Patent GB-153407-A (GB)
Abstract: 153,407. Western Electric Co., and Deakin, G. Aug. 23, 1919. Semi-automatic exchange systems.-Relates to a system in which outgoing calls from a manual main exchange to an automatic district office are made over trunks which terminate at both ends in selectors having terminals individual to the lines at the district office, the calls being dealt with by the exchange operator in just the same way as if the wanted subscribers were wired directly to the manual exchange. When an operator inserts a calling-plug in the jack individual to a wanted district-office subscriber, connexion is made to an idle trunk by a two-coordinate jackfinder, and a connector at the district-office end of the trunk is moved to corresponding terminals under control of registers which set themselves in accordance with the movements of the jack-finder. Incoming calls are connected to idle exchange trunks by call-finders at the district office. Provision is made for metering, coin-freed stations, re-ringing a called subscriber after he has disconnected himself, and for interrupting existing connexions in favour of trunk calls, without in any case requiring a different treatment on the part of the operator from that which she normally uses in the case of subscribers connected directly to the exchange. Calls from district office to main exchange. A calling district office subscriber A, Fig. 1, is connected to an idle main-exchange trunk by first and second call-finders, which test for the calling line over terminals 105, 115, and the sequence switch 120 associated with the second call-finder then moves to its 5th position, energizing relays 129, 137, 144, 106, 101 (but not the meter 102 which requires a stronger current) and de-energizing line relay 103, test relays 107, 108, 119, 122, and pilot relay 109. If two second callfinders should make connexion simultaneously, the divided current from terminal 115 is insufficient to energize the low-resistance holding-windings of their test-relays, which relapse and allow a third finder to make connexion, while the sequence switches of the two interfering finders automatically run through a cycle. The second call-finders are arranged in pairs, with their sequenceswitches 120 controlling one another's circuits over the contacts 124, 132 in such a way that one switch of the pair cannot move out of its 18th into its 1st position until the other switch has moved out of its 1st position. Bv this means only half the total number of second call-finders can be started hunting simultaneously. In the 5th position of the switch 120, contact 146 grounds one side of the exchange trunk to energize relay 202, Fig. 2, and call lamp 203, and the operator answers the call with a plug 205, energizing relay 201, which extinguishes the lamp. Supervisory relay 212 is now energized in series with relay 145, Fig. 1, which energizes relav 136 to drive switch 120 to its 8th position, in which conversation can take place after the operator has completed the connexion. The calling subscriber can signal the operator in the usual way by depressing his switchhook, de-energizing relay 144, which de-energizes supervisory cord relay 212 by cutting in the lefthand high-resistance winding of relay 145. The eventual disconnexion of the calling subscriber is signalled in the same way. Metering. The operator's metering-key 214 opens the exchange line, de-energizing relays 145, 136, and connects a high-voltage battery to the tip side of the line to energize a polarized relay 138, which energizes relay 151, which locks itself up, so that subsequently, during the release of the connexion, contact 127 in its 13th position connects a boosting-battery 149 to the circuit 114, 104 to energize the meter 102. The metering-key also drives switch 120 to its 12th position as described below. Coin-freed arrangements. Coin-freed stations have the tip side of the line connected to a polarized magnet 52 responsive to high-voltage current of one polarity to collect the coin and of the opposite polarity to restore the coin. Collection of the coin is effected by the operator's metering key 214, which excites the polarized relay 138, which energizes relay 130, which connects the tip side of the calling line to a high-voltage battery of the right polarity. Relay 130 also de-energizes relays 137, 144, so that switch 120 is driven to its 9th position, and afterwards, when key 214 is released, to its 12th position, in which relay 138 is disconnected, so that if the operator presses key 214 a second time, to check the operation of the coin machine, relay 216 and lamp 217 are not energized. If the coin is to be restored, the operator presses her coin-release key 215, as she would for a subscriber connected direct to the exchange, but this action is without effect as the current transmitted to the relay 138 is of the wrong polarity to excite it; but during the release of the connexion a restoring current is