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ALC.(Automatic Level Control): On Al lenses, also known as the peak/aversage control. Adjusting this control
allows the auto iris circuity to either take bright spots more into
consideration (peak), bringing out detail in
bright areas, or less into consideration (average) bringing out detail in
shadows.
Activity Detection: A feature of the Generation 3 video multiplexer range that uses video motion
detection techniques to improve the camera update times. It also gives a relay
closure.
Alarming: The ability of CCTV equipment to respond to an input signal, normally a simple
switch closure.
The response varies depending on equipment type, most common is for switcher
to 'hold' on the camera corresponding to the alarm input.
Analog: A single in which any level is represented by a directly proportional voltage;
not digital.
Angle of View: The maximum scene angle that can be seen through a lens.
Aperture: The lens opening that controls the amount of light reaching the pickup device
(image).
In television optics, it is the effective diameter of the lens that controls
the amount of light reaching the photoconductive or photoemitting image pickup
sensor
Aspect Ratio: The ratio of the picture frame width to the picture frame heght in standard TV
systems.
It is 4 units horizontal over 3 units vertical.
Aspherical Lens: A Lens designed with a non spherical shape so that it refracts the light passing
through it to either lower the lens aperture so that it passes more light or
decreases barrel distortion on
wide angle lenses.
Attenuation: In general terms, a reduction in signal strength.
A decrease or loss in a signal. Reduction of signal magnitude (loss) normally
measured in decibels.
Auto White Balance: Feature on color cameras whereby the camera constantly monitors the light and
adjusts its color to maintain white areas.
Automatic Frequency Control(AFC): An electronic circcuit used whereby the frequency of an oscillator is
automatically maintained within specified limits.
Automatic Gain Control(AGC): An electronic circcuit used by which the gain of a signal is automatically
adjusted as a function of its input or other specified parameter.
Automatic Iris Lens: A lens in which the aperture automatically opens or closes to maintain proper
light levels on the camera's pickup device.
Auto-Terminating: Feature whereby the equipment automatically selects the correct termination
depending on whether
the video output BNC is connected.
AGC: Automatic Gain Control.
A circuit for automatically controlling amplifier gain in order to maintain a
constant output voltage with a varying input voltage within a predetermined
range of input-to-output variation.
Aperture Correction: Compensation for the loss in sharpness of detail because of the finite
dimensions of the image elements or the dot-pitch of the monitor.
Auto Balance: A system for detecting errors in color balance in white and black areas of the
picture and automatically adjusting the white and black levels of both the red
and blue signals as needed for correction.
Auto Light Range: The range of light, e.g., sunlight to moonlight, over which a TV camera is
capable of automatically operating at specified output.
Automatic Brightness Control: In display devices, the self-acting mechanism which controls brightness of the
device as a function of ambient light.
Automatic Light Control: The process by which the illumination incident upon the face of a pickup device
is automatically adjusted as a function of scene brightness.
Aberration: A term from optics that refers to anything affecting the accuracy of the image
when compared with the original scene.
AC: Alternating Current.
AC/DC: Usually applied where a power supply can be either Alternating Current or
Direct Current.
A/D (AD): Usually refers to analog to digital conversion.
AIT: Advanced Intelligent Tape (AIT) a type of tape drive sometimes used for storage
of digital video images.
ASCII: American Standard Code for Information Interchange. A 128-character set
thatincludes 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.
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.
AWG: American Wire Gauge. A wire diameter specification based on the American
standard.
The smaller the AWG number, the larger the wire diameter. Alternatively :- the
measure of the diameter of a conductor. AWG is the U.S. standard measuring
gauge for certain conductors, including copper. The higher the AWG number the
thinner the wire. This measure stems from the fact that the original
measurement represented the number of times the wire was run through a wire
machine which thus reduced the diameter of the wire. Thus a 24-guage wire
was thinner than an 18-guage wire because it was run through a wire machine 6
more times than the 18-guage wire, reducing the overall diameter.
