P.O.S. - Abbreviation for point-of-sale (e.g., a cash register station).
PABX (private automatic branch exchange) - Equipment originally used as a means of switching telephone calls within a business site and from the site to outside lines. Can also be used for low speed transmission of data, in addition to voice.
Packet format - The exact order and size of the various control and information fields of a packet, including header, address and data fields.
Packet overhead - A measure of the ratio of the total packet bits occupied by control information to the number of bits of data, usually expressed as a percent.
Packet switching - A data communications technique in which data is transmitted by means of addressed packets and a transmission channel is occupied for the duration of transmission of the packet only. The channel is then available for use by packets being transferred between different data terminal equipment.
Packet - A collection of bits that contain both control information and data. The basic unit of transmission in a packet-switched network, control information is carried in the packet, along with the data, to provide for such functions as addressing, sequencing, flow control and error control at each of several protocol levels. A packet can be of fixed or variable length, but generally has a specified maximum length.
PACS - Physical access control system.
PAD (packet assembler/disasssembler) - In a X.25 packet-switched network, a device used to interface non- X.25 devices to an X.25 network; it may be synchronous or asynchronous, single or multiple channel.
Pad - A passive attenuation device used to reduce a signal’s amplitude.
Pair - Two insulated wires of a single circuit associated together; also known as a “balanced” transmission line.
PAL (phase alternating line) - A non-NTSC video format used mainly in Europe, Australia, China, India and many countries in Africa and the Middle East. It has6 25 lines of resolution with 50 fields per second or 25 frames per second.
PAM - Pulse amplitude modulation.
Parallel circuit - A circuit in which identical voltage is presented to all components, and the current divides among the components according to the resistances or the impedances of the components.
Parallel core conductor - A conductor constructed with a central core of parallel-laid wires surrounded by one layer of helically-laid wires.
Parallel stripe - A stripe applied longitudinally on a wire or cable parallel to the axis of the conductor.
Parallel transmission - A technique that sends bits simultaneously over a separate lines; normally used to send data a byte (eight bits over eight lines) at a time to a high-speed printer or other locally attached peripheral. Contrast with SERIAL TRANSMISSION.
Parity, parity check - Addition of overhead bits to ensure that the total number of 1s in a grouping of bits is either always even for even parity or always odd for odd parity. This permits detection of single errors. It may be applied to characters, transmission blocks or any convenient bit grouping.
Partial discharge (Corona) Extinction voltage - The voltage at which partial discharge (corona) is no longer detectable on instrumentation adjusted to a specific sensitivity, following the application of a specified higher voltage.
Passive - A non-powered element of a system.
Patch cable - In the IBM cabling system, a length of Type 6 cable with data connectors on both ends.
Patch cord - A flexible piece of electrical cord terminated at both ends with plugs, used for inter-connecting circuits on a patch board.
Patch panel - A terminating enclosure for connecting cables. See DISTRIBUTION PANEL.
Path loss - Actual signal attenuation from point of transmission to point of reception.
Pathway - A facility for the placement of telecommunications cable.
Payoff - The process of feeding a cable or wire from a bobbin, reel or other package. The payoff is the source reel. Wire is fed from a payoff reel onto a take-up reel.
PBDE - (Polybrominated diphenyl ether). A class of flame retardants sometimes used in wire and cable products. PBDEs are generally banned by European Union RoHS regulations.
PBX (private branch exchange) - A manual, user-owned telephone exchange. Sometimes used in a general sense to include both PBXs and PABXs.
PC - Personal computer.
PCB - Printed circuit board. Also referred to as PWB (printed wiring board) to distinguish this usage from the chemical usage (polychlorinated biphenyls–persistent organic pollutants that are banned in many countries).
PCM (pulse code modulation) - A modulation technique used to convert analog voice signals into digital form. Used for voice multiplexing on T1 circuits.
PCMCIA - Personal Computer Memory Card International Association.
PCP - (Neoprene) Polychloroprene.
PDN (public data network) - A packet switched or circuit switched network available for use by many customers. PDNs may offer value-added services at a reduced cost because of communications resource sharing, and usually provide increased reliability due to built-in redundancy.
PDS - See PREMISES DISTRIBUTION SYSTEM.
PDU - Power distribution unit.
PE - Polyethylene.
Peak - The maximum instantaneous value of a varying current or voltage. Also called crest.
Peak-to-peak - The amplitude difference between the most positive and the most negative excursions of a signal.
Peek - Poly ether ether ketone. A colorless organic thermoplastic used for its robustness.
Peel strength - The force necessary to peel a flexible member from another member that may be either flexible or rigid.
Percent conductivity - The ratio of the resistivity of the International Annealed Copper Standard (IACS) at 20°C to the resistivity of a material at 20°C, expressed in percent. Results are calculated on a weight basis or volume basis and so specified.
