This control is applied to the gain of the video amplifier stage/s following the imaging device. It is usually related to ALC in that if the iris is fully open and video output is low, the gain of the amplifier stage is increased. So to is the noise generated by the stage itself and preceding devices which is then visible as grain or snow on the screen. As 'useable sensitivity' indicates the minimum illumination at which a 'picture' can be discerned amongst this noise, it is useful to know the illumination level at which AGC switches on or off and how much noise (S/N ratio) you have
ALC(Automatic Light Control/auto-iris)
A servo control system applied to the iris of a camera/lens system to ensure a constant output level from the camera under varying light conditions by opening/closing the iris as required. This is usually contained in the lens body for power and video output sample from the camera. Other systems exist where the servo electronics are contained in the camera and a 4 wire connection is made to the lens.
Normally refers to the magnitude of a signal voltage ie. the video signal is produced and distributed at an amplitude of one volt peak to peak (p-p). Can also refer to the peak of a voltage above or below the base line
CCTV Guide
This control is applied to the gain of the video amplifier stage/s following the imaging device. It is usually related to ALC in that if the iris is fully open and video output is low, the gain of the amplifier stage is increased. So to is the noise generated by the stage itself and preceding devices which is then visible as grain or snow on the screen. As 'useable sensitivity' indicates the minimum illumination at which a 'picture' can be discerned amongst this noise, it is useful to know the illumination level at which AGC switches on or off and how much noise (S/N ratio) you have