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Common Pre-venTronics
CCTV Components
Fixed Cameras
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A fixed camera is designed to be stationary, may be
black & white or color, and views a single scene. When indoors, the CCD
camera may be exposed and mounted by a bracket fastened to the wall,
ceiling, or other structure. Indoor cameras may use domes or other housings
to conceal and/or protect the camera. Special housings are available for
correctional facilities and similar applications where the camera is
subject to physical attack.
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When used outdoors, an environmental housing which may
include a heater and blower protects the camera from the elements. Outdoor
cameras often use auto iris lenses. An auto iris lens extends the
operational light range of the camera and is particularly useful in areas
where the camera is subject to glare or bright sunlight.
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Cameras like those shown on the left (manufactured by
Silent Witness) are a complete integral assembly containing the CCD camera,
protective housing, and lens. Some models also have built in audio
microphones, heaters, etc.
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Covert Cameras
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A covert camera is a camera that is inconspicuous or
designed to look like something else. Covert cameras often look through a
small "pinhole" opening with the camera concealed behind the
wall, ceiling, or other structure. Covert cameras are available which look
like smoke detectors, sprinkler heads, thermostats, clocks, etc. Covert
cameras are normally used to record employee theft, vandalism, and other
activity where the camera is to be inconspicuous.
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Scanners
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A scanner is a motorized device which moves the camera
back and forth horizontally. Scanners are available for indoor or outdoor
use and are sometimes concealed in domed enclosures. Scanners are useful
when the camera needs to cover a larger area than possible with a fixed
mount, and the position of the camera does not need to be hid from view.
Scanners normally accompany a camera with a fixed viewing angle lens.
Outdoor scanner cameras often use auto iris lenses and enclose the camera
in an environmental housing. An auto iris lens may be used to extend the
operational light range of the camera. This is particularly useful in areas
where the camera is subject to glare or bright sunlight.
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Pan & Tilts
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A pan & tilt is similar to the scanner (shown with
housing and mount) but adds up and down motion as well as horizontal. Pan &
tilts usually accompany cameras with zoom and auto iris lenses. The zoom
lens allows the camera to see a wide range of viewing angles. The pan &
tilt may also have a "auto pan" feature which allows the camera
to scan back and forth like the scanner. Pan & Tilts may be concealed
in a domed enclosure. Some pan and tilts, when used in conjunction with the
proper controller, have the ability to go to preset camera positions.
Outdoor applications require an environmental housing for the camera.
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Discreet Dome Cameras
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A general term given
to today's high speed dome cameras. Advances in technology now allows
integrated cameras with high speed pan & tilt motors and
micro-processor controllers to have "robot like" maneuverability.
Dome cameras can pan at speeds up to 480° per second. The micro-processor
controller adds variable speed control, preshots, tours, zoom lens control,
text/character generation, and response to alarm capabilities. Control is
accomplished by a digital "joystick" controller. Dome camera
systems are easily expanded and are ideal in applications where the camera
is used to watch moving objects and/or automation is desired. The camera is
hidden from view by a plastic domed cover. Environmental versions are
available for outdoor use.
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Sequential Switchers
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Sequential switchers are a low cost device which allows
the viewing of multiple cameras on a single monitor and/or VCR. As the term
would imply, the switcher displays the cameras in a sequence. Sequential
switcher are ideal in small CCTV systems where it is not necessary to see
or record individual camera scenes at all times.
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Multiplexers, (quad, or higher)
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A multiplexer is a device that allows multiple cameras
to be displayed and/or recorded on a single monitor and/or VCR.
Multiplexers are ideal when the camera scenes need to be recorded or viewed
at all times. Common multiplexer sizes are 4 (quad), 8, and 16 camera
inputs. Monitor displays can usually be changed to show the cameras in
sequences, quad view, or multiples depending on the number of inputs.
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Matrix Switchers
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Matrix switchers are normally used in larger systems
with fixed cameras and sometimes small systems when dome cameras are being controlled.
A matrix allows any camera input to be displayed on any monitor output. In
a CCTV system, the matrix electronically functions like the telephone
switchboard operator of yesteryear. It's function is to "connect"
cameras coming in (inputs) to monitors and VCR's going out (outputs). A
matrix switcher system normally has three components, a keyboard or
joystick controller, an internal or external camera controller, and the
actual matrix switching circuitry. The keyboard or joystick controller is used
to program, call up, move cameras, and basically control the system. A dome
system normally uses joystick controllers which include variable speed
control. The camera controller is the "brain" of the system. It
stores the programs in memory, executes automated tasks, and performs the
functions given to it by the controller. The camera controller may be
internal to the switcher, an external hardware device, or a PC with special
software and hardware installed.
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Infra-red Illuminators
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Infra-red illuminators are used to create or add
illumination for night time surveillance. The illuminator produces light
which is invisible to the eye yet the camera sees it. Because of it's
invisibility, infra-red also works well in covert applications. Infra-red
illuminators come in solid-state low power versions (shown) and high power
versions with 120 VAC quartz lamps.
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Time Lapse VCRs
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Time lapse VCR's allow the recording of tapes longer
than the SLP mode of home recorders. Time lapse VCR's have a recording
capacity of 24 to 960 hours, depending on the model. Most models use an
industrial tape transport designed for continuous duty and include alrming
inputs which are used to start recording automatically.
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Monitors
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A video monitor is similar to a television set. It is
used to display the video scenes from the cameras. However, video monitors
normally produce a higher resolution picture than television sets, and are
designed to use a composite video signal rather than a broadcast signal.
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