ANSI: American National Standards Institute
ADSL: Asymmetric Digital Subscriber Line: Modems attached to twisted pair copper
wiring that transmit up to 8 Mbps downstream (to the subscriber) and up to
1Mbps upstream (from the subscriber), depending on line distance, loop plant
condition, electrical noise, and technology and implementation options. It is
known as Asymmetric because of the different data rates upstream and down
stream.
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, CDROM or DVD.
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.
ATW: Automatically adjusts the white balance in response to varying light conditions.
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, positive logic uses a positive voltage
to represent binary 1 and zero volts to represent binary 0.
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. In computer terms, a group of 4 bits is a nibble, 8 bits is a
byte and 16 bits a word.
Bitmap (BMP): A pixel-by-pixel description of an image. Each pixel is a separate element.
Also a computer file format for pictures.
Burst (colour burst or chroma burst): Ten cycles (PAL) or seven to nine cycles (NTSC) of sub-carrier placed near the
end of horizontal blanking to serve as the phase (colour) reference
for the modulated colour sub-carrier. It enables the monitors' Phase Locked
Loop to synchronize and track the change of phase during every line of video.
Byte: Byte is 8 binary bits (ones and zeroes).

The greater multiples of bytes are shown below
Kilobyte (1,024 bytes)
Megabyte (1,024 kilobytes, 10488576)
Gigabyte (1,024 Megabytes 1073741824 bytes)
Terabyte (1,024 Gigabytes 1099511627776 bytes)
Petabyte (1,024 Terabytes 1125899906842624 bytes)
Exabyte (1,024 Petabytes 1152921504606846976 bytes)
Zettabyte (1,024 Exabytes 1180591620717411303424 bytes)
Yottabyte (1,024 Zettabytes 1208925819614629174706176 bytes)
Back Porch: That portion of the composite picture signal which lies between the trailing
edge of the horizontal sync pulse and the trailing edge of the corresponding
blanking pulse.
Bar Test Pattern: Special test pattern for adjusting color TV receivers or color encoders. The
upper portion consists of vertical bars of saturated colors and white. The
power horizontal bars have black and white areas and I and Q signals.
Bounce: Sudden variations in picture presentation (brightness, size, etc.,) independent
of scene illumination
Brightness: The attribute of visual perception in accordance with which an area appear to
emit more of less light. (Luminance is the recommended name for the photo-
electric quantity which has also been called brightness.)
B.L.C.(Back Light Compensation): A feature of modurn CCD cameras which electronically compensates for high
background lighting to give detail which would normally be silhouetted.
Back Focus: The mechanical alifning of the imaging device with the focal point of the lens.
Most important on zoom lenses to ensure the image stays in focus throughout the
zoom range.
Balanced Signal: Method of transmitting video, usually over twisted pair cable, that consists of
two equal but opposite
signals being sent down two conductors.
Band Width: The frequency range of a signal. The span that the infomation-bearing signal
occupies or requires or the
difference between the lowest and highest frequency of a band.
Base-Band: Video Unmodulated video signal suitable for display on a monitor but not a
domestic TV.
Black Level: The level of the video signal that corresponds to the maximum limits of the
black areas of the picture.
Blanking (Field And Line Flyback Blanking): The operation of turning off the monitor display, or pick-up device, during
sync pluses to avoid thin white lines appearing on the picture.
Blooming: The halation and defocusing effect that occurs around the bright areas of the
picture (highlight)
whenever there is an increase in the brightness intensity.
BNC: Video connector, the most commonly used in CCTV.
Bridging: A term indicating that a high impedance video line is paralleled, usually
through a switch, to a source of
video. A separate overall video output.
C Mount/CS Mount: The two industry standards for mounting a lens on a camera. The C-Mount lens
has a 17.5mm flange
back distance. The CS-Mount lens has a 12.5mm flange back distance.
C.C.I.R.: The European TV standards 625 lines 50 fields.
Camera: A device that translates light into a video image and transmits that image to a
monitor for viewing.
It contains the image sensor and other electronic circuitry to create a video
signal.
Cathode Ray Tube (CRT): The picture tube in a video monitor that can reproduce the picture image seen
by the camera.
CATV: Short for Cable Access Television. The method for distributing RF signals via
coaxial cable rather than
radiated through the air.
