| 摘要 |
<p>PURPOSE:To enable the digitalization of a signal selecting circuit by comparing the receiving levels of different signals, selecting the signal of high level and sorting the frequency of the signal. CONSTITUTION:When a train enters from an ATC blocking zone of a carrier f1 and a signal fm into a blocking zone of a carrier f2 and a signal fl, the output level of a selecting and amplifying circuit F1A for the carrier f1 is gradually attenuated in the vicinity of the boundary between the zones, while the output level of a selecting land amplifying circuit F2A for the carrier f2 is gradually increased. Accordingly, the output of a level comparator LC varies from the output state of indicating f1>f2 of the received signal level to the output state of indicating f1<f2, and the output wave applied from a switching circuit X to a detection demodulating circuit D is switched from the waveform of the carrier f1 and the signal fm to the waveform of the carrier f2 and the signal fl.</p> |
