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CCTV GLOSSARY OF TERMS
AC
Alternating Current
A/D Converter
Analogue to Digital converter. An electronic device or circuit, which converts analogue
electrical signals into digital (binary) values.
Activity Detection
Commonly used in video multiplexers as a means of improving recording efficiency.
Cameras that have changes in programmed scene areas are recorded more frequently than
cameras with no scene changes. Not to be confused with VMD (Video Motion Detection).
Address
Addressing provides a means of identifying individual items that are located on a network. In
the Honeywell environment each Microsphere is given an address, the network is the RS485
twisted pair cabling.
AGC
Automatic Gain Control. A circuit that provides a method of keeping a signal at a constant
level. Cameras use AGC to keep the video signal level high under low light conditions.
ALC
Automatic Level Control. This is found on auto iris lenses and is a means of ‘fine tuning’the
sensitivity of the lens. If set to ‘peak’, bright areas can show more detail and if set to
‘average’dark areas will show more detail. The default setting is halfway on most lenses and
will suit the majority of installations.
Ambient Light Level
The measurement of light intensity on a scene under a specified set of conditions, usually
measured in LUX.
Angle of View
The maximum width of view available from a CCD imager, regardless of the lens fitted. The
bigger the CCD imager format, the wider the angle of view.
Aperture
A means of adjusting the amount of light passing through a lens. In the CCTV environment
the lens iris is the aperture control method.
Archive
This is the long-term removable storage of information, usually associated with digital
recorder. They often take the form of removable disks, tapes, CD, DVD etc.
Artefacts
The unwanted additions that are sometimes seen in compressed digital images. They are a
side affect of the compression process and tend to become more prevalent as greater
degrees of compression are applied.
Aspherical Lens
A lens that uses non-spherical optics to reduce the effects of geometrical distortion. The
effects of geometrical distortion increase as the lens angle becomes wider. Aspherical
lenses are a good choice where a wide field of view is required.
Auto Iris
A facility built into lenses to control the amount of light allowed through the lens. The auto iris
compensates for differing light levels, allowing the camera picture to be consistent under
varying light conditions.
Auto White Balance
This is a facility provided on most colour cameras to adjust while levels relative to other
colours.
Back Focus
The position of the imaging device in relation to the focal point of the lens, it is sometimes
referred to as ‘rack focus’. When setting up a zoom lens the back focus must be set to allow
correct tracking of focus throughout the zoom range.
Balanced Signalling
A means of transmitting signals using two wires, also often referred to as differential
transmission. It provides very high noise immunity because only the difference between the
two noise signals is seen as valid information. In the CCTV environment RS485 and RS422
are examples of balanced signals.
Bandwidth
The frequency response capability of a device or communications medium. The greater the
bandwidth, the larger the capacity of the system i.e. the more information carrying ability the
CCTV or network system has.
Baud Rate
Defines the speed of data transmission of a device in terms of bits per second, where ‘bit’can
be defined as a piece of binary information or ‘binary digit’.
Binary
This is the base two numbering system. A binary number can only be one of two values, 0 or
1. These individual values or ‘bits’ are lumped together into strings of data (see byte).
Computers operate exclusively in Binary.
Blooming
An effect seen when the iris of a lens is set incorrectly and allows too much light through to
the CCD imager. Bright areas of the scene lose definition and begin to merge with the
surroundings.
BLC
Back Light Compensation. A feature found on some cameras that allows it to deal with
different lighting levels in the scene of view, such as looking from a dark room into a doorway.
BLC enables detail to be seen in otherwise dark or shadowed areas where silhouetting would
otherwise occur.
BNC (Bayonet Neill Concelman)
Invented by the named after Amphenol Engineer Carl Concelman and Bell Labs Engineer
Paul Neill and was developed in the late 1940s. Used for terminating coaxial cables, the
main connector in the CCTV industry.
Byte
8 bits of data information. Also referred to as an octet. Generally a data byte represents a
single character.
Cameo
This is the 1/16th of the total area of a full screen or a single area of a 16 way screen
generated by a video multiplexer.
CCD
Charge Coupled Device. The solid state device that most CCTV cameras use to gather
images. Often referred to as an imager.
CCIR
Comite Consultatif International des Radiocommunications. The European TV standard of
625 lines, 50 fields.
CCTV
Closed Circuit Television
Chrominance
The colour element of a video signal
C Mount
Lens mount used on some CCTV cameras where the distance between the lens flange and
CCD is 12.5mm.
CS Mount Adaptor
A 5mm deep spacer ring that allows a C mount lens to be installed on a CS mount camera.
Coaxial Cable
A dual conductor cable where the outer conductor (screen / ground), is wound concentrically
around an insulator, which houses the central conductor. In the CCTV environment coaxial
cable is used to transmit video signals.
