CCTV Glossary - Common terms used in CCTV
A
Aberration: A term from optics that refers to anything affecting the fidelity of the image in
regards to the original scene
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 (or AD): Refers to analog to digital conversion
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 regulated 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 date 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 form one or two
characters to full-screen alphanumeric text. Such generators us 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.
Amplitude: The maximum value of a varying waveform.
Analog signal: Representation of data by continuously varying quantities. An analog electrical
signal has a different value if volts or amperes for electrical representation of the original
excitement (sound, light) within the dynamic range of the system.
ANSI: American National Standards Institute.
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 device.
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 disk, magnetic tape, floppy disk or DAT cartridge
.
Artifacts: Undesirable elements of 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 uppercase and lowercase 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 ration 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 an aspherical 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 blue 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 illumination.
AWG: American wire gauge. A wire diameter specification based on the American Standard. The
smaller the AWG number, the larger the wire diameter (see the reference table in the camera power
supply section).
B
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 buffer stage.
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 without aliasing.
Baseband: 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 the baseband.
Baud: Date 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 another.
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 2 digits 0 and 1 (as opposed to ten digits [0-9] in the
decimal system). In computer systems, the binary digits are represented by 2 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 state.
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 32.
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 if bandwidth, bit rate
is measured in bits per second. It is used to express the rate at which the compressed bitstream is
transmitted. The higher the bit rate, the more information that can be carried.
Blackburst (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 level.
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 sync level.
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 information.
Blooming: The defocusing of regions of a picture where brightness is excessive.
BNC: BNC stands for Bayonet-Neil-Concelman 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: Bidirectionally predictive coded picture; an MPEG term for a picture that is coded on
CCTV broadcast TV for transmitting a basic bandwidth video signal over a coaxial cable.
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 and ones).
C
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 1970’s, 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: Committee Consultatif International des Radiocommunique 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 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 6.75 MHz for the
chrominance channels with eight-bit digitizing for each channel. These sample frequencies were
chosen because they work for both 525-line 60 Hz and 625-line 50 Hz component video systems.
The term 4:2:2 refers to the ration 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 D1 digital videotape format conforms to ITU 601.
CCIR656: 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 pinouts, as well as the blanking, sync and multiplexing
schemes used in both parallel and serial interfaces.
CCTV: Close circuit television. A television system intended for only a limited number of viewers, as
opposed to broadcast TV.
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 from 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 disc 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
reduces 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 material.
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 decoder
circuits.
Chroma gain (chroma, color, saturation): In video, the gain of an amplifier as it pertains to
the intensity if colors in the active picture
.
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 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 color saturation levels.
CIE: Commission Internationale de l’Eclairage. 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 if 1” (2.54
mm) in diameter and 32 threads/inch, and the back flange-to-CCD distance of 17.526mm (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 required.
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. CODECs 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 2 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 resaved 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 so that on each
consecutive line, sub-carrier phase is changed 180 degrees with respect to the sync pulses. In the
PAL system, color sub carrier phase moves 90 degrees every frame. In NTSC this creates four
different filed 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 correct.
Color sub-carrier: The 3.58 MHz signal that carries color information. This signal is superimposed
on the luminance level. Amplitude of the color sub-carrier represents saturation and phase angle
represents hue.
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. 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 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 Oscilloscope)
Crosstalk: A type of interference of 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 12.5mm in order to have the lenses made
smaller, more compact and less expensive. CS-mount lenses can only be used on CS-mount
cameras.
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 tread 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.
D
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 in 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
transform (FDCT) or inverse discrete cosine transform (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 filed 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) material.
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: The change in the sub-carrier phase of a video signal caused by a change inn
the luminance level of the signal. The hue of colors in a scene change with the brightness of the
scene.
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 signal.
DIN: Deutsche Industrie-Normen. Germany’s standard.
Disk: A flat circular plate, coated with a magnetic material, on which data may be sorted by
selective magnetization of portions of the surface. May be a flexible floppy disk or rigid hard disk. It
could also be a plastic compact disc (CD) or digital video disk (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
devise 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 0.3mm.
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 digital signals.
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 (66x48x12mm) 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.
E
EBU: European Broadcasting Union.
EIA: Electronics Industry Association, which has recommended the television standard used in the
U.S., 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 brand.
Ethernet: A local area network used for connecting computers. Printer, 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.
F
FCC: Federal Communications Commission (U.S.).
