Glossary - P
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Packet - A series of bits containing data and control information, including source and destination node addresses, formatted for transmission from one node to another.
Packet Identifier (PID) - A unique integer value used to identify elementary streams of a program in a single- or multi-program MPEG-2 stream.
Packet Loop - A digital loop on which all information (signaling and user content) is encoded in packets.
Pairing - A partial or complete failure of interlace in which the scanning lines of alternate fields do not fall exactly between one another but tend to fall (in pairs) one on top of the other.
Passive Component - A component that requires no external source of power for it to function.
Passive Device - A circuit or network not using active devices such as tubes or transistors.
Password - A sequence of characters used to prevent unauthorized access to a computer or its files. It is entered along with its corresponding user ID, which are then compared against a list of authorized users before access is granted.
Pay Cable - Cable programming services for which subscribers pay an additional fee above the basic cable service charge. Also called Premium Cable.
Pay Cable Unit - Each premium service to which a household subscribes is counted as one unit.
Pay Per View (PPV) - Pay television programming for which cable subscribers pay a separate fee for each program viewed.
Pay Programming - Movies, sports, and made-for-cable specials that are available to the cable customer for a charge in addition to the basic fee.
Penetration - Ratio of the number of cable customers to the total number of households passed by the system.
Per-Inquiry Advertising - Direct response advertising for which the cable network or system running the commercial is paid based on the number of responses received rather than the air time used.
Performance Standards - The minimum technical criteria that must be met by cable television systems, consistent with standard set by the FCC or the local ordinance.
Phase - A relative quantity describing the time relationship between or among waves having identical frequency. The complete wave cycle is divided into 360 equal parts, called degrees of phase.
Phase Distortion - When the output of an amplifier fluctuates in phase, even though the input does not, the circuit introduces phase distortion into the signal.
Phase Jitter - Phase variations arising in a channel and caused by incidental frequency modulation of signals transmitted over the channel. This occurs when the carrier supply frequencies in a frequency-division-multiplexed carrier system are not perfectly constant.
Phase Modulation - When the information is impressed on a radio frequency signal by varying its phase angle.
Picture Element - One of many monochrome or color "dots" that make up a television picture.
Picture Tube - A cathode-ray tube used to produce an image by variation of the intensity of a scanning beam.
Plastic Optical Fiber (PoF) - A plastic cable used, for short distances only, as an alternative to fiber optic cable. Although plastic is not as transparent as glass, it is more malleable and less expensive. PoF is a possible choice for indoor networking.
Plug and Play - An Intel-developed hardware standard created to automate the setup and configuration of hardware devices connected to a computer. In theory, it allows you to "plug" a device into the computer and "play" it without going through a complicated setup process.
Point of Presence (POP) - The point where the inter-exchange carrier's responsibilities for the line begin and the local exchange carrier's responsibility ends. Location of a communications carrier's switching or terminal equipment.
Point-to-Point - A circuit connecting two nodes only, or a configuration requiring a separate physical connection between each pair of nodes.
Pole Attachment - When cable television systems use existing pole lines maintained by utilities, an attachment contract must be negotiated between the parties of interest.
Port - The physical connector on a device enabling the connection to be made.
Power Amplifier - An amplifier that delivers a certain amount of alternating-current power to a load. Used in audio frequency and radio frequency applications.
Power Cycle - The act of turning the electrical power to a device off and then back on, often used to reset the device.
Power Gain - An increase in signal power between one point and another. Used as a specification for power amplifiers.
Power Transistor - A semiconductor transistor designed for power-amplifier applications at audio and radio frequencies.
Predicted Grade A Contour - The line representing the service area in which a good picture is computed to be available 90 percent of the time at 70 percent of the receiver locations. Signal contours determine what educational channels are carried on a cable system and, in similar markets, what stations must be carried from other small markets.
Predicted Grade B Contour - The concentric area marking a television station's service area in which a good analog picture is computed to be available 90 percent of the time at 50 percent of the receiver locations.
Premium Cable - Cable programming services for which subscribers pay an additional fee above the basic cable service charge. Also called Pay Cable.
Profile - A record stored on a computer containing the settings and preferences for each of the users sharing that computer. Profiles can be set up in Windows, as well as Netscape and other shared Internet applications, and are also used to enable security features in a program (e.g., separate email profiles).
Program Non-duplication - Under FCC rules, a cable system must black-out the programming of a distant television station it carries, when the system would duplicate a local station's programming, on the request of the local station.
Program Stream - In MPEG-2, a multiplex of variable-length digital video and audio packets from one or more program sources having a common time-base.
Protocol - The set of rules or standards which enables communication between computers on a network, in its simplest form, a protocol is the language used by two computers to transfer information.
Provisioning - A telephone company term meaning to configure. Before an ISDN line can be used, it has to be correctly provisioned to work with the ISDN equipment the customer is installing and enabled for the various options the customer has requested.
Proxy Server - A network component between a LAN and the Internet providing security, administrative control and data caching. It is also a firewall that protects the network from intrusion.
Public Access - A non-commercial channel set aside by a cable system for use by the public, on a first come first serve, non-discriminatory basis.
Public Switched Telephone Network (PSTN) - The PSTN is the worldwide circuit-switched telephone network. Once only an analog system, telephone networks today increasingly are digital, even though most subscribers are connected via analog circuits.
Public Television - Noncommercial television broadcasting.
Pull Mode - The delivery method in which a subscriber demands and receives data from the provider.
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