AC Power

Alternating Current Power. In the United States, the standard AC Power is single-phase 117VAC/60Hz and is provided from power outlets in the house. 24V AC power can be produced from an AC Adapter.

 Alarm Sensor

Like Video Motion Detector, detects changes of motion to produce an alarm.

 Angle of View

The scene angle that a video camera lens can show on the monitor, like Diagonal Angle, Horizontal Angle and Vertical Angle, usually described in degree.

 Anti-aliasing

A procedure employed to eliminate or reduce (by smoothing and filtering) the aliasing effects.

The light gathering area of a lens, controlled by the iris.

Automatically adjusts the lens focus from surrounding scene and keeps a moving object in focus.

This is a feature of many CCTV cameras that helps keep the strength of the output signal constant, even when the light level changes. In other words, it boosts the signal strength at low light levels, and caps it at higher levels.

Cameras with an Auto Iris feature, have the ability to compensate for large variations in light levels. Particularly useful for cameras that need to compensate for changes from bright sunlight to dark shadows. The auto iris circuitry is normally linked to a motorised iris drive that physically opens and shuts the iris on the lens. Closing a physical iris is a much better way to protect a camera from being damaged by bright sunlight then simply using electronics to reduce the signal strength.

This is a feature of some cameras that automatically adjusts the color settings to maintain the quality of the white areas of the image.

This is the alignment of the rear of the lens to the imaging device.

This is a feature of cameras that automatically adjusts the image to compensate for bright sunlight or bright lights, to give more detail on the darker areas of the image. For example to focus on the detail of a face of a person that has the sunlight shining from behind.

Balun stands for Balanced - Unbalanced. It is a device used to interface between balanced lines and unbalanced lines. For example, twisted pair to co-axial.

BNC is a bayonet style connector for coaxial cable that is most commonly used for CCTV installations.

The manual bias control on a cathode ray tube or other display device that controls the average brightness and the contrast of a picture.

Video camera's CCD chips format; 2/3", 1/3", 1/4", etc.

Video image sensor. CCD or C-MOS chip.

Charge Coupled Device. One of the two main types of image sensing device used in cameras. It operates by converting light energy into electrical charge.

International Radio Consultative Committee; has made the technical recommendation for the European 625 line standard for video signals.

Closed Circuit Television. It does not broadcast TV signals but transmits them over a closed circuit through electrically conducting cable or wireless transmitter and receiver.

A unit containing an imaging device that produces a video signal in the baseband form, usually with synchronization pulses and color information (composite video).

An integrated circuit in which all the components (resistors capacitors and semiconductors) are micro-fabricated on a tiny piece of silicon or specialist material (silicon on sapphire. Often used to refer to the detector in a CCD camera.

CCTV lenses are available in two different lens mounts. "C-mount" lenses have a flange back distance of 17.5mm vs. 12.5mm for "CS-mount" lenses. Many of today's cameras can accept either type of lens, but it is important to make sure that camera and lens.

This refers to cable that has a central conductor, surrounded by a shield sharing the same axis. The shield can be made from a variety of materials including, braided copper, or lapped foil.
There are various standards for specific types of co-axial cable. The cable used for normal CCTV installations is called RG59.

A combined signal in a television transmission. Standard format such as NTSC, PAL or SECAM. The picture signal, blanking signal, and vertical/horizontal synchronizing signals are all combined.

Digital video pictures can be compressed with a number of techniques. These include, JPEG, M-JPEG, MPEG and Wavelet.

Cathode Ray Tube. The vacuum tube part of a monitor or television.

Installed between a CCTV camera and a monitor, it generates the information of Date, Time and camera ID.

Direct Current Power; can be derived from an AC adapter or from a battery. Among DC voltages of 6, 9, 12, 24, 28, 12VDC is most common in the CCTV industry.

The power or voltage ratio of two signals.

Also known as a personal video recorder (PVR) or hard disk video recorder. DVRs store recordings on a large hard drive, and most let you pause and replay live television. When used with an electronic program guide service, you can find and record shows automatically.

Dynamic Host Configuration Protocol; lets network administrators manage centrally and automate the assignment of IP addresses in an organization's network.

Dynamic Host Configuration Protocol; lets network administrators manage centrally and automate the assignment of IP addresses in an organization's network.

Domain Name System. A general purpose distributed, replicated, data query service. Its principal use is the lookup of host IP addresses based on host names.