CCD: Charged Coupled Device. This is a soild state semiconductor imaging device
often referred to as an
integrated circuit, chip or "image." Soild state cameras are sometimes referred
to as CCD cameras.
bright areas, or less into consideration (average) bringing out detail in
shadows.
CCTV: The common abbreviation for Closed Circuit Television. A private or closed
television system.
Chrominance (C): The part of the video signal corresponding to the color information.
Coaxial Cable: A type of shielded cable capable of carrying a wide range of frequencies (video
or radio) with very low
signal loss.
Contrast: The range of light and dark values in a picture or the radio between the
maximum and the minimum
brightness values.
Crosstalk: An undesired signal that interferes with the desired signal.
Chroma: That quality of color which embraces both hue and saturation. White, black, and
grays have no chroma.
Chroma Control: A control of color television receiver that regulates the saturation
(vividness) of colors in a color picture.
Clamp: A device which functions during the horizontal blanking or synchronizing
interval to fix the level of the picture signal at some predetermined reference
level at the beginning of each scanning line.
Color Burst: That portion of the composite color signal, comprising a few cycles of a sine
wave of chrominance subcarrier frequency, which is used to establish a
reference for demodulating the chrominance signal. Normally approximately 9
cycles of 3.579545 MHz.
Color Encoder: A device which produces an NTSC color signal from separate R, G, and B video
inputs.
Color Saturation: The degree to which a color is free of white light.
Composite Video Signal: The combined picture signal, including vertical and horizontal blanking and
synchronizing signals.
Compression: The reduction in gain at one level of a picture signal with respect to the gain
at another level of the same signal.
Convergence: The crossover of the three electron beams of a three-gun tri-color picture
tube. This normally occurs at the plane of the aperture mask.
CD: Compact Disc. A standard of media as proposed by Philips and Sony, where music
is stored in digital form.
DD: Direct Drive.
A method of controlling one form of auto iris lens (the other is video iris),
where the electronic has been removed from the lens and is built into the
camera. To use a DD lens with a camera, the camera must have a DD output.
DAT: 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 have led to a system for archiving digitized video
signals.
Decoder: The circuitry in a color TV receiver which transforms the detected color
signals into a form suitable to operate the color tube.
Definition: The fidelity of a television system to the original scene.
Depth of Focus: The range of sensor-to-lens distance for which the image formed by the lens is
clearly focused.
Digital Signal Processing ( DSP ): An algorithm within the camera that digitizes data (the image). Examples
include automatic compensate for backlight interference, color balance
variations and corrections related to aging of electrical components or
lighting. Functions such as electronic pan and zoom, image annotation,
compression of the video for network transmission, feature extraction and
motion compensation can be easily and inexpensively added to the camera feature
set.
Distortion: The deviation of the received signal waveform from that of the original
transmitted waveform.
Dynamic Range: The difference between the maximum acceptable signal level and the minimum
acceptable signal level.
dB ( Decibel ): A measure of the power radio of two signals. It is equal to ten times the
logarithm of the radio of the two
signals.
DC Type Lens: An auto-iris lens with internal circuit which receives voltage and a video
signal from the camera to adjust the
iris.
Depth of Field: The area in focus in front of and behind the subject.
Digital: A signal that levels are represented by binary numbers. These can be kept in a
store.
Digital Recording: This is the latest form of recording and is relatively new to the CCTV industry
as a result is not the most
economical method however it does have serveral advantages over the VCR
analogue tape recorders. First
of all it enables quick access to the desired image or picture. Digital images
can also be enhanced or
processed futher which can help detect images that may normally go unnoticed.
One of the better properties
of Digital Recording is that there is no replay degradation due to poor tape
quality and unlike conventional
video recording methods Digital Recording provides a clear image when paused.
Distribution: Amplifier A device that accepts a video signal and sends it out over a number
of independent outputs.
Duplex (Multiplexer): A multiplexer with two frame stores allowing it to show multi-screen pictures
while performing time multiplex recording.
Dwell Time: The length of time a switcher displays one camera before sequencing to the
next. Usually a variable selting.
