| 摘要 |
PURPOSE:To make it possible to control the sound of an adaptor TV sound multiplex receiving by the volume variable capacitor of a TV receiver or a remotecontrol reception output, by providing the adaptor with a change-over switch, pulse- width modulator and photocoupler. CONSTITUTION:A sound multiplex signal from sound output circuit 11 of TV receiver 8 is supplied to multiplex demodulation circuit 18 via composite switch 17 and input transformer 14 of the sound multiplex receiving adaptor. In circuit 18, LPF and BPF separate a main channel component and sub-channel component, which are FM-detected and inputed to electronic volume unit 19. The direct-current output of remote control receiver 9 is applied via volume variable capacitor 10 to pulse-width modulator 22, where it is modulated into a pulse signal. The pulse signal is detected 23 via photo coupler 15 and then amplified 24 in term of direct current, thereby controlling electronic volume unit 19. Volume unit 19 attenuates main and sub channel sound signals. Consequently, the volume adjustement of the sound multiplex adaptor can be made by the TV receiver or remote control receiver and convenient operation can also be realized. |