Digital Signal Processing. It usually refers to the electronic circuit section of a camera capable of processing or enhancing signals.

The length of time a switcher displays one camera before sequencing to the next.

Electronic Industries Association. American standard for B/W camera system.

This is an electronic implementation of an auto iris. It uses electronics to simulate the effect of opening and closing the iris, by increasing or decreasing the effective shutter time of the camera.

Compensates for moderate light changes in indoor applications without the use of auto iris lenses.

The most widely installed Local Area Network (LAN) technology. Specified in a standard IEEE802.3.10/100 BASE-T, the most commonly installed Ethernet system, provides transmission speed up to 100 megabits per second.

An external sync allows a piece of equipment to take its video synchronisation from another unit, so that it can align itself with the system as a whole.

A private network. It uses the Internet Protocol to securely share part of a business information with suppliers, vendors or others.

One video frame is composed of two fields; one field consists of the odd numbered lines in the frame and the other field consists of the even numbered lines.

The distance between the optical centre of a lens and the principal convergent
focus point.

The size of the cameras imager. Current standards are 1/2, 1/3, 1/4 inches.

A whole video image; is composed of two interlaced fields. A CCD chip produces 30 frames per second at NTSC system and 25 frames at PAL.

Degree of contrast in a video picture between output magnitude and input magnitude.

Hole Accumulated Diode. A type of CCD sensor with a layer designed to accumulate holes (in the electronic sense), thus reducing noise level.

High-Bandwidth Digital Content Protection. HDCP encryption is used with high-resolution signals over DVI and HDMI connections to prevent unauthorized duplication of copyrighted material.

As a network product, a hub may include a group of modem cards for dial-in users, a gateway card for connections to a Local Area Network (LAN), and a connection to a line.

Internet Control Message Protocol. A message control and error-reporting protocol.

The detector in the camera, either a tube or CCD solid state device.

Reference to the size of an image formed by the lens onto the camera pickup device. The current standards are: 1", 2/3", 1/2" and 1/3" measured diagonally.

PAL video signals transmit odd and even lines alternately. This is a 2:1 interlace. The two sets of lines are combined to form each single frame.

Devices with internal sync, have an internal crystal to provide sync pulses, without needing reference from any external device.

Low frequency light below the visible spectrum. This is often used for covert or semi-covert surveillance to provide a light source for cameras to record images in dark or zero light conditions.

Integrated Service Digital Network. A set of standard for digital transmission over ordinary telephone copper wire.

Internet Protocol. A set of rules to send and receive messages at the Internet address level.

This is a mechanical device that adjusts to vary the amount of light passing through the lens of a camera.

JPEG is a standard for coding/compression of still pictures. It is used in the CCTV systems to compress and store individual frames of video.

An optical device for focusing a desired scene onto the imaging device in a CCTV camera.

In CCTV, this usually refers to multiple cameras being powered by a common
alternative current (AC) source (either 24 V AC, 110 V AC or 240 V AC) and consequently have field frequencies locked to the same AC source frequency (50 Hz in CCIR systems and 60 Hz in EIA systems).

This refers to connecting an additional device in parallel with an existing video cable. For example, when driving a video recorder as well as a monitor from the same video signal.

Light unit for measuring illumination. It is defined as the illumination of a surface when luminous flux of 1 lumen falls on an area of 1 m2. It is also known as lumens per square meter. One lux is equal to approximately 0.09290 foot candle.

This is a device that allows any of its camera inputs to be switched to one or more of its monitor outputs. The outputs can of course also be video recorders.

The device used to view video pictures. These devices do not normally have television RF frequency receivers. They normally have composite, or component video inputs.

This refers to a black and white image rather than a color one.

A camera lens equipped with small electric motor that enables focusing lens, opening or closing the iris diaphragm, or changing the focal length.

MPEG is a standard used for coding and compression of moving images. It was developed by the Moving Pictures Experts Group. It is now used widely for the compression of video images. However MPEG isn't just one standard. They have developed several standards for different uses. For example MPEG-2 is used for DVD's and set top boxes. MPEG-4 was developed for multi-media applications for fixed and mobile web applications.

This is a device that takes inputs from 2 or more video channels and combines them into one signal. This is often done by using time division multiplexing, which interleaves frames from each channel in such a way that they can be split out again. Frequency division multiplexing uses different frequencies to achieve the separation of the signals.

This refers to a camera that is designed to record pictures and transmit them directly over a computer network or dialup internet connection. Network cameras normally do not have any analogue video outputs. The images are encoded directly in one of the standard compression techniques, such as JPEG or MPEG.

