Post Office Bridge with Meter

This is a Wheatstone bridge designed to locate a short circuit in a telephone or telegraph line by measuring the resistance of the wire to the short. It is called a "post office bridge" because this design was adopted by the British Post Office, which operated telegraph and telephone services as well as delivered mail. This bridge, which is in a box, has a built-in galvanometer. The upper plugs determine a ratio and the lower rows are a standard resistance.

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Electricity_and_Magnetism

Bridges

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