From the smallest business to the largest corporation, chances are they all rely
on some form of video surveillance to keep their workplace secure. With so many
advances in the video surveillance field and affordable options to choose from,
finding the system to suit your specific needs can seem confusing.
With our glossary, it has never been easier. This comprehensive glossary arms
you with the necessary knowledge to successfully carry out your search and make
the right consumer choices. As you research video surveillance products and
equipment, you may come across terms you're not familiar with or want more
information about. To help you better speak the language of video security, we
have provided the most commonly used acronyms, terms and definitions.
Below you will find hyperlinks to all twenty-six letters of the alphabet. To
find the term you are searching for, just click the letter that it begins with.
That will move the page up to those glossary terms that begin with that letter.
[A B C
D E F G H
I J K L M
N O P Q R
S T U V W
X Y Z Other]
Aberration- A term from optics that refers
to anything affecting the fidelity of the image in regards to the original
AC - Alternating current.
Activity detection - Refers to a method
built into some multiplexers for detecting movement within the camera’s field
of view (connected to the multiplexer), which is then used to improve camera
recording update rate.
AC/DC - Alternating current/direct current.
A/D (AD) - Usually refers to analog to
ADC - Analog to digital conversion. This is
usually the very first stage of an electronic device that processes signals into
digital format. The signal can be video, audio, control output and similar.
AGC - Automatic gain control. A section in
an electronic circuit that has feedback and regulates a certain voltage level to
fall within predetermined margins.
ALC - Automatic light control. A part of the
electronics of an automatic iris lens that has a function similar to backlight
compensation in photography.
Aliasing- An occurrence of sampled data
interference. This can occur in CCD image projection of high spatial frequencies
and is also known as Moiré patterning. It can be minimized by a technique known
as optical low pass filtering.
Alphanumeric video generator (also text inserter)
- A device for providing additional information, normally superimposed on the
picture being displayed; this can range from one or two characters to
full-screen alphanumeric text. Such generators use the incoming video signal
sync pulses as a reference point for the text insertion position, which means if
the video signal is of poor quality, the text stability will also be of poor
Amplitude - The maximum value of a varying
Analog signal - Representation of data by
continuously varying quantities. An analog electrical signal has a different
value of volts or amperes for electrical representation of the original
excitement (sound, light) within the dynamic range of the system.
ANSI - American National Standards
Anti-aliasing - A procedure employed to
eliminate or reduce (by smoothing and filtering) the aliasing effects.
Aperture - The opening of a 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. By increasing the F-stop
number (F/1.4, F/1.8, F/2.8, etc.) less light is permitted to pass to the pickup
Apostilb - A photometric unit for measuring
luminance where, instead of candelas, lumens are used to measure the luminous
flux of a source.
Archive - Long-term off-line storage. In
digital systems, pictures are generally archived onto some form of hard disc,
magnetic tape, floppy disk or DAT cartridge.
Artifacts - Undesirable elements or defects
in a video picture. These may occur naturally in the video process and must be
eliminated in order to achieve a high-quality picture. The most common are
cross-color and cross-luminance.
ASCII - American Standard Code for
Information Interchange. A 128-character set that includes the upper case and
lower- case English alphabet, numerals, special symbols and 32 control codes. A
7-bit binary number represents each character. Therefore, one ASCII-encoded
character can be stored in one byte of computer memory.
Aspect ratio - This is the ratio between the
width and height of a television or cinema picture display. The present aspect
ratio of the television screen is 4:3, which means four units wide by three
units high. Such aspect ratio was elected in the early days of television, when
the majority of movies were of the same format. The new, high definition
television format proposes a 16:9 aspect ratio.
Aspherical lens - A lens that has a
spherical surface. It is harder and more expensive to manufacture, but it offers
certain advantages over a normal spherical lens.
Astigmatism - The uneven foreground and
background blur that is in an image.
Asynchronous - Lacking synchronization. In
video, a signal is asynchronous when its timing differs from that of the system
reference signal. A foreign video signal is asynchronous before a local frame
synchronizer treats it.
ATM - Asynchronous transfer mode. A
transporting and switching method in which information does not occur
periodically with respect to some reference such as a frame pattern.
Attenuator - A circuit that provides
reduction of the amplitude of an electrical signal without introducing
appreciable phase or frequency distortion.
ATSC - Advanced Television System Committee
(think of it as a modern NTSC). An American committee involved in creating the
high definition television standards.
Attenuation - The decrease in magnitude of a
wave, or a signal, as it travels through a medium or an electric system. It is
measured in decibels (dB).
Auto iris (AI) - An automatic method of
varying the size of a lens aperture in response to changes in scene
AWG - American wire gauge. A wire diameter
specification based on the American standard. The smaller the AWG number, the
larger the wire diameter.
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Back-focus - A procedure of adjusting the
physical position of the CCD-chip/lens to achieve the correct focus for all
focal length settings (especially critical with zoom lenses).
Back porch - 1. The portion of a video
signal that occurs during blanking from the end of horizontal sync to the
beginning of active video; 2. The blanking signal portion that lies between the
trailing edge of a horizontal sync pulse and the trailing edge of the
corresponding blanking pulse. Color burst is located on the back porch.
Balanced signal - In CCTV this refers to a
type of video signal transmission through a twisted pair cable. It is called
balanced because the signal travels through both wires, thus being equally
exposed to the external interference, so by the time the signal gets to the
receiving end, the noise will be cancelled out at the input of a differential
Balun - This is a device used to match or
transform an unbalanced coaxial cable to a balanced twisted pair system.
Bandwidth - The complete range of
frequencies over which a circuit or electronic system can function with minimal
signal loss, usually measured to the point of less than 3 dB. In PAL systems the
bandwidth limits the maximum visible frequency to 5.5 MHz, in NTSC to 4.2 MHz.
The ITU 601 luminance channel sampling frequency of 13.5 MHz was chosen to
permit faithful digital representation of the PAL and NTSC luminance bandwidths
Base band - The frequency band occupied by
the aggregate of the signals used to modulate a carrier before they combine with
the carrier in the modulation process. In CCTV the majority of signals are in
Baud - Data rate, named after Maurice Emile
Baud, which generally is equal to 1 bit/s. Baud is equivalent to bits per second
in cases where each signal event represents exactly 1 bit. Typically, the baud
settings of two devices must match if the devices are to communicate with one
BER - Bit error rate. The ratio of received
bits that are in error relative to the total number of bits received, used as a
measure of noise induced distortion in a digital bit stream. BER is expressed as
a power of 10. For example, a 1 bit error in 1 million bits is a BER of 10–6.
Betamax - Sony’s domestic video recording
format, a competitor of VHS.
Bias - Current or voltage applied to a
circuit to set a reference operating level for proper circuit performance, such
as the high frequency bias current applied to an audio recording head to improve
linear performance and reduce distortion.
Binary - A base 2 numbering system using the
two digits 0 and 1 (as opposed to ten digits [0-9] in the decimal system). In
computer systems, the binary digits are represented by two different voltages or
currents, one corresponding to zero and another corresponding to one. All
computer programs are executed in binary form.
Bipolar - A signal containing both
positive-going and negative-going amplitude. May also contain a zero amplitude
B-ISDN - Broadband Integrated Services
Digital Network. An improved ISDN, composed of an intelligent combination of
more ISDN channels into one that can transmit more data per second.
Bit - A contraction of binary digit.
Elementary digital information that can only be 0 or 1. The smallest part of
information in a binary notation system. A bit is a single 1 or 0. A group of
bits, such as 8 bits or 16 bits, compose a byte. The number of bits in a byte
depends on the processing system being used. Typical byte sizes are 8, 16 and
Bitmap (BMP) - A pixel-by-pixel description
of an image. Each pixel is a separate element. Also a computer file format.