Percent plating - Quantity of plating on a conductor expressed as a percentage by weight.
Percentage conductivity - Conductivity of a material expressed as a percentage of that of copper.
Peripheral - Any device used to process data for entry into or extraction from a computer.
Personal computer - A microcomputer with an end-user-oriented application program (used by data processing professionals and non-professionals alike) for an assortment of functions.
PFA (Perfluoroalkoxy) - Teflon is the DuPont trademark for perfluoroalkoxy.
Phase modulation - One of three basic ways to add information to a sine wave signal; the phase of the sine wave, or carrier, is modified in accordance with the information to be transmitted. With only discrete changes in phase, this technique is known as phase shift keying (PSK).
Phase sequence - The order in which successive members of a periodic wave set reach their positive maximum values: a) zero phase sequence, no phase shift; b) plus/minus phase sequence, normal phase shift.
Phase shift - A change in the phase relationship between two alternating quantities. The phase angle between the input and output signals of a system.
Phase - The location of a position on a waveform of an alternating current, in relation to the start of a cycle. Measured in degrees with 360 corresponding to one complete cycle.
Photovoltaic wire (PV WIRE) - A UL cable type. 600 V, 1,000 V, 2,000 V insulated, stranded single conductor wire used to connect photovoltaic electricity generating panels to each other and to collection, distribution and utilization equipment.
Phy - The physical layer device, a circuit block that includes a PMD (physical media dependent), a PMA (physical media attachment), and a PCS (physical coding sub layer).
PIC - Polyethylene insulated cable.
Pick - Distance between two adjacent crossover points of braid filaments. The measurement in picks per inch indicates the degree of coverage.
Pickup - Any device which is capable of transforming a measurable quantity of intelligence (such as sound) into relative electrical signals, e.g., a microphone.
Pico - Prefix meaning one-millionth of one-millionth (10-12).
Picofarad - One-millionth of one-millionth of a farad. A micro microfarad or picofarad (abbreviation pf).
Pigtail wire - Fine stranded, extra flexible, rope lay lead wire attached to a shield for terminating purposes.
PILC cable - Paper insulated, lead covered. Old cable style present in many urban distribution networks. Most are scheduled for replacement due to lead content and age.
PIMF - Pairs in metal foil. Also referred to as S/FTP cable.
Pin assignment - A predetermined relationship between the terminals in a connector and the conductors in a cable that specifies the terminals to which each conductor is to be terminated.
Pin - Passive infrared.
Pinhole lens - Lens used for applications where the camera or lens must be hidden. Front of lens has a small opening to allow the lens to view an entire room through a small hole in a wall.
Pitch diameter - Diameter of a circle passing through the center of the conductors in any layer of a multi-conductor cable.
Pitch - In flat cable, the nominal distance between the index edges of two adjacent conductors.
PIV - Personal identity verification.
Planetary twister - A cabling machine whose payoff spools are mounted in rotating cradles that hold the axis of the spool in a fixed direction as the spools are revolved so the wire will not kink as it is twisted.
Plastic - High-polymeric substances, including both natural and synthetic products, but excluding the rubbers that are capable of flowing under head and pressure.
Plasticizer - A chemical added to plastics to make them softer and more flexible.
Plated hole - A hole with walls that have been plated with conductive material to provide an electrical connection between the conductive patterns on both sides of a printed circuit or an anchor for soldering an inserted wire.
PLC - Programmable logic controller. A type of industrial control system.
Plenum - The air return path of a central air handling system, either ductwork or open space over a suspended ceiling.
Plenum cable - 1. A cable that is UL Listed as having adequate fire resistance and low smoke producing characteristics for installation without conduit in ducts, plenums and other spaces used for environmental air, as permitted by NEC Articles 725-2(b) and 800-3(b). 2. Cable specifically designed for use in a plenum, the space above a suspended ceiling used to circulate air back to the heating or cooling system in a building. Plenum cable has insulated conductors often jacketed with Teflon or Halar to give them low flame - and low smoke – producing properties.
PLP - Packet layer protocol.
PLTC (power limited tray cable) - Rated 300 volts.
Plug - The part of the two mating halves of a connector that is movable when not fastened to the other mating half.
Ply - The number of individual strands or filaments twisted together to form a single thread.
PMD - 1. Physical medium dependant. The portion of the physical layer (PHY) responsible for interfacing to the transmission medium, the physical media dependent sub layer is responsible for transmission. 2. Polarization mode dispersion.
PoE (Power over Ethernet) - A system to transfer electrical power, along with data, to remote devices over standard twisted-pair cable in an Ethernet network. Defined by the IEEE 802.3af standard.
