The following information is a glossary of home security terms. If you are interested in learning more about an ADC, ACG, activity detection, an apostilb, and many other Home Security Terms, read the following.
The following information is cited from Spytown.
Aberration: A term from optics that refers to anything affecting the fidelity of the image in regards to the original scene
AC: Alternating current
Activity detection: Refers to a method built into some multiplexers for detecting movement within the camera's field of view (connected to the multiplexer), which is then used to improve camera recording update rate.
AC/DC: Alternating current / direct current
A/D (or AD): Refers to analog to digital conversion
ADC: Analog to digital conversion. This is usually the very first stage of an electronic device that processes signals into digital format. The signal can be video, audio, control output and similar.
AGC: Automatic gain control. A section in an electronic circuit that has feedback and regulated a certain voltage level to fall within predetermined margins.
ALC: Automatic light control. A part of the electronics of an automatic iris lens that has a function similar to backlight compensation in photography.
Aliasing: An occurrence of sampled date interference. This can occur in CCD image projection of high spatial frequencies and is also known as Moiré patterning. It can be minimized by a technique known as optical low pass filtering.
Alphanumeric video generator (also text inserter): A device for providing additional information, normally superimposed on the picture being displayed; this can range form one or two characters to full-screen alphanumeric text. Such generators us the incoming video signal sync pulses as a reference point for the text insertion position, which means if the video signal is of poor quality, the text stability will also be of poor quality.
Amplitude: The maximum value of a varying waveform.
Analog signal: Representation of data by continuously varying quantities. An analog electrical signal has a different value if volts or amperes for electrical representation of the original excitement (sound, light) within the dynamic range of the system.
ANSI: American National Standards Institute.
Anti-aliasing: A procedure employed to eliminate or reduce (by smoothing and filtering) the aliasing effects.
Aperture: The opening of a lens that controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled by the iris adjustment. By increasing the F-stop number (F/1.4, F/1.8, F/2.8, etc.) less light is permitted to pass to the pickup device.
Apostilb: A photometric unit for measuring luminance where, instead of candelas, lumens are used to measure the luminous flux of a source.
Archive: Long-term off-line storage. In digital systems, pictures are generally archived onto some form of hard disk, magnetic tape.