| 摘要 |
PURPOSE:To reject signal lack peculiar to a video disc player or malfunction for a short time due to noises or the like by detecting whether a disc set up on the player belongs to a PAL type or an NTSC type by real time. CONSTITUTION:It is supposed that the set-up disc is a PAL type disc and a regenerative voice signal (FM signal) from the disc is guided to BPFs 1, 2. When the number of rotation is zero at first, the regenerative voice signal is also zero, so that both points A, B are the L level and a point C is also the L level. When the number of rotation reaches 375rpm, a prescribed level for PAL, the points A, B are turned to L and H levels respectively. Although the point B is turned to the H level, the point C is kept at the L level as it is, so that the H level of the point B is absorbed by the L level through a diode 8 and a point D is still kept at the L level without turning to the H level. Therefore, the point C is kept at the L level as it is and a switch 5 is kept at the PAL circuit 7 side. |
