| 摘要 |
PURPOSE:To reduce the power consumption by detecting a level variation of a synchronizing pulse which is varied in accordance with whether a termination of an external output terminal exists or not, and turning on a power source line by a detecting output of the time of the termination. CONSTITUTION:A control circuit 20 is provided against a power source switch 15 for opening and closing a power source line of an encoder 7. In this state, a level of a synchronizing signal which is superimposed on a video signal SC obtained in external output terminals 3D, 3E is compared with a reference level by a comparator 21. A level of a synchronizing signal obtained when the terminals 3D, 3E are not terminated is turned off periodically by the switch 15, based on a comparing output. Also, when the terminals 3D, 3E is terminated by a VTR, etc., the switch 15 is turned on automatically. In this case, the comparing output is sent to a logical circuit 30, and whether a termination of the terminals 3D, 3E exists or not is detected. |