E.I.(Electronic Iris) Shutter: Electronic Iris shuttering is the ability of the camera to compensate for
moderate light changes in indoor
applications without the use of auto iris linses.
EIA.(Electronic Industry Association): US TV standard 525 lines 60 fields.
Equalization: The process of correcting losses of certain components in a signal.
Ext. Sync(External Sync): The ability of CCTV equipment, normally cameras, to accept one or more of the
standard sync formats so as
to align itself to the rest of the system.
EPROM: Erasable and Programmable Read Only Memory. An electronic chip used in many
different security products that stores software instructions for performing
various operations.
Focal Point: The point at which a lens or mirror will focus parallel incident radiation.
Footlambert (FL): A unit of luminance equal to 1/candela per square foot or to the uniform
luminance at a perfectly diffusing surface emitting or reflecting light at the
rate of one lumen per square foot. A lumen per square foot is a unit of
incident light and a footlambert is a unit of emitted or reflected light. For a
perfectly reflecting and perfectly diffusing surface, the number of lumens per
square foot is equal to the number of footlamberts.
Frame Frequency: The number of times per second that the frame is scanned. The U.S. standard is
30 frames per second.
Field: One half of a frame of video (262.5 scan lines).
Fiber Optic: The process of transmitting light throhgh a long, flexible fiber such as glass
or plastic, for the purpose of transmitting video, audio, or data over long
distances.
Field of View: The distance from the flange of the lens (beginning of the lens mount) to the
focal
plane. C-mount lenses
have a flange back distance of 17.526mm vs. 12.5mm for CS-mount.
Focal Length: The distance (in millimeters) from the lens to the surface of the image sensor.
The shorter the distance, the
wider the view: the longer the distance, the narrower (telephoto) the view.
Focus: The focal point. An adjustment to the lens optics to improve the clarity of the
picture.
Foot Candle(FC): A measurement of light. 1 lumen per square foot.
Fomat: The size of the camera's pickup device(image). Current standard formats are
1/4", 1/3", and 1/2".
Frame: A complete picture (525 scan lines). The frame consists of two fields of video
information.
F-Stop: A term used to indicate the speed of a lens. The smaller the f-number, the
greater is the amount of light passing through the lens.

Also called F Number and F System. Refers to the speed or ability of a lens to
pass light. It is calculated by dividing the focal length of the lens by its
diameter.
Genlock: An interference in the video signal that shows up as a vertical crawling of the
picture or an oscillating hum in the audio.
Ghost: A shadowy or weak image in the received picture, offset to either the right or
to the left of the primary image.
Gray Scale: The number of variations from white to gray to black.
Ground: An electrical connection point that is common to either a metal chassis, a
terminal, or a ground bus.
Ground Loop: Effects video pictures in the from of a black shadow bar across the screen or
as tearing in the top corner of a
picture. Caused by different earth potentials in a system.
Gamma: A numerical value, or the degree of contrast in a television picture, which is
the exponent of that power law which is used to approximate the curve of output
magnitude versus input magnitude over the region of interest.
Gamma Correction: To provide for a linear transfer characteristic from input to output device.
Hue: Corresponds to colors such as red, blue, etcetera.
Hum: Electrical disturbance at the power supply frequency or harmonics thereof.
Hardwired: Method of controlling camera points using multi-core cable.
Horizontal Resolution: The maximum number of individual picture elements that can be distinguished in
a single scanning line.
Hz (Hertz): Cycles per second
I.R.(Infra Red): A range of frequencies lower than visible red light used for covert
surveillance or as a low cost wireless video link.
I.S.D.N.(Intergrated Services Digital Network): Digital phone lines from which allow transmission of via fastscan at speeds of
128Kb/second: used with terminal adapters.
Image Burn (Retained Image): A change produced in or on the target of the pickup device witch remains after
the removal of a previously
stationary light image.
Image Device (Imager): The detector in the camera, either a tube or a CCD solid state device.
Impedance: The effective resistance of an electronic circuit to an A.C. signal.

The input or output characteristic of a system component that determines the
type of transmission cable to be used. The cable used must have the same
characteristic impedance as the component. Expressed in ohms. Video
distribution has standardized on 75-ohm coaxial and 124-ohm balanced cable.
