CCTV Glossary (A-Z)

A

AGC - Automatic Gain Control. A section in an electronic circuit hat has feedback and regulates a certain voltage level to fall within predetermined margins
ALC - Automatic Light Control. A part of the electronics of an automatic iris lens that has a function similar to backlight compensation in photography.
Auto iris - An automatic method of varying the size of a lens aperture in response to changes in scene illumination.

B

Back-focus - A procedure of adjusting the physical position of the CCD-chip/lens to achieve the correct focus for all focal length settings (especially critical with zoom lenses)
BLC - (Back Light Compensation). Electronic compensation for background lighting. Produces detail where the subject would normally be in silhouette.
BNC - it's the most popular connector in CCTV and broadcast TV for transmitting a basic bandwidth video signal over a coaxial cable

C

CCTV - Closed Circuit Television. A television system intended for only a limited number of viewers, as opposed to broadcast TV.
C-Mount - Industry standard thread mounting portion on the rear of a lens. Note a C mount lens can be used on a CS mount camera with a 5mm adaptor ring, however a CS mount lens cannot be used on a C mount format camera
CS-Mount - A new generation of lenses designed for 2/3",1/2" and 1/3" cameras incorporating CS-mounts. The distance from the flange surface to the focal point is 12.5mm. CS-mount lenses cannot be used on cameras with C-mount configuration. These lenses are smaller and cheaper than the C-mount equivalents.
CMOS - Technology involving Complementary Metal-Oxide Semiconductor (CMOS) to sense images. CMOS imagers now rival--and in some cases surpass--CCD technology in dynamic range and noise sensitivity and can offer improvements in resolution.

D

DB - Decibel, a logarithmic ratio of two signals or values, usually refers to power, but also voltage and current.
DHCP - A protocol that provides a means to dynamically allocate IP addresses to computers on a local area network. The system administrator assigns a range of IP addresses to DHCP and each client computer on the LAN has its TCP/IP software configured to request an IP address from the DHCP server. The request and grant process uses a lease concept with a controllable time period.
DNS - Domain Name Service - the system used to match server IP addresses to web site domain names.
DSL - Digital Subscriber Line, A family of digital telecommunications protocols designed to allow high speed data communication over the existing copper telephone lines between end-users and telephone companies.
DSP - Digital Signal Processing. This is a circuit that is specially designed for digital signals in processor-intensive applications, such as wireless communications links and image processing. DSP circuits are often used in consumer products, such as mobile phones, faxes and digital TVs.
Dynamic ISP Accounts - some Internet Service Providers and Online Services, such as AOL, rotate IP addresses so each time a user accesses the internet he or she uses a different IP address. Such systems may prevent the use of Network IP Cameras and other networked devices.

E

Ethernet - The most common standard for network communication in LANs (Local Area Networks).

F

Focal length - The distance between the optical center of a lens and the principal convergent focus point
F-number - In lenses with adjustable irises, the maximum iris opening is expressed as a ratio (focal length of the lens)/(maximum diameter of aperture). The maximum iris will be engraved on the front ring of the lens.
Frame -One Complete TV picture. 1 frame is made up of 2 fields interlaced together. A snapshot or still CCTV picture can only ever be a field as a frame is made up of 2 different pictures taken at a slightly different time. UK TV (PAL) there are 25 frames per second each of 625 scan lines.
Frame per second (FPS) - In digital video applications, refers to the number of video images that can be captured, displayed, or recorded in a second. Also referred to as the 'frame rate' or 'refresh rate FTP - File Transfer Protocol. Network cameras equipped with an embedded operating system, such as Linux, can use FTP to send images to a web site.

G

GB.- Gigabyte. Unit of computer memory consisting of about one thousand million bytes (a thousand megabytes). The actual value is 1,073,741,824 bytes.
GUI. - Graphical User Interface. A computer type display giving system status information.

H

HTML - A markup language used to structure text and multimedia documents and to set up hypertext links between documents, used extensively on the World Wide Web.
HDD - Hard Disk Drive. A magnetic medium for storing digital information on most computers and electronic equipment that process digital data.

I

IP - Internet Protocol. The IP part of TCP/IP; the protocol that is used to route a data packets from source to destination over the Internet and IP networks.
IR - Infra Red , frequency of light, invisible to the human eye, used for covert surveillance and low light camera use.
IR camera -(Infrared camera) have special infrared lights installed around the perimeter of the camera lens. This provides special light that the camera uses to capture a good picture even in total darkness. Iris - A means of controlling the size of a lens aperture and therefore the amount of light passing through the lens.
ISP - Internet Service Providers - companies that provide internet access and/or web site hosting.

K

KVM switch - Keyboard, video and mouse switch)- one set of keyboard, monitor and mouse can control 2 sets, 4 sets, 8 sets, 16 sets and up to 4096 sets of computers through KVM switch.

