| 摘要 |
PURPOSE:To extract a required signal different from a broadcasting signal without providing an alternation switch to a low frequency signal circuit, by providing a frequency modulating circuit between a local oscillating circuit and a frequency mixing circuit to perform FM modulation by an audible frequency signal. CONSTITUTION:An FM signal received by an antenna 1 and amplified by a high frequency amplifier 2 is mixed with a signal from a local oscillator 4 by a mixer 3, and the mixed intermediate frequency signal is amplified by an amplifier 6 and demodulated by a demodulator 7 to obtain a low frequency output. Since an FM modulator 5 is inserted between the local oscillator 4 and the frequency mixer 3, the intermediate frequency signal is superposed with a modulation signal by modulating the intermediate frequency signal with an audible frequency signal, and the audible frequency signal is taken out from an FM demodulator. |
