| 摘要 |
PROBLEM TO BE SOLVED: To surely demodulate a base band signal even when noise is in existence for a non-signal period where a communication line is not driven by an FSK(frequency shift keying) signal. SOLUTION: The demodulator detects a waveform-shaped FSK signal and is provided with a gate control means 4 providing an output of a detection signal when the FSK signal satisfies a prescribed condition, a 1st gate means 5 providing an output of the waveform-shaped FSK signal synchronously with a clock signal when an output of the gate control means 4 is in a prescribed state, and a detection means 6 demodulating the output of the 1st gate means 5 to a base band signal based on the clock signal. The 1st gate control means 5 detects it that the communication line 18 driven by the FSK signal and the FSK signal is outputted from the 1st gate means 5 and demodulated into a base band signal while the state is detected. On the other hand, a noise signal appearing when the communication line is not driven by the FSK signal is interrupted by the 1st gate means 5. |