L

LAN - Local Area Network. A computer communications system limited to no more than a few miles, usually in the same building, and utilizing high-speed connections of 2 to 100 megabits per second.
Linux - a freeware implementation of UNIX originally written by Linux Torvalds, which can be used with many different operating systems. Work on the kernel is coordinated by Torvalds, who holds the copyright on a large part of it. The rest of the copyright is held by many other contributors and their employers. The kernel as a whole is available under the GNU General Public License. Linux has been used in embedded operating systems used by some advanced Network IP Cameras.
Line-locked - In CCTV, this usually refers to multiple cameras being powered by a common alternative current (AC) source(either 24V AC, 110V AC or 240V AC) and consequently have field frequencies locked to the same AC source frequency (50 Hz in CCIR system and 60Hz in EIA system)
Looping - A piece of video equipment that allows video signals to pass through without being terminated.
Lux - 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 m. It is also known as lumen per square meter or meter-candelas.

M

Matrix switcher - A device for switching more than one camera, VCR, video printer and similar to more than one monitor, VCR, video printer and similar. Much more complex and more powerful than simple sequential video switchers.
Motion detection - Refers to the feature in some VCRs and DVRs to only record video if something in the image moves or changes. Therefore you don't have to look through hours of taped video looking for something to happen. It also saves a lot of space on the tape or hard drive.
Multiplexer - A device that can accept a number of camera inputs and almost simultaneously display them on a single monitor and/or record them. Multixplexers can also be used to transmit multiple cameras over the same transmission medium.

N

NTSC - National Television System Committee. American committee that set the standards for color television as used today in the U.S., Canada, Japan and parts of South America. NTSC television uses a 3.57945 MHz sub-carrier whose phase varies with the instantaneous hue of the televised color and whose amplitude varies with the instantaneous saturation of the color.

P

PAL - Phase alternating line. Describes the color phase change in a PAL color signal. PAL in a European color TV system featuring 625 lines per frame, 50fields per second and a 4.43661875-MHz sub-carrier. Used mainly in Europe, China, Malaysia, Australia, New Zealand, the Middle East and parts of Africa.
PDA - Personal Digital Assistant. A handheld computer that provides a calendar and organizer for personal information. A PDA normally contains at least one database with names and addresses, to-do lists and a notepad.
PPP - Point-to-Point Protocol. A method allowing one computer to connect to another, usually via a modem over a phone line.
Protocol - A set of formal rules describing how to transmit data, especially across a network. Low-level protocols define the electrical and physical standards to be observed, bit- and byte-ordering and the transmission and error detection and correction of the bit stream. High-level protocols deal with the data formatting, including the syntax of messages, the terminal to computer dialogue, character sets, sequencing of messages etc.
PAN & TILT scanner - a device that will move a camera both horizontally and vertically from a remote location.
PTZ camera - Pan, Tilt and zoom camera

Q

Quad - An analog device used to display 4 cameras simultaneously on a single monitor.

R

Resolution - A measure of the ability of a camera or television system to reproduce detail. The number of picture elements that can be reproduced with good definition
Router - an interconnection device that serves packets or frames containing certain protocols. Routers link LANs at the network layer. A device that finds the best path for a data packet to be sent from one network to another. A router does more processing than a bridge does. A router can be hardware or a combination of hardware and software. Network IP Cameras typically connect to a router, hub or switch.
RS-232 - A format of digital communication where only two wires are requited. It is also known as a serial data communication. The RS-232 standard defines a scheme for asynchronous communications, but it does not define how the data should be represented by the bits. It is very often used in CCTV communications between keyboards and matrix switchers or between matrix switchers and PTZ site drivers.
RS-485 - This is an advanced format of digital communications compared to RS-422. The major improvement is in the number of receivers that can be driven with this format, and this is up to 32.

S

Signal-to -Noise (S/N) - An S/N ratio can be given for the luminance signal, chrominance signal and audio signal. The S/N ratio is the ratio of noise to actual total signal, and it shows how much higher the signal level is than the level of noise. It is expressed in decibels(dB), and the bigger the value is, the crisper and clearer the picture and sound will be during playback. An S/N ratio is calculated with the logarithm of the normal signal and the noise RMS value
Static ISP Accounts - accounts offered by Internet Service Providers that allow users to identify a "static" IP address that never changes. Such accounts allow the easy use of Network IP Cameras and other networked devices.
S-VHS - Super Video Home System, a higher resolution recording medium than VHS Switcher- Sequential video switchers that wait until the current field has completed its cycle before switching to the next camera, even though the dwell time may have been exceeded. Thus reducing the amount of bounce seen between switching images.

T

TCP/IP- Transmission Control Protocol over Internet Protocol. The TCP/IP protocol defines how data can be transmitted in a secure manner between networks. TCP/IP is the most widely used communications standard and is the basis for the Internet.
Time-lapse VCR - A VCR that can be set to slow down its recording rate in order to extend the length of time that can be recorded on a standard tape up to as much as 960 hours. This is possible by recording one frame at time at set time intervals. Most units have an alarm input signal so it can be automatically switched to real time mode in case of an alarm.

U

URL - Uniform Resource Locator. An "address" on the network.
USB- (Universal Serial Bus) A plug-and-play interface between a computer and peripheral devices (scanners, printers etc)

V

Video Distributor - A device distributes multiple outputs of video signal from one camera input

W

White balance - An electronic process used in video cameras to retain true colors. It is performed electronically on the basis of a white object in the picture.