to the called party over relays 223, 224 and to the calling party over 224, 221. Release and metering. When relay 223 reenergizes over the called loop, metering control relay 225 pulls up over 263, 270, 250 and locks to ground at 246. When the calling party replaces his receiver relays 221, 223 fall back, but the circuit of the release magnet 232 is held open by relay 225. Release relay 222 is short-circuited but before it falls back, 226 operates over its upper winding and connects up an additional ground at 262 to hold the line switch and switching relay 229 during metering, relay 226 being slightly slow to release as its lower winding is short-circuited. The relapse of 222 completes the metering circuit over M, 256, 275, 244, 249 and release magnet 232 which does not operate, and when relays 225, 226 fall back the line switch releases and the first selector-repeater restores to normal. The removal of ground from the release wire causes the selectors S2, S3 to restore in known manner, and release relay 401 at the connector to fall back. If the called party has not replaced his receiver, switching relay 407 is maintained operated over 451, 416, the called loop, 434, 447 and vertical magnet 410, and holds the ringing cut-off relay 405 which maintains ground at 435 to mark the connector busy. When the called party replaces his receiver, relays 407, 405 fall back and the connect