PURPOSE: To obtain an adder output and to compress/expand the time axis by giving clocks of opposite phase to two CCDs, extracting the output at each 1/2 clock to eliminate the clock and changing the clock frequency.

CONSTITUTION: Two kinds of signal waveforms (a), (b) are inputted to the CCDs 3, 4 through input terminals 1, 2. Clocks of opposite phase are fed to the CCDs 3, 4 from a clock generator 5. The outputs are switched by a switch 6 at each 1/2 clock to obtain an output of waveform (e). The clock component included in the waveform (e) is eliminated by an LPF 7 to obtain an adder signal of then two input signals. Further, the time companding is attained simultaneously by changing the clock frequency from the generator 5 given to the CCDs 3, 4.