| 摘要 |
PURPOSE:To make unnecesary the band switching operation at channel selection, by switching the reception band of an electronic tuner, through the detection of a display bar stopped at the end of screen. CONSTITUTION:After converting a horizontal synchronizing pulse from a terminal 7 into a saw tooth wave at a wave shape circuit 1, a tuning voltage 8 from a tuner is added. The added output is wave shaped and inputted to a logical coupling circuit 5, and when a signal from a synchronizing detecting circuit 3 and a channel selection indicating circuit 4 is present, a bar display location signal is outputted from the circuit 5. A bar display location derecting signal generating circuit 16 forms detection signals 29, 30 corresponding to the left and right ends of screen from a horizontal sychronizing signal 26 and forms a band switchng signal 28 from the correspondence of a bar display signal from the circuit 5 at a bar display location detection 17 with the detection signal 29 or 30 to operate a band automatic switching circuit 18. Thus, the band switching operation at the channel selection is avoided and the operability is remarkably increased. |
