Automatic aperture control circuit for automatic diaphragm lens of CCTV camera

Abstract

In an automatic aperture control circuit for an automatic diaphragm lens of a CCTV camera, having a ballast power source circuit II which stabilizes an externally supplied power source, an input signal detector III, an output circuit IV, and an intermediate power source circuit V, in which opening and closing operations of a diaphragm is controlled in accordance with a diaphragm drive signal which is obtained from an image signal or a spurious signal, output from a CCTV camera, using an iris servo-meter apparatus VI, a surge prevention device is inserted between the portion of a power line P1 of the ballast power source circuit II on the input side and a ground line, and a low impedance fixed resistor R1 is inserted in series between a connection point of the power line P1 to the surge absorber and the reverse connection prevention diode D1 of the ballast power source II.

Dependencies are inferred from the claim text.