Bit rate - Bps = Bytes per second, bps =
bits per second. The digital equivalent of bandwidth, bit rate is measured in
bits per second. It is used to express the rate at which the compressed bit
stream is transmitted. The higher the bit rate, the more information that can be
Black burst (color-black) - A composite
color video signal. The signal has composite sync, reference burst and a black
video signal, which is usually at a level of 7.5 IRE (50 mV) above the blanking
Black level - A part of the video signal,
close to the sync level, but slightly above it (usually 20 mV - 50 mV) in order
to be distinguished from the blanking level. It electronically represents the
black part of an image, whereas the white part is equivalent to 0.7 V from the
Blanking level - The beginning of the video
signal information in the signal’s waveform. It resides at a reference point
taken as 0 V, which is 300 mV above the lowest part of the sync pulses. Also
known as pedestal, the level of a video signal that separates the range that
contains the picture information from the range that contains the synchronizing
Blooming - The defocusing of regions of a
picture where brightness is excessive. BNC - BNC stands for Bayonet-Neil-
Councilman connector, and it is the most popular connector in CCTV and broadcast
TV for transmitting a basic bandwidth video signal over a coaxial cable.
B-picture - Bidirectional predictive coded
picture; an MPEG term for a picture that is coded using motion compensated
prediction from a past and/or future reference picture.
Braid - A group of textile or metallic
filaments interwoven to form a tubular structure that may be applied over one or
more wires or flattened to form a strap.
Brightness - In NTSC and PAL video signals,
the brightness information at any particular instant in a picture is conveyed by
the corresponding instantaneous DC level of active video. Brightness control is
an adjustment of setup (black level, black reference).
Burst (color burst) - Seven to nine cycles
(NTSC) or ten cycles (PAL) of sub-carrier placed near the end of horizontal
blanking to serve as the phase (color) reference for the modulated color
sub-carrier. Burst serves as the reference for establishing the picture color.
Bus - In computer architecture, a path over
which information travels internally among various components of a system and is
available to each of the components.
Byte - A digital word made of 8 bits (zeros
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Cable equalization - The process of altering
the frequency response of a video amplifier to compensate for high frequency
losses in coaxial cable.
CAD - Computer-aided design. This usually
refers to a design of system that uses computer specialized software.
Candela [cd] - A unit for measuring luminous
intensity. 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: "the luminous intensity of a black body heated up to a
temperature at which platinum converges from a liquid state to a solid".
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. The new age
imaging device, replacing the old tubes. When first invented in the 1970s, it
was initially intended to be used as a memory device. Most often used in
cameras, but also in telecine, fax machines, scanners, etc.
CCD aperture - The proportion of the total
area of a CCD chip that is photosensitive.
CCIR - Committée Consultatif International
des Radiocommuniqué or, in English, Consultative Committee for International
Radio, 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
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 were chosen because they work for both
525-line 60Hz and 625-line 50Hz component video systems. 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 chrominance
channels are each sampled twice. The Dl digital videotape format conforms to ITU
CCIR 656 - The international standard
(renamed ITU 601) defining the electrical and mechanical interfaces for digital
television equipment operating according to the ITU 601 standard. ITU 656
defines both the parallel and serial connector pin outs, as well as the
blanking, sync and multiplexing schemes used in both parallel and serial
CCTV - Closed circuit television. Television
system intended for only a limited number of viewers, as opposed to broadcast
CCTV camera - A unit containing an imaging
device that produces a video signal in the basic bandwidth.
CCTV installation - A CCTV system, or an
associated group of systems, together with all necessary hardware, auxiliary
lighting, etc., located at the protected site.
CCTV system - An arrangement comprising of a
camera and lens with all ancillary equipment required for the surveillance of a
specific protected area.
CCVE - Stands for closed circuit video
equipment. An alternative acronym for CCTV.
CD - Compact disc. A standard of media as
proposed by Philips and Sony, where music and data are stored in digital format.
CD-ROM - Compact disk read only memory. The
total capacity of a CD-ROM when storing data is 640 MB.
CDS - Correlated double sampling. A
technique used in the design of some CCD cameras that reduce the video signal
noise generated by the chip.
CFA - Color filter array. A set of optical
pixel filters used in single-chip color CCD cameras to produce the color
components of a video signal.
Chip - An integrated circuit in which all
the components are micro-fabricated on a tiny piece of silicon or similar
Chroma crawl - An artifact of encoded video,
also known as dot crawl or cross-luminance, Occurs in the video picture around
the edges of highly saturated colors as a continuous series of crawling dots and
is a result of color information being confused as luminance information by the
Chroma gain (chroma, color, saturation) - In
video, the gain of an amplifier as it pertains to the intensity of colors in the
Chroma key (color key) - A video key effect
in which one video signal is inserted in place of areas of a particular color in
another video signal.
Chrominance - The color information of a
color video signal.
Chrominance-to-luminance inter-modulation (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 color saturation levels.
CIE - Commission Internationale de
l’Eclairagé. This is the International Committee for Light, established in
1965. It defines and recommends light units.
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. A major benefit of a clamp is the removal of low-frequency
interference, especially power line hum.
Cladding - The outer part of a fiber optics
cable, which is also a fiber but with a smaller material density than the center
core. It enables a total reflection effect so that the light transmitted through
the internal core stays inside.
Clipping Level - An electronic limit to
avoid overdriving the video portion of the television signal.
C-mount - The first standard for CCTV lens
screw mounting. It is defined with the thread of 1'' (2.54 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; only in the latter case an adaptor is
CMYK - A color encoding system used by
printers in which colors 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 on printing presses.
Coaxial cable - The most common type of
cable used for copper transmission of video signals. It has a coaxial cross-
section, where the center core is the signal conductor, while the outer shield
protects it from external electromagnetic interference.
CODEC - Code/Decode. An encoder plus a
decoder is an electronic device that compresses and decompresses digital
signals. Codec’s usually perform A/D and D/A conversion.
Color bars - A pattern generated by a video
test generator, consisting of eight equal width color bars. Colors are white
(75%), black (7.5% setup level), 75% saturated pure colors red, green and blue,
and 75% saturated hues of yellow, cyan and magenta (mixtures of two colors in
1:1 ratio without third color).
Color carrier - The sub-frequency in a color
video signal (4.43 MHz for PAL) that is modulated with the color information.
The color carrier frequency is chosen so its spectrum interleaves with the
luminance spectrum with minimum interference.
Color difference signal - A video color
signal created by subtracting luminance and/or color information from one of the
primary color signals (red, green or blue). In the Beta cam color difference
format, for example, the luminance (Y) and color difference components (R–Y
and B–Y) are derived as follows: Y = 0.3 Red + 0.59 Green + 0.11 Blue; R–Y =
0.7 Red – 0.59 Green – 0.11 Blue; B–Y = 0.89 Blue – 0.59 Green – 0.3
Red - The G-V color difference signal is not created because it can be
reconstructed from the other three signals. Other color difference conventions
include SMPTE, EBU-N1 0 and MII. Color difference signals should not be referred
to as component video signals. That term is reserved for the RGB color
components. In informal usage, the term “component video” is often used to
mean color difference signals.
Color field - In the NTSC system, the color
sub-carrier is phase-locked to the line sync so that on each consecutive line,
sub carrier phase is changed 180º with respect to the sync pulses. In the PAL
system, color sub carrier phase moves 90º every frame. In NTSC this creates
four different field types, while in PAL there are eight. In order to make clean
edits, alignment of color field sequences from different sources is crucial.
Color frame - In color television, four
(NTSC) or eight (PAL) properly sequenced color fields compose one color frame.
Color phase - The timing relationship in a
video signal that is measured in degrees and keeps the hue of a color signal
Color sub carrier - The 3.58MHz signal that
carries color information. This signal is superimposed on the luminance level.
Amplitude of the color sub carrier represents saturation and phase angle
Color temperature - Indicates the hue of the
color. It is derived from photography where the spectrum of colors 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. Color temperature
measurements are expressed in Kelvin.
Comb filter - An electrical filter circuit
that passes a series of frequencies and rejects the frequencies in between,
producing a frequency response similar to the teeth of a comb.
Comb - Used on encoded video to select the
chrominance signal and reject the luminance signal, thereby reducing cross-
chrominance artifacts or conversely, to select the luminance signal and reject
the chrominance signal, thereby reducing.
Cross-luminance artifacts - Introduced in
the S-VHS concept for a better luminance resolution.
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 - A signal in which
the luminance and chrominance information has 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 and it reduces the objects.
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. It is usually called magnifying glass,
since it magnifies the objects.
CPU - Central processing unit. A common term
used in computers.
CRO - Cathode ray oscilloscope (see
Crosstalk - A type of interference or
undesired transmission of signals from one circuit into another circuit in the
same system. Usually caused by unintentional capacitance (AC coupling).
