Patent GB-167162-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1921-07-15
Abstract: 167,162. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Richardson, R. G.). July 28, 1920, [Convention date]. Automatic exchange systems.- In a small exchange in which the connections are made entirely by relays, a calling subscriber A', Fig. 1, is connected by a relay set C<1> to an idle trunk, Figs. 2 and 3, comprising a chain of counting relays 1, 2, 3, &c., one for each subscriber, which are energized in turn by the calling impulses and complete the connection to the wanted line. There may be 19 lines in the system, numbered 1--9 and 01--00, the first digit 0 serving to energize a relay 0 which looks itself up and prepares circuits by which the next digit operates the succeeding relays 01, 02, etc.; or the capacity may be increased to 28 lines, the relay 00 acting like the relay 0 and being followed by relays 001 - - 000; or the same method may be applied to extend the capacity still further. In order that there may be only a single counting relay for each impulse, a relay set E, Fig. 2, is provided, which repeats the impulses alternately over a wire 131, to which the odd-numbered counting relays are connected, and over a wire 132, to which the even-numbered relays are connected. The counting relays have a common locking circuit 128 so arranged that each relay, when it locks itself up, opens the locking circuit of the previous relay, but the transfer relays 0, 00, &c. lock themselves independently of this circuit. Connection to idle trunk. Each line has a series of relays 17, 18, 19 corresponding to the different trunks. The energization of the line relay 16 closes circuits for all such relays of this series as correspond to idle trunks, but only the relay of the first idle trunk remains energized, since each relay opens the circuit of succeeding relays. The trunks are connected in different order to different groups of calling lines, so as to equalize the traffic. In the present instance it will be supposed that relay 18 becomes energized to connect the calling line to the second trunk 24 - - 27, energizing relays 100, 101, Fig. 2. Relay 101 disconnects battery from wire 25, to mark the trunk busy to other calls, and grounds wire 26 to lock relay 18 and to energize the cut-off relay 15. Operatior of the counting relays under control of the repeater E. The impulses transmitted by the calling subscriber are now repeated by relay 100 over civcuit 124, and are directed alternately to the wires 131, 132 by the repeater E, which operates as follows. When relays 100, 101 were first energized a circuit was closed through contact 114 and wire 126 for relay 152, which locked itself up, prepared a circuit for relay 151, and connected the impulse circuit 124 to wire 131. Each odd-numbered impulse, in addition to energizing an odd-numbered chain-relay, energizes relay 151, which locks itself, unlocks relay 152, and prepares the circuit of relay 150, and at the termination of each odd-numbered impulse relay 150 is energized, lock itself, unlocks relay 151, and prepares the circuit of relay 153. The impulse circuit 124 is now disconnected from wire 131 at contact 158 and is connected to wire 132 at contact 154. The next even-numbered impulse, in addition to energizing an even-numbered chain relay, energizes relay 153, which locks itself, unlocks relay 150, and prepares the circuit of relay 152, and at the termination of the impulse relay 152 is energized, locks itself, unlocks relay 153, and prepares the circuit of relay 151. The impulse circuit is thus disconnected from wire 132 and again connected to wire 131, and so on. The chain relays 1, 2, 3, &c. are energized in turn, each looking tself over circuit 129 in series with relay 103, unlocking the preceding relay, and preparing the circuit of the next relay. The first impulse energizes a slow-release relay 104, which remains energized as long as impulses continue and locks wire 127 to battery independently of contact 115, which is opened by relay 103. If the first digi is 0, the final impulse energizes the tenth chain relay 0. This relay locks itself in a circuit 125 which does not include relay 103, so that relay 103 as well as relay 104 becomes de-energized. The circuits D, E are now in the same condition as before any impulses were received, and the impulses of the second digit energize the chain relays 01, 02, &c. In the present instance it will be supposed that subscriber A<2>, Fig. 1, is wanted so that only a single digit of two impulses is transmitted after which the relay 104 becomes de-energized. Relay 103 remains energized in series with the chain relay 2 so that there is now no connection from battery to wires 126, 127 and further impulses in the calling-line would be without effect. Busy test and signal. After the energization of relay 2 and before the de-energization of relay 104 the wanted subscriber's test wire 13<1> is connected over circuit 128 to relay 102 so that if the line 2 is busy, relay 102 is energized, locking itself up at contact 110 and connecting a buzzer B to the calling circuit at contact 113. Supply of ringing current. On the other hand, if the line 2 is idle, relay 102 is not energized, and the relapse of relay 104 completes a circuit for energizing relay 105 over wires 128, 13<1> in series with the cut-off relay 15<1>. Relay 105 locks itself up, grounds the test circuit 128, 13', and ccnnects the wanted line to the upper winding of relay 102 and to a ringing-machine RM, consisting of a buzzer pendulum which vibrates about 20 times a second and connects wire 130 alternately to battery and ground. When the called subscriber answers, the ringing-machine is disconnected by the energization of relay 102. Release. The de-energization of relays 100, 101 when the calling subscriber disconnects himself unlocks all the relays.