Patent GB-320380-A (GB)
Title: Improvements in and relating to automatic or semi-automatic telephone systems
IPC: H04Q3/42
Filed: 1928-07-11
Abstract: 320,380. Standard Telephones & Cables, Ltd., and Wright, E. P. G. July 11, 1928. Automatic exchange systems.-In a reverting- impulse register-controller system, the registercontrollers for the group and final selecting stages are located at and individual to the switching stage. In the system described, each group of selectors is controlled by common equipment comprising a relay group and a register-controller, but the setting of a final selector in accordance with the units digit is controlled by impulses sent forward by the register-controller. The selectors are of the single motion type which are first stepped over groups of contacts until the desired group is reached, and then select an idle, or the wanted, line within the group. For group selection, the selectors are stepped by a selfinterrupting circuit which is opened, each time a selector reaches the first contact of a group, by a relay which is connected to such contacts of a control bank and sends an impulse to the register. The number of lines in each group may thus be readily varied but this may involve modification of the registers as described later. The register equipment of the group selectors comprises an instepping and revertively controlled outstepping register, and that of the final selectors comprises a tens register stepped out by reverting impulses and a units register which is stepped out to send impulses to the final selector. The group selectors have two sets of wipers. A modified register-controller for final selectors is also described in which the same instepping and outstepping registers are used for both digits. Group selector, Fig. 1. The common equipment is shown below the dot-and-dash line and includes an instepping register N11 - - 14 and an outstepping register N21 - - 24; the individual equipment comprises relay K for connecting up the common equipment, and switching relays HA, HB for the two sets of wipers. When the selector is seized, relays 2, K energize in series over both of their windings in a circuit including normal contacts of N11, N21 and N1. Relay 2 cuts out its low resistance winding to busy the common control group while K cuts into its upper winding, connects up the control group, and closes a circuit over wiper C for magnet R to drive the selector out of its normal position. Impulse relay 1 energizes over the calling loop and is followed by relay 4 which grounds the test wire T at 1, and at 4 disconnects relay 2 and completes a locking circuit for K. At each relapse of relay 1 during dialling, a circuit is completed for slow release relay 3 and the instepping magnet R1, and when the instepping register leaves normal, a circuit is closed over N12 for magnet R which steps the selector on to the first contacts of the first group, relay 5 being energized over wiper C to open the circuit of R. Relay 5 also completes a circuit from ground at 5(1) for relay 6 and the outstepping magnet R2 in series, the relay being, however, short-circuited over the interrupter contacts 12 of the magnet and also over N13, N23 if the first group is the wanted one. Assuming that the first group is not wanted, relay 6 pulls up when R2 operates, and completes the circuit of magnet R so that wiper C leaves the first group contact, relay 5 falls back, R2 de-energizes and drives the outstepping register and relay 6 relapses to complete the original circuit for magnet R. The selector is stepped on until wiper C reaches the first contact of the next group and, if this is the wanted group, relay 6 remains unoperated when relay 5 operates and magnet R2 pulls up, so that on the relapse of relay 3 at the end of the impulse train, relay 7 energizes in a circuit over N12 including N14, N24, locks itself, and at its contacts 2, 3 prepares the circuits of test relays P, Q. Relay 7 also removes the short-circuit about 6 which re-closes the circuit of magnet R. The selector now hunts over the group and when an idle outlet (battery over low resistance on the test terminal T1 or T2) is found relay P or Q energizes, locks up and completes a parallel circuit for relay HA or HB which switches through and opens the circuit of relay 1. Relay 4 falls back to release K and complete homing circuits for the registers, and when the instepping register reaches normal, relay 7 is unlocked and the common control equipment is completely restored. If all the outlets are busy, relay 8 operates over the last contact of the group and wiper C, locks up over N12, opens the circuit of R, and connects busy tone from BT to relay 1. The operation of 8 and relapse of 7 are made sufficiently slow to ensure that P or Q will operate if the last outlet is free. Modified trunking arrangements. The number of lines in a group may be varied by altering the contacts in bank C to which relay 5 is connected. This may necessitate modification of the crossconnections between the instepping and