A
|
| AC Adaptor: |
|
Also called a power supply. All CCTV devices need power. Each device has its own power requirements (usually 12 volts with minimum amperage). The power coming out of the wall (in the UK) is 240 DC. The adaptor converts the AC power to DC power and will adjust it to specified amperage. The power supply should be included with each item - you usually don’t have to buy these separately. |
| AGC Automatic Gain Control.: |
|
A circuit for automatically controlling amplifier gain in order to maintain a constant output voltage with a varying input voltage within a predetermined range of input-to-output variation. |
| Alarm input: |
|
An input connection to a security VCR or DVR that triggers the unit to start recording if the alarm is triggered. |
| Analogue: |
|
There are two main ways of doing things electronically, analogue or digital. An analogue signal can be represented as a series of sine waves. The term originated because the modulation of the carrier wave is analogous to the fluctuations of the human voice or other sound that is being transmitted. |
| Angle of view: |
|
For security cameras, this refers to the angular range in degrees that you can focus the camera on without distorting the image. When focusing close up, you can generally see a wide angle of view. If the focus is distant, the angle of view is smaller or narrower. |
| Aperture: |
|
In television optics, it is the effective diameter of the lens that controls the amount of light reaching the photoconductive or photo emitting image pickup sensor. |
| Aspect Ratio: |
|
The ratio of width to height for the frame of the televised picture. 4:3 for standard systems |
| Asymmetrical Digital Subscriber Line (ADSL): |
|
A method for moving data over regular phone lines. An ADSL circuit is much faster than a regular phone connection, and the wires used are the same wires used for regular phone service. ADSL supports data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate). ADSL requires a special ADSL modem. |
| Audio/Video Interleave (AVI): |
|
An AVI file is a sound and motion picture file that conforms to the Microsoft Windows Resource Interchange File Format (RIFF) specification. AVI files (which end with an .avi extension) require a special player that may be included with your web browser. |
| Auto Balance (AB): |
|
System for detecting errors in colour balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction. |
| Auto Iris: |
|
A lens in which the aperture automatically opens or closes to maintain proper light levels on the faceplate of the camera pickup device. |
| Automatic Brightness Control (ABC): |
|
In display devices, the self-acting mechanism which controls brightness of the device as a function of ambient light. |
| Automatic Gain Control (AGC): |
|
A process by which gain is automatically adjusted as a function of input or other specified parameter. |
| Automatic Iris Lens: |
|
A lens that automatically adjusts the amount of light reaching the imager. |
| Automatic Light Control: |
|
The process by which the illumination incident upon the face of a pickup device is automatically adjusted as a function of scene brightness. |
| Automatic White Balance (AWB): |
|
A feature on colour cameras that constantly monitors the light and adjusts its colour to maintain white areas. |
B
|
| 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. An important adjustment when a zoom lens is fitted. |
| Back Light Compensation (BLC): |
|
A feature on newer CCD cameras which electronically compensates for high background lighting to give detail which would normally be silhouetted. |
| Balun: |
|
A transformer that levels out impedance differences, so that a signal generated on to a coaxial cable can be transferred on to a twisted pair cable. |
| Bandwidth: |
|
The bandwidth determines the rate at which video can be sent through a network - the greater the bandwidth, the more video that can be sent in a given amount of time. Usually measured in bits-per-second. |
| Baud: |
|
The baud rate is how many bits can be sent or received per second. |
| Bitmap: |
|
A bitmap is digital graphic that basically consists of a map of dots. Bitmaps include GIF, JPEG and other file formats. |
| Black Level: |
|
The dark parts of a video signal corresponding to approximately 0.3 volts. |
| BLC: |
|
(back light compensation) A feature of modern CCD cameras, which electronically compensates for high background lighting, to give details that would normally be silhouetted. |
| BNC connector: |
|
It is a type of a connector used to interconnect two coaxial cables or connect a cable with other CCTV components. |
| Brightness: |
|
The attribute of visual perception in accordance with which an area appear to emit more of less light. (Luminance is the recommended name for the photo-electric quantity which has also been called brightness.) |
| Broadband: |
|
A general term for different types of high-speed, high-bandwidth connections to the Internet, including ADSL and cable. |
C
|
| Camera Format: |
|
