Patent GB-300497-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M1/52
Filed: 1928-10-08
Abstract: 300,497. Associated Telephone & Telegraph Co., (Assignees of Wicks, J.). Nov. 12, 1927, [Convention date]. Automatic exchange systems.-A subscriber A has, in addition to an ordinary dial RCD which controls the talking switches directly in the establishment of normal connections, a second dial CCD which is used for calling frequently-wanted subscribers. The operation of the second dial causes the calling loop to be switched over at a repeater R to a register-controller, Fig. 2, individual to the calling subscriber, and in response to a single train of impulses from the dial CCD, the register-controller sends out the complete number of the wanted line. The dial CCD may send up to 25 impulses, so that with registerswitches of similar capacity, this number of special calls may be provided for. The two dials may be mechanically combined in one unit. Ordinary call. The removal of the hand set completes a loop for relay 10 in series with a differential relay 70 which does not operate. Relay 10 operates relays 120, 20 whereby a bridge is completed across conductors 3, 4 for the usual line-switch. Impulses are repeated by relay 10 to control the switches in known manner, relay 40 operating during each digit to short-circuit the upper winding 73 of the repeating coil. Incoming call; ringing. When ringing-current is applied at a connector to conductors 3, 4, relay 100 responds, energizing relay 80 which causes the ringing-current to pass directly to the substation A. If the subscriber removes the hamdset during a ringing-period, the ring-cut-off relay at the connector operates directly over the calling loop, and on the release of relays 100, 80, relays 10, 120, 20 are energized. If, on the other hand, the hand-set is removed during a non-ringing period, relays 10, 120, 20 operate immediately and complete a loop over contacts 13, 21 for the ring-trip-relay. Call to frequently-wanted subscriber (No. 4150). For this call the dial CCD transmits the digit 1. Relays 10, 120, 20 energize as for an ordinary call and when dial COD is moved off normal, an earth connection over spring 26 causes differential relay 70 to operate and complete a circuit for relay 160 which starts the pendulum interrupter 30. The single impulse transmitted bv the dial is repeated by relay 10 over parallel circuits to magnets 55, 65 of the register switches 54, 64 respectively. At the end of the digit, the relapse of relay 40 causes two-step relay 110 to operate completely, energizing relays 130, 140. Relay 140 partially operates two-step relay 60 and connects relay 50 into the circuit of the interrupter 30. At the time when winding 30 is shortcircuited, relay 50 operates and causes relay 60 to operate fully and remove the short-circuit 61 from the pendulum contacts. When these contacts are next opened an impulse is sent over conductors 3, 4 and at the same time the release of relay 50 sends an impulse over lead 177<1> to magnet 177 of the impulse-sending switch 174. After four such impulses, a circuit is completed over lead 175', wipers 175, 68, 185 and contacts 112, 165 for relay 170 which releases relays 140, 50, 60 and transmits an impulse to magnet 186 of the control switch 184. Release magnet 176 of the sending-switch 174 energizes in parallel with magnet 186 and when the switch reaches normal, relay 170 is unlocked at off-normal contacts 178. Three further digits are transmitted in a similar manner, the control switch 184 then moving to position 5 in which a circuit is completed over wiper 58 and jumper 201 for relay 90 which releases relay 160 and closes a circuit for the release magnet 187 of switch 184. Relay 160 closes restoring circuits for switches 54, 64, During the transmission of impulses from the registercontroller, relay 160 completes a bridge across conductors 3, 4, this bridge including an impedance 169 which enables the calling subscriber to check audibly the impulses being sent out owing to induction through the repeating coil 72 - - 75.