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AC adaptor
Also called a power supply.
All CCTV devices needs power of some sort. Each device has its own
power requirements (usually 12 volts with a minimum amperage). The
power coming out of the wall (in the US) is 110 to 120 AC. The
adaptor converts the AC power to DC power and will adjust it to a
specified amperage.
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.
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.
AUTOMATIC BRIGHTNESS CONTROL
In display devices, the self-acting mechanism which controls
brightness of the device as a function of ambient light.
AUTOMATIC GAIN CONTROL
A process by which gain is automatically adjusted as a function of
input or other specified parameter.
AUTOMATIC IRIS LENS
A lens that automatically adjusts the amount of light reaching the
imager.
BANDWIDTH
The number of cycles per second (Hertz) expressing the difference
between the lower and upper limiting frequencies of a frequency
band; also, the width of a band of frequencies.
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.
BLOOMING
The defocusing of regions of the picture where the brightness is at
an excessive level, due to enlargement of spot size and halation of
the fluorescent screen of the cathode-ray picture tube. In a camera,
sensor element saturation and excess which causes widening of the
spatial representation of a spot light source.
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.)
BROADBAND
In television system use, a device having a bandpass greater than
the band of a single VHF television channel.
BURNED-IN-IMAGE
Also called burn. An image which persists in a fixed position in the
output signal of a camera tube after the camera has been turned to a
different scene or, on a monitor screen.
CCD
See Charge Coupled Device
C MOUNT
A television camera lens mount of the 16 mm format, 1 inch in
diameter with 32 threads per inch.
CCTV
Common abbreviation for Closed-Circuit Television.
CHARGE-COUPLED DEVICE
CCD. For imaging devices, a self-scanning semiconductor array that
utilizes MOS technology, surface storage, and information transfer
by shift register techniques.
COAXIAL CABLE
A particular type of cable capable of passing a wide range of
frequencies with very low signal loss. Such a cable in its simplest
form, consists of a hollow metallic shield with a single wire
accurately placed along the center of the shield and isolated from
the shield.
COLOR BURST
That portion of the composite color signal, comprising a few cycles
of a sine wave of chrominance sub carrier frequency, which is used
to establish a reference for demodulating the chrominance signal.
Normally approximately 9 cycles of 3.579545 MHz.
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.
CONTRAST
The range of light to dark values in a picture or the ratio between
the maximum and minimum brightness values.
dB
Basically, a measure of the power ratio of two signals. In system
use, a measure of the voltage ratio of two signals, provided they
are measured across a common impedance.
DECODER
The circuitry in a color TV receiver which transforms the detected
color signals into a form suitable to operate the color tube.
DEPTH OF FIELD
The in-focus range of a lens or optical system. It is measured from
the distance behind an object to the distance in front of the object
when the viewing lens shows the object to be in focus.
DEPTH OF FOCUS
The range of sensor-to-lens distance for which the image formed by
the lens is clearly focused.
DIGITAL SIGNAL PROCESSING
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.
FIELD
One of the two equal but vertically separated parts into which a
television frame is divided in an interlaced system of scanning. A
period of 1/60 second separates each field start time.
FIELD OF VIEW
The maximum angle of view that can be seen through a lens or optical
instrument.
FOCAL LENGTH
Of a lens, the distance from the focal point to the principal point
of the lens.
FOCAL PLANE
A plane (through the focal point) at right angles to the principal
point of the lens.
FOCAL POINT
The point at which a lens or mirror will focus parallel incident
radiation.
FRAME
The total area, occupied by the television picture, which is scanned
while the picture signal is not blanked.
GAIN
An increase in voltage or power, usually expressed in dB.
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.
GHOST
A spurious image resulting from an echo.
HUM
Electrical disturbance at the power supply frequency or harmonics
thereof.
INTERFERENCE
Extraneous energy which tends to interfere with the reception of the
desired signals.
IRIS
An adjustable aperture built into a camera lens to permit control of
the amount of light passing through the lens.
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
A transparent optical component consisting of one or more pieces of
optical glass with surfaces so curved (usually Spherical), that they
serve to converge or diverge the transmitted rays of an object, thus
forming a real or virtual image of that object.
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.
LIGHT
Electromagnetic radiation detectable by the eye, ranging in
wavelength from about 400 to 750 nm.
LOOP THROUGH
Also called looping. The method of feeding a series of high
impedance circuits (such as multiple monitor/displays in parallel)
from a pulse or video source with a coax transmission line in such a
manner that the line is bridged (with minimum length stubs) and that
the last unit properly terminates the line in its characteristic
impedance. This minimizes discontinuities or reflections on the
transmission line.
LOSS
A reduction in signal level or strength, usually expressed in dB.
Power dissipation serving no useful purpose.
LUX
International System (Sl) unit of illumination in which the meter is
the unit of length. One lux equals one lumen per square meter.
MONITOR
A unit of equipment that displays on the face of a picture tube the
images detected and transmitted by a television camera.
NTSC
Abbreviation for National Television Systems Committee. A committee
that worked with the FCC in formulating standards for the present
day United States color television system.
OUTPUT
The signal level at the output of an amplifier or other device.
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.
PIXEL
Short for Picture Element. A pixel is the smallest area of a
television picture capable of being delineated by an electrical
signal passed through the system of part thereof. The number of
picture elements (pixels) in a complete picture, and their geometric
characteristics of vertical height and horizontal width, provide
information on the total amount of detail which the raster can
display and on the sharpness of the detail, respectively.
PRIMARY COLORS
Three colors wherein no mixture of any two can produce the third. In
color television these are the additive primary colors red, blue and
green.
RESOLUTION (HORIZONTAL)
The amount of resolvable detail in the horizontal direction in a
picture. It is usually expressed as the number of distinct vertical
lines, alternately black and white, which can be seen in a distance
equal to picture height.
RESOLUTION (VERTICAL)
The amount of resolvable detail in the vertical direction in a
picture. It is usually expressed as the number of distinct
horizontal lines, alternately black and white, which can
theoretically be seen in a picture.
ROLL
A loss of vertical synchronization which causes the picture to move
up or down on a receiver or monitor.
SATURATION
In color, the degree to which a color is diluted with white light or
is pure. The vividness of a color, described by such terms as
bright, deep, pastel, pale, etc. Saturation is directly related to
the amplitude of the chrominance signal.
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.
SIGNAL-TO-NOISE RATIO
The ratio between useful television signal and disturbing noise or
snow.
SHOW
Heavy random noise.
SPIKE
A transient of short duration, comprising part of a pulse, during
which the amplitude considerably exceeds the average amplitude of
the pulse.
STANDARD MINIMUM SIGNAL
1000 micro-volts at 75 ohms (0dB mV) in RF systems; 0.7-VPP
non-composite, 1-VPP composite in video systems.
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.
VERTICAL RESOLUTION
The number of horizontal lines that can be seen in the reproduced
image of a television pattern.
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.
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