Video Security Glossary

Browse our glossary of video security terms.

  A

  3-Axis Mounting Bracket / 3-Axis Gimbal

  Cameras that feature a 3-axis mounting bracket (bullet cameras) or 3-axis gimbal (dome cameras) allow you to mount the camera virtually anywhere (wall or ceiling) and position the camera at any angle to achieve the field of view you desire.

  Access Control (Physical)

  The selective restriction of physical access to a physical location or other resource.

  Access Control System

  An interconnected set of controllers that manages the entrances and exits of secure areas, granting or denying access to individuals.

  Adaptive Contrast Enhancement (ACE)

  ACE works to increase contrast locally, and brings out image details to produce crisp, highly-detailed images.

  Angle of View

  May be expressed in Diagonal, Horizontal or Vertical. Smaller focal lengths give a wider angle of view.

  Anti-Pass back

  Anti-Pass back is an access control security measure that prevents a Cardholder from passing his or her access card to an individual behind   them, and allowing them access into a secured zone.

  Anti-Tailgating

  The term “tailgating” refers to instances when one person swipes their access card and another person or vehicle “tailgates” them on the entry. Anti-Tailgating is an access control security measure that will not allow a Cardholder to exit a Zone that they never entered as a valid   credentialed user.

  Aperture

  The opening of the lens that controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled   by the iris adjustment.

  Aspect Ratio

  The ratio of width to height for the frame of the televised picture. 4:3 for standard systems

  Auto Back Focus

  The camera automatically and seamlessly allows users to adjust focus of images, enabling quick and easy installation.

  Auto Iris Lens

  A lens with an electronically controlled iris, allowing the lens to maintain one light level throughout varying light conditions.

  Auto Pan

  Enables the camera to pan in and provide a detailed view of per-defined, specific areas, with adjustable speed and holding times.

  Auto White Balance

  The ability of a color camera to automatically balance flushes of white light into the aperture.

  Automatic Gain Control (AGC)

  A function on the camera (and many electronics) that automatically balances the gain, or volume, of the signal, with the ability to raise the volume if it is too low and lower it if too high.

  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.

  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

  Bandwidth is defined as either channel capacity or maximum throughput on your network.

  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

  BNC (British Naval Connector) is a connector used between coaxial cable and an input/output port, either male or female, in CCTV installations.

  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 in, 1/4 in, 1/3 in, 2/3 in and 1 in.

  CAT5 Cable

  A twisted pair type of cable used for network cabling and access control data functions.

  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 in - 1/2 in or 2/3 in. There are two types, frame transfer and interline transfer.

  CCD Image Sensor  

A light-sensitive imaging device that’s available in many network IP   video cameras. The CCD image sensor transforms light into electronic   signals and provides bright light sensitivity, to capture video in low   light conditions.

  960H Image Sensor

  View and record high-resolution video. A security camera with a 960H   image   sensor works with a 960H DVR to deliver a 33% larger image and   provide sharper, more detailed video   than standard DVRs which record   at D1 resolution. 960H produces a wider image than CIF or D1. This reduces image stretching on widescreen monitors, which is a common   problem with lower resolutions.

  CCIR

  Determines how many cameras can be recorded at one time. For example, a four-channel DVR allows you to record and view up to 4 video cameras   simultaneously.

Channels

The European 625-line standard for the video signal.

C-Mount

An industry standard for mounting a lens to a camera with a 1 in x 32   thread and a distance from the image plane of 17.52 mm from the shoulder of the lens. A C-mount lens may be used with a CS-mount camera with a 5-mm adapter ring.

CS-Mount

An industry standard for mounting a lens to a camera with a 1 in x 32   thread and a distance from the image plane of 12.52 mm from the shoulder of the lens. A CS-mount lens may not be used on a C-mount camera.  

Coaxial Cable

A type of cable capable of passing a wide range of frequencies with very low signal loss.

Compression

The reduction in gain at one level of a picture signal with respect to the gain at another level of the same signal.

Concealed Cable Management

Where the camera video and power cables are fed through a built-in mounting bracket, protecting the wiring from vandals and criminals, and   to provide a cleaner installation. For applications requiring external   wiring, there may be a gap in the base of the camera’s mounting bracket   for convenience.

