Patent GB-191416411-A (GB)
Title: Improvements in Automatic Telephone Systems.
Filed: 1914-07-09
Granted: 1915-07-09
Abstract: 16,411. Betulander Automatic Telephone Co., Bryant, G. H., and Ward, F. M. July 9. Automtrtic exchange systems.-In a system in which the subscribers are divided into groups served by different groups of connectors, each connector FC, Fig. 6, is associated with a finding-switch JF by which it can be connected with any of the trunks from the call-finders CF, each call - finder trunk being multipled through all the switches JF. An auxiliary switch or group marker GM, operated by the first set of impulses, closes a starting-circuit through a distributor D2, associated with the wanted group of connectors, to the first idle connector of the group, and the finding-switch JF of this connector is set in action and makes connexion with the calling trunk. In large exchanges, there may be secondary call-finders between the call-finders CF and the trunks with which the group markers are associated. The capacity of the secondary finders may be reduced by dividing them into two groups serving different sets of trunks from the primary finders, corresponding switches of the two groups being connected to the same outgoing trunk. In the same way, the capacity of the finders JF may be reduced by connecting them in pairs to the connectors FC. Call-finder CF and distributor D1. In response to a call on a line X, the line relay L1 closes a circuit through the wiper DW1 of the distributor D1 to the magnets M1, T1 of the first idle call-finder of the group to which the calling line has access. The call-finders are of the gravity type described in Specification 6465/13, and the energization of the magnets M1, T1 allows the finder to drop. The first circuit of these magnets is opened at the offnormal switch RS1, but they remain energized over the test wiper W1 until the unearthed test terminal of the calling line is reached, whereupon they de-energize and. arrest the finder. The de-energization of the magnet T, connects ground to the test circuit and energizes the cut-off relay CO1, which disconnects the line relay L1. In the meantime, the movement of the finder from its normal position has closed a circuit through the wiper DW2 of the distributor D1 to the magnets M5, A5, which lift the distributor shaft until an idle finder is reached. If the distributor reaches its top position without arriving at an idle finder, the shaft-switch RS4 closes a circuit for a relay CR, which locks itself up and closes a circuit for the magnet M. but open-circuits the magnet A5. The energization of the magnet M5 when the magnet A, is de-energized causes the release of the switch D1, which drops to its lowest position, in which a projection S opens the locking-circuit of the relay CR, and the distributor then steps up again until an idle finder is discovered. If all the finders of the group are busy, the circuit 60 of the relay CR is everywhere disconnected from battery at the off-normal switches RS1, so that the distributor stays in its top position and is restrained from useless hunting. Group marker GM, finding-switch JF, and distributor D2. As soon as the calling line is found, the relays IR1, GR and the magnet A2 are energized. The first set of impulses, which are in the form of interruptions of the line circuit X, are repeated to the magnet M2, which steps up the switch GM to select one of the relays MR1, MR2, MR3, &c. As soon as the switch GM leaves its normal position, the original circuit of the magnet A2 is opened; but this magnet remains energized by a contact of the magnet M2 as long as impulses are passing. At the termination of the series of impulses, the magnet A2 de-energizes and completes the circuit of the selected relay, for example MR3, and this relay closes a starting- circuit through the wiper DW2 of the distributor D2 to the magnets M3, T3 of the finder JF of the first idle connector trunk of the wanted group. The switch JF acts in the same way as the call-finder CF to find the calling trunk, which the relay MR3 has marked selectable by disconnecting earth from its test circuit. The magnets M3, T3 then de - energize, and the latter connects the earthed relay RR to the test circuit so as to restore the trunk to a non- selectable condition and to energize the relay CO2, which opens the starting - circuit. The distributor D2 operates in the same way as D1 to prepare a starting-circuit for the next idle connector trunk. Connector FC. The connector is of the kind described in Specifications 19,553/11 and 13,173/14. The second set of impulses is repeated by the relay IR1 over the a side of the trunk to the relay IR2, which repeats them to the magnet T4, which drops the connector shaft and wipers over ten sets of terminals at a time. A relay DR is energized as long as the impulses pass and then de-energizes and prepares circuits for the relay ER and magnet M4. The final set of impulses is therefore repeated to the magnet M4, which steps up the connector shaft and wipers from one set of contacts to the next. As long as this series of impulses is passing, the relay ER is energized and local circuits are closed for the magnets A4, T4. Supply of ringing-current. At the termination of the final set of impulses, the magnets ER, A4, T4 de-energize (unless the wanted line is busy, in which case the relay T4 remains energized over the test circuit), and the magnet T4 drops the wipers LW5, LW6 on to the terminals of the selected line, completing a ring- ing-circuit through the control relay SR. When the subscriber answers the call, the current in the ringing-circuit is sufficiently increased to energize the relay SR, which connects the called line to the back-bridge relay FR and locks itself under control of the relay RR by opening a short circuit across its upper winding. Release. The release is under the control of the calling subscriber. When he hangs up his receiver, the relays IR1, GR de-energize, and a circuit is completed for the call-finder magnet A1, which completes an interrupter circuit for the magnet M1 and a steady circuit for the magnet T1, whereby the finder is stepped up until it regains its normal top position. A circuit is also closed for the magnet M2, which drops the group marker GM to its normal bottom position. The release of the group marker deenergizes the relay MR3, which open-circuits the connector relay RR, the de-energization of which energizes the magnet A3, whereby the finder JF is released in the same way as the finder CF. At the same time, the relay ER is energized and completes a steady circuit for the magnet A, and an interrupter circuit for the magnet M4, whereby the connector is stepped up to its normal top position.