POF (polymer optical fiber) - One of the media projected to become the heart of an automotive LAN. Current experimentation and technological agreements between key companies may result in technological advancements to ultimately herald the introduction of LANs in transportation vehicles. The POF media would become the communications backbone of the vehicle.
Point-to-point connection - See LINK.
Point-to-point wiring - An interconnecting technique wherein the connections between components are made by wires routed between connecting points.
Polar transmission - See BIPOLAR TRANSMISSION.
Polarization - 1. The orientation of a flat cable or a rectangular connector. 2. Orientation of the electric field in an electromagnetic wave. Common characteristic of antennas.
Polishing - Act of smoothing ends of optical fibers to an “optically smooth” finish, generally using abrasives.
Polyamide - The chemical name for nylon.
Polyaramid - Generic name for Kevlar. Sometimes also referred to as a ramid fiber.
Polybutadiene - A type of synthetic rubber often blended with other synthetic rubbers to improve their properties.
Polychloroprene - See NEOPRENE.
Polyester - Polyethylene terephthalate, used extensively as a moisture-resistant cable core wrap. Mylar is DuPont’s trademark for polyester.
Polyethylene - A thermoplastic material having excellent electrical properties.
Polyhalocarbon - A general name for polymers containing halogen atoms. The halogens are fluorine, chlorine, bromine and iodine.
Polyimide - A relatively high-temperature plastic developed for use as a dielectric or jacketing material. Kapton is DuPont’s trademark for polyimide.
Polymer optical fiber - One of the media projected to become the heart of an automotive LAN. Current experimentation and technological agreements between key companies may result in technological advancements to ultimately herald the introduction of LANs in transportation vehicles. The POF media would become the communications backbone of the vehicle.
Polymer - A substance made of many repeating chemical units or molecules. The term polymer is often used in place of plastic, rubber or Elastomer.
Polyolefins - A family of plastics including cross-linked polyethylene and various ethylene copolymers.
Polypropylene - A thermoplastic similar to polyethylene but stiffer and having higher softening point (temperature).
Polyurethane - Broad class of polymers noted for good abrasion and solvent resistance. Can be solid or cellular form.
Polyvinyl chloride (PVC) - A general purpose thermoplastic used for wire and cable insulations and jackets.
Porosity - Generally defined as the percentage of space occupied by voids in an insulation cross section.
Port concentrator, port concentration - A device that allows several terminals to use a single computer port; a concentrator link in which the port concentrator simplifies the software Demultiplexing used in lieu of the Demultiplexing normally performed by the computer-site concentrator.
Port - 1. An entrance to or exit from a network; an access point ford at an entry or exit. 2. A computer interface capable of attaching to a modem for communicating with a remote terminal.
Position coding - Identification of conductors by their location, possible only when conductors are located in assigned positions with relation to each other throughout the entire length of a cable.
Positive sequence impedance - The electrical impedance of a three-phase power cable during normal operation. A cable parameter used by electrical system engineers to calculate voltage drop. “Positive sequence” refers to the phase relationship of the currents in the conductors.
Post equalization - A method of equalizing the signal that comes from the customer equipment to the D4 channel bank. Equalization provides a near-linear level for all frequencies in the voice-frequency band.
Pots - Acronym for plain old telephone service.
Potting - Sealing by filling with a substance to exclude moisture.
Power cables - Cables of various sizes, constructions and insulations, single or multi-conductor, designed to distribute primary power to various types of equipment.
Power factor - The cosine of the phase difference between current and applied voltage.
Power loss - The difference between the total power delivered to a circuit, cable or device, and power delivered by that device to a load.
Power ratio - The ratio of the power appearing at the load, to the input power. Expressed in dB, it is equal to 10 log10 (Px/P1) where P1 is input power and P2 is the power at the load.
Power - The amount of work per unit of time. Usually expressed in watts and equal to I2R.
PPE - Polypropylene ethylene.
PPP (point-to-point protocol) - PPP is the Internet standard for transmission of IP packets over serial lines. PPP supports a sync and sync lines.
PPS - Pictures per second. Sometimes referred to as ips (images per second).
PPTP - Point to point tunneling protocol.
Preamble - An alternating sequence (1, 0, 1, 0. . .) signaling the beginning of a packet.
Prebond - Stranded wire that has been fused, topcoat tinned or overcoat tinned.
Premises distribution system - The transmission network inside a building or group of buildings that connects various types of voice and data communications devices, switching equipment and other information management systems together, as well as to outside communications networks. The system consists of all the transmission media and electronics, administration points, connectors, adapters, plugs and supports hardware between the building’s side of the network and the terminal equipment required to make the system operational.
Premises network - See CABLE SYSTEM.
Premolded splice - A joint made of pre-molded components assembled in the field.
Preposition lenses - Zoom lenses that utilize a variable-resistor (potentiometer) to indicate zoom or focus position to the lens controller. After initial setup, this allows the operator to view different preset areas quickly without having to readjust the zoom and focus each time.
