A B C D E F G H I J L M NO P R S T U V W Y Z

A
AGC (Automatic Gain Control)
Usually a switchable circuit that allows the camera to provide a ‘useable’ picture during low light levels.

Alarm
Alarm is a facility that allows external alarms like PIR's, reed switches, vibration sensors etc. to be connected to the CCTV switcher so that a nominated camera is switched on when an alarm signal is received.

Algorithms
Complex mathematical formulae or rules used to solve problems. In video, they are used to achieve digital compression of a video picture.

APC
(Adaptive Picture Control) VCR function which automatically detects the condition of the recording head and the videotape and then sets the optimum record head current to prevent over-modulation.

Ambient Light Level
Lighting level that is normal for a certain area. It generally does not alter. It can also mean the background light level of a certain area.

Analogue
A signal in which any level is represented by a directly proportional voltage; not digital.

Analog circuits
Electronic circuits made up of components that can handle analog signals. Examples: Resistors, capacitors etc.

Angle of View
The angle of view (not the focal length) alters when a lens is used in an alternative format. The angle decreases as format size increases.

Aperture
The ‘opening’ of a lens, and the measure of its light gathering capability. Measured in F numbers, being the ratio between the focal length and the effective aperture of the lens. Generally the lower the better.

Aspherical Lens
A lens designed with a non-spherical shape so that it refracts light passing through it.

ATM
It is a type of ISDN technology using constant size 53 byte cells instead of variable size packets. Because cells do not change size, they switch much faster and more efficiently.

Auto Iris
A circuit fitted to the lens iris which allows the aperture of the lens to automatically adjust to varying light levels, providing a constant picture.

B

Backbone
Backbone is the infrastructure that is used to inter-connect the various local area networks to build a wide area network.

Bandwidth
Bandwidth is the range of frequencies or data that pass through an electrical/electronic amplifying, processing or transmission unit without attenuation or loss

Binary
A base 2 numbering system using two digits 0 and 1.

Bits
It is the short form for binary digit

BLC (Back Light Compensation)
Electronic compensation for background lighting. Produces detail where the subject would normally be in silhouette.

BNC
Video connector most commonly used in CCTV

Bridge
A network device that logically separates a single network into segments.

Brightness
Brightness represents the intensity of illumination of the reproduced picture.

Byte
Group or word of bits. Usually has 8 bits.

C

Camera
Camera is an electronic device that converts light into an electrical signal.

CCD (Charge Coupled Device)
Is a solid-state device in a camera that converts light falling on it into an electrical signal.

Chromiance (C)
The part of the video signal corresponding to colour information.

CGI
The Common Gateway Interface (CGI) is a standard for interfacing external applications with information servers, such as HTTP or Web servers. A CGI program can be written in any language that allows it to be executed on the system, such as: C/C++, PERL, Visual Basic etc.

Compression
It is a process of reducing the size of digital signal.

Compression ratio
It is the ratio between the size of data before compression and after compression.

Compressor
It is a process of reducing the size of digital signal.

C Mount
Industry standard type of screw threaded lens mount.

CS Mount (Special C Mount)
As a C Mount with a shorter screw thread.

CS to C Mount Adaptor
5mm spacer ring to allow the use of C Mount lenses on CS mount cameras.

Co-Axial cable
Any cable that has a conductor and shield sharing the same axis.

Composite Video
The combination of all electronic information required to produce a video signal.

CPU
Central Processor Unit. It is the brain of a digital system like the computer, where all the manipulation or processing of digital data is done. Its speed is measured in Hertz. It also tells the number of instructions it undertakes per sec.

CRT
Cathode Ray Tube The means by which pictures are displayed on a monitor.

D

DD (Direct Drive)
An auto iris lens where the size of aperture is governed by the camera not by the lens.

DDNS
DDNS stands for Dynamic Domain Name Server: This is a service provided by different service providers, and is suitable for situations where the IP address is dynamic and keeps changing. The user registers a host name with a service provider and whenever the dynamic IP address changes, the DDNS service provider automatically updates the DNS servers all over the world

Data Rate
It is amount of data being handled by a device every second.

