The CCTV Glossary
A BC  D EF  G HI  J KL  M NO  P QR  S TU  V WX Y  Z
Home

C
Cable equalization.  The process of altering the frequency bands of a video signal to
compensate for the loss of high frequency in a cable.  The video equivalent to a graphic equalizer
in a stereo system.
CAD.  Computer Aided Design.  This usually refers to a design of system that uses computer
specialized software to model reality in a controllable fashion.
Candela [cd] (or candle power).  A unit for measuring luminous intensity.  The modern definition is
The candela is the luminous intensity, in a given direction, of a source that emits monochromatic
radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of
1/683 watt per steradian.   The frequency chosen is that to which the eye is most sensitive.
This frequency is normally referred to as the corresponding wavelength: 555 nanometer.  The
strange choice of the number 683 is to make the value identical to that obtained with the previous
version of the unit: the emission from 1 square centimeter of glowing, solidifying platinum.
The old definition is :-  One candela is approximately equal to the amount of light energy
generated by an ordinary candle.  Since 1948 a more precise definition of a candela has
become: "1/60 of the light emitted from 1cm² of the surface of a blackbody radiatorheld at
the temperature at which platinumconverges from a liquid state to a solid (i.e. freezes)."
CATV.  Community Antenna TeleVision.
C-band.  A range of microwave frequencies, 3.7~4.2 GHz, commonly used for satellite
communications.
CCD.  Charge-Coupled Device.  A "bucket brigade" shift register device which when combined
with photodiodes is the modern imaging device, replacing the old tubes.  When first invented in
the 1970s, it was designed to be used as a memory device, as an analogue shift register.
 Most often used in cameras, but also in telecine, fax machines, scanners, etc.
CCD Iris.  A term used by some manufacturers to describe automatic shutter control, to
compensate for changes of lighting in a scene, without having any moving parts.
CCIR.  Committée Consultatif International des Radiocommuniqué, which is the European
standardization body that has set the standards for television in Europe.  It was initially
monochrome; therefore, today the term CCIR is usually used to refer to monochrome
cameras that are used in PAL countries.
CCIR 601.   An international standard (renamed ITU 601) for component digital television
that was derived from the SMPTE RP1 25 and EBU 3246E standards. ITU 601 defines the
sampling systems, matrix values and filter characteristics for Y, Cr, Cb and RGB component
digital television.  It establishes a 4:2:2 sampling scheme at 13.5 MHz for the luminance
channel and 6.75MHz for the chrominance channels with eight bit digitizing for each channel.
These sample frequencies werechosen because they work for both 525 line 60Hz and 625 line
50Hz component videosystems.  The term 4:2:2 refers to the ratio of the number of luminance
channel samples to the number of chrominance channel samples; for every four luminance
samples, the two chrominance channels are each sampled twice.
CCITT Committée Consultatif Internationale de Telegraphique et Telephonique.  The CCITT,
now known as the ITU-T (for Telecommunication Standardization Sector of the International
Telecommunications Union), is the primary international body for fostering co-operative
standards for telecommunications equipment and systems. It is located in Geneva, Switzerland.
CCTV.  Closed Circuit TeleVision.  A television system intended as a "closed" system, rather
than broadcast, to be viewed by only a very limited number of viewers e.g. 1 camera to 1
monitor in its simplest form.
CCTV camera.  A unit containing an imaging device that produces a video signal in the baseband
form, usually with synchronization pulses and colour information (composite video).
CCTV installation.  A CCTV system, or an associated group of systems, together with all
necessary hardware, auxiliary lighting, etc., located at a site to be monitored.
CCTV system.  An arrangement comprising of a camera and lens with all ancillary equipment
required for the surveillance of a specific area.
CCVE.  Stands for Closed Circuit Video Equipment.  An alternative acronym for CCTV
created by a manufacturer.
CD.  Compact Disc.  A standard of media as proposed by Philips and Sony, where music is
stored in digital form.
CD-ROM.  Compact Disk Read Only Memory.  The total capacity of a CD-ROM when storing
data is up to 700 MB (including header information).
CDS.  Correlated Double Sampling.  A technique used in the design of some CCD cameras that
reduces the video signal noise generated by the chip.
