Pioneer Electronic Corporation

Universal Pioneer Corporation

Tohru Nakajima

Hisao Nakamura

A video signal output circuit which permits switching an output video signal from one input video signal source to another without loss of synchronization of the video monitor. A first pulse signal is produced synchronized with the vertical synchronizing signal of the first video signal. A first detector circuit detects the phase difference between the first pulse signal and a second pulse signal synchronized with the vertical synchronizing signal of the second video signal, and the period of generation of the first pulse signal is controlled in response to the phase detected phase difference. A second phase detector detects when the phase difference between the first pulse signal and the second pulse signal is within a predetermined range easily tolerated by the monitor. Switching from the first to the second video source is permitted when this phase difference is within the predetermined range.

Video signal output selection circuit

A video disc and reproducing device therefor in which a recognition signal for identifying the content of an audio program, specifically whether two recorded audio signals are in the stereophonic mode or in a split mode, is recorded along with the audio signal and a video signal. The recognition signal may be multiplexed in either a frequency division multiplex system or in a time division multiplex system. The reproducing device includes a selection switch provided for selecting whether a pair of sum and difference signals, in the stereophonic mode, or whether the first and second audio signals directly, in the case of the multiplex mode, are coupled to inputs of a modulator which outputs an RF signal adapted to be inputted to a television tuner. A pilot signal is included with the output of the modulator. The pilot signal is amplitude modulated with one of two different frequency sinewaves. The one of the sinewaves which is used to modulate the pilot signal and the selection switch is controlled by a recognition signal detector.

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Saitama, Japan

Tohru Nakajima