Patent GB-828454-A (GB)
Title: Improvements in or relating to power feed arrangements for telecommunication or like systems
Inventor: DODD GEORGE ALEXANDER
IPC: H04B3/44
Filed: 1956-12-07
Abstract: 828,454. Feeding unattended repeaters. BRITISH TELECOMMUNICATIONS RESEARCH Ltd. Nov. 21, 1957 [Dec. 7, 1956], No. 37508/56. Addition to 744,340. Class 40 (4). In a system in which repeaters are normally supplied with power from a source at one end of the line, on the occurrence of a fault likely to prejudice the power supply, a local supply is connected up at an intermediate station and following stations continue to be fed through this station, but from the local supply connected up thereat. The equipment of a station is shown in the condition it assumes prior to the switching on of the normal source, the local supply being connected up over back contacts of MR and extended to following station(s) over back contacts of ML, switch S, back contacts of MC and the line windings of magnetic amplifier MA. Power incoming from the left is connected over back contacts of MD to the dummy load DL equivalent to the load of all the subsequent stations, and is also fed via the power attenuator PA and auto-transformer AT to the relay power unit PU1. The output of PU1 operates MC, MR, ML and the slow-to-operate T. Normal power supply is thus extended to the station shown and to the subsequent station(s). Relay T also lights lamp LP to indicate normal power feed in operation, extinguishes the stand-by power lamp LS, and opens a point in the alarm circuit 10, 11. Relay power unit PU2 feeds relays for controlling local equipment and particularly relay SA and similar relays which delay the connection of power to the H.T. circuits of the repeater valves, as described in the main patent, until the filaments have heated up, the contacts of SA being shown operated in Fig. 2. Operation under fault conditions.-If the section following the repeater station shown becomes open-circuited, the voltage output of AT rises by more than 20% so that the device A operates to close its " high " contacts H, whereupon relay AA comes up and releases MD to cut-off the power supply to subsequent stations and introduce the dummy load DL. Lamp LA is lighted to indicate the state of affairs to a repair man. At the next station, failure of the main power supply causes all the M relays to release, thus switching over to the local power supply which is also fed to subsequent stations. If a fault occurs in the station prior to that shown, which removes the load thereat without interrupting the power supply, the voltage at the station shown rises by more than 20% and relay AA will operate with the results set out above. Failure of normal power supply to the station shown results in release of all the M relays and changeover to the local supply thereat. In the event of a cable earth fault beyond the station shown, the magnetic amplifier MA will be unbalanced and relay CB will be operated as a result. CB locks up to the local supply, releases MD to disconnect the forward power supply, lights lamp LC and completes the alarm circuit. Device V (Fig. 2) operates if the voltage varies by more than 5% in either direction and brings up VV (Fig. 1) which lights lamp LV and completes the alarm circuit, but does not initiate changeover of supply. The switch S may be used to ensure that each station operates on local power supply when alterations to transformer tappings or dummy loads have to be made.