Insertion Loss: The signal strength loss that occurs when a piece of equipment is inserted into
a line.
Intensifier: An electronic device that creates an output image brighter than the input
(original) image Optical amplifier.
Interlace: A scanning process where every other horizontal line is scanned in one field
while the alternate lines are
scanned in the next field to produce a complete picture frame.
Internal Sync (Crystal Controlled): A camera that generates its sync pulses without reference to any other
sourse.Normally using a crystal
controlled oscillator.
Iris: The adjustable opening (mechanical diaphragm) through which light can pass and
be regulated.
Incident Light: The light that falls directly on an object.
Interline Transfer: A technology of CCD design, where rows of pixels are output from the camera.
The sensor's active pixel area and storage register are both contained within
the active image area. This differs from "frame transfer" cameras that move all
active pixels to a storage register outside of the active area.
Isolation Amplifier: An amplifier with input circuitry and output circuitry designed to eliminate
the effects of changes made at either upon the other.
Jitter: Small, rapid variations in a waveform due to mechanical disturbances or to
changes in the characteristic of components. Supply voltages, imperfect
synchronizing signals, circuits, etc.
Lens Speed: Refers to the ability of a lens to transmit light, represented as the ratio of
the focal length to the diameter of the lens. A fast lens would be rated
f/8. The larger the f
number, the slower the lens.
Lightt: Electromagnetic radiation detectable by the eye, ranging in wavelength from
about 400 to 750 nm.
Loss: A reduction in signal level or strength, usually expressed in dB. Power
dissipation serving no useful purpose.
Low-Frequency Distortion: Distortion effects which occur at low frequencies. In television, generally
considered as any frequency below the 15.75-kHz line frequency.
Lumen (LM): The unit of luminous flux. It is equal to the flux through a unit solid angle
(steradian) from a uniform point source of one candela or to the flux on a unit
surface of which all points are at a unit distance from a uniform point source
of one candela.
Lumen/FT2: A unit of incident light. It is the illumination on a surface one square foot
in area on which a flux of one lumen is uniformly distributed, or the
illumination at a surface all points of which are at a distance of one foot
from a uniform source of one candela.
Lens: A transparent optical component that converges light rays to from a two
demensional image of that object.
Level Control: Main iris control. Used to set the auto-iris circuit to video level desired by
the user. After set-up, the circuit will
adjust the iris to maintain this video level in changing lighting conditions.
Turning the control towards High
will open the iris, towards Low will close the iris.
Line Amplifier (Video Line corrector): A device to make good the loss of signal strength and quality due to long cable
runs.
Line Lock: To synchronize the field sync pulses, of an AC powered camera, to the frequency
of the voltage input (line voltage)
Looping ( Loop Through ): A term indicating that a high impedance device has been permanently connrcted
in a parallel to a video
source. Individual balanced video outputs for each video input.
Luminance (Y): The part of a video signal that consists of the monochrome data.
Lux: A unit measuring the intensity of light. One foot-candle=10 lux.
manual Iris Lens: A Lens with a manual adjustment to set the iris opening(F stop) in a fixed
position.
Generally used for fixed lighting applications.
Matrix Switcher: Matrix Switcher A switcher able to route any of its camera inputs any of its
monitor output: a name usually reserved for large
systems, that often includes telemetry control.
MATV: Short for Multiple Access Television. The method for distributing RF TV signals
by broadcasting them
through the air.
Mechanical Focus (Back-Focus, Racking): The mechanical aligning of the imageing device with the focal point of the
lens: most important on zoom lenses to ensure the image stays in focus
throughout the zoom range.
Microwave: Radio frequencies between 1-30 GHz used for video tranmission over medium/long
distance.
Minimum Object Distance (M.O.D.): The closest distance a given lens will be able to focus upon an object. This is
measured from the vertex(front) of the lens to the object. Wide angle lenses
generally have a smaller M.O.D. than large focal
length lenses.
Modulate: To change or vary some parameter such as varying the amplitude of a signal for
amplitude modulation or the
frequency of a signal for frequency modulation. A Modulator is the curcuit that
Modulates the signal.