Primary insulation - The first layer of nonconductive material applied over a conductor, whose prime function is to act as electrical insulation.
Primary - The transformer winding that receives the energy from a supply current.
Printing wiring - A printed circuit intended to provide point-to-point electrical connections.
Private line - See LEASED LINE.
Private network, private line - Telecommunications network owned by the customer or reserved for exclusive use by the customer. Same as leased line.
Production (routine) tests - Tests made on components or subassemblies during production for the purpose of quality control.
PROM (programmable read-only memory) - Permanently stored data in a nonvolatile semiconductor device.
Propagation delay skew - The difference in delay between the fastest and slowest pairs within the same cable sheath.
Propagation delay - The transmit time through a link, network, system or piece of equipment.
Propagation time - Time required for a wave or pulse to travel between two points on a transmission line.
Propagation velocity - The velocity of the propagation of a wave or pulse along a transmission path.
Proprietary LAN - A LAN that runs the equipment of only one manufacturer.
Protective covering - A field-applied material to provide environmental protection over the splice or housing, or both.
Protocol analyzer - A test unit that provides compatibility with leading integrated network management systems to optimize troubleshooting and centralized performance analysis of enterprise networks.
Protocol converters - Devices that transform one protocol to another in order to provide compatibility between systems using different protocols. In ISN, the Model 4271 Protocol Converter translates ASCII data to bisynchronous data and, in reverse, converts bisynchronous data to ASCII data. The model 4276 performs a similar translation between ASCII data and SNA/SDLC protocol.
Protocol - A set of procedures for establishing and controlling communications.
Proximity effect - Non-uniform current distribution over the cross-section of a conductor caused by the variation of the current in a neighboring conductor.
PSAACRF - Power sum insertion loss to alien crosstalk ratio far-end. A computation of signal coupling from multiple pairs of disturbing channels, to a disturbed pair in another channel measured at the far-end and relative to the received signal level in the disturbed pair at the far-end. Also referred to as power sum alien equal-level far-end crosstalk (PSAELFEXT).
PSAFEXT - Power sum alien far-end crosstalk. A computation of signal coupling from multiple near-end disturbing channel pairs into a disturbed pair of a neighboring channel or part thereof, measured at the far-end.
PSANEXT - Power sum alien near-end crosstalk. A computation of signal coupling from multiple near-end disturbing channel pairs into a disturbed pair of a neighboring channel or part thereof, measured at the near-end.
PSN (packet switching network) - A network that enables external computers and terminals to communicate with other computers linked to the network. PSN uses packet switching to transmit data. Connections to PSN are governed by a series of recommendations known collectively as X.25.
PSNEXT - Power sum near-end crosstalk. A computation of the unwanted signal coupling from multiple transmitters at the near-end into a neighboring (non-energized) pair measured at the near-end.
PT - Thermostat cable with solid conductor, individual insulation, twisted together.
PTFE (TFE Teflon) - Polytetrafluoroethylene.
PTSS - Passive transmission subsystem.
PTT (post telephone and telegraph authority) - The government agency that functions as the communications common carrier and administrator in many areas of the world.
Pulling eye - A device attached to a conductor to pull cable into or from a duct.
Pulse cable - A type of coaxial cable constructed to transmit repeated high voltage pulses without degradation.
Pulse width modulation - Modulating a pulse train by varying the pulse width in proportion to the modulating signal’s significant characteristic.
Pulse - A current or voltage which changes abruptly from one value to another and back to the original value in a finite length of time.
Punch-down block - A 2-foot piece of metal and plastic that allows you to connect telephone wiring coming from two remote points. Also called a 66-block or quick-connect block.
PUR - Polyur ethane.
PVC (permanent virtual circuit) - In a packet-switched network, a fixed virtual circuit between two users; no-call setup or clearing procedures are necessary; the PDN equivalent of a leased line; contrast with switched virtual circuit.
PVC (polyvinyl chloride) - A common insulating and jacketing material used on cables.
PVC-I - A MIL-DTL-17 coax jacket type. A black polyvinyl chloride with excellent weathering and abrasion properties, but is a contaminating type and will cause cable attenuation to increase with age. Can be used for direct burial.
PVC-II - A MIL-DTL-17 coax jacket type. A gray polyvinyl chloride material which is semi-non-contaminating.
PVC-IIA - A MIL-DTL-17 coax jacket type. A black or gray polyvinyl chloride material that is non-contaminating. It has good weathering and abrasion-resistant properties and can be used for direct burial.
PVDF - Kynar, Atochem trademark for polyvinylidene fluoride.
PWB - Printed wiring board. Replacing PCB in common usage to avoid confusion with chemical PCBs.
PYROMETER - See THERMOCOUPLE.