A resistance box contains a series of resistors of different values for the purpose of estimating and comparing various resistances. Usually the resistance is accurate to high precision, ranging from laboratory/calibration grade accuracy of 20 parts per million, to field grade at 1%.
The main application of the resistance box is to control the specific value of current to flow through a circuit. They offer a convenient way of selecting and quickly changing a resistance in laboratory, experimental and development work without needing to attach resistors one by one, or even stock each value. The range of resistance provided, the maximum resolution, and the accuracy characterize the box.
This resistance box was made by Townson & mercer of London with the values: 1, 2, 2, 5, 10, 20, Inf, 50, 100, 200, 200, 500, 1000, 100, 10, 10, 100, 1000. 2 Morse keys are also featured.
In a spotty condition
