| 摘要 |
PURPOSE:To output an alarm signal depending on a symptom of an abnormality by detecting the abnormality of the shared television viewing system. CONSTITUTION:A television signal received by an antenna is amplified by an amplifier (not shown) and the result is outputted to an input terminal 11 for an abnormality detector. If the amplifier is oscillated abnormally, a detection output 16A exceeds a setting level and an alarm signal is outputted to a terminal 37. Moreover, when an input level is exceeded and intermodulation takes place, a detection output 20A or 24A exceeds the setting level and an alarm output is outputted to the terminal 37. If radio wave propagation is wrong and the signal level is decreased, a detection output 28A for a VHF Low channel is decreased and a detection output 32A for a VHF High channel is decreased and an alarm output is outputted to an output terminal 38. The alarm output is not raised when the radio wave is stopped at the end of broadcast. |
