| 摘要 |
PURPOSE:To eliminate a channel selecting IC and at the same time to prevent variations of the lock state due to the static electricity, by using a mechanical lock switch. CONSTITUTION:Mechanical lock switches S1-Sn are used for channel selection, and at the same time the end of the other side of the lock switch is connected to the reference potential point via a switching transistor TR27. The TR27 is kept off while the program of a timer 2 is being executed (during channel selection by the timer) in order to make switches S1-Sn ineffective. Otherwise the TR27 is turned on to make these switches effective. Therefore, in case a channel selector is used to a VTR for example, no change is produced to the channel which is under video recording. |