D

D1

Full resolution that displays 720 x 480 pixels (NTSC).

Digital Day/Night

Day/night cameras are designed to work equally well in low light conditions as during the daytime. Digital day/night cameras use an electronic filter to block out infrared light during the daytime to produce true-to-life color images. At nighttime the camera switches to black & white mode which enables it to view infrared light and capture clear black and white images of the area under surveillance.

Day/Night (True)

Day/night cameras with true day/night (ICR) deliver a sharp image in   low light and nighttime conditions. An IR cut filter blocks out infrared   light to produce true-to-life color images during the daytime. In low   light conditions and at night, the filter is removed, letting infrared   light pass through to provide crisp, well-defined black and white   images.

Depth of Field

he 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.

Digital Noise Reduction (DNR)

Digital Noise Reduction (DNR) technology offers several benefits. First, DNR delivers a cleaner signal, resulting in up to 70% disk space savings - so you can store more video evidence on your hard drive.  Next, cameras equipped with DNR technology deliver a more visually appealing   image, making it easier to identify suspects. Finally, DNR technology   makes it easier for your camera to distinguish between true motion and   image noise - allowing for your DVR to be more efficient in motion   detection - especially in low light conditions. How it works: The chip   in a camera is constantly picking up noise (fine static) in your images, especially in low-light modes. DNR technology compensates for this, correcting imperfections in the image by removing a sizable percentage of   this noise. When a DVR or computer is processing the video data, it must   compress and save every part of the image that is moving. The less   noise in the image, the less data the DVR will save, and the more real   motion it will detect.

2D + 3D Digital Noise Reduction (DNR)

2D + 3-D DNR incorporates frame-to-frame noise reduction with spatial   noise reduction to produce clear video images with less noise, in low   light conditions. Noise reduction is critical for video because noise   affects image quality. Cameras with 2D + 3-D DNR produce sharper, more   accurate video images with less ghosting.

3D Digital Noise Reduction (3D-DNR)

3D-DNR incorporates frame-to-frame noise reduction with spatial noise   reduction to produce clear video images with less noise, in low light   conditions. Noise reduction is critical for video because noise affects   image quality. Cameras with 3D-DNR produce sharper, more accurate video   images.

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 gang 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 Slow Shutter

Allows you to see clear images in extreme low light conditions without the need for artificial illumination. DSS technology (also known as 'sense-up' or 'sense-up') enables very low light capabilities by slowing down shutter speed to allow lighter to be collected by the CCD imager. This means that the camera can capture color images in conditions of near darkness. The user can adjust these settings to specify conditions that engage this feature automatically.

Digital Wide Dynamic Range (D-WDR)

Enables the camera to produce clearer images in less than ideal lighting conditions. D-WDR balances the contrast of light and shadow to improve visibility in dark areas within a scene.

Distortion

The deviation of the received signal waveform from that of the original transmitted waveform.

Door Controller

In access control systems, a door controller is a data gathering device that often includes software to make access control decisions. 

Door Strike

A plate mounted on the door jamb to accept and restrain a bold when the door closes.

Door Switch

A type of switch that communicates whether a door is open (switch open) or closed (switch closed).

Dual NICs

Some DVRs feature dual NICs (network interface cards) to enhance security and throughput by   enabling your IP cameras to run on a separate network. This minimizes degradation of other networked   applications, provides network fail-over protection and allows for an easier installation.

Dual Voltage

Most video security cameras will use either 24 volts AC or 12 volts DC. This video security camera offers   dual voltage, enabling you to use either an AC or DC power source, eliminating the worry of whether your power source is compatible with your security camera.

Dynamic IP Address

An IP address that changes every time you log in to your computer. This decreases internet security risks   but is less reliable than a static IP address.

Dynamic Profile Streaming

This camera feature enables you to create up to 7 different streaming   profiles based on codec, resolution, and frame rate. It offers region   of interest streaming capabilities for focused viewing of specific   regions in   the field of view for increased video and bandwidth   efficiency.

