| 摘要 |
PROBLEM TO BE SOLVED: To easily judge the validity of an input signal and the presence or the absence of a hit through simple configuration by using a two-frequency mixture receiving element, a latch circuit and a level comparator. SOLUTION: An input amplifier 1 impedance-converts and amplifies the PB(push button) signal of a two-frequency mixture signal from an input terminal 9, and inputs it to an exponential function amplifier 2 and a band pass filter 5. The exponential function amplifier 2 sets the level difference of the low and the high groups of the PB signal narrow, and supplies it to a PB receiving element 3. Here, a prescribed frequency clock is given from a clock source 8, and a code (b) corresponding to the PB signal, a valid/invalid signal (a) and a detection signal (c) are outputted. Besides, the detection signal (c) is outputted from a reset trigger latch circuit 4 through a resistor R and a capacitor C. On the other hand, the output of the band pass filter 5 is converted into a DC signal by an amplitude value conversion circuit 6, and is supplied to the level comparator 7, and a signal exceeding the prescribed level is detected. Thus, the validity and the level of the input signal and the presence or the absence of the hit are easily judged. |
