| P-P (Peak-to-Peak) |
The voltage of a signal measured between its most positive and negative points. CCIR standard video is 1 volt P-P. |
P.A.L. (Phase
Alternate Line. See
CCIR) |
Colour TV system used in the UK |
PABX (Private
Automatic Branch
Exchange) |
An in-house telephone switching system that interconnects telephone extensions to each other, as well as to the outside telephone network. |
| Password |
A special word, code or symbol that must be presented to the computer system to gain access to its resources. It identifies the user to the computer system. |
PCI‚ (Peripheral
Component
Interconnect) Bus |
PCI Local Bus is a high-performance bus that provides a processor- independent data path between the CPU and high-speed peripherals. PCI is a robust interconnect mechanism designed specifically to accommodate multiple high-performance peripherals for graphics, full-motion video, SCSI and LANs. |
PCMCIA (Personal
Computer Memory
Card International
Association) |
A non-profit trade association founded in 1989 to standardise a method for connecting peripherals to PCs. PCMCIA created a 16- bit socket that’s "Plug-and-Play" compatible and can be automatically configured by a software driver called PCMCIA Card Services. |
Peak White Inverter
(Eclipser) |
An electronic circuit that turns any white part of a video signal, over a preset level, to black. If installed in the auto iris video line it decreases the contrast of one picture, bringing out detail otherwise lost in shadow. |
| Pedestal |
The portion of a video signal between the sync. pulses and the black level. |
| Peer-to-Peer |
Communications in which both sides have equal responsibility for initiating, maintaining and terminating the session. |
Phase Adjustable
(see line lock) |
The ability to delay the line locking process, so as to align cameras fed from A.C. voltages on different phases. |
| Photocell |
Automatically switches on the infra-red lights when light levels fall to a preset level. |
| Pico |
Order of magnitude; 10 –12 |
| PIN |
Personal Identification Number. |
PING (Packet
InterNet Groper) |
A utility used to determine if a TCP/IP device is available and responsive on a network or at an Internet site. |
| PL259/UHF Connector |
Screw on video connector, now largely replaced by the BNC type. |
| Plasma |
A type of flat screen display. |
| Port |
That portion of a computer through which a peripheral device may communicate. |
POTS (Plain Old
Telephone Service) |
The basic analogue service provided by the public telephone network, without any added facilities. |
PPP (Point-To-Point
Protocol) |
A data-link protocol that provides dialup access over serial lines by encapsulating protocols in specialised Network Control Protocol packets. These packets can be used to replace a network adaptor driver which allows remote users to log on to the network as if they were in-house. |
| Presets |
The pre-positioning of pan, tilt and zoom cameras by the use of potentiometers in the moving parts of the camera head. These allow the control equipment to store and move to a set reference point when the controller dictates or when an alarm exists. Special telemetry equipment is required. |
| Protocol |
A standard for sending coded messages between computers and peripherals. |
| Protocol Converter |
Data transmission converter i.e. RS232 to RS485 or vice versa. |
| Proximity |
Radio frequency technology used in Access Control, where the card or tag needs to be presented to a reader. Read ranges vary but are not normally greater than 15cms. |
PSTN (Public
Switched Telephone
Network) |
Any switching communication system- such as Telex, TWX or public telephone networks- that provides circuit switching to many customers. |
| PSU |
Power supply unit. |
| Pulse |
A positive or negative change in voltage that conveys information to a circuit. |
PVP™ (Parallel Video
Processing) |
Multiplexer dual framestore that gives near real-time record capability in 3 hour mode and improves multi-screen updates by 50%. |