E

EIA

Electronic Industries Alliance. Monochrome video signal standard used in North America and Japan: 525 lines 60Hz

Electronic image stabilization

This camera feature automatically stabilizes your video images and minimizes the appearance of shaky images to produce steady, sharp images.

Electric Door Strike

Door unlocking hardware that’s installed in the door jamb and works with a mechanical lock or latch mechanism. An electric door strike can   be connected to a door controller which can power the strike and other   door peripherals.

Equalizer

An electronic circuit that introduces compensation for frequency discriminative effects of elements within the television system, particularly long coaxial transmission systems.

Event Notification

The device will send a notification when a triggered event has occurred.

Ethernet

The most widely used LAN transmission network. Based on a bus network   topology, it runs at a maximum speed over 100 meters of 10Mbit/s. It   operates over conventional co-axial cable, thin wire co-axial cable and   un-shielded twisted pair cabling. This has several implementations - 10Base5 for use over conventional co-axial cable, 10BaseF for use over   optic fiber, and 10BaseT for use over Unshielded Twisted Pair (UTP) cabling.

F

Fail Safe Door

A door that will unlock automatically in the event of a power failure to permit entering and exiting through   the door.

Fail Safe Lock

An electric lock that is locked when the power is on, but automatically unlocks when there is a power   failure.

Fail Secure Door

A door that automatically locks during a power failure, preventing anyone from entering, but allowing them   to exit during an emergency.

Fail Secure Lock

An electric lock that is normally unlocked when the power is on, but automatically locks during power   failure.

F-Number

Indicates the brightness of the image formed by the lens, controlled   by the iris. The smaller the F-number the brighter the image.

Field of View

The horizontal or vertical scene size at a given length from the camera to the subject.

Fixed Lens

A fixed focal lens does not allow the FOV to be adjusted; the camera's focal length is permanently set.

Flush & Surface Mount

Flexible 3-part housing construction allows indoor cameras to be flush mounted and outdoor cameras can   be either surface or flush mounted. Also, the base of our dome housings is conveniently constructed to   act as a back-bracket for flush mounting the camera on ceilings.

Focal Length

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

Form C Contact

A type of relay or switch (often referred to as a single pole double   throw or SPDT), that contains three   connections: normally open (NO), normally closed (NC) and common.

Frame Rate

The number of frames per second that the camera produces.

F-Stop

A term used to indicate the speed of a lens. The smaller the F-number the greater amount of light passes through the lens.

FTP (File Transfer Protocol)

A network protocol used to transfer files from one computer to another, or between devices connected to   the network.

G

Gain

An increase in voltage or power, usually expressed in db.

Galvanometric

This is one method used on Auto Iris and Direct Drive lenses to move the iris vanes, open and closed using a coil operation.

Gamma Correction

An electronic correction carried out by the camera circuitry to balance the brightness seen by the camera to that of the monitor.

Gang Box Mounting

Provides easier, more convenient installation of indoor dome cameras, via a double gang mount pattern.   This feature allows the camera to be   mounted directly to installed boxes without the need for an additional plate.

Gateway

A node that allows connection to another network using another protocol.

Ground Loop

An alternating current (AC) that can be produced in a cable. This is   usually caused by parts of the system being fed from different electrical sources resulting in different earth potentials at each end of the signal path. This results in interference of the video pictures in the form of a black shadow bar across the screen or as a tearing effect in the top comer of a picture.

Ground Loop Transformer

An isolation transformer. There is no direct connection between input and output.

H

H.264 Compression

H.264 is a stable, proven and widely used compression technology, with unbeatable recording picture quality and a small compression ratio that saves valuable hard drive storage space (5-10 times smaller than MPEG-4).

HD CCTV

HD CCTV is a standard for high definition analog-based closed-circuit television technology.

HD-SDI

HD-SDI technology delivers high quality live HD video over coax with   exceptional resolution and image   detail. HD-SDI technology delivers   image quality that is far superior to analog CCTV and provides a cost-effective video surveillance solution that's easy to install and   integrate with existing CCTV systems.

Before HD-SDI, the only way to get HD resolution was through a megapixel IP camera. HD-SDI is the   future of analog and an alternative to IP.

