A resistance box in the path of an electric current, for the purpose of increasing the general resistance to the current flow. The box contains coils of wire made of a metal that is a poor conductor of electricity. When the current is first turned on to a motor, as that of a streetcar, it is important that it should be done gradually, so that the motor will not start off at once with full force. This is accomplished by sending the current through a rheostat. If the box have 12 coils, the current is sent at first through the whole of them, then, by turning the handle, through 11, 10, 9, and so downward, until all the coils are cut out and the entire strength of the current reaches the motor, and sets it turning at full speed