CS-Mount - A newer standard for lens
mounting. It uses the same physical thread as the C-mount, but the back
flange-to- CCD distance is reduced to 12.5 mm in order to have the lenses made
smaller, more compact and less expensive. CS-mount lenses can only be used on
CS-to-C-mount adaptor - An adaptor used to
convert a CS-mount camera to C-mount to accommodate a C-mount lens. It looks
like a ring 5 mm thick, with a male thread on one side and a female on the
other, with 1' diameter and 32 threads/inch. It usually comes packaged with the
newer type (CS-mount) of cameras.
CVBS - Composite video bar signal. In
broadcast television this refers to the video signal, including the color
information and syncs.
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D/A (also DA) - Opposite to A/D, i.e.,
digital to analog conversion.
Dark current - Leakage signal from a CCD
sensor in the absence of incident light.
Dark noise - Noise caused by the random
(quantum) nature of the dark current.
DAT (digital audio tape) - A system
developed initially for recording and playback of digitized audio signals,
maintaining signal quality equal to that of a CD. Recent developments in
hardware and software might lead to a similar inexpensive system for video
archiving, recording and playback.
DB - Decibel. A logarithmic ratio of two
signals or values usually refers to power, but also voltage and current. When
power is calculated the logarithm is multiplied by 10, while for current and
voltage by 20. DBS - Direct broadcast satellite. Broadcasting from a satellite
directly to a consumer user, usually using a small aperture antenna.
DC - Direct current. Current that flows in
only one direction, as opposed to AC. DCT - Discrete cosine transform.
Mathematical algorithm used to generate frequency representations of a block of
video pixels. The DCT is an invertible, discrete orthogonal transformation
between time and frequency domain. It can be either forward discrete cosine
transforms (FDCT) or inverse discrete cosine transforms (IDCT).
Decoder - A device used to recover the
component signals from a composite (encoded) source.
Degauss - To demagnetize.
Delay line - An artificial or real
transmission line or equivalent device designed to delay a wave or signal for a
specific length of time.
Demodulator - A device that strips the video
and audio signals from the carrier frequency.
Depth of field - The area in front of and
behind the object in focus that appears sharp on the screen. The depth of field
increases with the decrease of the focal length, i.e., the shorter the focal
length the wider the depth of field. The depth of field is always wider behind
the objects in focus.
Dielectric - An insulating (nonconductive)
Differential gain - A change in sub-carrier
amplitude of a video signal caused by a change in luminance level of the signal.
The resulting TV picture will show a change in color saturation caused by a
simultaneous change in picture brightness.
Differential phase - A change in the
sub-carrier phase of a video signal caused by a change in the luminance level of
the signal. The hue of colors in a scene change with the brightness of the
Digital disc recorder - A system that allows
recording of video images on a digital disc. Digital signal - An electronic
signal where every different value from the real-life excitation (sound, light)
has a different value of binary combinations (words) that represent the analog
DIN - Deutsche Industrie-Normen. Germany’s
Disk - A flat circular plate, coated with a
magnetic material, on which data may be stored by selective magnetization of
portions of the surface. May be a flexible, floppy disc or rigid hard disk. It
could also be a plastic compact disc (CD) or digital video disc (DVD).
Distortion – Non-proportional
representation of an original.
DMD - Digital micro-mirror device. A new
video projection technology that uses chips with a large number of miniature
mirrors, whose projection angle can be controlled with digital precision.
DOS - Disk operating system. A software
package that makes a computer work with its hardware devices such as hard drive,
floppy drive, screen, keyboard, etc.
Dot pitch - The distance in millimeters
between individual dots on a monitor screen. The smaller the dot pitch the
better, since it allows for more dots to be displayed and better resolution. The
dot pitch defines the resolution of a monitor. A high-resolution CCTV or
computer monitor would have a dot pitch of less than 0.3 mm.
Drop-frame Time Code - SMPTE time code
format that continuously counts 30 frames per second, but drops two frames from
the count every minute except for every tenth minute (drops 108 frames every
hour) to maintain synchronization of time code with clock time. This is
necessary because the actual frame rate of NTSC video is 29.94 frames per second
rather than an even 30 frames.
DSP - Digital signal processing. It usually
refers to the electronic circuit section of a device capable of processing
Dubbing - Transcribing from one recording
medium to another.
Duplex - A communication system that carries
information in both directions is called a duplex system. In CCTV, duplex is
often used to describe the type of multiplexer that can perform two functions
simultaneously, recording in multiplex mode and playback in multiplex mode. It
can also refer to duplex communication between a matrix switcher and a PTZ site
driver, for example.
DV-Mini - Mini digital video. A new format
for audio and video recording on small camcorders, adopted by the majority of
camcorder manufacturers. Video and sound are recorded in a digital format on a
small cassette (66×48×12 mm), superseding S-VHS and Hi 8 quality.
D-VHS - A new standard proposed by JVC for
recording digital signals on a VHS video recorder.
Dynamic range - The difference between the
smallest amount and the largest amount that a system can represent.
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EBU - European Broadcasting Union.
EIA - Electronics Industry Association,
which has recommended the television standard used in the US, Canada and Japan,
based on 525 lines interlaced scanning. Formerly known as RMA or RETMA.
Encoder - A device that superimposes
electronic signal information on other electronic signals.
Encryption - The rearrangement of the bit
stream of a previously digitally encoded signal in a systematic fashion to make
the information unrecognizable until restored on receipt of the necessary
authorization key. This technique is used for securing information transmitted
over a communication channel with the intent of excluding all other than
authorized receivers from interpreting the message. Can be used for voice, video
and other communications signals.
ENG camera - Electronic News Gathering
camera. Refers to CCD cameras in the broadcast industry.
EPROM - Erasable and programmable read only
memory. An electronic chip used in many different security products that stores
software instructions for performing various operations.
Equalizer - Equipment designed to compensate
for loss and delay frequency effects within a system. A component or circuit
that allows for the adjustment of a signal across a given band.
Ethernet - A local area network used for
connecting computers, printers, workstations, terminals, etc. within the same
building. Ethernet operates over twisted wire and coaxial cable at speeds up to
10 Mbps. Ethernet specifies a CSMA/CD (carrier sense multiple access with
collision detection). CSMA/CD is a technique of sharing a common medium (wire,
coaxial cable) among several devices.
External synchronization - A means of
ensuring that all equipment is synchronized to the one source.
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FCC - Federal Communications Commission
FFT - Fast Fourier Transformation.
Fiber optics - A technology designed to
transmit signals in the form of pulses of light. Fiber optic cable is noted for
its properties of electrical isolation and resistance to electrostatic and
Field - Refers to one-half of the TV frame
that is composed of either all odd or even lines. In CCIR systems each field is
composed of 625/2 = 312.5 lines, in EIA systems 525/2 = 262.5 lines. There are
50 fields/second in CCIR/PAL, and 60 in the EIA/NTSC TV system.
Film recorder - A device for converting
digital data into film output. Continuous tone recorders produce color
photographs as transparencies, prints or negatives.
Fixed focal length lens - A lens with a
predetermined fixed focal length, a focusing control and a choice of iris
Flash memory - Nonvolatile, digital storage.
Flash memory has slower access than SRAM or DRAM.
Flicker - An annoying picture distortion,
mainly related to vertical syncs and video fields display. Some flicker normally
exists due to interlacing; more apparent in 50 Hz systems (PAL). Flicker shows
also when static images are displayed on the screen such as computer generated
text transferred to video. Poor digital image treatment, found in low-quality
system converters (going from PAL to NTSC and vice versa), creates an annoying
flicker on the screen. There are several electronic methods to minimize flicker.
F-number - In lenses with adjustable irises,
the maximum iris opening is expressed as a ratio (focal length of the lens)/
(maximum diameter of aperture). This maximum iris will be engraved on the front
ring of the lens.
Focal length - The distance between the
optical center of a lens and the principal convergent focus point.
Focusing control - A means of adjusting the
lens to allow objects at various distances from the camera to be sharply
Foot-candela - An illumination light unit
used mostly in American CCTV terminology. It equals ten times (more precisely,
9.29) of the illumination value in luxes.
Fourier Transformation - Mathematical
transformation of time domain functions into frequency domain.
Frame, (See also Field) - Refers to a
composition of lines that make one TV frame. In CCIR/PAL TV system one frame is
composed of 625 lines, while in EIA/NTSC TV system of 525 lines. There are 25
frames/second in the CCIR/PAL and 30 in the EIA/NTSC TV system.