HDMI Output

HDMI supports standard, enhanced or HD video. Some DVRs feature an HDMI output which delivers enhanced image clarity with crisp images and   enables you to view your security camera video in HD on   your HDTV   screen. HD images can be reproduced with the HDMI support for HD display.

Hertz (Hz)

The number of variations per second (e.g. picture frames, alternating of the current, etc.).

HTTP

Hypertext transfer protocol.

HTTP Port 80

Normally this is the HTTP port address that cameras can communicate over.

Hybrid DVR 

Supports both analog and IP cameras, enabling you to utilize   existing legacy analog technology, while   providing flexibility to   migrate to an IP solution and take advantage of the many benefits of IP   technology.   

I

Impedance (input or output)

The input or output characteristic of a system component that determines the type of transmission cable to be used. Expressed in ohms.

Infrared (IR)

Infrared (IR) cameras feature built-in illuminators that project infrared light, which is nearly invisible to the human eye but very visible to IR surveillance cameras. This technology allows you to capture crystal clear, black and white video of suspects who feel protected by complete darkness. IR cameras are very effective in covering targeted areas with little or no light, ranging from exterior parking areas and entryways, to interior rooms requiring 24 hours   surveillance. For coverage of wider areas, consider adding an additional external infrared illuminator.

Input/output (I/O) Device

An I/O device facilitates elevator control and multi-door monitoring (in/out only).

Internet Protocol (IP)

The primary communications protocol in the internet protocol suite for sending and receiving data packets   across network boundaries.

IP-based Access Control

IP access control technology utilizes the network to provide secure network-controlled access and   management of physical doors at a facility or location.

IP Address

The network location of an IP camera, which can be located using a Web browser on a PC. (example 192.168.1.100)

IP Rating

IP (also known as Ingress Protection) rating is a standard rating of   protection offered by an enclosure (such as a security camera enclosure). An IP rating consists of the letters “IP” followed by two a two-digit number. The first number represents the level of protection an enclosure has against solids, moving parts   and dust, and the second   number represents the level of protection against moisture, fluids and   water.

IR Illuminator Wavelengths

IR illuminators work with day/night cameras to provide IR illumination for low light environments and enable you to capture video at night. IR illuminators are equipped with varying wavelengths” generally from 730 nm to 950 nm. An IR illuminator with a 730-nm wavelength requires a less light sensitive camera   and produces a   strong, very visible red glow, while an 850-nm wavelength IR   illuminator produces a faint visible glow, making it semi-covert. An IR   illuminator with a 940-nm wavelength produces a glow that is   virtually invisible to the human eye, which makes it an ideal choice for   most covert applications. A 940 nm   illuminator must be used with a   very light sensitive camera with no IR cut filter, or if the camera does   have   an IR filter, it must be removed for optimal results.

Iris

Mechanism within a lens to regulate the amount of light that passes through, and falls upon, the image sensor. It can be controlled manually   or automatically.

J

Jitter

Small, rapid variations in a waveform due to mechanical disturbances   or to changes in the characteristic of components. Supply voltages, imperfect synchronizing signals, circuits, etc.

Junction Box Mounting

Outdoor dome cameras feature J box mounting enabling the camera to be   directly mounted to an installed junction box, providing faster, easier installation.

L

LAN

A LAN (Local Area Network) consists of a group of computers and network devices that share common   resources within a small physical area, such as inside an office building. A LAN uses Ethernet or Wi-Fi for   network communication and typically offers high data and transfer rates.

Lens

A transparent optical component consisting of one or more pieces of optical glass with surfaces curved (usually spherical), so that they converge or diverge the transmitted rays of an object, forming a real or   virtual image of that object.

Lens Format

he approximate size of a lens-projected image. In most cases the lens will project an image slightly greater than the designated image size to insure the pickup device is completely covered. It is recommended that camera and lenses are the same format size. A lens larger format size can be used on a smaller format camera; however, a smaller format lens should never be used with a larger format camera.

Lens Speed

Refers to the lens aperture or its ability to transmit light. This is measured in F-stops.

Line Locked

A camera that is synchronized to the frequency of its AC power supply.

Local De-warping

Some fisheye or 360 cameras feature local DE-warping which enables viewing of portions of the full video   image produced by the fisheye without distortion.