Monitor: A device that coverts electronic signals into the video image that was generted
by the camera and lens. The
picture end of a CCTV system.
Monochrome: Having only one color. In television it is black and white.
Multiplex (Time Multiplex): Using one carrier to send more than one signal. In video multiplexers,
achieving this by sending a different
cameras output in each successive field or frame of a video signal, in a from
that can later be retrieved as
signal camera pictures.
MUX: A multiplexer.
Monochrome Signal: In monochrome television, a signal wave for controlling the brightness values
in the picture. In color television, that part of the signal wave which has
major control of the brightness values of the picture, whether displayed in
color or in monochrome.
Non-Composite Video: A video signal containing all information except sync.
NTSC ( National Television Standards Committee. See E.I.A. ): National Television Systems Committee. American committee that set the
standards for colour 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 colour and whose amplitude varies with the
instantaneous saturation of the colour. NTSC employs 525 lines per frame and
59.94 fields per second (usually taken as 60 fields per second).
N/D (Neutral Density): A filter that attenuates light equally over the whole visible spectrum.
Noise: Undesired signal(s) that corrupts the original video signal and may reduce
image quality.
Ohm: The unit of resistance. The electrical resistance between two points of a
conductor where a constant difference of potential of 1 Volt applied between
these points produces in the conductor a current of 1 Ampere, the conductor not
being the source of any electromotive force.
It can be represented by the formula V = I x R, where: V = Voltage I = Current
R = Resistance.
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.
Pan and Tilt: A device upon which a camera can be mounted that allows movement in both the
azimuth (pan) and in the vertical plane (tilt).
Pan/Tilt Preset Positioning: Follower pots are installed on pan/tilt unit to allow feedback to the
controller and provides information relevant to horizontal and vertical
positioning, allowing the controller to quickly adjust to a pre-selected scene
automatically.
Patch Panel: A panel where circuits are terminated and facilities provided for
interconnecting between circuits by means of jacks and plugs
Progressive Scan: The progressive scan format outputs data from the camera (the signal) in
sequential order as it is scanned. The scan format produces a full frame of
video in a continuous stream, rather than half the image per output sequence in
traditional RS-170 CCD cameras. Standard RS-170 video is interlaced and output
in two separate fields, generating essentially half the image at a time. With
Cohu's new 6600 Series Progressive Scan Camera, a new, full image is output
from the camera every 1/60th second, making it ideal for machines to more
quickly process and display information, or act according to programmed
instructions
PAL: Phase Alternate (sometimes alternating) Line. Describes the colour phase
change in a PAL colour signal. PAL is the European colour encoding TV system
featuring 625 lines per frame, 50 fields per second and a 4.43361875 MHz sub-
carrier (4.43 MHz).
Used mainly in Europe, China, Malaysia, Australia, New Zealand, the Middle East
and parts of Africa.
PSTN ( Public Switched Telephone Network ): Standard phone lunes used to transmit fastscan pictures via modems.
Pan: Side-to-side movement of a camera (on a horizontal axis).
Passive: A non powered element of a system.
Peak-To-Peak: The amplitude difference between the most positive and the modt negative
excursions of a signal.
Peripheral: An optional device that can enhance a CCTV system, for example, a multipler,
VCR, photo printer, etc.
Phase Adjustable (See Line Lock): The ability to delay the line locking process, so as to align cameras fed from
A.C voltages on different phases.
Photocell: Automatically switches on the infra-red lights when light levels fall to a
preset level.
Pinhole Lens: Lens used for applications where the camera/lens must be hidden. Front of lens
has a small opening to
allow the lens to view an entire room through a small hole in a wall.
Pip: Picture in picture.
Pixel: Picture element. The smallest cell or area of a CCD chip capable of displaying
detail on a screen.
The greater the number of pixels, the higher the resolution.
Presets: The pre-positioning of pan, tilt and zoom cameras by the use of potentiometers
in the moving parts of the
camera head. These allow the control eqipment to store and move to a set
reference point when the
controller dictates or when an alarm exists. Special telemetry equipment is
required.
