| 摘要 |
PURPOSE:To facilitate the switching of the receiving signal system, by driving automatically the system switching circuit of a signal receiver in accordance with the receiving band and by means of the voltage which is used to switch the receiving band of the tuner of a TV receiver. CONSTITUTION:In case a TV receiver can receive both the I and D systems of a CCIR, the receiving signal given through an antenna 1 is supplied to a circuit 6 that delivers a video intermediate frequency (VIF) signal and a voice intermediate frequency (SIF) signal via a UHF tuner 2 and a VHF tuner 3, respectively. The VIF signal (d) is supplied to a video circuit, and the SIF signal (e) is supplied to a voice circuit. The band switching voltages (a'-c') are supplied to a band switching circuit 4 from a band switching voltage generating circuit 5, and the switching signals (a-c) of the tuners 2 and 3 are supplied from the circuit 4. The signal (a') of the UHF is applied also to a system switching circuit 8, and a system switching circuit 7 works by the driving output of the circuit 8. Thus the receiving of the I system is possible when the VHF band is received; and the receiving of the D system is possible when the VHF band is received; and the receiving of the D system is possible when the VHF band is received respectively. |