Loop Out

A loop out connection enables you to run video stream from a single camera to a separate monitor on   every channel. This feature is especially ideal for public view monitors and reception desks.

Loss Detection

The automatic video loss detection feature allows you to program your   DVR to alert you when your   camera loses its signal due to power failure, severe weather or tampering. You can get an alert from an external device such as an alarm or trigger another camera to start recording.

Lumen/FT2

A unit of incident light. It is the illumination on a surface one square foot in area on which a flux of one lumen is uniformly distributed, or the illumination at a surface all points of which are at one foot from a uniform source of one candela.

Luminance

Luminous intensity (photo-metric brightness) of any surface in each   direction per unit of projected area of the surface as viewed from that   direction, measured in footlockers (fl).

Lux

International System (Sl) unit of illumination in which the meter is   the unit of length. One lux equals one lumen per square meter.

M

Magnetic Contact

A device that sends a signal when the magnetic field between two monitored access points is broken.

Magnetic Lock (Mag Lock)

A locking device that consists of an electromagnet and a strike plate   that works in conjunction with a   mechanical lock or latch mechanism, and uses electromagnetic attraction to lock and unlock a door.

Manual Iris Lens

A lens with a manual adjustment to set the iris opening (aperture) to   a fixed position. This type lens is generally used in fixed lighting   conditions.

Matrix Switcher

A combination of electromagnetically or electronic switches which route several signal sources to one or more designations.

Megapixel

Pixels are used as a unit of measure. In the security industry, it’s a   measure of resolution. Mega refers to   1 million, therefore, megapixel   means one million pixels. If you have a 2.0-megapixel camera, in   actuality   you have a 2-million-pixel camera.

MIMO

MIMO (multiple in, multiple out) is a method of utilizing multiple radio antennas at both the transmitter and   the receiver to improve communication performance for wireless network communications.

Monochrome

Black and white with all shades of gray.

Motion Detection

DVR: Allows you to pre-define motion detection zones and sensitivity   for each individual camera. When motion is detected by the DVR, this   will trigger a preprogrammed event (usually a recording), or it can   activate an external device, such as an alarm. This benefit allows you   to save hard drive space by only recording relevant video in the areas   you care about. It also saves time: you don t have to sift through   countless hours of useless video where nothing is happening -  you can   quickly scan through the captured activity in the pre-defined area of   coverage.

Camera: Allows you to integrate your cameras with external devices - to engage that device upon the detection of motion. Common devices include security lights, alarms, access control devices, and more.

MPEG-4

Moving Picture Experts Group, version 4. A form of compression that makes transmission and storage of images easier.

Multiplex Operation

Multiplex operation enables simultaneous live viewing, recording, playback, and backup. This allows you   to view live video from your DVR   locally or via your network, play back existing recorded video, or make backups without stopping recording.

Multi-streaming

Enables you to set your recording resolution at one rate and watch live video at another rate.

Mustering

An access control software feature that quickly verifies where individuals in a zone at a location   for easy tracking and identification.

N

ND Filter

A filter that attenuates light evenly over the visible light spectrum. It reduces the light entering a lens, thus forcing the iris to open to its maximum.

Network IP Camera

An IP (internet protocol) or network IP camera captures and transmits   live and recorded video images   directly over a network. A network   camera requires a high-speed internet connection, router, Ethernet cable and IP address to function, and it plugs directly into your   network router and transmits data through   the network.

Network Video Recorder (NVR)

An NVR is a hardware box that receives video streams over a LAN (local area network) or WAN (wide   area network) and records the video streams in digital format onto a hard disk. Recording and playback of   video can be managed remotely from any compatible device such as a PC, laptop or smartphone that is   connected to the network.

Noise

The word "noise" originated in audio practice and refers to random spurts of electrical energy or interference. In some cases, it will produce a "salt-and-pepper" pattern over the televised picture. Heavy noise is sometimes referred to as "snow".

NTP

Network time protocol.

NTP Server

A central source that can set the time of all network devices.

NTSC

National Television Standards Committee. Color Video Signal standard used in North American and Japanese: 525 Lines, 60Hz.

