PURPOSE: To simplify a structure and to stabilize operations, by a method wherein taps, which are arranged at specified spaces on a conductive body formed in an endless shape, a brush which slides over the conductive body, and a circuit, which selects the two taps and applies a voltage to said taps, are installed.

CONSTITUTION: For example, 15 taps 320W3214 are arranged at equal intervals on an endless conductive body having a resistance layer formed on a substrate. A brush 34 is located on a shaft 35 rotating in synchronism with a carrier of, for example, serial type printer. Two taps, out of taps 320, 325, and 3210, feeding a voltage V, are selected by a switching signal S1 transmitted to analogue switches AS1WAS3. Through designation of a given tap position by means of a space address signal S2, a tap switching circuit 36 outputs a voltage Vr1 of said tap. A comparator 37 compares said voltage with an output voltage Vr2 of the brush, and rotates the brush to a specified position through the working of a space control circuit 39 and a motor M. This causes simplification of a structure and stabilization of operations.