| 摘要 |
PURPOSE:To exactly detect a trouble due to distortion increment by fetching cross modulation component from a TV signal to a pilot signal through the second filter which allows direct current component to be intercepted to pass and monitoring their levels by a level detector which detects levels. CONSTITUTION:The signal included by a transmitting signal as well as a non- modulated pilot signal enter in an input terminal 1 and is amplified by a line amplifier 8. The pilot signal receiving cross modulation is extracted by the first filter and is amplified by a pilot signal amplifier 19 then a envelope line is taken out after being detected by a detector 20. While an output of the detector 20 includes the cross modulation component, the second filter 9 permits only alternating component to pass and even a high frequency to be attenuated in order to improve S/N of the detecting signal. The detected signal is detected levelwise by a level detector 11 after being amplified by a detecting amplifier 10 and is decided levelwise after allowing the above signals to pass through a pertinent time constant circuit by a decision device 12. If a detected signal level goes to abnormally high, the above decision device 12 will output fault generating signal due to distortion increment to a decision output terminal 13. |