Frame store - An electronic device that
digitizes a TV frame (or TV field) of a video signal and stores it in memory.
Multiplexers, fast scan transmitters, Quad compressors and even some of the
latest color cameras have built-in frame stores.
Frame switcher - Another name for a simple
multiplexer, which can record multiple cameras on a single VCR (and play back
any camera in full screen) but does not have a mosaic image display.
Frame synchronizer - A digital buffer that,
by storage and comparison of sync information to a reference and timed release
of video signals, can continuously adjust the signal for any timing errors.
Frame transfer (FT) - Refers to one of the
three principles of charge transfer in CCD chips. The other two are interline
and frame-interline transfer.
Frame-interline transfer (FIT) - Refers to
one of the few principles of charge transfer in CCD chips. The other two are
interline and frame transfer.
Frequency - The number of complete cycles of
a periodic waveform that occur in a given length of time. Usually specified in
cycles per second (Hertz).
Frequency modulation (FM) - Modulation of a
sine wave or carrier by varying its frequency in accordance with amplitude
variations of the modulating signal.
Front porch - The blanking signal portion
that lies between the end of the active picture information and the leading edge
of horizontal sync.
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Gain - Any increase or decrease in strength
of an electrical signal. Gain is measured in terms of decibels or number of
times of magnification.
Gamma - A correction of the linear response
of a camera in order to compensate for the monitor phosphor screen nonlinear
response. It is measured with the exponential value of the curve describing the
non-linearity. A typical monochrome monitor’s gamma is 2.2, and a camera needs
to be set to the inverse value of 2.2 (which is 0.45) for the overall system to
respond linearly (i.e., unity).
Gamut - The range of voltages allowed for a
video signal, or a component of a video signal. Signal voltages outside of the
range (i.e., exceeding the gamut) may lead to clipping, crosstalk or other
Gen-lock - A way of locking the video signal
of a camera to an external generator of synchronization pulses.
GHz - Gigahertz. One billion cycles per
GB - Gigabyte. Unit of computer memory
consisting of about one thousand million bytes (a thousand megabytes). Actual
value is 1,073,741,824 bytes.
GND - Ground (electrical).
Gray scale - A series of tones that range
from true black to true white, usually expressed in 10 steps.
Ground loop - An unwanted interference in
the copper electrical signal transmissions with shielded cable, which is a
result of ground currents when the system has more than one ground. For example,
in CCTV, when we have a different earthing resistance at the camera, and the
switcher or monitor end. The induced electrical noise generated by the
surrounding electrical equipment (including mains) does not discharge equally
through the two earthings (since they are different) and the induced noise shows
up on the monitors as interference.
GUI - Graphical user interface.
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HAD - Hole accumulated diode. A type of CCD
sensor with a layer designed to accumulate holes (in the electronic sense), thus
reducing noise level.
HDD - Hard disk drive. A magnetic medium for
storing digital information on most computers and electronic equipment that
process digital data.
HDDTV - High definition digital television.
The upcoming standard of broadcast television with extremely high resolution and
aspect ratio of 16:9. It is advancement from the analog high definition, already
used experimentally in Japan and Europe. The picture resolution is nearly 2000×1000
pixels, and uses the MPEG-2 standard.
HDTV - High definition television. It
usually refers to the analog version of the HDDTV. The SMPTE in the US and ETA
in Japan have proposed a HDTV product standard: 1125 lines at 60 Hz field rate
2:1 interlace; 16:9 aspect ratio; 30 MHz RGB and luminance bandwidth.
Head end - The electronic equipment located
at the start of a cable television system, usually including antennas, earth
stations, preamplifiers, frequency converters, demodulators, modulators and
Helical scan - A method of recording video
information on a tape, most commonly used in home and professional VCRs.
Horizontal Drive (also Horizontal sync) -
This signal is derived by dividing sub-carrier by 227.5 and then doing some
pulse shaping. The signal is used by monitors and cameras to determine the start
of each horizontal line.
Horizontal resolution - Chrominance and
luminance resolution (detail) expressed horizontally across a picture tube. This
is usually expressed as a number of black to white transitions or lines that can
be differentiated. Limited by the bandwidth of the video signal or equipment.
Herringbone - Patterning caused by driving a
color-modulated composite video signal (PAL or NTSC) into a monochrome monitor.
Horizontal retrace - At the end of each
horizontal line of video, a brief period when the scanning beam returns to the
other side of the screen to start a new line.
Horizontal sync pulse - The synchronizing
pulse at the end of each video line that determines the start of horizontal
Hertz - A unit that measures the number of
certain oscillations per second. Housings, environmental. Usually refers to
cameras’ and lenses containers and associated accessories, such as heaters,
washers and wipers, to meet specific environmental conditions.
HS - Horizontal sync.
Hue (tint, phase, chroma phase) - One of the
characteristics that distinguishes one color from another. Hue defines color on
the basis of its position in the spectrum, i.e., whether red, blue, green or
yellow, etc. Hue is one of the three characteristics of television color: see
also Saturation and Luminance. In NTSC and PAL video signals, the hue
information at any particular point in the picture is conveyed by the
corresponding instantaneous phase of the active video sub carrier.
Hum - A term used to describe an unwanted
induction of mains frequency.
Hum bug - Another name for a ground loop
Hyper-HAD - An improved version of the CCD
HAD technology, utilizing on-chip micro-lens technology to provide increased
sensitivity without increasing the pixel size.
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IDE - Interface device electronics. Software
and hardware communication standard for interconnecting peripheral devices to a
I/O - Input/Output.
I/P - Input. A signal applied to a piece of
electric apparatus or the terminals on the apparatus to which a signal or power
I2R - Formula for power in watts (W), where
I is current in amperes (A), R is resistance in ohms (W).
IEC - International Electro technical
Commission (also CEI).
Imaging device - A vacuum tube or solid
state-device in which the vacuum tube light-sensitive face plate or solid-state
light-sensitive array provides an electronic signal from which an image can be
Impedance - A property of all metallic and
electrical conductors that describes the total opposition to current flow in an
electrical circuit. Resistance, inductance, capacitance and conductance have
various influences on the impedance, depending on frequency, dielectric material
around conductors, physical relationship between conductors and external
factors. Impedance is often referred to with the letter Z. It is measured in
ohms, whose symbol is the Greek letter omega - W.
Input - Same as I/P.
Inserter (also alphanumeric video generator)
- A device for providing additional information, normally superimposed on the
picture being displayed; this can range from one or two characters to
full-screen alphanumeric text. Usually, such generators use the incoming video
signal sync pulses as a reference point for the text insertion position, which
means if the video signal is of poor quality, the text stability will also be of
poor quality. Interference - Disturbances of an electrical or electromagnetic
nature that introduce undesirable responses in other electronic equipment.
Interlaced scanning - A technique of
combining two television fields in order to produce a full frame. The two fields
are composed of only odd and only even lines, which are displayed one after the
other but with the physical position of all the lines interleaving each other,
hence interlace. This type of television picture creation was proposed in the
early days of television to have a minimum amount of information yet achieve
Interline transfer - This refers to one of
the three principles of charge transferring in CCD chips. The other two are
frame transfer and frame-interline transfer.
IP - Index of protection. A numbering system
that describes the quality of protection of an enclosure from outside
influences, such as moisture, dust and impact.
IRE - Institute of Radio Engineers. Units of
measurement dividing the area from the bottom of sync to peak white level into
140 equal units. 140 IRE equals 1Vpp. The range of active video is 100 IRE. IR
light - Infrared light, invisible to the human eye. It usually refers to
wavelengths longer than 700 nm. Monochrome (B/W) cameras have extremely high
sensitivity in the infrared region of the light spectrum.
Iris - A means of controlling the size of a
lens aperture and therefore the amount of light passing through the lens.
ISDN - Integrated Services Digital Network.
The newer generation telephone network, which uses 64 kb/s speed of transmission
(being a digital network, the signal bandwidth is not expressed in kHz, but
rather with a transmission speed). This is much faster than a normal PSTN
telephone line. To use the ISDN network you have to talk to your communications
provider, but in general a special set of interface units (like modems) are
ISO - International Standardization
ITU - International Telecommunications Union
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JPEG - Joint Photographic Experts Group. A
group that has recommended a compression algorithm for still digital images that
can compress with ratios of over 10:1. Also the name of the format itself.
