| 摘要 |
PURPOSE:To increase an automatic channel selection speed, by raising a phase detecting sensitivity in a horizontal AFC circuit, while executing automatic channel selection, and improving the loop gain of the horizontal AFC circuit. CONSTITUTION:An output of an RSFF108 in a channel switching circuit part 1 executes automatic channel selection from the point of time when a key of channel-up or channel-down is inputted, and it is generated until the channel selecting operation ends by a channel in which a TV broadcasting radio wave exists. Subsequently, by use of a signal indicating that the automatic channel selection is being executed, a detecting sensitivity of a horizontal AFC circuit is raised only in the course of the automatic channel selection, and the leading-in range is widened, so that a leading-in time of the horizontal AFC circuit is shortened as the result. In this way, an automatic channel selection speed is increased to the maximum. |
