Post Office Box Dial Type Post Office Box Dial Type – Physics Laboratory Instrument Post office box is constant coils. 6 dial each consisting of 10 steps. Provided with four ratios of 1, 10, 100, 1000 ohms and 2 ratios dials. And then with Manganian coils 5 dials. Plug type, in polished wooden box with hinged lid and panel to show circuit connections. Coils of constantan wire double silk covered are wound non- inductively. 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 contact for battery and galvanometer fitted. Accuracy of coils 100 to 500 ohms 0.05% and of the rest coils 0.1%. Available in coils – 4 dials , Constant coils 4 dials , Manganian coils Features: Precise design Simple usage Resistant against rus
