Through examination on requirements for audio-timer used in a variety of experimental conditions revealed that the “universal” audio-timers should provide for following characteristics: 1) numbers of unit interval time (UIT) should be as many as required for the most complex sequence of the intervals and should be subject to selection neither more nor less than required, 2) UIT should have sufficiently wide time range with necessary time-analytic power 3) time setting should be performed precisely, easily and speedily and should be directly eradable on the time-calibrated dial, 4) time setting on one of the UIT should not affect the other, 5) versatility of sequence patterns of UIT should be available, 6) synchronization with the input signal phase should be provided for. Analog UIT generators such as monostable multivibrator and phantastron are capable of use for audio-timer, if their advantages are put together to use. The type of timers are available on the commercial base and widely used up to now. Digital timers, if so called, however, have many advantages over the analog timers. The Multi-Interval Digital Timer designed by the author (Fig. 5) can have the characterististics mentioned above.