Codec
Coder / Decoder. Is an electronic device, which compresses and decompresses digital
signals (Binary). Codecs usually perform A to D or D to A conversion.
Composite Video
A complete video signal, in which the Luminance (brightness) and Chrominance (colour)
information is combined using one of the international coding standards NTSC, PAL etc.
Conditional Refresh
A technique used by some digital video transmission products. Only the parts of the picture
that change are updated. Occasional complete images are transmitted according to the rules
of the standard or when changes in the scene are too great for the conditional technique to
manage. MPEG and H261 are typical conditional refresh coding standards.
Crosstalk
Undesirable interaction between signals. Typically seen as interference on screen, which
takes the form of noise, patterning or a whole host of other effects.
DAT
Digital Audio Tape. Often wrongly referred to as an archive media for digital recorders. DAT
is in fact a bespoke format designed for the audio environment, and is not suitable for CCTV
data storage.
Data Compression
A series of techniques that are designed to reduce the size of data in order to save space or
transmission time.
DCT
Discreet Cosine Transfer. This limits the AGC range in an image allowing increased
compensation on a digital recording.
DDS
Digital Data Storage. Suitable as a long term archive method for compatible digital recorders.
Available in a number of formats and capacities from DDS2 (4Gb per tape) through DDS3
(12Gb per tape) to DDS4 (20Gb per tape).
Digital Zoom
A facility provided on some video multiplexers and CCTV cameras, which allows the image to
be ‘zoomed into’, the higher the zoom ration the more ‘blocky’the image can become.
Dropout
A temporary reduction or loss of a signal.
DSP
Digital Signal Processing. A system supported by some CCTV cameras, which allows
intelligent manipulation of the video signal in the camera for features such as backlight
compensation.
DTMF
Dual Tone Multi Frequency. Used as an analogue dialling method by telephones and
modems. In telephone this is also referred to as ‘touch tone dialling’and is also used as a
telemetry signalling method by some CCTV manufacturers.
Duplex
In electronic terms this means the ability to simultaneously send and receive signals. In
CCTV, this term is associated with video multiplexers that have 2 frame stores. A duplex
multiplexer can display multiple live images whilst recording all cameras to tap. It can also
simultaneously play and record if 2 VCR’s are used.
DVD
Digital Versatile Disk. Very similar to a CD in appearance but with a larger storage capacity.
Used as removable archive media in some DVR’s. Available in both single and double sided
media.
Dwell
The time period in which a switcher will remain on one camera input before switching to the
next in the sequence. It can also refer to the time spent by a device at a preset position when
in tour mode.
Distribution Amplifier
A device designed to feed a single video it audio signal to several pieces of equipment. It
can reduce the possibility of losses and crosstalk when looping a signal through multiple
pieces of equipment.
EI
Electronic Iris. This is a system within CCTV cameras where an electronic shutter is built into
the camera. It allows a normal fixed iris lens to be fitted in a wider range of applications. It
should not be assumed that EI would negate the need for an auto iris lens.
EIA
Electronic Industry Association. The USA television standard. Also known as NTSC (525
lines to a single frame of a video).
Ethernet
Ethernet is the most widely utilised network technology. Specified in a standard, IEE 802.3,
Ethernet was originally developed by Xerox and then developed further by Xerox, DEC, and
Intel. It is now a popular means of distributing data and / or video.
Exwave / Exview
Are terms relating to an enhanced CCD imager that features improved light gathering
techniques, which give improved low light sensitivity, particularly near the IR end of the
spectrum.
Fibre Optics
Transmission of signals via fibre optic cable. Signals via the fibre optic cable are transmitted
as light. Specialised interfaces are used at each end of the fibre optic cable to convert the
video and telemetry data signals. Fibre interfaces are available in two types, single mode
that allows one signal type down one fibre cable and multimode that allows two or more
signals via a single fibre cable.
Field
A field is one half of a complete TV picture and can comprise of all odd lines or all even lines.
Flow Control
This is a means of controlling the flow of data via hardware and or / software on
asynchronous communications links, including networks.
Focal Length
This is a distance from the centre of the lens to a point at which images come into focus. The
CCD imager is usually set at this point to ensure image clarity. This value is what denotes
the angle of view and size of the target image.
Frame
A complete TV picture comprising of two fields, one odd and one even.
Frame Integration
A technique used by some CCTV cameras, which allows for extreme low light sensitivity.
Exposure times are increased as light levels drop, allowing good images when most
conventional cameras can no longer give a picture. It has the side effect of reducing video
updates (video appears delayed on screen), reducing as levels of integration get higher.
Frame Store
Is digital memory capable of containing a frame of video in digital format.
F-Stop
In photography, this is a term used to indicate the speed of a lens in terms of exposure. It
directly relates to the iris setting of the lens and thus the amount of light allowed through.
The smaller the f-stop setting, the more light is allowed through.
