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.