| 摘要 |
PURPOSE:To take a self-diagnosis without disturbing the opposite equipment by changing levels of a comparison signal according to a diagnostic state. CONSTITUTION:When there is an input signal stationarily, the signal inputted from an antenna 1 passes through a receiving filter 2 and is converted by a frequency converter 7 into an intermediate frequency signal, which is inputted to a level detector 8 and a signal demodulator 14. In this case, a controller 10 turns off a switch circuit 4 and controls a switch circuit 9 so as to connect a high level comparison signal 11 to a level detector 8. Where there is the input signal, a level detector 8 detects the intermediate frequency signal and compares it with the high level comparison signal 11, but the input signal has a sufficiently high level, so a squelch signal is outputted from a squelch signal output terminal 13. When a self-diagnosis is taken in the absence of a reception input signal, the controller 10 drives the switch 4 for a predetermined time to close the switch and supplies a signal equivalent to the received signal to an intermediate frequency converter 7 through a relay terminal 3. |
