Post Office Box

A: Plug type, in polished teak wood box with hinged lid and black bakelite panel lined in white colour to show circuit connections. Coils of constantan wire double sild covered are wound non-inductively and have a negligible temperature co-efficient. Three pairs of ratio arms are each 10, 100, 1000 ohms and resistance arms contains 16 coils from 1 to 5000 ohms with infinity plug. Total value 11,110 ohms. Two spring keys having special contact for battery and galvanometer fitted. Accuracy of coils 100 to 500 ohms + 0.05% and of the rest coils +