Full Frame Refresh
A technique used by some video transmission systems where a full picture is transmitted
each refresh / update, regardless of the amount of scene changes. JPEG is a full frame
capture standard.
Ghosting
Phenomena seen when multiple image outlines appear on the same picture, generally
caused by incorrect video termination or cable faults.
Gigabyte
1024 Megabytes = 1 Gigabyte.
Ground loop
Is a condition caused when multiple earth points on a system cause
Currents to flow via the screening on the cable. Causes picture disturbance, normally in the
form of black bars across the picture.
H.261
Coding standard user for conditional refresh capture and transmission of digital video images.
Represents the video part of the H.323 specification for videoconferencing protocols.
Half duplex
This refers to communications links that are capable of running in either transmit
Or receive mode, but not both modes currently. To achieve half-duplex operation the mode of
the communications link is effectively ‘turned round’between transmit to receive modes when
necessary.
Home position
A preset position that is defined as a ‘home return’point. Usually related to a timer based on
keyboard activity, when the timer expires the camera will be driven to home preset position.
IDE
Integrated drive electronics. Common hard disk and internal peripherals interface.
Infrared
Frequency range within the spectrum of light that is invisible to the human eye. CCTV
Illumination is usually designed around the infrared range of 730 – 815 nanometres.
IP rating
A system of rating a piece of equipment against dust and water ingress.
ISDN
Integrated Services Digital Network. Infrastructure of digital telephone services worldwide.
Most commonly used to transmit remote digital video signals.
JPEG
Joint Photographic Experts Group. Standard used for full frame capture and transmission of
digitalised video images.
Kilobyte
1024 Bytes = 1 Kilobyte.
Launch amp
A video amplifier that allows the video signal to be transmitted over long distances via normal
co axial cable. This is achieved by increasing the amplitude of the video signal at the camera,
and in most cases, also the high frequency (HF) content of the signal. Featured as standard
on Honeywell Microspheres.
LAN
Local area network, usually within the same building or series of buildings.
Leased line
An analogue or digital telephone line that is available at all times and does not require any
call set up procedures. These lines are generally used as a permanent data trunk connection.
Most commonly found as a permanently connected means of delivering remote digital video.
Looping
Also referred to as loop through. Refers to equipment that will allow a video signal to pass
through by providing a video in and also a video out connector for every camera input. Most
looping equipment allows easy selection and de-selection of the video termination.
Luminance
The brightness element of a video signal.
LUX
Measurement used to express light intensity.
Matrix switcher
A video switcher that allows any camera to be selected on any monitor.
Megabyte
1024 Kilobytes = 1 Megabyte.
Memory
Digital information storage device.
Microwave transmission
Free space link commonly used in CCTV where normal cables cannot be used. The
frequency range is usually between 1 to 30 gigahertz
Modem
Modulator/demodulator. It provides an analogue to digital interface to allow computers
And other devices to transmit and receive digital information via analogue telephone lines.
Monochrome
Black and white CCTV equipment.
MPEG
Motion Picture Experts Group. Standard user for conditional refresh capture and transition of
digital video images.
Multicast
Networking term, which describes data that is sent from a single user that can be received by
multiple users on the network. Commonly used for video transmission on LANs and WANs.
Multiplexer
A piece of equipment that processes multiple camera inputs and organises the identification,
Recording and playback of all cameras to and from video tape. Also capable in most cases of
generating multiple camera displays.
Noise
Unwanted elements that are present on a signal.
NTSC
National Television System Committee. The colour TV system used in the US, Canada,
Japan and parts of South America. 525 lines, 60 fields per sec.
Opto isolator
A component or piece of equipment that provides electrical isolation between circuits or data
communications media.
PAL
Phase Alternating Line. The colour TV system used in the UK, Europe and some other parts
Of the world, 625 lines, 50 fields per sec.
Pan
Camera movement on the horizontal plane.
Peak to peak
The measurement of a signal from the lowest negative value to the highest
Positive value. This is most commonly found when specifying video signal levels
as 1 volt peak to peak.
Pedestal
The area of a video signal that lies between the top of sync level and the bottom
of black level.
Pinhole lens
A lens that features a very small opening ideally suited to covert applications where the
camera can be concealed.
Pixel
Term used for a single picture element. A monitor or TV has a display
That comprises millions of pixels; each pixel is illuminated with varying intensity
To created the picture display.
PPP
Point-to-Point Protocol. One of the suites of TCP/IP
Protocols that are primarily used in serial point to point
Communications such as null modem, dial up type PSTN and ISDN connections.
Presets
Functionally that is supported by some telemetry equipment
Position related feedback is provided by the zoom lens and pan/tilt head. Either the telemetry
receiver or matrix stores this feedback whenever a position is stored as a preset. The system
operator can recall preset positions very quickly with the minimum of key presses.
