| 摘要 |
PURPOSE:To eliminate the need for a band pass filter and to corresond immediately to the change in a tone frequency, by discriminating a tone signal as a single level signal independently of the frequency. CONSTITUTION:An incoming signal is rectified at a full wave rectifier circuit 10, one signal is smoothed at a smoothing circuit 11 and the amplitude gain of the other is adjusted at a voltage division circuit 12, and the input from the circuit 12 is compared at a comparison circuit 13 so that the input may sliced with the input from the circuit 11. The compared output is formed at a binarizing circuit 14 and integrated at an integration circuit 15, and the integrated output is level-sliced at a slicer circuit 16 and an output B is outputted. With the output B at zero, the signal is discriminated as a tone signal and with the B at 1, the signal is discriminated as a signal other than the tone signal. Through the discrimination as a single level signal like this, no BPF is required and the system can handle readily, even if the tone frequency is changed. |