Decimal
A base 10 numbering system using ten digits 0, 1,2,3,4,5,6,7,8,9.

Depth of Field
The distance between the furthest and nearest points, at the same level of definition within a certain view.

dB (Decibel)
A logarithmic ratio comparing voltage input power. Also a measurement of sound levels.

Digital
A signal represented by a series of binary numbers.

DHCP
Dynamic Host Configuration Protocol is used in a TCP/IP protocol network to send client configuration data including TCP/IP address, subnet mask to the clients.

DNS
Domain Name Server (DNS): When the user types in 'www.panasonic.com ', the DNS server in the network converts it into an IP address, which is then used in all communications.

DSL
Digital Subscriber Line is a high-speed network connection using standard POTS or PSTN telephone cable

DSP
Digital Signal Processing chip is like a mini computer with its own RAM, CPU and different application software. As required the software is activated to manipulate the digital signal.

DVR (Digital Video Recorder)
Device that uses digital techniques to record CCTV images to a hard disk. The results can be of a higher quality than VHS or SVHS.

Duplex (Multiplexer)
A multiplexer with two frame stores, allowing two modes of operation simultaneously, e.g. recording and playback.

Dwell Time
Amount of time that a sequential switcher allows between the viewing of the different cameras connected to it.

Dynamic Address
This is not a permanent address and is a good solution to overcome the shortage of IP addresses. The Dynamic Host Configuration (DHCP) server allocates temporary IP addresses to the devices connected to the network. If a device logs on to the network, it is given a temporary IP address for a fixed time period or the same IP address is given to another device when the original user logs off.

E

EI
(Electronic Iris/Shutter) CCD Iris which eliminates the need for an Auto Iris Lens. The CCD Iris automatically controls the light intensity by adjusting the electronic shutter speed to mimic auto iris control.

F

F Stop
Figure given to the ratio between a lens aperture and its length.

Field
One half of a frame, consisting either the odd or even numbered lines, 50 fields are transmitted every second.

Firewall
A combination of hardware and software that protects the network from attack by hackers who could gain access through the public networks.

Fixed Lens
A lens with fixed focal length.

Focal Length
Distance from the optical centre of a lens to the focal plane. Generally referred to in millimetres.

Focal Point
Point at which light is passing through a lens aperture and its length.

Frame
Frame is the basic unit of a moving picture. At least 24 frames per sec are required for a moving picture to look continuous.

Frame Store
Digital information store capable of holding a complete frame of video information.

Frequency
The number of completed cycles of a waveform that occurs in a given length of time. Usually specified in cycles per second (Hertz)

Frequency Range
Frequency Range is the number of different frequencies that are included in the analog signal Usually specified in cycles per second (Hertz)

FTP
File Transfer Protocol (FTP) is a type of TCP, which is specifically used to transfer files between computers and uses the Port 20 or 21.

G

Galvanometric (galvometric)
A method of converting the electrical currents produced by auto iris circuits into a physical movement of the iris diaphragm. Used in both Auto Iris and Direct Drive lenses.

Gamma
Unit of measurement for one amount of contrast in an image.

Gateway
The hardware and software needed to connect two disparate network environments

GenLock
A means of locking, or synchronising, one video source to a second video source or reference signal.

Ground Loop
A condition that occurs when two or more grounded points in an electrical system develop a conductive loop between them. This can cause interference in the receipt of video images.

GUI
Graphical User Interface interfaces the PC to any external device. Hot areas on the computer screen can be programmed to activate a function or activity in the device.

H

Hard disk
A magnetic medium for storing digital information on most computers and electronic equipment that process digital signal.

HDR (Hard Disk Recorder)
See DVR – Digital Video Recorder

Hexadecimal
A base 16 numbering system using ten digits and 6 alphabets -0,1,2,3,4,5,6,7,8,9,A, B, C, D, E, F

HTML
Hyper Text Markup Language is a set of codes to format text and graphics that will be displayed in a browser. The code defines how the data will be displayed.

HTTP
Hyper Text Transfer Protocol: The protocol used for communication between a Web server and Web browser and usually uses the port 80

Hub
A network device that serves as a central connection point for several devices. A hub repeats the signal it receives on one port to all other ports.