Undesired signals that corrupt the original video signals and may reduce the image quality.

This is standard for TV signals developed by the National Television Standards Committee in the USA. The UK and Europe, use a similar, but different standard known as PAL.

This is the standard for TV signals used in the UK. It stands for Phase Alternating Line.

A camera mounting device that allows movement in both side ways and up or down.

This is a type of lens with a very small aperture. Normally used for covert applications, where it can easily hide behind or within another object.

The smallest cell or area in a picture. The greater number of pixels, the higher the resolution of the scene.

Point-to-Point Protocol over Ethernet.

A specific set of rules, procedures or conventions relating to format and timing of data transmission between two devices. A standard procedure that two data devices must accept and use to be able to understand each other.

A device that compresses up to 4 video signals and simultaneously displays them on a monitor.

Reverse Address Resolution Protocol. For host machines that don't know their IP address.

A device on the internet that determines the next network point to which a data should be forwarded.

A transmitting and receiving of signals for controlling remote devices such as pan and tilt units, lens functions, wash and wipe control and similar. It may also refer to the hand held controls for some VCRs and other CCTV equipment.

A device on the internet that determines the next network point to which a data should be forwarded.

A format of digital communication using a three wire unbalanced presentation.
The RS-232 standard defines the presentation and voltages for asynchronous communications, but it does not define how the data should be represented by the bits, i.e., it does not define the overall message format and protocol.  It is very often used in computers, CCTV and communications between keyboards and matrix switchers.

This is an advanced format of digital communication when compared to RS-232.
A major difference is that the presentation is balanced line and the signaling is differential. In simple terms, the signal transmitted is read at the receiving end as the difference between the two wires without a reference to earth.  So if there is common mode noise induced along the line, it will be cancelled out.  RS-422 can drive lines of up to 1200m and distribute data on to up to 10 receivers.

This is an advanced format of digital communications compared to RS-232. It is a balanced line transmission system. The major improvement over RS422 is in the number of receivers that can be driven with this format, up to 32. It is classically a half.

A digital communications interface in which data are transmitted and received sequentially along a single wire or pair of wires. Common serial interface standards are RS-232 and RS-422.

Signal to Noise Ratio. This is the ratio between the signal strength and the noise levels on an audio or video signal.

Simple Mail Transfer Protocol. TCP/IP used in sending and receiving e-mail.

Transmits luminance and color portions separately, using multiple wires, thus avoiding the color encoding process and its inevitable loss of picture quality.

Transmission Control Protocol / Internet Protocol. The basic communication language or protocol of the Internet.

Installed between a CCTV camera and a monitor, it generates the information of Date, Time and camera ID.

Video recorder that can record frames with pauses between them thereby extending the time that a standard cassette will hold.

This refers to a 75 Ohm terminator that is used to terminate each end of a video line.

This is a measure of the resolution of a video device. Higher number is higher resolution. 380 TVL is considered medium resolution. 470 TVL or greater is considered high resolution.

A cable composed of two small insulated conductors twisted together. Since both wires have nearly equal exposure to any interference, common mode noise is high, but the differential noise is slight thus common mode noise is rejected in a twisted pair line. Twisted pair cable is used for balanced line transmission.

This refers to a type of lens that has the facility to change the focal length. This allows adjustment of the magnification and field of view of the camera.

A device that accepts signals from a video camera / microphone and records video/audio on magnetic tape in a cassette. The VCR can play back recorded video/audio on a television set or CCTV monitor.

A system that uses the video signal from a camera to determine if there is any movement in the picture and set of an alarm.

Switcher or Sequential Switcher. A device that allows the video signals from multiple cameras to be displayed on a monitor, or recorded on a VCR one at a time in sequence.

This is a device that accepts inputs from CCTV cameras using the PAL, composite video signal. It digitizes the signal and then transmits images via a network, dialup or GSM connection. Advanced video servers have built-in video motion detection, and can buffer images while they are being uploaded to a remote server, where they are recorded.

This is a compression technique used to give high compression without degrading the image quality.

A method of sending video pictures in 2 separate parts down 2 separate cables. The component parts are Y and C.

A lens of continuously variable focal length.

The ratio of the starting focal length (wide position) to the ending focal length (telephoto position) of a zoom lens. A lens with a 10X zoom ratio will magnify the image at the wide angle end by 10 times.