PAL
Phase Alternating Line:
is a color television system and
the standard used in Western Europe, Australia,
parts of Africa and Asia. PAL has 625 horizontal
scanning lines and 50 fields per sec.
Persistency
of vision:
The retina of the human eye retains
an image for 40ms. This characteristic
is called persistency of vision and is
used to make a picture appear continuos
by flashing images on the retina at a
rate faster than 24 images per sec.
Phase
adjustment:
is a camera adjustment used to
synchronise all the cameras in the system
by altering the phase of the power supply.
Phase
angle:
is the angle at any point of
the sine wave of an AC power supply and
varies between 0 to 360 deg. over a cycle.
Phosphor:
is a material which is capable
of emitting light. It is used in fluorescent
lamps, monitors etc. The duration of the
emission depends on the type of phosphor.
Photon:
is the basic unit of light.
Picture
tearing:
occurs when the horizontal sync
pulses are distorted or lost and the monitor
is unable to latch on to them causing
the horizontal lines to be displaced in
a random manner. This is seen as a tearing
of the picture on the monitor.
Pincushion
distortion:
is a type of distortion caused
due to non uniform scanning in the monitor
which makes the picture to bulge inwards.
Pinhole
lens:
is a small lens with a diameter
of 1.5mm to 9.5mm used for covert surveillance.
Pixel
( picture element):
is the basic unit of a CCD chip
which accumulates charge depending upon
the amount of light falling upon it. A
typical CCD chip has over 300,000 pixels.
Polarizer:
is a type of filter which reduces
glare by intercepting reflected light
from surfaces like water , glass. etc.
Polycarbonate
glass:
is a type of toughened glass
which can be used in housings for use
in high vandal areas.
Polyethylene:
is a type of plastic used to
make outer jackets for cables.
Potentiometer:
is an electronic component in
which the resistance can be changed by
a movable contact point. It is used in
pan tilt heads and zoom lenses to record
pre-set positions.
Power
line interference:
is a type of interference caused
by main power lines and usually seen as
horizontal bands on the monitor.
Preamplifier:
is a type of amplifier used to
increase the output of a low level source
allowing the signal to be processed by
other devices.
Pre
set:
is a term used in CCTV to define
pre determined positions of a pan tilt
head and zoom lens.
Pressure
mat:
is a device which is activated
by the application of pressure and is
used to open doors, gates etc. It can
also activate the switcher to bring the
nominated camera up for extended viewing.
Primary
Color:
is a basic colour which cannot
be obtained by mixing other colours. Red,
green and blue are the three primary colors
which can be mixed to produce other colours.
PSTN
Public Switched Telephone Network:
is a type of analogue telephone
network currently in use all over the
world.
PTZ
controller:
is a device used to control the
movement of the pan tilt head and zoom
lens from a remote location. |
