PURPOSE: To execute a low energy consumption by separately controlling individual analog elements, stopping a band-pass filter at the time of recording and stopping an amplifier and a comparator at the time of reproducing.

CONSTITUTION: The control of the analog device of a microphone amplifier, a DA converter, a comparator and a band-pass filter is made into two systems, one is made into the control for recording in which the microphone amplifier, DA converter and comparator can be controlled, and the other is made into the control for reproducing in which the DA converter and band-pass filter can be controlled. Namely, a microphone amplifier 7, a DA converter 9 and a comparator 8 are operated at the time of recording, and the DA converter and a band-pass filter 11 are operated at the time of reproducing. Thus, the consumed current portion of the band-pass filter at the time of the recording action can be reduced, and the consumed current portions of the microphone amplifier and comparator at the time of the reproducing action can be reduced.