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Activity Detection: A feature of the video multiplexer range that uses video motion detection techniques to improve the camera update times.

Alarming: The ability of CCTV equipment to respond to an input signal, normally a simple contact closure. The response varies depending on equipment type. Many cameras have alarming functions built-in; however, most CCTV installations today use the DVR as a central monitoring of motion and alarm responses.

A.L.C. (Automatic Level Control): On AI lenses, also known as the peak/average control. Adjusting this control allows the auto iris circuitry to either take bright spots more into consideration (peak), bringing out detail in bright areas, or less into consideration (average) bringing out

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

Angle of view: The angular range that can be focused with a given lens. Small focal lengths give a wide angle of view, and large focal lengths give a narrow field of view. A 3.0 mm lens and lower is considered a wide angle lens.

Aperture: The opening of a camera lens that controls the amount of light reaching the surface of the pickup device (CCD). The size of the aperture is controlled by the iris adjustment. By increasing the f stop number (f1.4, f1.8, f2.8, etc.) less light is permitted to pass to the pickup device.

Aspect ratio: The ratio of the picture frame width to the picture frame height in standard broadcast TV systems. It is typically 4 units horizontal over 3 units vertical or a 4:3 ratio.

Aspherical Lens: A lens with a non-spherical shape refracts the light passing through it. It is typically used on wide angle lenses to decrease distortion or fisheye effect or it is used to allow more light to pass by lowering the lens aperture

Attenuation: A decrease or loss in a signal. The longer a cable extends, the more attenuation, or weaker signal occurs.

Automatic Frequency Control (AFC): An electronic circuit used whereby the frequency of an oscillator is automatically maintained within specified limits.

Automatic gain control (AGC): A feature that is used to automatically adjust the signal strength based on certain parameters based on the signal input and other specified parameter. Found on many DVRs.

Auto Iris lens: A lens in which the aperture automatically opens or closes to maintain proper light levels on the camera pickup device (CCD). This function allows the lens to automatically adjust to lighting conditions. Used in all outdoor cameras and many indoor with outside reflecting light or changing ambient light levels.

Automatic Level Control (A.L.C.): A feature on Auto iris lenses (also known as the peak/average control). This allows the Auto Iris lens to either take bright spots more into consideration (peak), that allows detail in bright areas, or less into consideration (average) bringing out detail of shadows or darker areas of the picture view.

Auto-Terminating: Feature whereby the equipment automatically selects the correct termination depending on whether the video output BNC is connected.

Auto White Balance: A feature on many color cameras that monitors the light and adjusts its color to maintain the light areas.


BNC: British Naval Connector. A trivia question somewhere. The traditional CCTV camera termination method. BNC connectors come in twist-on or crimped connections.

Back focal distance: There is a mechanical back focal distance -The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount. Optical back focal distance is thedistance from the rear most portion of the lens glass to the image plane. .

Back Light Compensation (B.L.C.): A feature on professional CCTV cameras which electronically compensates for high background lighting to give detail which would normally be silhouetted. It allows adjustment to compensate for shadows and dark areas in the camera view.

Bandwidth: A measure of the load and capacity of information over a network. Video transmission takes more bandwidth to transmit over a network than text.

Black level: The video signal level that corresponds to the maximum limits of the black areas of the picture.


"C" mount/"CS" mount: CCTV lenses come in two different lens mounts. The "C-mount" lenses have a flange back distance of 17.5mm vs. 12.5mm for "CS-mount" lenses. C-mount lenses can be used on CS-mount cameras by utilizing a 5mm adapter or adjusting the camera for C-mount lenses. Because of the shorter back focal distance, CS-mount lenses can only be used on CS-mount cameras. CS-mount lens cannot be used on a C-mount camera. Most CCTV cameras accept either C or CS-mount lenses.

CCD. (Charged Coupled Device): A CCD is an electronic chip that is the receiving device on a camera. Sony CCDs are the most popular and largest share of CCD market

CCTV: The common abbreviation for Closed Circuit Television. The common term for a “closed” video system or one that is used for the specific purpose as to not broadcast and is typically used for video security and surveillance.

Candlepower: The unit measure of a light intensity.

COAXIAL CABLE: A type of cable capable of passing a range of frequencies with low loss. It consists of a hollow metallic shield in which one or more center conductors are put in place and isolated from one another and from the shield. Common conductor material is copper and aluminum is used in cheaper coax cable. Siamese coax is coax cable with a pair of wires for camera power.