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kb/s - Kilobits per second. Thousand bits
per second. Also written as kbps.
Kelvin - One of the basic physical units of
measurement for temperature. The scale is the same as the Celsius, but the 0ºK
starts from -273ºC. Also the unit of measurement of the temperature of light is
expressed in Kelvin’s or K. In color recording, light temperature affects the
color values of the lights and the scene that they illuminate.
K factor - A specification rating method
that gives a higher factor to video disturbances that cause the most observable
KHz - Kilohertz. Thousand Hertz.
Kilo baud - A unit of measurement of data
transmission speed equaling 1000 baud.
Kilobyte - 1024 bytes.
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Lambertian source or surface - A surface is
called a Lambert radiator or reflector (depending whether the surface is a
primary or a secondary source of light) if it is a perfectly diffusing surface.
LAN - Local Area Network. A short distance
data communications network (typically within a building or campus) used to link
together computers and peripheral devices (such as printers, CD ROMs and modems)
under some form of standard control.
Laser - Light amplification by stimulated
emission of radiation. A laser produces a very strong and coherent light of a
LED - Light Emitting Diode. A semiconductor
that produces light when a certain low voltage is applied to it in one
Lens - An optical device for focusing a
desired scene onto the imaging device in a CCTV camera.
Level - When relating to a video signal it
refers to the video level in volts. In CCTV optics, it refers to the auto iris
level setting of the electronics that processes the video signal in order to
open or close the iris.
Line-locked - In CCTV, this usually refers
to multiple cameras being powered by a common alternative current (AC) source
(either 24 V AC, 110 V AC or 240 V AC) and consequently have field frequencies
locked to the same AC source frequency (50 Hz in CCIR systems and 60 Hz in EIA
Liquid crystal display (LCD) - A screen for
displaying text/graphics based on a technology called liquid crystal, where
minute currents change the reflectiveness or transparency of the screen. The
advantages of LCD screens are very small power consumption (can be easily
battery driven) and low price of mass-produced units. The disadvantages are
narrow viewing angle, slow response (a bit too slow to be used for video),
invisibility in the dark unless the display is back lighted, and difficulties
displaying true colors with color LCD displays.
Lumen [lm] - A light intensity produced by
the luminosity of 1 candela in one radian of a solid angle.
Luminance - Refers to the video signal
information about the scene brightness. The measurable, luminous intensity of a
video signal. Differentiated from brightness in that the latter is
non-measurable and sensory. The color video picture information contains two
components, luminance (brightness and contrast) and chrominance (hue and
saturation). The photometric quantity of light radiation.
LUT - Look-up table. A cross-reference table
in the computer memory that transforms raw information from the scanner or
computer and corrects values to compensate for weakness in equipment or for
differences in emulsion types.
Lux [lx] - Light unit for measuring
illumination. It is defined as the illumination of a surface when luminous flux
of 1 lumen falls on an area of 1 m2. It is also known as lumen per square meter,
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MAC - Multiplexed analog components. A
system in which the components are time multiplexed into one channel using time
domain techniques, i.e., the components are kept separate by being sent at
different times through the same channel. There are many different MAC formats
Manual iris - A manual method of varying the
size of a lens’s aperture.
Matrix - A logical network configured in a
rectangular array of intersections of input/output channels.
Matrix switcher - A device for switching
more than one camera, VCR, video printer and similar, to more than one monitor,
VCR, video printer and similar. Much more complex and more powerful than video
MATV - Master antenna television.
MB - Megabyte. Unit of measurement for
computer memory consisting of approximately one million bytes. Actual value is
1,048,576 bytes. Kilobyte × Kilobyte = Megabyte.
MB/s - Megabytes per second. Million bytes
per second or 8 million hits per second. Also written as Mbps.
Mb/s - Megabits per second. Million bits per
second. Also written as Mbps.
MHz - Megahertz. One million hertz.
Microwave - One definition refers to the
portion of the electromagnetic spectrum that ranges between 300 MHz and 3000
GHz. The other definition is when referring to the transmission media where
microwave links are used. Frequencies in microwave transmission are usually
between 1 GHz and 12 GHz.
MOD - Minimum object distance. Feature of a
fixed or a zoom lens that indicates the closest distance an object can be from
the lens’s image plane, expressed in meters. Zoom lenses have MOD of around 1
m, while fixed lenses usually much less, depending on the focal length.
Modem - This popular term is made up of two
words: modulate and demodulate. The function of a modem is to connect a device
(usually computer) via a telephone line to another device with a modem.
Modulation - The process by which some
characteristic (i.e., amplitude, phase) of one RF wave is varied in accordance
with another wave (message signal).
Moiré pattern - An unwanted effect that
appears in the video picture when a high-frequency pattern is looked at with a
CCD camera that has a pixel pattern close (but lower) to the object pattern.
Monochrome - Black-and-white video. A video signal that represents the
brightness values (luminance) in the picture, but not the color values
MPEG - Motion Picture Experts Group. An ISO
group of experts that has recommended manipulation of digital motion images.
Today there are a couple of MPEG recommendations, of which the most well known
are MPEG-1 and MPEG-2. The latter one is widely accepted for high definition
digital television, as well as multimedia presentation.
MPEG-1 - Standard for compressing
progressive scanned images with audio. Bit rate is from 1.5 Mbps up to 3.5 Mbps.
MPEG-2 - The standard for compression of
progressive scanned and interlaced video signals with high quality audio over a
large range of compression rates with a range of bit rates from 1.5 to 100 Mbps.
Accepted as a HDTV and DVD standard of video/audio encoding.
Multiplexer - A device that combines several
input signals into a single output signal in such a manner that each of the
input signals subsequently can be recovered.
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Noise - An unwanted signal produced by all
electrical circuits working above the absolute zero. Noise cannot be eliminated
but only minimized.
Non-drop frame time code - SMPTE time code
format that continuously counts a full 30 frames per second. Because NTSC video
does not operate at exactly 30 frames per second, non-drop-frame time code will
count 108 more frames in one hour than actually occur in the NTSC video in one
hour. The result is incorrect synchronization of time code with clock time.
Drop-frame time code solves this problem by skipping or dropping 2 frame numbers
per minute, except at the tens of the minute count.
Non-interlaced - The process of scanning
whereby every line in the picture is scanned during the vertical sweep.
NTSC - National Television System Committee.
American committee that set the standards for color television as used today in
the US, Canada, Japan and parts of South America. NTSC television uses a 3.57945
MHz sub-carrier whose phase varies with the instantaneous hue of the televised
color and whose amplitude varies with the instantaneous saturation of the color.
NTSC employs 525 lines per frame and 59.94 fields per second.
Numerical aperture - A number that defines
the light gathering ability of a specific fiber. The numerical aperture is equal
to the sine of the maximum acceptance angle.
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O/P - Output.
Objective - The very first optical element
at the front of a lens.
Ocular - The very last optical element at
the back of a lens (the one closer to the CCD chip).
Ohm - The unit of resistance. The electrical
resistance between two points of a conductor where a constant difference of
potential of 1 V applied between these points produces in the conductor a
current of 1 A, the conductor not being the source of any electromotive force.
Oscilloscope (also CRO, from cathode ray oscilloscope)
- An electronic device that can measure the signal changes versus time. A must
for any CCTV technician.
Over scan - A video monitor condition in
which the raster extends slightly beyond the physical edges of the CRT screen,
cutting off the outer edges of the picture.
Output impedance - The impedance a device
presents to its load. The impedance measured at the output terminals of a
transducer with the load disconnected and all impressed driving forces taken as
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PAL - Phase alternating line. Describes the
color phase change in a PAL color signal. PAL is a European color TV system
featuring 625 lines per frame, 50 fields per second and a 4.43361875-MHz
sub-carrier. Used mainly in Europe, China, Malaysia, Australia, New Zealand, the
Middle East and parts of Africa. PAL-M is a Brazilian color TV system with phase
alternation by line, but using 525 lines per frame, 60 fields per second and a
3.57561149 MHz sub-carrier.
Pan and tilt head (P/T head) - A motorized
unit permitting vertical and horizontal positioning of a camera and lens
combination. Usually 24 V AC motors are used in such P/T heads, but also 110 VAC,
i.e., 240 VAC units can be ordered.