O

Screen Display

A camera's On-Screen Display (OSD) allows you to fine tune virtually   every setting of your camera to achieve the best possible image quality.   Without OSD, you are dependent upon the factory settings of the camera, and subject to any impact to the camera experienced during delivery or   installation. With the convenient design features of DIGIOP Black   cameras, including 2nd video out and on-board one-finger joystick   controls, you can adjust your every aspect of your camera at the point   of installation - without having to run back-and-forth to your DVR or   monitor. Aspects you can control include wide dynamic range, auto iris   exposure settings, day/night settings, and many more.

ONVIF Compliant

An ONVIF compliant product conforms to ONVIF (Open Network Video Interface Forum) specifications for   IP-based security products. ONVIF defines a common protocol for the exchange of information between   different network video devices from different manufacturers, to allow greater interoperability in multi- vendor network video systems.

Output

The signal level at the output of an amplifier or other device.

Overwrite Protection

This optional feature allows you to prevent files from being overwritten when the hard drive is full, or you   can pre-program the DVR to overwrite recorded video to ensure continuous recording it’s your   choice.

P

Pan & Tilt

A device that can be remotely controlled to provide both vertical and horizontal movement for a camera.

Peak-to-Peak

The measurement of a video signal from the base of the sync pulse to   the top of the white level. For a full video signal this should be one   volt.

Peer-to-Peer Communication

Some IP-based door controllers in an access control system are independent of a network or PC work station and feature peer-to-peer communication which keeps data flowing, even if a server connection is interrupted.

Phase Adjustable

The ability to delay the line locking process to align cameras fed from AC voltages of distinct phases.

Photo Detector

A device at the receiving end of an optical fiber link that converts light to electrical power.

Photocell

A device that automatically switches on the infra-red lights when light levels fall to a pre-set level.

Pic-in-Pic

An electronic device that superimposes the view from one camera over that of another.

Privacy Zone Masking

This security camera feature enables you to set privacy zones for select areas within the field of view, that   need to be kept private while viewing and recording video.

Power over Ethernet

PoE allows IP (internet protocol) devices to receive power and data over existing LAN (local area   network) cabling; eliminating the need   to install a separate power cable, simplifying installation and   lowering cabling costs.

Power Over Ethernet+ (PoE+)

This feature enables high-draw PTZ camera to utilize Power over Ethernet (PoE) on a single CAT5 cable.

Progressive Scan

Video signals are generated using horizontal lines. Progressive scan, also referred to as non-interlaced   scanning, draws every line of an   image in sequence. The main advantage with progressive scan is that motion appears smoother and more realistic.

Proximity

A common access control card technology that uses radio frequency to communicate between a   proximity card and a reader.

Proximity Card (Prox Card)

An access control credential that is encrypted with proximity technology and can be read by a proximity   reader without having to physically insert the card into the reader, to grant a   cardholder access to   a location.

Proximity Reader (Prox Reader)

A device that can read encoding on access control credentials such as   a proximity card or badge, and   sends data to a controller to grant or   deny access.

PTZ (Pan, Tilt Zoom)

A pan-tilt-zoom camera is a camera that is capable of remote directional and zoom control.

Q

Quad Splitter

A product that can display the views from 4 cameras simultaneously on   one monitor. It is also possible to select any individual camera for   full-screen display on real time monitoring, dependent on model.

R

Random Interlace

A method of combining two fields to make one frame where strict timing is not a requirement.

Request to Exit Button (REX) In access control, a button that must be pushed to release the door to exit.   

Reflectance

The ratio of light returned from a surface expressed as a percentage.

Reflected Light

Scene illumination multiplied by reflectance. This is the amount of light returned to the camera and determines the quality of picture.

Refracted Index Profile

A description shown in the form of a diagram illustrating how the optical density of an optical fiber alters across its diameter.

Re-generators

Devices placed at regular intervals along a transmission line to detect weak signals and re-transmit them. These are seldom required in fiber optic systems. (Often incorrectly referred to as 'repeaters').

Remote Switcher

A video switcher to which the cables from the cameras are connected and which contains the switching electronics. This unit may be remotely   located and connected to a desktop controller by a single cable for each   monitor.

