| 摘要 |
PURPOSE:To announce the reception of an urgency signal by generating a single tone from a speaker when the urgency signal arrives at an antenna, and also to make it possible to listen to the urgency signal freely. CONSTITUTION:An urgency signal when arriving at antenna 1 is passed through high- frequency amplifier 14 and mixed by the 1st mixer 15 and 2nd mixer 16 with signals from the 1st local oscillator 12 and 2nd local oscillator 13 for urgency channels, and the signal is inputted via intermediate-frequency amplifier 17 to audio demodulator 18, where the urgency signal is demodulated. Audio frequency oscillator 19 is allowed to oscillate only when an urgency signal arrives, and the output of oscillator 19 is outputted via audio amplifier 10 with switch 20 closed to make it possible to listen to it at the same time as a received signal except that of an urgency channel, so that the arrival of an urgency signal can be known. |
