PURPOSE: To simplify rate adjustment by making the reset pulses width of a frequency dividing part adjustable from the outside.

CONSTITUTION: The output end of an oscillating part 1 is connected to the first stage flip-flop FF11 of a frequency dividing part 2 and the first stage flip-flop FF21 of a control part 6, the output of the final stage flip-flop FF1n of the frequency dividing part 2 to a monostable multivibrator MM, the output end of the monostable multivibrator MM to a watch part and the NAND gate 4 of the control part 6 and the output end of the NAND gate 4 to the reset input end of the final stage flip-flop FF1n. Then, when a suitable pulse is inputted from the terminal B to the flip-flop FF31 by a certain means from the outside, the reset pulse width of the frequency dividing part 2 is suitably changed via the control part 6, thus rate adjustment is readily accomplished.