PURPOSE: To constitute a unit cheaply and improve the precision by making it possible to use pulses synchronized with external clocks for integration.

CONSTITUTION: Input pulses and polarity pulses are applied to control circuit 21, and input pulses are subjected to addition or subtraction by counter 22, and polarity pulses control addition and subtraction of counter 26 dependent upon clock 2. Upper three bits of the output of counter 22 are exchanged for five bits by decoder 23 (by this exchange, an integration constant is converted to generate non-linear functions), and next, these five bits and lower four bits of counter 22 are inputted to nine- bit counter 24; and next, counter 24 substracts synchronously with clock 1 when the value is set by a preset signal, and counter 24 stops subtraction when contents of the counter become zero. Continuously, gate 25 is opened for clock 2 to input clock 2 to counter 26 when contents of counter 24 are not zero, and gate 25 is closed to stop clock 2 when contents of counter 26 are zero.