| 摘要 |
<p>PURPOSE:To protect the photo electric conversion element of pick up tube, by throttling lens iris when power supply is OFF in television camera. CONSTITUTION:The voltage fed from the power input terminal 1 charges up the capacitor 4 via the power switch 2 and the diode 3 and it is fed to the output amplifier 9. The iris control voltage is inputted to the amplifier 9 via the switch 6 when the power supply voltage is fed to control lens iris. When the power supply is disconnected, the switch 6 is selected and the voltage across the capacitor 4 is set to a voltage so that the iris is operated to the end with the resistors 7 and 8 and the lens iris is throttled via the output amplifier. Accordingly, even if a camera is left under sun light at outdoor, expensive pick up tube can not be damaged.</p> |