Composite video: The combined video signal that includes the picture signal, the vertical and horizontal blanking and synchronizing pulses. It is a simple two-wire connection that is commonly used in video monitors and monitor output on DVRs.

Crosstalk: An undesired signal or noise that interferes with the signal.


Database: A collection of data used and produced by a computer program.

db (Decibel): A measure of the power ratio of two signals. A unit used to express relative difference in power or intensity, usually between two acoustic or electric signals, equal to ten times the common logarithm of the ratio of the two levels.

DC TYPE lens: An auto-iris lens with internal circuitry that receives the video signal from the camera to adjust the iris. Common Auto-Iris lens

Default Gateway: The IP Address of the Router that is used to send information from one network to another.

Depth of field: The front to back zone in a field of view which is in focus in the picture scene. With a greater depth of field, more of the scene, near to far, is in focus. Increasing the f-stop number increases the depth of field of the lens. The lens aperture should be set at the highest f-stop number usable with the available lighting. The better the lighting, the greater the depth of field possible. The depth of field is the area in front of the camera which remains in focus. The larger the f-number the greater is the depth of field.

Digital Recording: This is the latest form of recording and is relatively new to the CCTV industry as a result is not the most economical method however it does have several advantages over the VCR analogue tape recorders. First of all it enables quick access to the desired

Duplex (multiplexer): A multiplexer that allows the user to look at multi-screen images while performing time multiplex recording.

Dwell Time: The length of time a monitor or DVR maintains a view on a given camera before moving on to the next view. Many DVRs will rotate between views based on alarms and the dwell time allows a specified time to view each screen before it is refreshed


E.I. (Electronic Iris): Automatically changes a CCD camera¹s shutter to mimic Auto Iris control, allowing fixed or manual iris lenses to be used in a range of areas that used to require an auto iris lens. Not as efficient as Auto-Iris lenses and cameras

Electronic shuttering: Electronic shuttering is the ability of the camera to compensate for moderate light changes in indoor applications without the use of auto iris lenses.

Ethernet: A type of LAN connection and protocol that is recognized as an industry standard. Used on most all IP networks


f-number: The f-number indicates the brightness of the image formed by the lens, controlled by the iris. A smaller f-number allows a brighter image.

f-stop: A term used to indicate the speed of a lens. The smaller the f-number, the larger the amount of light passing through the lens.

Facial Capture: In order to obtain facial capture surveillance for positive identification purposes, cameras should be mounted at vertical height conducive for facial capture (for example, in light switches). Lenses selected should produce identification level imaging and no less than 120% vertical image of the person.

Field: 60 fields are transmitted every second and one half of a frame, consisting of either the odd or the even numbered lines..

Flange back: The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount.

Focal length: The focal length determines the size of the image and the angle of the field of view seen by the camera through the lens. The focal length is the distance from the center of the lens to a plane at which point a sharp image of an object viewed at an infinite distance from the camera is produced. That is the distance from the center of the lens to the pickup device.

Foot-candle: It is the light intensity (illumination) of a surface one foot distant from a source of one candela. It is equal to one lumen per square foot. (1FC = 1 lm ft2). The foot-candle is the unit used to measure incident light.

Frame: The total area of the picture which is scanned while the picture signal is not blanked.

Full Duplex: The simultaneous data transmission in both directions of a signal path


Gen-lock: A method used to synchronize one or more cameras by external means such as: composite video, composite sync, horizontal or vertical sync. Old stuff…

Ghost: A shadowy or weak image in the received picture, offset either to the right or to the left of the primary image. It is the result of transmission conditions where secondary signals are created and received earlier or later than the primary signal. Weak video signals from the camera.

Ground: An electrical connection point that is common to a metal chassis, a terminal, or a ground bus that is grounded

Ground Loop: Caused by different earth potentials in a system. In other words, one of them or both are not grounded properly. It sometimes affects video pictures in the form of a black shadow bar across the screen or as poor video at top corner of a picture.


H.264: The latest mpeg4 Part 10 codec is H.264 which provides better compression of video images together with a range of features supporting high-quality, low-bitrate streaming video. The latest and greatest in video compression for CCTV as of 7/2006.

Horizontal blanking: The blanking signal that is provided at the end of each scanning line of the video signal

Horizontal (hum) bars: Horizontal bars, alternately black and white, which extend over the entire picture. They are known as venetian-blinds. They may be stationary or move up or down. They are often caused by poor wiring and AC power (60 Hertz) interfering with the video signal.

Horizontal resolution: The maximum number of individual picture elements that can be distinguished in a single scanning line.


