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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.
Anti-aliasing A procedure employed to eliminate or reduce (by smoothing and filtering) the aliasing effects.
Auto-Focus Lens Automatically adjusts the lens focus from surrounding scene and keeps a moving object in focus.
Automatic Gain Control (AGC) 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.
Back Light Compensation (BLC) 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.
Brightness Control The manual bias control on a cathode ray tube or other display device that controls the average brightness and the contrast of a picture.
Camera Sensor Video image sensor. CCD or C-MOS chip.
CCIR International Radio Consultative Committee; has made the technical recommendation for the European 625 line standard for video signals.
CCTV 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.
CCTV Camera A unit containing an imaging device that produces a video signal in the baseband form, usually with synchronization pulses and color information (composite video).
Chip 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.
C Mount Lens & CS Mount Lensr 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.
Composite Video 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.
Compression Digital video pictures can be compressed with a number of techniques. These include, JPEG, M-JPEG, MPEG and Wavelet.
CRT Cathode Ray Tube. The vacuum tube part of a monitor or television.
DC Power 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.
Decibel (dB) The power or voltage ratio of two signals.
Direct Drive (DD) Dynamic Host Configuration Protocol; lets network administrators manage centrally and automate the assignment of IP addresses in an organization's network.
DHCP Dynamic Host Configuration Protocol; lets network administrators manage centrally and automate the assignment of IP addresses in an organization's network.
DNS 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.
DSP Digital Signal Processing. It usually refers to the electronic circuit section of a camera capable of processing or enhancing signals.
Dwell Time The length of time a switcher displays one camera before sequencing to the next.
EIA Electronic Industries Association. American standard for B/W camera system.
Electronic Iris (EI) 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.
Electronic Shutter (ES) Compensates for moderate light changes in indoor applications without the use of auto iris lenses.
Ethernet 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.
External Sync 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.
Extranet A private network. It uses the Internet Protocol to securely share part of a business information with suppliers, vendors or others.
Focal Length (FL) The distance between the optical centre of a lens and the principal convergent focus point.
Format The size of the cameras imager. Current standards are 1/2, 1/3, 1/4 inches.
Frame 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.
Gamma Degree of contrast in a video picture between output magnitude and input magnitude.
HAD Hole Accumulated Diode. A type of CCD sensor with a layer designed to accumulate holes (in the electronic sense), thus reducing noise level.
HDCP 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.
HUB 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.
ICMP Internet Control Message Protocol. A message control and error-reporting protocol.
Image Device The detector in the camera, either a tube or CCD solid state device.
Image size 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.
Interlace 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.
Internal Sync. Devices with internal sync, have an internal crystal to provide sync pulses, without needing reference from any external device.
Infra Red (IR) 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.
ISDN Integrated Service Digital Network. A set of standard for digital transmission over ordinary telephone copper wire.
JPEG 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.
Lens An optical device for focusing a desired scene onto the imaging device in a CCTV camera.
Line Lock 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).
Loop 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.
Matrix Switcher 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.
Monitor 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.
Monochrome This refers to a black and white image rather than a color one.
Motion Detection 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.
Motorized Lens A camera lens equipped with small electric motor that enables focusing lens, opening or closing the iris diaphragm, or changing the focal length.
MPEG 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.
Network Camera 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.
Noise Undesired signals that corrupt the original video signals and may reduce the image quality.
NTSC 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.
PAL This is the standard for TV signals used in the UK. It stands for Phase Alternating Line.
Pan and Tilt A camera mounting device that allows movement in both side ways and up or down.
Pixel The smallest cell or area in a picture. The greater number of pixels, the higher the resolution of the scene.
PPPoE Point-to-Point Protocol over Ethernet.
Protocol 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.
Quad A device that compresses up to 4 video signals and simultaneously displays them on a monitor.
RARP Reverse Address Resolution Protocol. For host machines that don't know their IP address.
RCA A device on the internet that determines the next network point to which a data should be forwarded.
Remote control 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.
Router A device on the internet that determines the next network point to which a data should be forwarded.
RS-232 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.
RS-422 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.
RS-485 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.
Serial Interface 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.
S/N Ratio Signal to Noise Ratio. This is the ratio between the signal strength and the noise levels on an audio or video signal.
SMTP Simple Mail Transfer Protocol. TCP/IP used in sending and receiving e-mail.
S-Video Transmits luminance and color portions separately, using multiple wires, thus avoiding the color encoding process and its inevitable loss of picture quality.
TCP/IP Transmission Control Protocol / Internet Protocol. The basic communication language or protocol of the Internet.
Time/Date Generator Installed between a CCTV camera and a monitor, it generates the information of Date, Time and camera ID.
Termination This refers to a 75 Ohm terminator that is used to terminate each end of a video line.
Television Lines (TVL) 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.
Twisted-pair 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.
Vari-Focal 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.
Videocassette Recorder (VCR) 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.
Video Switcher 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.
Video Server 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.
Wavelets This is a compression technique used to give high compression without degrading the image quality.
Y/C A method of sending video pictures in 2 separate parts down 2 separate cables. The component parts are Y and C.
ZOOM LENS A lens with the ability to change its focal length manually or through the use of a controller to cover a variety of needs.
ZOOM RATIO The ratio of the starting focal length (wide) to the ending focal length (telephoto) of a zoom lens. A 10X zoom will magnify the image at the wide end by 10 times. Examples of a 10X zoom lenses; 8mm~80mm, 12mm~120mm.