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GPO Tester AT4557

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Manufacturer Made for the (British) GPO (General Post Office)
Model Tester AT4557
Age Difficult! The earliest parts are from 1941, but the last rebuild stamp is from 1967, so take your pick!
Service Data No
Condition The case is nice, but the lid is missing, its also missing 6 knobs from the Left hand side of the front panel.
Dimensions About 20"x12"x6" (550mm x 300mm x 150mm) Exclu
Comments This was rescued from a skip at work, when an old storeroom was cleared out. The unit is designed to test the Post Office 3000 and 600 series relays, which were (mainly) used in telephone exchanges, and is powered from the exchange 50V supply, rather than have its own internal supply. The terminals along the bottom allow for connection of power, and there are two sets of terminals to connect to relay coils (this allows the testing of balanced relays for line circuits, and relays with a seperate holding coil, as used in some selector circuits). The variable controls on the left side (missing Knobs), allow you to set the various operate and release currents, and the switches allow the corect sequence of operation for each type of relay, with the meter giving a reading of the circuit current.

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Copyright J.Beacon & M.Wroe-Parker 2003