Quad: A device that compresses up to four video signals and simultaneously displays
the images onto one monitor.
QCIF: Quarter Common Intermediate Format. A videoconferencing format that specifies
data rates of 30 frames per second (fps), with each frame containing 144 lines
and 176 pixels per line. This is one fourth the resolution of Full CIF. QCIF
support is required by the ITU H.261 videoconferencing standard.
RAID: Redundant array of inexpensive 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.
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. It may
also refer to the hand held controls for some VCRs and other CCTV equipment.
ROM: Read Only Memory.
An electronic chip, containing digital information that does not disappear when
power is turned off.
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.
RG-59: A video coaxial cable with 75 Ohm characteristic impedance. A type of coaxial
cable that is most common in use in small to medium-size CCTV systems. It has
an outer diameter of approx. 6 mm and it is a good compromise between maximum
distances achievable (up to 266m) and good transmission.
RS-422: This is an advanced format of digital communication when compared to RS-232.
A major difference is that the presentation is balanced line and the signalling
is differential.
In simple terms, the signal transmitted is read at the receiving end as the
difference between the two wires without a reference to earth. So if there is
common mode noise induced along the line, it will be cancelled out. RS-422 can
drive lines of up to 1200m and distribute data on to up to 10 receivers.
RS-485: This is an advanced format of digital communications compared to RS-232. It is
a balanced line transmission system. The major improvement over RS422 is in
the number of receivers that can be driven with this format, up to 32.
It is classically a half duplex 2 wire presentation.
RF (Radio Frequency): A frequency at which coherent electromagnetic radiation of energy is useful for
communication purposes. Also, the entire range of such frequencies.
Ripple: Amplitude variations in the output voltage of a power supply caused by
insufficient filtering.
Rack Mount(19" Rack): An industrial standard housing 19" wide, its height is measured in units(U's)
of 1.75".
Radio Frequency(R.F.): Signals with a repetition rate above audible range, but below the frequencies
associated 4 With heat and light.
Random Interlace: A scanning technique commonly used in CCTV systems in which there is no
external control over the scanning process. That is, there is no fixed
relationship between adjacent lines and successive fields.
Range Finder: Used to determine the focal lengh needed and what the picture will look like on
the monitor. The user looks
through the device and adjusts the range finder to the desired picture. Numbers
on the outside of the range
finder indicate the focal length needed.
Raster: The rectangular pattern of scanning lines upon which the picture is produced.
The illuminated face of the TV
monitor without the video information present.
Reflected Light: The scene brightness or the light being reflected from a scene.
Resolution: A measure of the ability of a camera or television system to reproduce detail.
Typically refers to the number
of picture elements that can be reproduced with good definition.
Roll: A loss of vertical sync which causes the picture to move up or down on the TV
screen.
RS-232: A commonly used computer serial interface.
SECAM: Color TV system used in France.
SVHS (Super Video Home System): New format high resolution VHS video recorders, capable of giving greatly
improved picture if all features are
usd. VHS compatible.
S/N Ratio (Signal To Noise Ratio): Measure of noise levels of a video signal; the higher the number the better.
Saturation (Color): The vividess of a color. I is directly related to the amplitude of the
chrominance signal.
Scanner: A pan oly unit.
Scanning: The rapid movement of the election beam in a pickup device of a camera or in
the CRT of a television
receiver. It is formatted in a line-for-line manner across the photo sensitive
surface which produces or
reproduces the video picture. When referred to a video surveillance field, it
is the panning or the horzontal
camera motion
Sensitivity: A camera's ability to reproduce a given scene with a given amount of light.
Usually expressed on footcandles
or lux.
Sensor: A device that indicates a change of state in response to an event or stimulus.
See Image Device.
Sequential Switcher: Sequential switcher is commonly used device in small to medium sized CCTV
systems. The sequential switcher altenates the displayed video image from one
camera to the next. However, with sequential switching not all cameras can
be viewed simultaneously.
Simplex (Multiplexer): A multiplexer with 1 frame store that can either time multiplex records or show
multi-screen pictures in live or
play back. It cannot record the multiplexer pictures whilst showing multi-
screen pictures.
