| 摘要 |
<p>To detect whether an input FM signal, such as a reproduced video signal, which includes particular frequency components representing predetermined information, was recorded in a first or second mode, with the modes having different frequency bands, a first output signal is produced when a particular frequency component in one of the frequency bands is detected (23, 25) and a second output signal is produced when a different frequency component, approximately equal to the difference between twice a predetermined frequency included in the other of the frequency bands and the particular frequency in the one frequency band, is detected (24, 26). A mode identifying signal indicative of the frequency band occupied by the FM signal is produced (27) in response to the first and second output signals.</p> |