The approximate size of a camera image pickup device. This measurement is derived from the diagonal line of a chip. Common formats are 1/6”, 1/4”, 1/3”, 2/3” and 1”. |
| Category (CAT): |
|
5 Cable Cable that is capable of transmitting data at high speeds (100 megabits per second and faster). CAT 5 cable is commonly used for voice and data applications. Usually comes with RJ45 connectors. |
| CCD: |
|
Charge coupled device, a flat thin wafer that is light sensitive and forms the imaging device of most modern cameras. Size is measured diagonally and can be 1/3”-1/2” or 2/3”. There are two types, frame transfer and interline transfer. |
| CCIR: |
|
The European 625 line standard for the video signal. |
| Charge-Coupled Device (CCD): |
|
CCTV cameras with CCD sensor will give sharper, better defined pictures. All professional level cameras will be CCD. |
| Circuit Switched Data (CSD): |
|
A GSM transmission standard that allows data to be transferred at up to 14.4kbps. |
| CMOS Complementary Metal Oxide Semiconductor: |
|
Similar to a CCD, it also detects light for conversion into a signal. Lesser image clarity than CCD, but more compact in size with lower power usage. |
| C-Mount: |
|
An industry standard for mounting a lens to a camera with a 1” x 32 thread and a distance from the image plane of 17.52mm from the shoulder of the lens. A C-mount lens may be used with a CS-mount camera with a 5mm-adapter ring |
| Coaxial Cable: |
|
A particular type of cable capable of passing a wide range of frequencies with very low signal loss. Such a cable in its simplest form, consists of a hollow metallic shield with a single wire accurately placed along the center of the shield and isolated from the shield. |
| Codec: |
|
Short for compressor/decompressor, a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both. Examples of Codecs include Wavelet, MPEG-4, JPEG. |
| Composite Video Signal: |
|
The combined picture signal, including vertical and horizontal blanking and synchronizing signals. |
| Compression Technology: |
|
This is the Codecs used for compressing and decompressing video data. |
| Contrast: |
|
The range of light to dark values in a picture or the ratio between the maximum and minimum brightness values. |
| CS-Mount: |
|
An industry standard for mounting a lens to a camera with a 1” x 32 thread and a distance from the image plane of 12.52mm from the shoulder of the lens. A CS-mount lens may not be used on a C-mount camera |
D
|
| Day/Night Cameras: |
|
Day/Night Cameras are regular cameras with an especially sensitive CCD chip that allows a good image to be captured in very low ambient lighting (regular lighting - not infrared). |
| Definition: |
|
The fidelity of a television system to the original scene. |
| Depth of Field: |
|
The in-focus range of a lens or optical system. It is measured from the distance behind an object to the distance in front of the object when the viewing lens shows the object to be in focus. |
| Depth of Focus: |
|
The range of sensor-to-lens distance for which the image formed by the lens is clearly focused. |
| DialUp Line: |
|
A connection to the internet through a normal telephone line. Speeds of up to 56Kbps can be achieved over a 56K modem. |
| Digital Signal Processing: |
|
An algorithm within the camera that digitizes data (the image). Examples include automatic compensate for backlight interference, color balance variations and corrections related to aging of electrical components or lighting. Functions such as electronic pan and zoom, image annotation, compression of the video for network transmission, feature extraction and motion compensation can be easily and inexpensively added to the camera feature set. |
| Digital Video Recorder (DVR): |
|
A digital video recorder is basically a computer that converts the incoming (analogue) signal from the cameras to digital, and compresses it, and stores it. The DVR replaces the function of a multiplexer (or quad or switcher) and a security VCR. There are many advantages of digital video recorders over their analogue counterparts. |
| Distortion: |
|
The deviation of the received signal waveform from that of the original transmitted waveform. |
| Distribution Amplifier: |
|
A device that provides several isolated outputs from one looping or bridging input, and has a sufficiently high input impedance and input-to-output isolation to prevent loading of the input source. |
| Downstream: |
|
The downloading of data from the Internet to the PC. ADSL has both upstream and downstream data rates. |
| Duplex: |
|
A circuit that permits transmission in both directions. In CCTV, duplex is often used to describe the type of multiplexer that can perform two functions simultaneously: recording in multiplex mode and playback in multiplex mode. |
| Dynamic IP address: |
|
The term used to describe how an IP address is dynamically assigned to computers as and when needed. Unlike Static IP addresses, the IP address is temporary e.g. when you connect to your ISP using a dial-up connection , you PC or router will be dynamically assigned an IP address whilst you are on-line. This form of IP addressing is commonly used for consumer ADSL service.
|
