| 摘要 |
PURPOSE:To improve the operation of a fade-in and fade-out and to simplify the device by controlling auto iris operation by charging or discharging the capacitor of a time constant circuit by providing a linear switch. CONSTITUTION:With VCR switch 25 turned on, the charge of capacitor 20 is discharged via variable resistance 21 and at the same time, the base voltage of transistor TR18 drops to put the auto iris into normal operation with control signal input 2 greater, so that a fade-in will be possible. At this time, no charge is accumulated in capacitor 20, TR18 is turned off and auto iris driving coil 10 is operated by input 2. When switch 25 is turned off for the completion of picture recording, capacitor 20 is charged and TR18 turns on to raise the base voltage of TR11 gradually. As a result, electric current flows through coil 10 from the emitter side of TR11 to the emitter side of TR9 to close the auto iris forcibly, providing a fade-out. |
