| 摘要 |
PURPOSE:To detect noise in a signal transmission frequency band and prevent the erroneous interception of an output due to disturbance from an adjacent channel by cascading two kinds of band-pass filters which pass and stop a pilot signal according to its frequency. CONSTITUTION:A demodulated signal is sent to an output terminal OUT and a pilot frequency passing filter 2 through a branching circuit 1. The filter 2 extracts only the components of frequencies near the frequency of the pilot signal and sends them to the cascaded pilot-frequency stopping filter 3. The filter 3 cuts of the signal of the pilot signal and its noise output is sent out through an amplifier 4 and compared with a specific level and decided to cut off the transmission output of a terminal OUT-1 on the basis of the decision result. |
