P

	Packets
	A block of information sometimes called a cell, frame, data unit, service unit, or signalling unit. Although each of these elements do have unique attributes, in essence, all are packets.
	PAL (Phase Alternative Line System)
	The European TV standard for scanning television signals. Frames are displayed at 25 frames per second. Used in most European countries. (Other standards: NTSC (USA) and Secam (France/Former USSR))
	Point-to-point videoconference
	Videoconference between two sites.
	POP (Point of Presence)
	This is a point-of-presence of an Internet service provider, used to facilitate remote users' access to the range of applications and IP addresses in the internet work.
	PPP (Point-to-Point Protocol)
	Provides a standard means of encapsulating data packets sent over a single-channel WAN link. It is the standard WAN encapsulation protocol for the interoperability of bridges and routers. PPP is also supported in workstations, allowing direct dial-up access from a personal computer to a corporate LAN or Internet Service Provider. Using PPP ensures basic compatibility with non-Ascend devices. Both the dialling side and the answering side of the link must support PPP.
	PRI (Primary Rate Interface)
	An ISDN subscriber line, consisting of twenty-three 64 kbps B channels in North America (thirty 64 kbps channels elsewhere) and one 64 kbps D channel, used for signalling purposes.
	Proprietary compression algorithm
	A vendor-specific algorithm for compression of a video signal. A videoconferencing system using a proprietary algorithm can only communicate with a remote site using the same algorithm. Many vendors also adhere to standard compression algorithms to facilitate communication across platforms. (i.e. .H.320)
	Public Room
	Videoconferencing service offered to the public on a fee-for-usage basis.
	Px64
	Common reference to the CCITT standards (H.261 et. al.), which describe methods to allow for videoconferencing system interoperability.