Description
● Post office box is a wheat stone bridge style testing device with pegs and spring arms in order to close the electrical circuit to measure the properties of the circuit under test.
● Housed in a polished wooden box with hinged cover, the plug type comprises of three pairs of ratio coils of 10, 100 and 1000 ohms and 16 series coils from 1 to 5000 ohms, total 11,110 ohms, giving a range from 0.01 ohm to 1,111,000 ohms.
● Fitted with two spring keys attached to terminals for connecting to a battery and galvanometer.