I.R. (Infrared): A range of frequencies lower than visible red light used for covert surveillance or as a low cost wireless video link. An Infrared can view at “No-Light” conditions by illuminating the IR LEDs that surround the camera lens.

IP Address (Static and DHCP): Identifies a particular computer on a network to other computers. An IP address is similar to your home address. In a neighborhood, each house has a unique address; on a network each computer must have a unique address. There are two types of IP Addresses - static and DHCP. A Static address is where someone physically connects to a computer and defines the IP address for that computer. A static address does not change unless someone physically changes it. DHCP or a Dynamic address is dynamically assigned from a server that contains a pool of addresses. The server leases the computer one of the available addresses for a specified amount of time. Once the specified time has expired, the computer renews the lease or requests a new IP address.

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. 1/3” is most common

Impedance: The opposition which a circuit or component offers to the flow of electric current. It is expressed in ohms and is equal to the ratio of the effective value of the voltage applied to the circuit to the resulting current flow. In A.C. circuits, the impedance is a complex quantity that includes both resistance and reactance. In D.C. circuits, it is purely resistive.

Incident light: The ambient light that is directly over an object.

Interlace: A scanning process where every other horizontal line is scanned in one field while the alternate lines are scanned in the next field to produce a complete picture frame.

Internet: A public network of computers and people sharing information. Anyone can access the Internet through an Internet service provider. I heard this may get popular!

Intranet: A private network of computers using that allows a group within a company to share information across their group network and not outside the internal network.


JPEG: A digital image format commonly used in digital recording, for storing high-quality color and grayscale photographs in compressed bitmap form.


Lag: The image retention of an object after the object has been scanned. Sometimes, it causes a smearing effect.

LAN: Local Area Network; multiple computers connected together to share information. Shared information could be e-mail, files, and printers.

Line Lock: In an AC-powered camera, it synchronizes the field sync pulses, to the frequency of the voltage input (line voltage).

Lux: A unit of measuring the intensity of light. (1 FC = 10 Lux). A common measurement of a CCTV camera’s ability to view in low-light conditions.


Manual iris lens: A lens with a manual adjustment to set the iris opening (F stop). Generally used for indoor or fixed lighting applications.

Matrix Switcher: A switching device that routes camera inputs to any monitor outputs for viewing

Mechanical Focus (back-focus): The mechanical aligning of the imaging device with the focal point of the lens; it is most important on zoom lenses to be sure the image stays in focus throughout the zoom range.

Minimum object distance (MOD): The closest distance a given lens will be able to focus upon an object. This is measured from the vertex (front) of the lens to the object. Wide angle lenses generally have a smaller MOD than large focal length lenses.

Monochrome: Having only one color. In CCTV and television it is black and white.

Motion Detection: A feature that uses the video signal from a camera to determine movement (pixel changes) and react by recording the video or setting an alarm condition

MPEG: MPEG is a video compression method commonly used in digital recording. MPEG-1 is a standard for CD-ROM video and audio. MPEG-2 is a standard for full-screen, broadcast quality video.MPEG-4 is a standard for video telephony.


Network: Computers connected together to share information. Think of a network as a city and the computers as houses within the city. Two types of networks are LAN and WAN.

Noise: Random electronic noise signals that are not part of the primary signal. Electrical energy or interference.

NTSC: NTSC (National Television System Committee) is an organization that formulated the standards for the current United States color television system. This system is used in most countries of the Americas, as well as other parts of the world. NTSC employs 525 lines per frame, 29.97 frames per second and 59.94 fields per second.


Passive: A non powered element of a system. Baluns are an example of a passive device.

PAL: PAL (Phase Alternation Line) is a European color TV system featuring 625 lines per frame, 25 frames per second and 50 fields per second. PAL is used mainly in Europe, China, Malaysia, Australia, New Zealand, the Middle East, and parts of Africa.

Pinhole lens: Lens used for security applications where the camera/lens must be hidden. Front of lens has a small opening to allow the lens to view an entire room through a small hole in a wall or device.

Pixel: Short for picture element, Pixels are the tiny dots of information that make up a digital image. The more pixels there are on the camera's image sensor (CCD or CMOS), the higher the image resolution will be. The higher the resolution, the clearer an enlarged print can be.

Power: The rate at which electrical energy is applied to or taken from a device. Power is expressed in terms of watts.

Pre-position lenses: Allows the operator to view different pre-set areas quickly without having to re-adjust the zoom and focus each time.


Quad: A CCTV device that switches up to four (Quad) video signals and simultaneously displays the images onto one monitor.


Raster: The rectangular pattern of scanning lines upon which the picture is produced. The illuminated portion of the video monitor.

