| 摘要 |
PURPOSE:To select surely a tone signal of different level and frequency, by providing a means making an output of the 2nd band pass filter ineffective when an output of the 1st band pass filter is detected. CONSTITUTION:When a tone signal in a frequency f1 at low level is transmitted to a tone signal detecting circuit 8, the tone signal is supplied to a detecting circuit 13 via an amplifier 9, a band pass filter 10, an amplifier 12 and a capacitor C1. Then, a transistor(TR) Q3 of the detector 13 is turned on and an output signal (a) of the detector 13 goes to ''O''. This is the same when a tone signal of high level in a frequency f2 is transmitted to the tone signal detecting circuit 8, and an output (b) of the detector 14 goes to ''O''. |