outstepping registers. For example, if digits 5 and 6 are not used contacts 4, 5, 6 of N13 are strapped together and contacts 7 - - 10 of N13 are crossconnected to 5 - - 8 of N23, banks N14, N24 being similarly treated. Final selector, Fig. 2. The individual relays comprise the feed bridge relays 2A, 2D, supervisory relay 2B and the relay 2K which connects up the common equipment including the tens register R11 - - 13 and units register R21 - - 23. When the selector is seized, relays 22, 2K energize, relay 2K locks up over its lower winding and completes the impulsing circuit over relay 21 which energizes relay 24 to prepare a stepping circuit for magnet R1 of the tens register, the magnet R of the selector being energized over 2B(6), C, 2K(10), 2K(9) to step the selector off normal. At each relapse of 21 during dialling, a circuit for R1 is completed over relay 23, the tens unit is registered, and on the relapse of 23 at the end of the impulse train, relay 27 operates over R11 and locks over R22. Relay 27 transfers the impulsing circuit to magnet R2 to register the units digit, and closes a self-interrupting circuit for the magnet R of the selector. The first contact of each group in the control bank C of the selector is connected over 2K(11) to relay 25 which operates when the selector reaches the first of such contacts, opens the circuit of magnet R at 25(2) and closes a circuit over relay 26 and 25(1) for magnet R1, relay 26 being, however, short-circuited. If the wanted line is in the first tens group, a parallel circuit is closed over the last contact of R12 for relay 28 which locks up, opens the circuit of relay 25, and transfers the control to the units register. If the wanted line is in a subsequent group, relay 25 remains operated and when relay 26 operates on the removal of the short-circuit at the interrupter contacts of R1, a driving circuit of the selector is completed. When the selector leaves the first contacts of the group, relay 25 falls back followed by relay 26 and magnet R1 so that the original driving circuit for the selector is restored and the tens register takes one step. The selector steps itself on until the first contacts of the next group are reached, and the above described operations are repeated until the selector reaches first contacts of the wanted group in which case the register, will have been driven to its last contacts. Relay 28 now pulls up as previously described and when series relay 23 relapses after registration of the units digit, a circuit for 27 is completed over interrupter contacts of magnet R2 and R21. Relay 27 completes parallel circuits for magnets R, R2 and 27 falls back when R2 operates, so that the selector and units register step simultaneously until the circuit of 27 over R21 is permanently opened when the register arrives at its last contacts. The locking circuit of relay 27 is opened at R22 but a fresh holding circuit for 28 is completed at this point. Busy test and signal. The test circuit extends from R21 over 2H (lower) and contacts 2 of relay 27 before it has relapsed and if the line is busy, tone from BT is connected to the negative wire over 28 (i) and relay 21 when 27 falls back. Ringing; completion of connection; release of common equipment. If the line is free, relay 2H energizes and locks, opens the holding circuit of 28 and completes the ringing circuit over relay 2F and the return lead RR, a signal being passed back to the calling party over 2H(1). When the called party replies, relay 2F cuts off the ringing and energizes supervisory relay 2B which connects up the feed relays 2A, 2D and completes the connection. Relay 2B locks up over 2A(1), grounds the test wire and releases relay 2K so that the common equipment is disconnected and all the, operated relays thereof fall back. The tens register steps to normal over R11. When relay 24 has fallen back, the last two contacts of R21 are connected together at 24(4) and relay 2Y operates over the interrupter contacts of R2 to complete a circuit for the magnet R2 which steps the units register to normal and releases 2Y. Release. This is dependent on both calling and called parties. When the calling party hangs up, relay HA or HB at the group selector falls back to complete a homing circuit for magnet R. At the final selector relays 2A and 2B release and a circuit over lead CSH is closed to operate an alarm if the called party does not hang up within a predetermined interval. Relay 2D falls back when the called party hangs up, opens the alarm circuit and completes a homing circuit for magnet R over wiper C the first group contacts of which are connected to the remaining contacts over 2K(11). Modified register-controller for final selectors. An instepping and outstepping register may be used for both digits. The instepping register commences to step on receipt of the tens irnpluses and the selector starts to chase as soon as possible, the outstepping register recording the groups as they are reached. When the slow release relay falls back at the end of the