Resolution: That is the number of picture elements (pixels) that can be reproduced on the video or picture. It is a factor of the pickup device or the monitor characteristics and the video signal bandwidth. It is the measure of the ability of a camera or television system to reproduce detail and the higher the resolution the higher the quality of the video.

Roll: A loss of vertical sync which causes the picture to move up or down on the TV screen.

Router: A router is a device that connects two networks. The router reads the destination address of information sent over a network and then sends the information to the next route point A traffic cop.

RS232: A commonly used computer serial interface.

RS485: A commonly used CCTV serial interface for PTZ control and for POS interfaces


Sensitivity: The amount of current developed per unit of incident light. How sensitive to light is a CCD Camera. It can be measured in watts with the reference of an unfiltered incandescent source of light at 2870 K degrees to the pickup device surface area. It can be then expressed in foot-candles.

Server: A computer and its software that provides some service for other computers connected to it through a network.

Signal to noise ratio: The ratio between the video signal and unwanted electrical noise.

Simplex (multiplexer): A multiplexer that allows the user to look at multi-screen images or perform time multiplex recording.

Spot Monitor: A feature on DVRs that allows a secondary monitor (s) to monitor certain video channels.

S/N (Signal to noise) Ratio: Measure of noise levels of a video signal: the higher the number the better.

Sync: Electronic pulses that are inserted in the video signal for the purpose of maintaining the picture information in the correct position.


Termination: A non-inductive resistor that has the same resistance as the characteristic of the cable being used.

Tracking: A zoom lens' ability to remain in focus during the entire zoom range from wide angle to telephoto position. Also a CCTV feature that allows a camera to track an object by focusing in on an object that is sensed by motion detection.

T.V.L. (Television Lines - Resolution): The maximum number of changes between light and dark on a picture across 3/4 of the width dictates the resolution of a CCTV product, measured in TVL. Broadcast video is 540 TVL. CCTV high resolution is currently considered 480 TVL and above.


Vertical retrace: The return of the electron beam to the top of a television picture tube screen or a camera pickup device (CCD) target at the completion of the field scan.

Video Motion Detection: A feature that uses the video signal from a camera to determine movement (pixel changes) and react by recording the video or setting an alarm condition

Video type lens: An auto-iris lens type that does not use an internal circuit to control the iris. All iris control signals come from a circuit located within the camera.


WAN: Wide Area Network; A communications network that uses such devices as telephone lines, satellite dishes, or radio waves to span a larger geographic area than can be covered by a LAN


Zoom lens: A lens system that may be effectively used as a wide angle, standard or telephoto lens by varying the focal length of the lens.


 Ethernet specification

Cable Type
Max Length
10BASE-T Cat3 UTP 100 m 10 Mbps RJ45 star IEEE 802.3i
10BASE-FL MMF 2000 m 10 Mbps ST star IEEE 802.3j
100BASE-TX Cat5 UTP, Cat5e FTP 100 m 100 Mbps RJ45 star IEEE 802.3u
100BASE-FX Micro MMF 412 m (half duplex)
2000 m (full duplex)
100 Mbps (half duplex)
200 Mbps (full duplex)
SC star, point-point IEEE 802.3u
1000BASE-T Cat5e / Cat6 UTP (4 pairs) 100 m 1 Gbps RJ45 star IEEE 802.3ab
1000BASE-CX Twinax STP 25 m 1 Gbps HSSDC star, point-point IEEE 802.3z
1000BASE-SX Micro MMF 550 m (50u)
275 m (62.5u)
1 Gbps SC point-point IEEE 802.3z
1000BASE-LX SMF or MMF 550 m (MMF)
5000 m (SMF)
1 Gbps SC, LC point-point IEEE 802.3z
10 GBASE-SR MMF 300 m 10 Gbps 850nm serial LAN point-point IEEE 802.3ae
10 GBASE-LR MMF 10,000 m 10 Gbps 1310nm serial LAN point-point IEEE 802.3ae
10 GBASE-ER MMF 40,000 m 10 Gbps 1550nm serial LAN point-point IEEE 802.3ae

Physical Media Types

Twisted pair Consists of multiple insulated wires that are twisted together in pairs to prevent crosstalk UTP, STP, ScTP Cat3(16MHz), Cat5(100MHz), Cat5e(100MHz), Cat6(250MHz)
Coaxial cable Consists of a center conductor surrounded by a plastic jacket with braided shield 75Ω, 50Ω RG-58 (thinnet), RG-8(thicknet), RG-62(ARCnet)
Fiber optic cable Consists of a center glass core surrounded by glass cladding and other protective materials SMF , MMF 8~10um(SMF), 50~62.5um(MMF), 125um(clad), EMI immune

