PURPOSE: To make it possible to vary the full-scale time of a timer without adding a capacitor, rotary switch, etc.

CONSTITUTION: Pulse counters 21 to 23 of oscillator 10 output count numbers 10 times, 60 times and 600 times as much as that of counter 20 sequentially. By combining input voltages to input terminals D1 and D2, control circuit 40 selects a counter used for a timer time so as to vary the count number. In this way, since pulse-counter outputs of the oscillator varying its oscillation frequency are made 10 time, 60 times and 600 times by varying the value of an externally-attached resistor, a capacitor, rotary switch, etc., are not added and the need for adjusting dispersion caused by the variation in capacity is eliminated, so that the full-scale time can be varied only by varying the voltage of the externally-attached input terminal.