Glossary

We have provided a comprehensive list of security equipment, terms and commonly used phrases to enhance your understanding of your security system. If it's not on the list let us know and we will endeavour to find it for you and add it to the site.

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Term	Definition
24 Hour zone	A device that remains armed constantly. Examples of 24 hour devices are Fire and Panic.
ADSL Filter	A four wire splitter designed specifically to work with your ADSL service and security system.
AGC	Automatic Gain Control - electronic circuitry to increase the video signal in low light conditions. This usually introduces 'noise' in the picture giving a grainy appearance. Camera specifications must always have AGC off.
Alarm Activated VCR	After pressing 'record', a normal VCR takes about 20 seconds before it starts recording usable pictures. With an alarm activated recorder it can be set so that the tape is ready to start recording in about one second. The signal to beginning recording can be from an alarm or any other input.
Alarm Input	A device that is monitored by the access control panel. An alarm signal will be generated if the device is activated.
Alarm Screens	These are standard window screens that have a special wire woven in the screening. They are designed to detect someone cutting the screen.
Alpha Display	A Keypad that displays the condition of the system in text rather than with LED's.
Anti-Passback	A feature that will not allow any card to re-enter unless it has been used to exit. This requires that readers be used for both entry and exit.
Aperture	The light gathering area of a lens, controlled by the iris.
Arming	The process of "Turning On" the alarm system.
Aspect Ratio	The ratio of the vertical to the horizontal image size. This is 3:4.
Attenuation	This refers to signal loss in a transmission system.
Audio Detector	A device designed to detect a break-in by analyzing the sound waves generated by the breaking of glass etc.
Automatic Iris	A lens that adjusts automatically to allow the right amount of light to fall on the imaging device. There is a tiny motor and amplifier built in which receives a control signal from the camera to maintain a constant one volt peak to peak (pp) video level.
Back Focus	A mechanical adjustment in a camera that moves the imaging device relative to the lens to compensate for different back focal lengths of lenses. This is important when a zoom lens is fitted.
Back Up Battery	A rechargeable battery that provides power to your security system in the event of power failure. Like a car battery these need replacing every few years so don't forget to have yours replaced next time you have a maintenance check on your alarm system.
Balanced Signal	A video signal is converted to a balanced signal to enable it to be transmitted along a 'twisted pair' cable. Used in situations where the cabling distance is too great.
Balun	An acronym for Balanced/Unbalanced. A device to change one cabling media to another (like coaxial cable to twisted pair cable)
Bandwidth	The complete range of frequencies over which a circuit or electronic system can function with minimal signal loss.
Bar Code	Bar codes, employ a pattern of bars and spaces of varying widths to represent the user information. This is the same technology that is used by stores for inventory control and check out counters. Since the bar code is visible it is easy to duplicate and as such is not considered to be a good choice for systems where security is a major concern.