Types of Media Connectors

Lock Method
Developed by
RJ11 Registered Jack modular connector (6P2C) snap-in telephone equipments, PBX Bell Telephone Labs
RJ45 Registered Jack modular connector (8P8C) snap-in twisted pair ethernet, PoE, ISDN, T1, token ring Bell Telephone Labs
F-type F-type coaxial connector (75Ω) screw-on broadband cable, CATV, CCTV  
BNC Bayonet Nut Coupling (50Ω) bayonet thin ethernet, RF applications Bell Labs, Amphenol
ST Straight Tip fiber optic connector bayonet fiber optic ethernet AT&T
SC Subscriber/Square Connector snap-in fiber optic gigabit ethernet IBM
LC Local Connector (SFF) snap-in fiber optic gigabit ethernet Lucent
MT-RJ Mechanical Transfer Registered Jack (SFF) snap-in fiber optic ethernet AMP
IEEE 1394 FireWire (i.Link) snap-in digital devices, consumer electronics Apple, Sony, Samsung, Matshusita, IBM, JVC, …
USB Universal Serial Bus (1.1 & 2.0) snap-in digital devices, computer peripherals HP, Compaq, Lucent, Microsoft, Intel, NEC, Philips

Network Connectivity Devices

Hub Connects all nodes in a network together; transmissions received in 1 port are rebroadcast to all ports Layer 1 concentrator (passive), repeater (active), MAU
Switch Connects all nodes/segments in a network together; filters and forwards packets; isolate collision domains Layer 2 multiport bridge, configure VLANs
Bridge Connects 2 network segments with dissimilar media types; isolate collision domains within a segment Layer 2 wired or wireless
Router Connects 2 networks with different topologies; maps nodes & routes packets; isolates broadcast domains Layer 3 Brouter, IOS
Gateway Connects 2 networks with different protocols or technologies; could be hardware or software Layer 4, 5, 6, 7 connection to ISP, PABX
NIC An expansion card installed in a device to connect/interface to the network; particular to media & protocol Layer 1, 2 PCI, USB, PCMCIA, built-in M/B
CSU/DSU A 2 in 1 device used to connect a digital carrier to the network equipment; provides diagnostics & buffering - T1, T3; V.35 interface
ISDN adapter The terminal adapter used to connect to the internet via ISDN technology - BRI TA
WAP A device used to connect mobile PCs to a wired network wirelessly via RF technology Layer 1, 2 infrastructure mode, WiFi
Modem A device that changes digital to analog signal and vice versa; modulator/demodulator - POTS (V.92), xDSL, cable
Transceiver A device that transmits or receives analog or digital signals; allows a NIC to connect to a different media type - media converter, DIX/AUI
Firewall A stand-alone device or software used to protect networks from spyware, hackers, worms, phising, trojans - port blocking, packet filtering, proxy server, DMZ

Classful IP Addressing

Default Subnet
No of Subnets
No of Hosts/Subnet
Class A ~ 126 16,777,214
Class B ~ 16,384 65,534
Class C ~ 2,097,152 254

Reserved IP Address Blocks

CIDR address block
Reference Network or wire address RFC 1700 Private network (Class A) RFC 1918 Public data network RFC 1700 Reserved RFC 1797 Localhost (Loop back address) RFC 1700 Reserved - Zeroconf , APIPA RFC 3927 Private network RFC 1918 Documentation and example code RFC 3330 IPv6 to Ipv4 relay RFC 3068 Private network (Class C) RFC 1918 Network benchmark tests RFC 2544 Reserved RFC 3330 Multicasts (former Class D) RFC 3171 Experimental (former Class E) RFC 1700 Broadcast -

Tools for Network Cabling and Troubeshooting

Wire crimper Used to affix an UTP/STP cable to a modular connector or plug
Punchdown tool Used to affix several cables to a punchdown block or a patch panel found in wiring cabinets
Media tester/certifier Used to test continuity or polarity of cables, trace shorts along the line; can’t be used on live/active wires
Tone generator Used along with a probe to verify cable continuity, identify wiring faults, determine line voltage and polarity; can be used in active wires

Types of Raid

No of drives
RAID 0 2 disk stripping without fault tolerance
RAID 1 2 disk mirroring/duplexing
RAID 0+1 4 a mirror of stipes
RAID 5 3 stripping with parity
RAID 10 4 stripe of mirrors