Pan unit - A motorized unit permitting
horizontal positioning of a camera.
Peak-to-peak (pp) - The amplitude (voltage)
difference between the most positive and the most negative excursions (peaks) of
an electrical signal.
Pedestal - In the video waveform, the signal
level corresponding to black. Also called setup.
Phot - A photometric light unit for very
strong illumination levels. One phot is equal to 10,000 luxes.
Photodiode - A type of semiconductor device
in which a PN junction diode acts as a photo sensor.
Photo-effect - Also known as
photoelectric-effect. This refers to a phenomenon of ejection of electrons from
a metal whose surface is exposed to light.
Photon - A representative of the quantum
nature of light. It is considered as the smallest unit of light.
Photopic vision - The range of light
intensities, from 105 lux down to nearly 10–2 lux, detectable by the human
Pinhole lens - A fixed focal length lens,
for viewing through a very small aperture, used in discrete surveillance
situations. The lens normally has no focusing control but offers a choice of
Phase locked loop (PLL) - A circuit
containing an oscillator whose output phase or frequency locks onto and tracks
the phase or frequency of a reference input signal. To produce the locked
condition, the circuit detects any phase difference between the two signals and
generates a correction voltage that is applied to the oscillator to adjust its
phase or frequency.
Photo multiplier - A highly light-sensitive
device. Advantages are its fast response, good signal-to-noise ratio and wide
dynamic range. Disadvantages are fragility (vacuum tube), high voltage and
sensitivity to interference.
Pixel or picture element - Derived from
picture element. Usually refers to the CCD chip unit picture cell. It consists
of a photo sensor plus its associated control gates. The smallest visual unit
that is handled in a raster file, generally a single cell in a grid of numbers
describing an image.
Plumb icon - Thermionic vacuum tube
developed by Philips, using a lead oxide photoconductive layer. It represented
the ultimate imaging device until the introduction of CCD chips.
Polarizing filter An optical filter that
transmits light in only one direction (perpendicular to the light path), out of
360° possible. The effect is such that it can eliminate some unwanted bright
areas or reflections, such as when looking through a glass window. In
photography, polarizing filters are used very often to darken a blue sky.
POTS - Plain old telephone service. The
telephone service in common use throughout the world today. Also known as PSTN.
P-picture - Prediction-coded picture. An
MPEG term to describe a picture that is coded using motion-compensated
prediction from the past reference picture.
Preset positioning A function of a pan and
tilt unit, including the zoom lens, where a number of certain viewing positions
can be stored in the system’s memory (usually this is in the PTZ site driver)
and recalled when required, either upon an alarm trigger, programmed or manual
Primary colors - A small group of colors
that, when combined, can produce a broad spectrum of other colors. In
television, red, green and blue are the primary colors from which all other
colors in the picture are derived.
Principal point - One of the two points that
each lens has along the optical axis. The principal point closer to the imaging
device (CCD chip in our case) is used as a reference point when measuring the
focal length of a lens.
PROM - Programmable read only memory. A ROM
that can be programmed by the equipment manufacturer (rather than the PROM
Protocol - A specific set of rules,
procedures or conventions relating to format and timing of data transmission
between two devices. A standard procedure that two data devices must accept and
use to be able to understand each other. The protocols for data communications
cover such things as framing, error handling, transparency and line control.
PSTN - Public switched telephone network.
Usually refers to the plain old telephone service, also known as POTS.
PTZ camera - Pan, tilt and zoom camera.
PTZ site driver (or receiver or decoder) An
electronic device, usually a part of a video matrix switcher, which receives
digital, encoded control signals in order to operate pan, tilt, zoom and focus
Pulse - A current or voltage that changes
abruptly from one value to another and back to the original value in a finite
length of time. Used to describe one particular variation in a series of wave
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QAM - Quadrature amplitude modulation.
Method for modulating two carriers. The carriers can be analog or digital.
Quad compressor (also split screen unit) -
Equipment that simultaneously displays parts or more than one image on a single
monitor. It usually refers to four quadrants display.
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Radio frequency (RF) - A term used to
describe incoming radio signals to a receiver or outgoing signals from a radio
transmitter (above 150 Hz). Even though they are not properly radio signals, TV
signals are included in this category.
RAM - Random access memory. Electronic
chips, usually known as memory, holding digital information while there is power
applied to it. Its capacity is measured in kilobytes. This is the computer’s
work area. RAID. Redundant arrays of independent disks. This a technology of
connecting a number of hard drives into one mass storage device, which can be
used, among other things, for digital recording of video images.
Random interlace - In a camera that has a
free-running horizontal sync as opposed to a 2:1 interlace type that has the
sync locked and therefore has both fields in a frame interlocked together
accurately. Registration. An adjustment associated with color sets and
projection TV’s to ensure that the electron beams of the three primary colors
of the phosphor screen are hitting the proper color dots/stripes.
Resolution - A measure of the ability of a
camera or television system to reproduce detail. The number of picture elements
that can be reproduced with good definition.
Retrace - The return of the electron beam in
a CRT to the starting point after scanning. During retrace, the beam is
typically turned off. All of the sync information is placed in this invisible
portion of the video signal. May refer to retrace after each horizontal line or
after each vertical scan (field).
Remote control - A transmitting and
receiving of signals for controlling remote devices such as pan and tilt units,
lens functions, wash and wipe control and similar.
RETMA - Former name of the EIA association.
Some older video test charts carry the name RETMA Chart.
RF signal - Radio frequency signal that
belongs to the region up to 300 GHz.
RG-11 - A video coaxial cable with 75-W
impedance and much thicker diameter than the popular RG-59 (of approximately 12
mm). With RG-11 much longer distances can be achieved (at least twice the
RG-59), but it is more expensive and harder to work with.
RG-58 - A coaxial cable designed with 50-W
impedance; therefore, not suitable for CCTV. Very similar to RG-59, only
RG-59 A type of coaxial cable that is most
common in use in small to medium-size CCTV systems. It is designed with an
impedance of 75-W. It has an outer diameter of around 6 mm and it is a good
compromise between maximum distances achievable (up to 300 m for monochrome
signal and 250 m for color) and good transmission.
Rise time - The time taken for a signal to
make a transition from one state to another; usually measured between the 10%
and 90% completion points of the transition. Shorter or faster rise times
require more bandwidth in a transmission channel.
RMS - Root Mean Square. A measure of
effective (as opposed to peak) voltage of an AC waveform. For a sine wave it is
0.707 times the peak voltage. For any periodic waveform, it is the square root
of the average of the squares of the values through one cycle.
ROM - Read only memory. An electronic chip,
containing digital information that does not disappear when power is turned off.
Routing Switcher - An electronic device that
routes a user-supplied signal (audio, video, etc.) from any input to any
user-selected output. This is a broadcast term for matrix switchers, as we know
them in CCTV. RS-125. A SMPTE parallel component digital video standard.
RS-170 - A document prepared by the
Electronics Industries Association describing recommended practices for NTSC
color television signals in the United States.
RS-232 - A format of digital communication
where only two wires are required. It is also known as a serial data
communication. The RS-232 standard defines a scheme for asynchronous
communications, but it does not define how the data should be represented by the
bits, i.e., it does not define the overall message format and protocol. It is
very often used in CCTV communications between keyboards and matrix switchers or
between matrix switchers and PTZ site drivers. The advantage of RS-232 over
others is its simplicity and use of only two wires.
RS-422 - This is an advanced format of
digital communication when compared to RS-232. The basic difference is in the
need for four wires instead of two as the communications is not single-ended as
with RS-232, but differential. In simple terms, the signal transmitted is read
at the receiving end as the difference between the two wires without common
earth. So if there is noise induced along the line, it will be cancelled out.
The RS-422 can drive lines of over a kilometer in length and distribute data to
up to 10 receivers.
RS-485 - This is an advanced format of
digital communications compared to RS-422. The major improvement is in the
number of receivers that can be driven with this format, and this is up to 32.
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Saturation (in color) - The intensity of the
colors in the active picture. The degree by which the eye perceives a color as
departing from a gray or white scale of the same brightness. A 100% saturated
color does not contain any white; adding white reduces saturation. In NTSC and
PAL video signals, the color saturation at any particular instant in the picture
is conveyed by the corresponding instantaneous amplitude of the active video
Scanning - The rapid movement of the
electron beam in the CRT of a monitor or television receiver. It is formatted
line- for-line across the photo-sensitive surface to produce or reproduce the
video picture. When referred to a PTZ camera, it is the panning or the
horizontal camera motion.