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 electric isolation and resistance of electrostatic and
electromagnetic interference.
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 functions.
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 screen such as computer-generated text transferred to
video. Poor digital image treatment, found in low-quality system converts (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
cameras to be sharply defined.
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 files) 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 framestores.
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 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.
G
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
distortions.
Gen-lock: A way o locking the video signal of a camera to an external generator of
synchronization pulses.
GHz: GigaHertz. One billion cycles per second.
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 tomes 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 the 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.
H
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.
HDTV: High definition digital television. The upcoming standard of broadcast television with
extremely high resolution and aspect ratio of 16:9. It is an advancement from the analog high
definition, already used experimentally in Japan and Europe. The picture resolution is nearly 2000 x
1000 pixels, and uses the MPEG-2 standard.
Headend: The electronic equipment located at the start of a cable television system, usually
including antennas, earth stations, preamplifiers, frequency converters, demodulators, modulators
and related equipment.
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 star a new line.
Horizontal sync pulse: The synchronizing pulse at the end of each video line that determines the
start of horizontal retrace.
Hertz: An 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 videosub-carrier.
Hum: A term used to describe an unwanted induction of mains frequency.
Hum bug: Another name for a ground loop corrector.
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.
I
IDE: Interface device electronics. Software and hardware communication standard for
interconnecting peripheral devices to a computer.
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 is applied.
I²R: Formula for power in watts (W), where I is current in amperes (A), R is resistance in ohms (?).
IEC: International Electrotechnical 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 imagem can
be created.
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, ?.
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 televisions fields in order to produce a full
frame. The two fields are composed of only odd and 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 flickerless motion.
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 kbps 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 required.
ISO: International Standardization Organization.
ITU: International Telecommunications Union (also UIT)
J
JPEG: Joint Photographic Experts Group. A group that has recommended a compresiion algorithm
for still digital images that can compress with ratios of over 10:1. Also the name of the format itself.
K
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 Celcius, but the 0°K starts from -273°C. Also the unit of measurement of the temperature of
light is expressed in Kelvins 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 picture degradation.
kHz: Kilohertz. Thousand Hertz.
Kilobaud: A unit of measurement of data transmission speed equaling 1000 baud.
Kilobyte: 1024 bytes.
L
Lambertian source or surface: A surface is called a Lambert radiator or reflector (depending
whether the surface is a primary or 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 single frequency.
LED: Light emitting diode. A semiconductor that produces light when a certain low voltage is applied
to it in one direction.
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.
Link-locked: In CCTV, this usually refers to multiple cameras being powered by a common
alternative current (AC) source (either 24 VAC, 110 VAC, or 240 VAC) and consequently have field
frequencies locked to the same AC source frequency (50 Hz in CCIR systems and 60 Hz in EIA
systems).
Lumen [Im]: 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
nonmeasurable 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 or
metre-candelas.
M
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 and standards.
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 switchers.
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 x 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: Mega hertz. 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 (chrominance).
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 3.5Mbps.
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 HDTV and DVD standard of video/audio encoding.
N
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.
Noninterlaced: 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 U.S, 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.
O
O/P: Output
Objective: The very first optical element at the front of the lens.
Ocular: The very last element at the back of the 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.
Overscan: 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 zero.
P
PAL: Phase alternating line. Describes the color phase change in 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 VAC motors are used in such P/T heads, nut 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 a 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 photosensor.
Photo-effect: Also known as photoelectric-effect. This refers to a phenomena 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 smalles unit of
light.
Photopic vision: The range of light intensities, from 105 lux down to nearly 10¯²lux, detectable
by the human eye.
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 iris functions.
Pixel: Derived from picture element. Usually refers to the CCD chip unit picture cell. It consists of a
photosensor plus its associated control gates.
Phase-locked loop (PLL): A circuit containing as 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: The smallest visual unit that is handled in a raster file, generally a
single cell in a grid of numbers describing an image.
Plumbicon: Thermionic vacuum tube developed by Phillips, 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 encoded 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 recall.
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 that the PROM manufacturer).
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 protocol 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 functions.
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
motions.
Q
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.
R
Radio frequency (RF): A term used to describe incoming radio signals to a receiver or outgoing
signals from a radio transmitter (above 150Hz). Even though they are not properly radio signals, TV
signals are included in this category.
RAID: Redundant arrays memory. This 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.
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.
Random interlace: In a camera, 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 TVs to ensure that the
electron beams of the threes 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 e