P.O. Box comprises three pair of ratio coils of 10, 100 and 1000 ohms and 16 series coils. Total 11110 ohms. Two tapping keys are provided for battery and galvanometer.

Standard Quality

a) Manganin Coils, Accuracy: Ratio coils 0.05%, others 0.1%

b) Precision Quality, Constantan Coils, Accuracy: Ratio of Coils 0.02%, others 0.05%

c) Educational Quality, Constantan Coils, Accuracy: Ratio of Coils 0.1% and others 0.2%