PURPOSE: To realize a high-speed process with use of a low-speed element and to convert a circuit into an LSI, by forming an exclusive circuit which calculates a modulating/demodulating operation equation and processing in parallel and in overlapping the linear equations having a large number of process steps.

CONSTITUTION: The nT is read out of an ROM with the timing of a timer T at the carrier sampling part (a) of an arithmetic circuit for modulated carrier output. Then a prescribed operation is carried out to deliver the modulated carrier wave f(nt) to an output terminal L. The outut of a part (b) is applied to the part (a) of the arithmetic circuit via a lock H. The desired spectrum distribution is calculated for the output of a part (c) through arithmetic circuits A1 and B2 plus an adder, etc. of the part (b). Then the linear equations which are produced based on a block table C of the part (c) are processed in parallel and in overlapping. A high-speed process is attained with use of a low-speed element. Thus a circuit can be easily converted into an LSI such as a modulating/demodulating operation system, an automatic equalization control operation system, a demodulated clock timing automatic control operation system, etc.