Scanner - When referring to a CCTV device it
is the pan only head, when referring to an imaging device it is the device with
CCD chip that scans documents and images.
Scene illumination - The average light level
incident upon a protected area. Normally measured for the visible spectrum with
a light meter having a spectral response corresponding closely to that of the
human eye and is quoted in lux.
Scotopic vision - Illumination levels below
10–2 lux, thus invisible to the human eye. SCSI. Small computer systems
interface. A computer standard that defines the software and hardware methods of
connecting more external devices to a computer bus.
SECAM - Sequential Couleur Avec Memoire,
sequential color with memory. A color television system with 625 lines per frame
(used to be 819) and 50 fields per second developed by France and the former
U.S.S.R. Color difference information is transmitted sequentially on alternate
lines as an FM signal.
Serial data - Time-sequential transmission
of data along a single wire. In CCTV, the most common method of communicating
between keyboards and the matrix switcher and also controlling PTZ cameras.
Serial interface. A digital communications interface in which data are
transmitted and received sequentially along a single wire or pair of wires.
Common serial interface standards are RS-232 and RS-422.
Serial port - A computer I/O (input/output)
port through which the computer communicates with the external world. The
standard serial port is RS-232 based and allows bidirectional communication on a
relatively simple wire connection as data flow serially.
Sidebands - The frequency bands on both
sides of a carrier within which the energy produced by the process of modulation
Signal-to-Noise ratio (S/N) - A S/N ratio
can be given for the luminance signal, chrominance signal and audio signal. The
S/N ratio is the ratio of noise to actual total signal, and it shows how much
higher the signal level is than the level of noise. It is expressed in decibels
(dB), and the bigger the value is, the crisper and clearer the picture and sound
will be during playback. An S/N ratio is calculated with the logarithm of the
normal signal and the noise RMS value.
Silicon - The material of which modern
semiconductor devices are made. Simplex. In general, it refers to a
communications system that can transmit information in one direction only. In
CCTV, simplex is used to describe a method of multiplexer operation where only
one function can be performed at a time, e.g., either recording or playback
Single-mode fiber - An optical glass fiber
that consists of a core of very small diameter. A typical single-mode fiber used
in CCTV has a 9 mm core and a 125 mm outer diameter. Single-mode fiber has less
attenuation and therefore transmits signals at longer distances (up to 70 km).
Such fibers are normally used only with laser sources because of their very
small acceptance cone.
Skin effect - The tendency of alternating
current to travel only on the surface of a conductor as its frequency increases.
Slow scan - The transmission of a series of
frozen images by means of analog or digital signals over limited bandwidth
media, usually telephone.
Smear - An unwanted side effect of vertical
charge transfer in a CCD chip. It shows vertical bright stripes in places of the
image where there are very bright areas. In better cameras smear is minimized to
almost undetectable levels.
SMPTE - Society of Motion Picture and
SMPTE time code - In video editing, time
code that conforms to SMPTE standards. It consists of an 8-digit number
specifying hours: minutes: seconds: frames. Each number identifies one frame on
a videotape. SMPTE time code may be of either the drop-frame or non-drop- frame
Snow - Random noise on the display screen,
often resulting from dirty heads or weak broadcast video reception.
S/N ratio - See Signal-to-noise ratio.
Spectrum - In electromagnetism , spectrum
refers to the description of a signal’s amplitude versus its frequency
components. In optics, spectrum refers to the light frequencies composing the
white light which can be seen as rainbow colors.
Spectrum analyzer - An electronic device
that can show the spectrum of an electric signal. SPG. Sync pulse generator. A
source of synchronization pulses.
Split-screen unit (quad compressor) -
Equipment that simultaneously displays parts or more than one image on a single
monitor. It usually refers to four quadrants’ display.
Staircase (in television) - Same as color
bars. A pattern generated by the TV generator, consisting of equal width
luminance steps of 0, +20, +40, +60, +80, and +100 IRE units and a constant
amplitude chroma signal at color burst phase. Chroma amplitude is selectable at
20 IRE units (low stairs) or 40 IRE units (high stairs). The staircase pattern
is useful for checking linearity of luminance and chroma gain, differential gain
and differential phase. Start bit. A bit preceding the group of bits
representing a character used to signal the arrival of the character in
Sub-carrier (SC) - Also known as SC: 3.58
MHz for NTSC, 4.43 MHz for PAL. These are the basic signals in all NTSC and PAL
sync signals. It is a continuous sine wave, usually generated and distributed at
2V in amplitude, and having a frequency of 3.579545 MHz (NTSC) and 4.43361875
MHz (PAL). Sub-carrier is usually divided down from a primary crystal running at
14.318180 MHz, for example, in NTSC, and that divided by 4 is 3.579545. Similar
with PAL. All other synchronizing signals are directly divided down from
S-VHS - Super VHS format in video recording.
A newer standard proposed by JVC, preserving the downwards compatibility with
the VHS format. It offers much better horizontal resolution up to 400 TV lines.
This is mainly due to the color separation techniques, high-quality video heads
and better tapes. S-VHS is usually associated with Y/C separated signals.
Sync - Short for synchronization pulse.
Sync generator (sync pulse generator, SPG) -
Device that generates synchronizing pulses needed by video source equipment to
provide proper equipment video signal timing. Pulses typically produced by a
sync generator could be sub-carrier, burst flag, sync, blanking, H and V drives
and color black. Most commonly used in CCTV are H and V drives.
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T1 - A digital transmission link with a
capacity of 1.544 Mbps. T1 uses two pairs of normal twisted wires. T1 lines are
used for connecting networks across remote distances. Bridges and routers are
used to connect LANs overT1 networks.
T1 channels - In North America, a digital
transmission channel carrying data at a rate of 1.544 million bits per second.
In Europe, a digital transmission channel carrying data at a rate of 2.048
million bits per second. AT&T term for a digital carrier facility used to
transmit a DS-1 formatted digital signal at 1.544 Mbps.
T3 channels - In North America, a digital
channel that communicates at 45.304 Mbps commonly referred to by its service
designation of DS-3.
TBC - Time base correction. Synchronization
of various signals inside a device such as a multiplexer or a time base
TDG - Time and date generator.
TDM - Time division multiplex. A
time-sharing of a transmission channel by assigning each user a dedicated
segment of each transmission cycle.
Tearing - A lateral displacement of the
video lines due to sync instability. It appears as though parts of the images
have been torn away.
Teleconferencing - Electronically linked
meeting conducted among groups in separate geographic locations.
Telemetry - Remote controlling system of,
usually, digital encoded data, intended to control pan, tilt, zoom, focus,
preset positions, wash, wipe and similar. Being digital, it is usually sent via
twisted pair cable or coaxial cable together with the video signal.
Termination - This usually refers to the
physical act of terminating a cable with a special connector, which for coaxial
cable is usually BNC. For fiber optic cable this is the ST connector. It can
also refer to the impedance matching when electrical transmission is in use.
This is especially important for high frequency signals, such as the video
signal, where the characteristic impedance is accepted to be 75-W.
TFT - Thin-film-transistor. This technology
is used mainly for manufacturing flat computer and video screens that are
superior to the classic LCD screens. Color quality, fast response time and
resolution are excellent for video.
Time lapse VCR (TL VCR) - A video recorder,
most often in VHS format, that can prolong the video recording on a single tape
up to 960 hours (this refers to a 180 min tape). This type of VCR is often used
in CCTV systems. The principle of operation is very simple – instead of having
the video tape travel at a constant speed of 2.275 cm/s (which is the case with
the domestic models of VHS VCRs), it moves with discrete steps that can be
controlled. Time Lapse VCRs have a number of other special functions very useful
in CCTV, such as external alarm trigger, time and date superimposed on the video
signal, alarm search and so on.
Time lapse video recording - The
intermittent recording of video signals at intervals to extend the recording
time of the recording medium. It is usually measured in reference to a 3-hr
(180-min) tape. Time multiplexing. The technique of recording several cameras
onto one time lapse VCR by sequentially sending camera pictures with a timed
interval delay to match the time lapse mode selected on the recorder.
