Patent GB-1009504-A (GB)
Title: Improvements in or relating to line connector arrangements for use in telephone or like systems
Inventor: PARIS HOWARD VAREY
IPC: H04L12/00
Filed: 1961-11-15
Abstract: 1,009,504. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Nov. 15, 1961, No. 40795/61. Heading H4K. In a satellite system, for use with both telephone and Telex subscribers, in which links less in number than the subscribers are taken into use as required to interconnect subscribers' equipments at the main exchange and the satellite, arrangements are provided at the main exchange for indicating a Telex subscriber as idle when he is not connected to a link. This indication may be removed however if the Telex equipment is closed down. The system is similar to that described in Specification 962,645 in which when a subscriber takes a link into use, he retains it until it is required for another call, even though he may have finished using it. As shown in the main exchange equipment, if the subscriber is not connected to a link LK is back, so that LS is operated to place idle battery on the final selector P wire. Battery is also placed on the wire PX to show that the telex station is not closed down. Call from Telex station.-If the subscriber is already connected to a link LK is up and LS is held in a circuit over R, S from + 80V to earth in the subscriber's station. Operation of the CALL key brings up DC which puts -80V on the R wire to release LS. If the subscriber is not connected to a link, the -80V on R brings up line relay LR, which causes the subscribers' equipments at the satellite and main exchange to be interconnected over a link whereupon LK comes up to release LS and operate RL. This causes the uniselector DM to hunt for a free first group selector, AH operating over DM3 when one is found to cut the drive. Relay H then comes up and holds over DM3, and G follows to release AH. Dialling is now effected by transmitting +80V over the R-wire and when selection is complete a further -80V signal is mounted over the S-wire to bring up CM which disconnects the dial and connects up the teleprinter. When the subscriber operates the CLEAR key, + 80V is connected to the R-wire to release the group selector. Relay H is then no longer held over DM3 and its release homes the uniselector DM and brings up LS, whereupon G releases. Call to Telex station.-Such a call is initiated by earth on the final selector P wire to bring up LL which then initiates connection to the subscriber's equipment at the satellite as described in Specification 962,645. When this is complete -80V from the final selector over the S wire brings up CM to connect up the teleprinter. Close-down of substation.-The subscriber must first operate the calling key to effect seizure of a link and connection to the main exchange equipment, and then switches off his power supply. A group selector is seized as before, but due to the absence of holding battery from the subscriber on the R lead, the group selector does not revert a hold signal for H, which releases. Relays G and RL thus stay up, the latter preventing LS from re-operating. Idle potential is thus removed from the final selector P wire and potential is also removed from PX to indicate that the station has closed down. To open up again the subscriber operates the call key followed by the clear key. The former causes a link to be allotted to connect the equipments at the satellite and main exchange together and the latter operates LS to release G. The circuit is now marked idle and ready for use.