RS-485 Controls

RS-485 controls allow camera settings to be changed remotely without   the operator being physically present at the camera location.  This is   done by using an RS-485 controller which is typically set up at the   viewing station or control room.

S

SD Card Slot

Provides convenient offloading of video onto an SD card.

Sense-up

Sense-up automatically enhances DSS (digital slow shutter) and keeps   the shutter open for a long time to   allow extra light into the camera   to produce brighter images in low light conditions.

Sensitivity

For a camera usually specified in lux to provide indication of light level required to gain a full video signal from the camera.

Shutter

Ability to control the integration (of light) time to the sensor to less than 1/60 second.

Signal-to-Noise Ratio

Signal to noise ratio, a measurement of the noise level in a signal expressed in dB (decibels). In a video signal values from 45dB to 60dB   produce an acceptable picture. Less than 40dB is likely to produce a “noisy” picture.

Smart Card

An access card that can be integrated with different technologies including bio-metric, magnetic stripe, proprietary proximity and contain information about the cardholder.

SMART IR Array

Most cameras are not able to adjust IR output based on object distance, which often results in a washout for over-IR-exposed scenes, or a darkened image for under-IR-exposed scenes. SMART IR allows the camera to automatically adjust IR intensity as the subject moves closer to or further away from the camera, so you always have a clear image that is not washed out or too dark.

Smart Zoom

Smart zoom automatically digitally zooms in on areas the camera senses motion in to get a more detailed image and then zooms back out.

Spot Filter

A neutral density filter placed at the center of one of the elements (or on an iris blade) to increase the high end of the F-stop range of   the lens.

Sun/Rain Shield

Some cameras come with an adjustable sun/rain shield to prevent glare   and direct contact from the elements, to deliver the cleanest   possible video signal.

Switch Box

The first-of-its-kind Switch Box NVR delivers an IP network recording   solution without the complexity.   The Switch-box NVR features an   integrated 4 or 8-port PoE (Power over Ethernet) network switch to power the IP network cameras directly through the network   cable eliminating the need to purchase a   separate network switch.  The   all-in-one Switch Box NVR delivers an easy-to-install, plug-and-play IP-   based recording solution.

T

Tampering Detection

Tamper detection is a tamper notification feature that sends an alert   if the viewing angle of the cameras   changes, or if the viewing area   has been blocked.

Telemetry

The system by which a signal is transmitted to a remote location to control the operation of equipment. In CCTV systems this may include controlling pan, tilt and zoom functions, switch on lights, move   to pre-set positions etc. The controller at the operating position is   the transmitter and there is a receiver at the remote location. The   signal can be transmitted along a simple twisted pair cable or along the   same coaxial cable that carries the video signal.

Telemetry Transmitter

The unit that is at the control position of a CCTV system and contains the keys, joysticks etc. for the remote control of pan/tilt/zoom cameras.

Termination

The video cable requires an impedance of 75 ohms at normal video signal bandwidth. This is often called 'low Z'. There is a switch on the back of the monitors to select either 75 ohms or 'high Z' (sometimes 'high/low'). If a signal is looped through more than one monitor all   should be set to 'high' except at last, which should be to 'low' or 75 ohms.

Tight Buffered

A type of cable in which the optical fibers are tightly bound.

Time/Date Stamp

With this DVR feature, the time and date of recorded images can be superimposed on the video while it is being monitored and recorded. This feature is ideal not only for easily identifying the exact date and time of an event during playback, but because the information becomes   part of the video image, it is also   useful when providing recorded   video evidence to authorities.

Time Lapse VCR

A type of industrial video recorder that can be set to record continuously over prolonged periods. Typically, this can be from three hours to 480 hours, achieved by the tape mechanism moving in steps and recording one frame at a time. This means that if set to record over   extended periods much information can be lost. For instance, in the 72-hour mode, only 3 frames/second will be recorded instead of 25 frames/second   in the real-time mode. On receipt of an alarm signal these machines can   be automatically switched to real time mode. With rapid advances in   digital storage and retrieval techniques the mechanical video recorder   is now nearing the end of its life in industrial security systems.

Twisted Pair Cable

Consists of two independent wires or conductors that are twisted together to cancel out signal interference from external sources.

