Post Office Box, Wheatstone Bridge

With two ratio dials of 10,100 and 1000 ohms each and a resistance arm of four dials, each of ten coils of 1, 10, 100 and 1000 ohms, giving total resistance of 11,110 ohms, with 4 mm socket terminals for battery, galvanometer and unknown resistance. Highly stable resistances are used. Accuracy ±0.1%.