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P-z

PAL	Phase Alternate Line Colour Video Signal standard for most of Europe, Australia and the Middle East - 625 Lines, 50Hz.
PAN & TILT	Pan & Tilt head a device that will move a camera both horizontally and vertically from a remote location.
PATCH PANEL	A panel that joins or terminates many different circuits.
PCM	Pulse Coded Modulation.
PEAK TO PEAK	A value based on the maximum positive and maximum negative points of a waveform, for video the standard is 1V peak to peak.
PEAK WHITE INVERTER	Circuitry that will convert white highlights over a pre-set brightness threshold to black. This is useful for car registration recognition when headlights are on.
PH	Pin hole, normally refers to a pin hole lens.
PHOTO DETECTOR	A device fitted to a fibre optic link to convert light to electrical power.
PHOTOCELL	A device used to detect changes in light level and provide an automatic switched output when lighting levels fall to a predetermined level.
PHOTON	Quantum of electromagnetic energy, a particle of light is a Photon.
PICO	Order of magnitude 10 -12.
PIGTAIL	Short length of fibre optic cable attached to another component such as a source of coupler.
PIP	Picture in Picture device used to superimpose one video signal over another in one display.
PIR	PIR is the abbreviation of “Passive Infra Red”, which is a motion sensor to detect heat from moving objects, such as human bodies and animals. When any motion is detected, P.I.R. will trigger the alarm system. The TV will show you what your cameras see. With P.I.R., you can always keep an eye on visitors at the front door, intruders in the garage, or any place within its detection coverage. With it, our products can detect moving objects within wider detection coverage to provide our customers optimum security and protection.
PIXEL	In a digital display a pixel is the smallest individual dot that can be separately illuminated.
PL259	UHF connector now largely replaced by the BNC connector.
PRE-SETS PRE-SET CONTROLLER	Pre-positioning of P/T/Z/F (Pan/Tilt/Zoom/Focus) functions on functional cameras, activated by alarm inputs or operator selection. A function contained within a telemetry system that, on receipt of a signal, causes a particular camera to pan, tilt and zoom to a predetermined field of view. Most systems can accommodate up to sixteen pre-set positions for each camera. This is an especially useful feature on larger systems with alarmed areas.
PROTOCOL	A set of rules governing the flow of information in a communications system.
PSTN	Public Switched Telephone Network analogue communications network used for day to day telephony and data transmission.
PSU	Power Supply Unit.
QUAD SPLITTER	A device used to display 4 cameras simultaneously on a single monitor.
RACK MOUNT	Piece of equipment that can be housed into a rack enclosure, industry standard is 19" width (to outside of mount) with the height measured in U. 1U = 1.75 inches. (44.45 mm)
RANDOM INTERLACE	Method of television scanning that does not define a strict relationship between adjacent scan lines in sequential fields.
RASTER	Pre-defined scanning area for a television picture tube.
REFLECTANCE	The level of light that is reflected off any given surface, normally shown as a percentage.
REFLECTED LIGHT	Scene illumination multiplied by reflectance. This is the light level available for the camera and determines picture quality.
REFRACTION	Deflection of light at certain angles when it enters obliquely from another medium of different density.
REGENERATORS	Units placed at regular intervals along a transmission system to detect weak signals and strengthen them.
REMOTE SWITCHERS	A video switcher with a main switching box whose controller can be sited remotely via a single or pair of cables. REMOTE SWITCHER: A video switcher which is connected to the camera cables and which contains the switching electronics. This unit may be remotely located and connected to a desk top controller by a single cable for each monitor.
REPEATER	Device that amplifies and then re-transmits a signal.
RISE-TIME	The time required for the leading edge of a pulse to rise from 10% to 90% of its total amplitude.
RS170	Video Sync Pattern for the United States 525 lines 60Hz.
RS232	Computer terminology for communications networks.
RS422	Computer terminology for communications networks.
RS485	Computer terminology for communications networks.
RX	Receiving equipment.
SCANNER	Device for remotely controlling the horizontal movement of a camera pan only.
SCART	Standard European connector for carrying audio and video signals.
SCENE ILLUMINATION	The density of light in LUX falling on the area to be viewed. For best results the ratio of the lightest to the darkest areas should not be more than a factor of two.
SCREEN SPLITTER	Device used to display two cameras on a single monitor, splitting the screen horizontally or vertically.
SECAM	Sequential Colour & Memory colour television broadcast system used in France.
SENSITIVITY	For a camera usually specified in lux to provide indication of light level required to gain a full video signal from the camera.
SHUTTER	Electronic circuit found in many CCD cameras which allows the light gathering period of the camera to be manually altered.
SIMPLEX	Term seen in video multiplexers. With a simplex multiplexer you can only perform one function of recording or playing back at a time, i.e.. if you are reviewing images from tape, you cannot record images or view live images in a multiscreen format.
SIT	Silicon Intensified Target form of camera used in very low light levels.
SLAVE	A secondary item (control position) that performs the same, or limited functions, of the master position.