Celsius.  The Systeme Internationale (SI) unit of temperature equivalent to the Centigrade scale.
It does not use the prefix "degrees".
CFA.  Colour Filter Array.  A set of optical filters (usually individual pixel sized) used in single chip
colour CCD camerasto produce the colour components of a video signal.
Chip.  An integrated circuit in which all the components (resistors capacitors and semiconductors)
are micro-fabricated on a tiny piece of silicon or specialist material (silicon on sapphire).  Often
used to refer to the detector in a CCD camera.
Chroma Burst.  See Colour carrier
Chroma crawl.  An artefact of encoded video, also known as dot crawl or cross-luminance.
It occurs in the video picture around the edges of highly saturated colours as a continuous series
of crawling dots and is a result of colour information being confused as luminance information
by the decoder circuits.
Chroma gain (chroma or colour, saturation).  In video, the gain of an amplifier as it pertains to
the intensity of colours in the active picture.
Chroma key (colour key).  A video key effect in which one colour or video signal is inserted in
place of all areas of a particular colour in another video signal.
Chrominance.  The colour information of a colour video signal.
Chrominance-to-luminance intermodulation (crosstalk, cross-modulation).  An undesirable
change in luminance amplitude caused by superimposition of some chrominance information
on the luminance signal.  Appears in a TV picture as unwarranted brightness variations caused
by changes in colour saturation levels.
CIE.  Commission Internationale de l'Eclairagé.  This is the International Committee for Light,
established in 1965.  It defines and recommends light units.
CIE Model.  A colour model based on human perception developed by the CIE (Commission
Internationale de l'Eclairage) committee. While widely regarded as the most accurate colour
model, CIE is unsuitable for many technologies, including colour printing and colour monitors.
Consequently, these systems need to use other colour models, such as CMYK and RGB. There
is a growing trend, however, to make all colour models relative to the CIE model. This would
make it easier to translate from one model to another.
CIF.   Common Intermediate Format.  A video format used in videoconferencing systems that easily
supports both NTSC and PAL signals. CIF is part of the ITU H.261videoconferencing standard.
It specifies a data rate of 30 frames per second (fps), with each frame containing 288 lines and 352
pixels per line.   A related standard, QCIF (Quarter CIF), transfers one fourth the amount of data
and is suitable for videoconferencing systems that use telephone lines.
Clamping (DC).  The circuit or process that restores the DC component of a signal.  A video
clamp circuit, usually triggered by horizontal synchronizing pulses, re-establishes a fixed DC
reference level for the video signal.  DC clamping can, in some cases remove of
low-frequency interference, especially mains hum.
Cladding.  The outer part of an optical fibre cable, which is also glass but with a different
refractive index to the central core.  It enables "total internal reflection" so that the light
transmitted through the central core stays, inside that core.
Clipping Level.  An electronic limit to avoid overdriving the video portion of the television
signal.
C-mount.  Cine mount.  The first standard for CCTV lens screw mounting.  It is defined with
the thread of 1'' (25.4 mm) in diameter and 32 threads/inch, and the back flange-to-CCD
distance of 17.526 mm (0.69'').  The C-mount description applies to both lenses and cameras.
C-mount lenses can be put on both, C-mount and CS-mount cameras, but must use a C-mount
adaptor when used on a CS-mount camera.  If a C adaptor is used on a C-mount camera the
image will only focus at very short range, it can then be considered as an economy macro
adaptor.
C-mount adaptor.  An adaptor used to convert a CS-mount camera to C-mount to accommodate
a C-mount lens.  It is simply a ring 5 mm thick, with a male thread on one side and a female
on the other side.  It has a 1'' diameter and 32 threads/inch, as the cameras and lenses.  It often
comes packaged with the newer type (CS-mount) of cameras.
CMYK.  A 4 colour encoding system used by many computer printers, in which colours are
expressed by the "subtractive primaries" (cyan, magenta and yellow) plus black (called K). The
black layer is added to give increased contrast and range.
Coaxial cable.  The most common type of cable used for copper transmission of video signals.
It has a coaxial (sharing the same axis) cross-section, where the centre core is the signal
conductor, while the outer shield protects it from external electromagnetic interference.
