Patent GB-270782-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1926-01-16
Abstract: 270,782. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. Jan. 16, 1926. Automatic and semi-automatic exchange systems.-In systems in which first code selectors are accessible to subscribers and to operators the battery feed relays in the first code selector are disconnected from the talking wires in operatororiginated calls when the called party replies but the line relay is held under control of the operator over a further wire. If a busy condition is encountered, a signal is given and the connection is automatically released. The first code selector is of double wiper simultaneous hunting type. Specifications 170,385, 233,007, and 264,557 are referred to. Control by subscriber. The first code selector FCS is seized over the terminals 1 - - 4, terminals 5, 7 and 6, 8 being connected together at the operator's position. Line release and dialling relays L, B, C and relays BS, I, A pull up, the switch RCS selects an A-digit switch, and relay K then switches through and makes a holding circuit for relav B. Dialled digits are repeated at L<1> to the A-digit switch (which is of the kind described in Specification 264,557) and register controller. Relay A repeats the first code digit to magnet V. At the first impulse, the double dog springs DD energize a shunt field stepping relay which locks up over the springs ON2. At the end of the digit, relay C energizes the rotary magnet and relay E and then the magnet falls back. If both trunks are busy, relay E pulls up and causes a further step, but if either is idle, one of the switching relays N, H pulls up and locks itself, cutting out the other. When the number has been sent, relay K releases the register apparatus in known manner and restores release-control to the calling party. Control by operator. The insertion of a plug in jack J energizes relay S and seizes the first code selector and the call is set up as described above. When the called party replies, the usual metering ground connected up by the supervisory relay D energizes relay LR which locks itself in series with relay L, disconnects the bridged relays I, D, and the line relay L, and completes a metallic talking circuit. Busy signal and automatic busy release. If any of the selectors meets a busy condition it connects busy flash to the negative wire. Relay I follows these impulses, unlocks relay BS, and is then able to energize relay BR which guards the calling line, removes ground from wiper PW or PW' to release the selectors ahead, releases relay B to release the first code selector and connects busy tone and flash from BTF to the line relay in place of ground. During the battery periods relay BR is held by impulses over wire h. If the A-digit switch is unsuccessful, busy flash sent back over 106 influences relay I as before, relay BR is energized, and relay B released. Relay K is thus shunted out and releases the A-digit switch. Standstill-releases. In the case of a time pulse cut-off, after the first digit has been dialled, relay M is operated by the time-pulse battery connected to 105. The time pulse relay in the register controller also opens the out-impulsing loops 101, 106, releasing relay A, which sends an impulse to the vertical magnet and pulls up again when the pulse goes off. Relay C is thus released and relay BR pulls up over M2, C6, unlocks relay B to release any switches ahead, and connects NU tone and flash over the lower winding of relay L to the incoming + wire. The same effect is produced if an unobtainable number is called. In case the subscriber does not dial any digits, relay A is not released by the time pulse relay at the A-digit switch. Relay C therefore remains energized and relay BR is disconnected, so that no tone signal is given. Relay M however is energized but the time pulse and lights lamp SL. Specification 248,891 also is referred to.