| 摘要 |
PURPOSE:To obtain a signal switching circuit which sets a television mode automatically by performing channel-selecting operation in external mode, by outputting the 1st signal from a switch circuit on the basis of a signal generated according to the channel-selecting operation. CONSTITUTION:The 1st signal from an antenna 2 is passed through a tuner 3 and an IF circuit 4 and detected by a video detector 5, whose output is supplied to the 1st input terminal 7 of the 1st switch circuit 6. A sound IF signal, on the other hand, is amplified and then FM-detected, and its output is supplied to the 1st input terminal 18 of the 2nd switch circuit 17. The 2nd signals (video signal and sound signal) reproduced by a VTR, video disk, etc., are supplied to the 2nd input terminals 8 and 19 of the 1st and the 2nd switch circuits 6 and 17. In this case, a control signal is supplied from a channel selecting device 25 to terminal 22 and 23 of the 1st and the 2nd switch circuits 6 and 17 and when channel-selecting operation is performed in external mode, the switch circuits 6 and 17 are set in television mode automatically. |
