Sony ISSUE 3 Camcorder User Manual


 
CCTV Systems Control
While the majority of cameras are installed in a fixed position, in order for the
operator to be able to follow an incident it can be very useful to have the
facility to pan, tilt and zoom the camera.
This is achieved by the use of a mechanical pan and tilt head on which the camera
is mounted and a zoom lens which are controlled remotely by telemetry signals. As
in most instances the camera will be fitted outdoors and therefore it will be
necessary to use a housing which will protect it from the elements or to use a
dome camera.
Telemetry
There are two types of electronic telemetry: one uses a twisted pair, where long
distances are involved; the second uses coaxial cable – in fact, the same cable that
carries the video signal. The basic form of telemetry control system uses digital
techniques to produce a pulse code modulated (PCM) signal. This is a signal which
has a series of 16 pulses and, depending upon the function required (pan/tilt or
zoom), sends the appropriate pulses to a receiver which interprets them and carries
out the function.
Housings and Enclosures
These protect the CCTV camera/lens assembly. Used in both internal and external
applications, housings also protect against dust, vandalism and extreme weather
conditions.
Many different housings are available with accessories, such as thermostatically
controlled viewing windows, sunshields, blowers for hot environments and heaters
for use in extreme cold.
Domes
Domes operate in much the same way as a conventional pan, tilt and zoom camera
except that they are generally more compact and have the added advantage of
being discreet – both aesthetically and for the purpose of surveillance. It is not
usually possible to see in which direction the camera within the dome is directed.
Conventional housings score over domes in terms of robustness and there is less
chance of the optical distortion created by the spherical dome cover.
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