U

Unbalance Signal

A composite video signal, transmitted along a coaxial cable, is an example of an unbalanced signal. (See balanced signal).

Unterminated

Video input of a piece of equipment, wired to allow the video signal to be fed to further equipment. Does not necessarily include extra sockets for the extra cables.

UPS (Uninterruptible Power Supply)

A battery, attached to a piece of hardware, for example a server, that provides back up power for conducting an orderly shutdown if the server's normal power supply fails.

UTP (Unshielded Twisted Pair)

The standard cabling used for telephone lines. The standard IEEE 802.3, 10BaseT, defines use of Ethernet over UTP for rates up to 10Mbit/s. The general LAN medium of choice for the 1990s. Cameras with built-in UTP (also called video balun) allows you to send video over longer distances, allowing you to position your cameras further away from the recording device without losing quality of your video signal. While a standard analog camera can deliver signal up to approximately 300 ft. over a standard CAT5 cable, UTP extends transmission capabilities   up to 750 ft. UTP also allows you to use CAT5 cable (instead of coaxial   cable) for longer runs, resulting in an easier installation due to the   smaller wire size and a significant cost savings for larger jobs.

V

Varifocal Lens

A camera lens with variable focal length in which the focus changes as focal length (and, therefore, the magnification) changes. This is different to a par focal, or "true" zoom lens, which remains in focus as   the lens zooms (focal length and magnification change). Varifocal lenses   offer greater flexibility over fixed lenses as they allow the lens   aperture to be adjusted as needed. Varifocal lenses come in a range of   apertures, including 2.8-12 mm, 3.5-8 mm, and 6-60mm. The greater the   aperture size, the more magnified the image will appear with greater   detail being captured. A smaller aperture size will result in a wider   view with less detail being captured.

Vertical Resolution

The number of horizontal lines that can be seen in the reproduced image of a television pattern.

Video Amplifier

A wide band amplifier used for passing picture signals.

Video Balun

A video balun (sometimes referred to as a UTP balun), enables an installer to replace traditional coaxial   cable with CAT5 and other forms of twisted pair cabling, to wire security cameras in analog CCTV   installation applications. Video baluns enable CAT5 cabling to be run over longer distances for less   money than coaxial cable.

Video Band

The frequency band width utilized to transmit a composite video signal.

Video Compression

Video compression is a process during which a video stream is analyzed and unnecessary parts of the   data are discarded to make a large video file smaller in size.

Video Signal (Non-Composite)

The picture signals. A signal containing visual information and horizontal and vertical blanking (see also Composite Video Signal) but not sync.

W

WAN (Wide Area Network)

A network that covers a larger geographical area than a LAN and where   telecommunications links are implemented, normally leased from the   appropriate PTO(s). Examples of WAN include packet switched networks, public data networks and Value-Added Networks.

Wavelet

Compression that is optimized for images containing low amounts of data. The relatively inferior image quality is offset against the low bandwidth demands on transmission mediums.

White Level

The brightest part of a video signal corresponding to approximately 1.0 volt (0.7 volts above the black level).

Wide Dynamic Range (WDR)

Enables the camera to deliver video with near perfect exposure in the   harshest of lighting conditions. To accomplish this, wide dynamic cameras use advanced digital processing to capture two images at different exposures, and then combine them into a single image. WDR cameras are ideal for challenging lighting situations, such as doorways or windows to the outside, considering car headlights, or any application considering a direct light source. They are also ideal in opposite conditions, such as looking from a well-lit area into a darker area.

Wiegand

A proprietary information coding format used for encoding access cards, key tags, proximity readers, and other access control related products and devices.

Workstation

Term used freely to mean a PC, node, terminal or high-end desktop processor (for CAD/CAM and similar intensive applications) - in short, a device that has data input and output and operated by a user.

Y

Y/C

A color camera producing separate luminance (Y) and chrominance (C) signals to provide greatly improved picture quality from video recorders. Can only be used with a restricted range of equipment.

Z

Zoom

To enlarge or reduce, on a continuously variable basis, the size of a televised image primarily by varying lens focal length.

Zoom Lens

An optical system of continuously variable focal length, the focal plane remaining in a fixed position.