Privacy zone
A feature present on some CCTV equipment to comply with the data protection act.
The feature allows sensitive areas of a PTZ cameras view to be blanked out so that
They cannot be viewed. Good implementations of privacy allow the privacy areas
To be scaled according to the zoom ratio of the camera, so they are small on wide angle
Views and grow larger if an operator tries to zoom in on a privacy area.
Protocol
A set of rules that govern how elements of a system inter-communicate.
PSTN
Public Switched Telephone Network. Standard analogue telephone system.
Quad
Either a 4 way video processing unit or the 4 way screen generated by a video multiplexer.
Rack mount
A recognised standard mounting system. All equipment is 19’’wide and a number of units
high. The unit of height is known as ‘U’1U= 1.75’’
RAID
Redundant array of independent drives commonly used as extended storage on DVRs in the
CCTV environment. A purpose built series of hard disk drives that appear to the host as a
single large disk, this is achieved by a RAID controller card that is built into the unit. RAID
arrays are normally SCSI based.
RAM
Random Access Memory. Digital memory that can be both written to and read.
Resolution
A measurement of the ability of a piece of CCTV equipment or system to display
Detail. Measured in TV lines.
ROM
Read Only Memory. Digital memory that can only be read.
RS232
Data transmission presentation used in many short distance serial data applications.
RS422
4 wire balanced, party line multi-drop data transmission presentation, used in many
telemetry and matrix switcher networks. One pair is used for data transmission on the other
pair for data reception.
RS485
2 wire balanced, party line multi-drop data transmission presentation, used in many telemetry
and matrix switcher networks. Can run in simplex or half-duplex mode.
SCSI
Small Computer System Interface. A fast parallel data interface commonly found as an
external interface on digital recorders.
Simplex
In electronic terms a device that can either send or receive, but not both simultaneously. In
the CCTV environment this refers to a video multiplexer that has one frame store, which can
record all cameras to tape or generate multi-screen displays.
S video/SVHS
A method of transmitting video signals in their two component parts, chroma and luma. It
provides higher resolution than composite signalling but can only be used over very short
distances. Also known as Y/C.
Sync
The timing information element of a video signal.
Termination
System used to create an ideal matched set of conditions on a transmission link. Correct
termination keeps signal levels within specification and prevents reflections and standing
waves on the link. In CCTV correct termination of the video signal is extremely important so
that optimum picture quality without distortion is achieved.
T1
Digital communications link that is most commonly found in the USA and Canada. T1
supports a data rate of 1.544 megabits per second.
TCP/IP
Transmission control protocol/Internet protocol. Title given to suite of protocols that are used
on computer networks, without which the Internet signal would be not possible.
Telemetry
A system that provides camera control via coding. The coding is either sent with the video
signal or is transmitted as data via a network.
Terabyte
1024 Gigabytes = 1 Terabyte.
Terminal adaptor
A device that is the ISDN equivalent of a modem. The terminal adaptor provides an interface
between the host and the ISDN network termination box and provides call set up and
answering.
Termination
A method of matching electrical signals to the transmission medium. In the CCTV
environment termination is important for the video signals and also any data networks using
RS485 or RS422.
Time lapse VCR
A VCR that achieves extended recording periods by slowing the tape motion across the
recording heads.
Tour
Facility provided by some CCTV control systems where a PTZ camera or dome can be
programmed to tour between a specified series of presets. It is usually possible to program a
dwell time to stay at each preset and also a speed value at which the camera will travel
between presents.
Twisted pair
Refers to a generic cable type, originally from the telecommunications industry where internal
cable pairs are twisted together equally for the entire cable length. This type of cable is ideal
for balanced data transmission.
Varifocal lens.
A lens that has an adjustable focal length.
VDA
Video distribution amplifier. A device that gives multiple video outputs from a single video
input. Generally used where a single video has to feed multiple pieces of equipment. Co axial
telemetry will not be passed through a VDA.
VMD
Video Motion Detection. A specialised piece of equipment that is capable of detecting
changes in video images, then creating a physical output and in some cases and audible
output. True VMD units can manage to discern between weather, light changes and even
movement of the tower or pole without alarming.
WAN
Wide area network. Geographically dispersed network.
Worm
Write Once Read Many. Refers to digital storage media that can be written to once only.
Zoom ratio
A rating used to express the zoom capability of a lens from wide angle to narrow angle; it is
calculated by dividing the wide-angle value in mm by the narrow angle value in mm. For
example, a lens that has an 8 mm wide angle and a 64mm narrow angle will be rated as 8:1
10 base T
Terminology used to describe network specification. In this case it literally means 10
megabits per second, baseband signalling, twisted pair cabling.
The above material has been kindly provided by Honeywell International with whom copyright
resides. All the above information is given without prejudice and for guide purposes only.
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