sent to the tip side of the calling line by contact 131 in its 13th position.. Release. When the calling subscriber has disconnected himself and the operator withdrawn the answering-plug, switch 120 is driven to its 18th position, from which it is driven to normal over contact 132 and contact 124 of the switch belonging to the other cali-finder of the same pair, provided this switch has left its normal position. Calls from main exchange to district office. The operator inserts a calling-plug 255, Fig. 2, in a jack 254 individual to the wanted subscriber. An idle trunk to the district office is connected to this jack by a finding-switch, Fig. 4, pre-selected by a switch 450, and is extended to the wanted line by a connector, Fig. 5, at the district office. The jack-finders and connectors are 200-point switches, with 10 levels of 20 sets of terminals, which are inversely connected; for example, if a given subscriber is wired to the 17th set of terminals in the 4th level of the connectors, the exchange jack individual to him will be wired to the 3rd set of terminals in the 6th level of the finders. The selection of the proper level in the connector is determined by a tens register 480, Fig. 4, and the selection of the proper set of terminals in the selected level of the connector is determined by a hundreds-and-units register 490, both registers being set by the corresponding movements of the jack-finder. Jack-finder and registers, Fig. 4. The sleeve relay 265, Fig. 2, closes a circuit through contact 457 of pre-selecting switch 450 to relay 423 of an idle jack-finder, so as to drive switch 400 to its 3rd position, energizing the brush-choosing magnet 430. As this magnet rotates its spindle, interrupter 435 intermittently closes a circuit through both windings of relay 495, the left-hand branch passing through the tens register 480. Each time this circuit is closed, relay 495, being differentially wound, does not at first respond, but register 480 moves forward to its next position, short-circuiting left-hand winding of relay 495 at contact 481 as it passes, so that relay 495 is energized and holds open the register starting-circuit as long as the impulse continues. In this way the register is advanced in step with the brushchoosing spindle. When register 480 reaches a position corresponding to the tens digit of jack 254, it closes a circuit 487 for test relay 406, which locks itself in series with relay 407, which opencircuits magnet 430 and drives switch 400 to its 4th position, in which relays 406, 407 are de-energized. The brush-carriage magnet 440 is now energized to trip and rotate the selected set of brushes, and the hundreds-and-units register 490 is advanced in step with it under control of interrupter 445 and relay 495. When the brushes reach the terminals of jack 254, relay 406 is energized in series with relav 266 and locks itself in series with relay 407, which open-circuits magnet 440 and drives switch 400 to its 5th position. Contact 405 now closes a circuit to advance switch 450 to pre-select another idle finder. Connector, Fig. 5. In the 5th position of switch 400, relay 423 is bridged across the trunk 461, 462 and is energized in series with relay 506, Fig. 5, so that switches 400, 500 are advanced to their 6th and 2nd positions. The brush-choosing magnet 520 is now energized and rotates its spindle, and interrupter 525 intermittently grounds the wire 462, short-circuiting relay 423, which co-operates with relay 495 to advance the tens register 480, step-by-step. When the register reaches its normal position, contact 482 closes a circuit for driving switch 400 to its 7th position and for energizing relay 425, which open-circuits relay 506, which de-energizes magnet 520 and drives switch 500 to its 5th position. In the 7th position of switch 400, relay 425 is open-circuited and relay 506 is again energized in series with relay 423, which drives switch 400 to its 8th position, and as soon as switch 500 reaches its 5th position the brush-carriage magnet 530 is energized to trip and rotate the selected set of brushes. The interrupter 535 now controls relays 423, 495 to advance the hundreds-and-units register 490 in step with the brushes, and when register 490 reaches its normal position, relay 425 deenergizes relay 506 to stop the movement, and switches 400, 500 advance to their 13th and 10th positions. The brushes are now on the terminals of the wanted line. Busy test. As switch 500 runs through its 6th position it closes the circuit of test-relay 556. If the wanted line is busy, relay 556 fails to energize and switch 500 stops in its 10th position, connecting up a busy-tone apparatus 546 and intermittently energizing relays 540, 537. The trunk 461, 462 is thus intermittently opened, and these signals are repeated by relay 409 to the operator's cord circuit, where they operate the supervisory signal 256. The connexion is released when the operator takes down the plug 255, the