Patent GB-358564-A (GB)
Title: Transmission system for telephony or the like
IPC: H04B3/20
Filed: 1930-07-10
Abstract: 358,564. Two-way repeaters. STANDARD TELEPHONES & CABLES, Ltd., HODGSON, K. G. and GROVE, S. H., Columbia House, Aldwych, London. July 10, 1930, No. 20885. [Class 40 (iv).] In a cable transmission system in which a courier current is sent from either terminal station on the arrival of speech thereat, the direction of transmission is determined by the first courier current to arrive at an intermediate control station. A temporary transmitting condition is established at a terminal station at the same time as the courier current is sent out, and is rendered permanent either by the arrival of an impulse returned from the intermediate station or automatically provided no courier current originated at the other terminal station is received from the intermediate station. First system, Figs. 1 and 2. Speech currents arriving at the terminal station A, Fig. 1, energize relay S2, which releases relay S3, whereupon relays S5, S17 operate, connecting the transmitting branch TB to the cable C and disconnecting the receiving branch RB. Courier current now flows from a source T until sluggish relay S4 pulls up. At the intermediate station D, Fig. 2, the courier current energizes relay S7 which releases relay S8, whereupon relays S10, S11 operate closing the transmitting branch TB1 and opening the receiving branch RB1. In addition relays S12, S13 operate in turn to send back an impulse from a source T1 to the station A, where it energizes relay S15. Relay S16 operates its armature to the righthand position to close holding circuits for relays S5, S17 when sluggish relay S6 pulls up. Relay S24 further disables the receiving branch RB. Relay S7 at the station D is maintained energized by speech currents after the courier current ceases. When speech ceases, relay S3 re-energizes and polarized relay S16 operates its armature to the left-hand position, releasing relays S5, S17. Assuming now that a courier current from the terminal station B (not shown) arrives at the intermediate station D before the courier current from the station A, relay SO corresponding to relay S8 is released, and ground is removed from the circuit controlled by relay S8, so that the courier current from A is ineffective, and the temporary transmitting condition at the station A is removed when relay S6 pulls up. Speech currents from B energize relay S25 which controls relay S1 to further disable the transmitting branch TB. Second system, Figs. 3, 4, and 5. Speech currents arriving at the terminal station A, Fig. 3, energize relays S3, S7 to establish a temporary transmitting condition and to send out courier current until relay S6 pulls up, as in Fig. 1. At the intermediate station E, Fig. 4, the courier current energizes relay S8, which releases relay S9, and relays S12, S13 establish the temporary transmitting condition to the intermediate control station D, Fig. 5, where relays S15, S16 respond in similar manner, and relays S17, S18 establish a permanent transmitting condition in the direction of the terminal station B (not shown). At the stations A, E, sluggish relays S4, S5 and S11, S14 pull up in turn, and holding circuits are closed for relays S3, S7 and S12, S13. If on the other hand a courier current from B is received at the station D just before that from A, relay S20 corresponding to relay S16 is released and ground is removed from the circuits controlled by relay S16, so that the courier current from A is ineffective. The courier current from B releases relays S10, S26 at the stations E, A so that the temporary transmitting condition in the direction of B is removed when relays S11, S14 and S4, S5 pull up. If desired, a control current may be sent from the transmitting station to restore the circuits at the conclusion of speech, as in Specification 348,574, the circuits at the top and bottom of Fig. 3 for example being replaced by those in Figs. 7 and 6.