CODEC.  COder/DECoder.  An encoder plus a decoder is an electronic device that compresses
and decompresses digital signals.  It is also used to refer to conditional refresh video equipment.
Colour bars.  A pattern generated by a video test generator, consisting of eight equal width
colour bars.  Colours are white (75%), black (7.5% setup level), 75% saturated pure colours red,
green and blue, and 75% saturated hues of yellow, cyan and magenta (mixtures of two
colours in 1:1 ratio without third colour).  The colours appear in the order White, Yellow, Cyan,
Green, Magenta, Red, Blue, Black.
Colour carrier.  The sub-carrier frequency in a colour video signal (4.433619 MHz for PAL &
3.58MHz for NTSC) that is phase modulated with the colour information.  The colour carrier
frequency is chosen soits spectruminterleaves with the luminance spectrum with minimum
interference.  This signal is superimposed on the luminance level.  The amplitude of the colour
sub-carrier represents saturation and phase angle represents hue.
Colour difference signal.  A video colour signal created by subtracting luminance and/or colour
information from one of the primary colour signals (red, green or blue).  In the Betacam colour
difference format, for example, the luminance (Y) and colour difference components
(R-Y and B-Y) are derived as follows:
                         Y = 0.3 Red + 0.59 Green + 0.11 Blue       also  (Y)
                         R-Y = 0.7 Red - 0.59 Green - 0.11 Blue     also  (U)
                         B-Y = 0.89 Blue - 0.59 Green - 0.3 Red     also  (V)
The G-Y colour difference signal is not created because it can be calculated from the other
three signals.  The colour difference signals are, sometimes, wrongly referred to as component
video signals.  That term is reserved for the RGB colour components.
Colour phase.  The timing relationship in a video signal that is measured in degrees and keeps
the hue of a colour signal correct.
Colour temperature.  Indicates the hue of the colour.  It is derived from photography where the
spectrum of colours is based upon a comparison of the hues produced when a black body
(as in Physics) is heated from red through yellow to blue, which is the hottest.  Colour
temperature measurements are expressed in Kelvin (not degrees Kelvin).
Comb filter.  An electrical filter circuit that passes a series of frequencies and rejects the
frequencies in between, it combs out the frequencies.  Used on a composite video signal, to
separate the chrominance signal and reject the luminance signal, or to select the luminance
signal and reject the chrominance signal.  This filter is found in S-VHS VCRs to separate the
chrominance and luminance so that a composite video input can be recorded in S-VHS
format.  These filters can also be found in some multiplexers to give a Y - C output for
recording on an S-VHS recorder.
Composite sync.  A signal consisting of horizontal sync pulses, vertical sync pulses and
equalizing pulses only, with a no-signal reference level.
Composite video signal CVS.  A signal in which the luminance and chrominance information
have been combined using one of the coding standards NTSC, PAL, SECAM,etc.
Concave lens.  A lens that has negative focal length, i.e., the focus is virtual (in front of the
lens) and it reduces theobjects.  A concave lens cannot project an image.
Contrast.  A common term used in reference to the video picture dynamic range, i.e., the
difference between the darkest and the brightest parts of an image.
Convex lens.  A convex lens has a positive focal length, i.e., the focus is real (behind the lens).
 It is usuallycalled magnifying glass, since it magnifies the objects.  It can be used to project
an image.
CPU.  Central Processing Unit.  A common term used in computers.
CRO.  Cathode Ray Oscilloscope (see Oscilloscope).
Crosstalk.  A type of interference where one signal is present in some measure on a second
signal in a system.  The amount of crosstalk is measured as a ratio and expressed in dB.  It
can be caused by unintentionalcapacitance (AC coupling) or more commonly by bad Earth
connections on a connector panel.
CRT.  Cathode Ray Tube. A vacuum tube used for visual displays.
CS-Mount.  Cine Short mount.  The newer standard for lens mounting.  It uses the same
physical thread as theC-mount, but the back flange-to-CCD distance is reduced to 12.5 mm.
The lenses are smaller, more compact and less expensive.  CS-mount lenses can only be
used on CS-mount cameras.
CVBS.  Composite Video Burst Signal.  In broadcast television this refers to the video signal,
including the colour information and syncs.
Top                                                                                                                                               Home