| 摘要 |
PURPOSE:To simplify the constitution to improve economic characteristic of the total system, by constituting the receiver by the audio frequency generating device which generates an audio frequency signal and the amplifying device which amplifies the audio frequency signal level in proportion to the detection level. CONSTITUTION:The receiving signal given to terminal R is detected by detecting device D. The detection output of device D becomes the control input of amplifying device A. Device A amplifies the level of the audio frequency signal from audio frequency generating device L in proportion to the level of the detection output and sends the amplified result to speaker device S. Consequently, when the strength of the signal transmitted from the emergency car becomes large according to approach of the emergency car, the level of the detection output becomes large, and the output level of the amplifying device becomes large, and the output of the speaker becomes large. Thus, since the audio frequency signal generating device is provided in the receiver side, it is unnecessary to add audible signal information into the transmission signal and provide the demodulating circuit in the receiver side. |
