| 摘要 |
<p>An apparatus for controlling synchronization of on-screen display information in an auto-search mode of a radio-frequency receiver ( 2 ) connected to scan an incoming signal for valid channel frequencies, includes a picture intermediate frequency phase-locked loop detector ( 17 ) for supplying an output signal indicating whether an intermediate frequency demodulator is in an unlocked mode which is the case if the incoming signal frequency does not correspond to a valid channel frequency, or in a locked mode, which is the case if the incoming signal frequency does correspond to a valid channel frequency, a video detector ( 18 ) for detecting a video property in the incoming signal, a synchronization phase control loop ( 6, 8, 10 ) which is closed if the video property is detected and the output signal indicates the locked mode, a memory for storing the frequency of the incoming signal as a valid channel when the phase control loop ( 6, 8, 10 ) is closed, and a horizontal oscillator ( 8 ) connected to free run when the phase control loop ( 6, 8, 10 ) is open. This stabilizes an on-screen display even when no signal is present or a weak signal is present.</p> |
