| 摘要 |
PROBLEM TO BE SOLVED: To obtain a circuit for protecting a camera against a failure when a conventional camera having a high current value is connected erroneously by detecting a camera having a high driving current value with a constant current drive single cable power supply superposition system camera. SOLUTION: A constant current level fed from a power supply section is detected by a constant current level detection circuit and when the larger one of two kinds of constant current level is detected, an electronic switch is turned off by a time constant circuit so that the power supply of the camera is turned on/off repeatedly and a monitor image can be recognized. Furthermore, a protection circuit is constituted of an inexpensive circuit in place of a current detection comparator such that the DC voltage at the output terminal increases when a current not lower than a constant level is supplied and power supply to the camera power supply is interrupted eventually by detecting an overvoltage through a simple voltage comparator. COPYRIGHT: (C)2005,JPO&NCIPI
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