Spot Filter: A small insert used in a lens to increase the f-stop range of the lens.
Switcher: A device used to switch the video signal from two or more camera on a monitor.
Sync: Abbreviation for synchronization. Electronic pulses that ae inserted into video
signal for the purpose of
assembling the picture information in the correct position.
Shutter: Ability to control the integration (of light) time to the sensor to less than
1/60 second; e.g: stop motion of moving traffic.
Standard Minimum Signal: 1000 microvolts at 75 ohms (0dB mV) in RF systems; 0.7 Vp-p non-composite,
1Vp-p composite in video systems.
Smear: An unwanted side effect of vertical charge transfer in a CCD chip.
It shows as vertical white (or sometimes red) stripes in parts of the image
where there are very bright highlights. In some modern chip sets smear is
minimized to almost undetectable levels.
Tearing: A term used to describe a picture condition in which groups of horizontal lines
are displaced in an irregular manner
Test Pattern: A chart especially prepared for checking overall performance of a television
system. It contains various combinations of lines and geometric shapes. The
camera is focused on the chart, and the pattern is viewed at the monitor for
fidelity.
Transients: Signals which exist for a brief period of time prior to the attainment of a
steady-state condition. These may include overshoots, damped sinusoidal waves,
etc
T1 channels: In North America, a digital transmission channel carrying data at a rate of
1.544 Mbps. In Europe, a digital transmission channel carrying data at a rate
of 2.048 Mbps.
TFT: Thin-Film-Transistor. This technology is used mainly for manufacturing flat
computer and video screens that are superior to the classic LCD screens.
Colour 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 just under 24mm/s (which is the case with the domestic models
of VHS VCRs), it moves with discrete steps that can be controlled. TL VCRs can
have a number of other special functions for use in CCTV systems
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 when using a 3-
hr (180-min) tape.
TCP/IP: Transmission Contorl Protocol / Intenet Protocol
Tracking: The angle and speed at which the tape passes the video heads.
UPS: Uninterruptible Power Supply. These are power supplies used in the majority of
high security systems, whose purpose is to back-up the system when the mains
power fails. The duration of this depends on the size of the UPS, usually
expressed in output VA (or kVA), and the hold up time expected from fully
charged batteries. There are two common types, "off line"
and "on line". Off line uses a switch to change from mains to battery
operation, thus there can be a short break in the output. On Line UPSs are a
type where the convertor is always working, hence there is no switch over break
at the ouput.
Underscan: Decreases raster size in both H and V so that all four edges of the picture are
visible on the monitor.
UTP: Unshielded Twisted Pair. A cable medium with one or more pairs of twisted
insulated copper conductors bound in a single sheath, with no overall or
individual screen. Now the most common method of bringing telephone signals
and data to the desktop.
Video Distribution Amplifier ( VDA ): A special amplifier for buffering the video signal so that it can be supplied
to a number of items of equipment at the same time. Each output will need to
be individually terminated at 75 Ohms.
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.
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.
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 difficult to set up for use externally but can be useful
in carefully controlled situations. Modern VMD systems can learn the scene and
ignore such things as tree and foliage movement.
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.
Varifocal: A lens type that the focal length can be infinitely varied to give the exact
image desired. It is similar to a manual zoom lens, except that a varifocal
lens cannot be zoom tracked.
Vertical Resolution: The number of horizontal lines that can be seen in the reproduced image of a
television pattern.
Video Amplifier: A wideband amplifier used for passing picture signals.
Video Signal (Non-Composite): The picture signal. A signal containing visual information and horizontal and
vertical blanking (see also Composite Video Signal) but not sync.
WAN: Wide Area Network.
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 colours. It is
performed electronically and is set on the basis of a white object in the
picture.
Y Signal: A signal transmitted in color television containing brightness information.
This signal produces a black and white picture on a standard monochrome
receiver. In a color picture it supplies fine detail and brightness
information.
Zoom: To enlarge or reduce, on a continuously variable basis, the size of a televised
image primarily by varying lens focal length.
Zoom Lens: An optical system of continuously variable focal length, the focal plane
remaining in a fixed position.