Hz (Hertz)
A measure of frequency – cycles per second.

I

IEEE
Institute of Electric and Electronics Engineers Inc. is an international organization that sets standards for various electrical and electronic issues

Image Intensifier
Device which uses photo multiplier technology to amplify the available light to increase the sensitivity of the camera.

Impedance
Impedance is the input and output characteristic of any electrical system and is measured in ohms. For maximum signal transfer, the input and output impedance should be the same

Interlace (2:1 interlace)
Scanning process for reducing the image flicker consisting of successively scanned lines of which adjacent lines belong to different fields.

IP address
It is part of the TCP/IP protocol suite and is responsible for network addressing and routing.

IR (Infra Red)
A range of light frequencies below the visible spectrum. Can be used for the transmission of information or for providing additional illumination for cameras.

Iris
Iris is a diaphragm which is inbuilt in a lens that can be adjusted either manually or automatically to vary the amount of light passing through the lens and falling on the CCD chip.

ISDN (Integrated Services Digital Network)
Digital phone line with transmission speeds of up to 128kb per second. Used with PMS video transmission systems.

ISP
Internet Service Provider is a company that provides direct access to the Internet for home or business users.

J

Java
A programming language developed by Sun Microsystems which can run on any platform which has a Java Virtual Machine installed.

JPEG
Joint Photographic Expert Group is an ISO standard for still or single frame compression.

L

L2TP
Layer 2 Tunneling Protocol is a non-proprietary protocol created by the Internet Task Force for encrypting IP packets for transmission through the Internet. The host and destination routers must have the L2TP protocol installed to create a Virtual Private Network.

LAN
Local Area Network is a small network usually restricted to single or close by buildings.

LASER
Light amplification by stimulated emission of radiation. A laser produces a very strong and coherent light of a single frequency.

Line Fed Camera
A camera that received its power along the same cable that is used to send its picture back to the monitor.

Line Lock
Method of synchronising AC powered cameras.

Lines
It is the measurement of resolution for an analog video signal. Higher the bandwidth of the signal means a higher number of picture lines.

Linux
A version of Unix developed by Linus Torvalds. Runs on Intel based PC's and is generally free.

Lux
Metric unit, a measure of light.

Luminance
Luminance is that part of the video signal which contains the information on the brightness of the picture

M

Matrix Switcher
A switching unit able to route any camera inputs to any monitor outputs, often include telemetry control.

MAC
Media Access Control is a part of the network interface card NIC) that controls the way multiple devices use the same media channel.

Mbps
Mega (106) bits per sec. It is an indication of data rate

Mechanical Focus (back-focus, racking)
The mechanical aligning of the imaging device with the focal point of the lens; most important on zoom lenses to ensure the image stays in focus throughout the zoom range.

Microwave
Radio frequencies between 1-30gHz for video transmission over medium/long distances.

Modem
(Modulate/Demodulate) device for the transmission of data via dial-up networking.

Monochrome
Black and White picture comprising of a number of levels of grey scales.

MPEG
Moving Picture Expert Group is an ISO standard for moving image compression.

MPEG 1
A MPEG standard for compressing scanned images with audio. Bit rate is from 1.5Mbps to 3.5 Mbps.

MPEG 2
A popular MPEG standard for interlaced video signal with high quality audio with a scalable bit rate from 1.5 Mbps to 100 Mbps. Accepted as a HDTV and DVD standard

Multiplex (time multiplex)
Method of transmitting or recording many video signals at the same time, by recording the output from each camera in successive fields or frames of a video signal. These can then be retrieved later as a single picture.

N

N/D (Neutral Density)
Filter which is positioned on the rear of the lens, enabling the camera to operate in difficult lighting conditions, by widening its operating parameters.

NIC
Network Interface Card connects any network device to the transmission medium.

Noise
It is an unwanted signal generated by electronic components. The noise in a video signal causes a grainy or snowy effect on the image.

NTSC
National Television System Committee is a color television system and the standard used in the USA and Japan. NTSC has 525 horizontal scanning lines and 60 fields per sec.