T-pulse to bar - A term relating to
frequency response of video equipment. A video signal containing equal amplitude
T- pulse and bar portions is passed through the equipment and the relative
amplitudes of the T-pulse and bar are measured at the output. A loss of response
is indicated when one portion of the signal is lower in amplitude than the
Tracking - The angle and speed at which the
tape passes the video heads.
Transcoder - A device that converts one form
of encoded video to another, e.g., to convert NTSC video to PAL. Sometimes
mistakenly used to mean translator.
Transducer - A device that converts one form
of energy into another. For example, in fiber optics, a device that converts
light signals into electrical signals.
Translator - A device used to convert one
component set to another, e.g., to convert Y, R-Y, B-Y signals to RGB signals.
Transponder - The electronics of a satellite
that receives an up linked signal from the earth, amplifies it, converts it to a
different frequency and returns it to the earth.
TTL - Transistor-transistor logic. A term
used in digital electronics mainly to describe the ability of a device or
circuit to be connected directly to the input or output of digital equipment.
Such compatibility eliminates the need for interfacing circuitry. TTL signals
are usually limited to two states, low and high, and are thus much more limited
than analog signals. Thru-the-lens viewing or color measuring.
Twisted-pair - A cable composed of two small
insulated conductors twisted together. Since both wires have nearly equal
exposure to any interference, the differential noise is slight.
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UHF signal - Ultra high frequency signal. In
television it is defined to belong in the radio spectrum between 470 MHz and 850
Unbalanced signal - In CCTV, this refers to
a type of video signal transmission through a coaxial cable. It is called
unbalanced because the signal travels through the center core only, while the
cable shield is used for equating the two voltage potentials between the coaxial
Under scan - Decreases raster size H and V
so that all four edges of the picture are visible on the monitor.
UPS - Uninterruptible power supply. These
are power supplies used in the majority of high security systems, whose purpose
is to back-up the system for at least 10 minutes without mains power. The
duration of this depends on the size of the UPS, usually expressed in VA, and
the current consumption of the system itself.
UTP - Unshielded twisted pair. A cable
medium with one or more pairs of twisted insulated copper conductors bound in a
single sheath. Now the most common method of bringing telephone and data to the
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Variable bit rate - Operation where the bit
rate varies with time during the decoding of a compressed bit stream.
VDA - See video distribution amplifier.
Vector scope - An instrument similar to an
oscilloscope, that is used to check and/or align amplitude and phase of the
three color signals (RGB).
Velocity of propagation - Speed of signal
transmission. In free space, electromagnetic waves travel at the speed of light.
In coaxial cables, this speed is reduced by the dielectric material. Commonly
expressed as percentage of the speed in free space.
Vertical interval - The portion of the video
signal that occurs between the end of one field and the beginning of the next.
During this time, the electron beams in the monitors are turned off (invisible)
so that they can return from the bottom of the screen to the top to begin
Vertical interval switcher - A sequential or
matrix switcher that switches from one camera to another exactly in the vertical
interval, thus producing roll-free switching. This is possible only if the
various camera sources are synchronized.
Vertical resolution - Chrominance and
luminance detail expressed vertically in the picture tube. Limited by the number
of scan lines.
Vertical retrace - The return of the
electron beam to the top of a television picture tube screen or a camera pickup
device target at the completion of the field scan.
Vertical shift register - The mechanism in
CCD technology whereby charge is read out from the photo sensors of an interline
transfer or frame interline transfer sensor.
Vertical sync pulse - A portion of the
vertical blanking interval which is made up of blanking level. Synchronizes
vertical scan of television receiver to composite video signal. Starts each
frame at same vertical position.
Vestigial sideband transmission - A system
of transmission wherein the sideband on one side of the carrier is transmitted
only in part.
VGA - Video graphics array.
Video bandwidth - The highest signal
frequency that a specific video signal can reach. The higher the video
bandwidth, the better the quality of the picture. A video recorder that can
produce a very broad video bandwidth generates a very detailed, high quality
picture on the screen. Video bandwidths used in studio work vary between 3 and
Video distribution amplifier (VDA) - A
special amplifier for strengthening the video signal so that it can be supplied
to a number of video monitors at the same time.
Video gain - The range of light-to-dark
values of the image that is proportional to the voltage difference between the
black and white voltage levels of the video signal. Expressed on the waveform
monitor by the voltage level of the whitest whites in the active picture signal.
Video gain is related to the contrast of the video image.
Video equalization corrector (video equalizer)
- A device that corrects for unequal frequency losses and/or phase errors in the
transmission of a video signal.
Video frame store - A device that enables
digital storage of one or more images for steady display on a video monitor.
Video in-line amplifier - A device providing
amplification of a video signal. Video matrix switcher (VMS). A device for
switching more than one camera, VCR, video printer and similar to more than one
monitor, VCR, video printer and similar. Much more complex and more powerful
than video switchers.
Video monitor - A device for converting a
video signal into an image.
Video printer - A device for converting a
video signal to a hard copy printout. It could be a monochrome (B/W) or color.
They come in different format sizes. Special paper is needed.
Video signal - An electrical signal
containing all of the elements of the image produced by a camera or any other
source of video information.
Video switcher - A device for switching more
than one camera to one or more monitors manually, automatically or upon receipt
of an alarm condition.
VITS - Video insertion test signals.
Specially shaped electronic signals inserted in the invisible lines (in the case
of PAL, lines 17, 18, 330 and 331) that determine the quality of reception.
Video wall - A video wall is a large screen
made up of several monitors placed close to one another, so when viewed from a
distance, they form a large video screen or wall.
VOD - Video on Demand. A service that allows
users to view whatever program they want whenever they want it with VCR-like
control capability such as pause, fast forward and rewind.
VHF - Very high frequency. A signal
encompassing frequencies between 30 and 300 MHz. In television, VHF band I uses
frequencies between 45 MHz and 67 MHz, and between 180 MHz and 215 MHz for Band
III. Band II is reserved for FM radio from 88 MHz to 108 MHz.
VHS - Video home system. As proposed by JVC,
a video recording format used most often in homes but also in CCTV. Its
limitations include the speed of recording, the magnetic tapes used and the
color separation technique. Most of the CCTV equipment today supersedes VHS
VLF - Very low frequency. Refers to the
frequencies in the band between 10 and 30 kHz. VMD. Video motion detector. A
detection device generating an alarm condition in response to a change in the
video signal, usually motion, but it can also be change in light. Very practical
in CCTV as the VMD analyzes exactly what the camera sees, i.e., there are no
VR - Virtual Reality. Computer-generated
images and audio that are experienced through high-tech display and sensor
systems and whose imagery is under the control of a viewer.
VS - Vertical sync.
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WAN - Wide area network.
Waveform monitor - Oscilloscope used to
display the video waveform. Wavelet. A particular type of video compression that
is especially suitable for CCTV. Offers higher compression ratio with equal or
better quality to JPEG.
White balance - An electronic process used
in video cameras to retain true colors. It is performed electronically on the
basis of a white object in the picture.
White level - This part of the video signal
electronically represents the white part of an image. It resides at 0.7 V from
the blanking level, whereas the black part is taken as 0 V.
Wow and flutter - Wow refers to low
frequency variations in pitch while flutter refers to high-frequency variations
in pitch caused by variations in the tape-to-head speed of a tape machine.
W-VHS - A new wide-VHS standard proposed by
JVC, featuring a high resolution format and an aspect ratio of 16:9.
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Y/C - A video format found in Super-VHS
video recorders. Luminance is marked with Y and is produced separate to the C,
which stands for chrominance. Thus, an S-VHS output Y/C requires two coaxial
cables for a perfect output.
Y, R-Y, B-Y - The general set of component
video signals used in the PAL system as well as for some encoder and most
decoder applications in NTSC systems; Y is the luminance signal, R-Y is the
first color difference signal and B-Y is the second color difference signal.
Y, U, V - Luminance and color difference
components for PAL systems; Y, B-Y, R-Y with new names; the derivation from RGB
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Z - In electronics and television this is
usually a code for impedance. Zoom lens. A camera lens that can vary the focal
length while keeping the object in focus, giving an impression of coming closer
to or going away from an object. It is usually controlled by a keyboard with
buttons that are marked zoom-in and zoom-out.
Zoom ratio - A mathematical expression of
the two extremes of focal length available on a particular zoom lens.
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