| 摘要 |
PURPOSE:To detect the generation of a fault even when the level of a sound signal is in a low state by comparing a reference signal corresponding to the level of the sound signal and a comparison signal. CONSTITUTION:The sound signal that a sound signal source 1 outputs is inputted in a power amplifier 3 via a modulation amplifier 2 composed of an adding circuit 2a and an amplifier 2c. In the amplifier 3, a carrier wave signal is supplied from a carrier wave signal source 4 and an amplitude modulated wave is generated by the sound signal from the amplifier 2. The modulated wave is radiated into space by an antenna 6 via a matching circuit 5. A reference signal for fault detection takes out the part of the sound signal by the form of voltage from the output side of the circuit 2a and adds the part to a comparator circuit 8 via a square circuit 9. The comparison signal utilizes the current of a DC power source 2d, branches in the form of voltage at a connection point A and,joins the circuit 8. At the time of the generation of a fault, current increases and the comparison signal becomes large. When the comparsion signal becomes larger than the reference signal, the circuit 8 transmits a fault detection signal and controls the amplifier 3 through a timer 10. |