SLOWSCAN	Old form of video transmission over telephone networks, replaced these days by fastscan or DVST systems.
SN RATIO	Signal to noise ratio, a measurement of the noise level in a signal expressed in dB (decibels). In a video signal values from 45dB to 60dB produce an acceptable picture. Less than 40dB is likely to produce a 'noisy' picture.
SOFTWARE COMPRESSION	Video data compression achieved by computer program processing.
SPECTRAL RESPONSE	Sensitivity of an imaging device to different frequencies of light. Visible light is 300 to 730nm, IR is 715 850nm and invisible IR 850nm+.
SPEED OF UPDATE	The time taken to refresh a single picture.
SPIKE	An amplitude surge. An undesirable momentary increase in electrical current or signal.
S-VHS	Super Video Home System a higher resolution recording medium than VHS.
SWIVEL MOUNT	Used on camera and housing mounts to allow precise positioning of cameras.
SYNC GENERATOR	Device that produces a synchronisation signal.
SYNCHRONISATION	The occurrence of two or more electrical events at the same time in sync.
SYNCHRONOUS DATA	Data and synchronisation pulses sent at the same time, used for more sophisticated communications.
TA	Terminal Adaptor used to connect video transmission products to an ISDN digital telephone line.
TDG	Time & Date generator device used to overlay the time and date on a video signal.
TELEMETRY	The system by which a signal is transmitted to a remote location in order to control CCTV equipment e.g. to control pan and tilt and zoom functions, switch on lights, move to pre-set positions etc. The controller at the operating position is the transmitter and there is a receiver at the remote location. The signal can be transmitted along a simple 'twisted pair' cable or along the same coaxial cable that carries the video signal.
TERMINATION	In CCTV the termination is 75 ohms; if a signal is being looped then equipment should be set to Hi-Z (un-terminated)
TIME BASE CORRECTION	Method used to align unsynchronised camera signals, widely used by video multiplexers and quad splitters.
TIME LAPSE VCR	A VCR that can slow down its recording rate, used to extend the length of recording on a standard 3 hour tape to as much as 960 hours. Achieved by the tape moving in steps and recording one frame at time. This means that if set to record over long periods much information can be lost. On receipt of an alarm signal these machines can be automatically switched to real time mode.
TOUCH SCREEN CONTROL	A system by which all the camera controls are displayed on the screen of a special monitor. To control any function simply requires the screen to be touched a the appropriate symbol which can be to select a camera or pan, tilt and zoom. The system is computer driven and can include maps, diagrams etc. that are automatically displayed according to the alarm received.
TP	Twisted Pair an electrical wire consisting of two conductors twisted around each other.
TRANSDUCER	Device used to convert a form of energy into electrical energy.
TVL	Television Lines used to describe the resolution of a camera or VDU.
TX	Transmitting equipment.
UNBALANCED SIGNAL	Term used for coaxial cable transmission.
UNTERMINATED	Input to a unit in a CCTV system that requires looping to another piece of equipment.
VARIFOCAL	A type of lens that allows manual adjustment between two focal points to provide the desired field of view.
VCR	Video Cassette Recorder
VIDEO MOTION DETECTION	A method of detecting movement in the view of the camera by the electronic analysis of the change in picture contrast.
VDU	Video Display Unit.
VERTICAL INTERVAL	Sequential video switchers that wait until the current field has completed its cycle before
SWITCHER	Switching to the next camera, even though the dwell time may have been exceeded. Thus reducing the amount of bounce seen between switching images.
VHS	Video Home System VCR format and name given to 1/2" cassette tape used in VCR's.
VIDEO LAUNCH AMPLIFIER	An amplifier placed between the video source and the transmission cable, used where the signal needs to be processed before being launched over coaxial or twisted pair cables.
VMD	Video Motion Detection (not activity detection) - a process of determining motion by complicated electronic analysis of picture signal and/or neutral computing techniques.
V.24	List of definitions between terminal equipment and modems.
V.34	28800 bps modem for PSTN and leased line circuits.
WAVELENGTH	Distance between the same two points on adjacent waves, or the time necessary for a wave to complete a single cycle.
WDM	Wavelength Division Multiplexing.
2 WIRE	Transmission medium using the same two wires for transmit and receive channels. Either leased line or dial up.
4 WIRE	Transmission system using 2 separate pairs of wire for the transmit and receive channels. Leased line or dial up can only be achieved on PSTN by dialling 2 separate numbers.
WHITE BALANCE	Used in colour CCD cameras. White should be referenced and determined by colour temperature for the truest colour rendition.
WHITE LEVEL	The brightest part of a picture corresponding to 1V peak to peak (0.7V above black level).
X.21	General purpose interface between data terminal equipment and data circuit terminating equipment for synchronous operation on public data networks i.e.. ISDN.
Y/C	Video signal containing separate luminance (Y) and chrominance (C) to provide greatly improved picture quality from VCR's i.e.. S-VHS.
ZOOM RATIO	A lens with variable elements giving adjustable magnification and differing fields of view in one, i.e. 12:1.