Telecom Dictionary - Definitions of terms
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 - In data communication, a sequence of binary digits, including data and control signals, that is transmitted and switched as a composite whole. Note: The data, control signals, and possibly error control information, are arranged in a specific format.
Packet Assembler/Disassembler (PAD) - A functional unit that enables data terminal equipment ( DTE ) not equipped for packet switching to access a packet- switched network .
Packet Entry Event - A packet layer reference event that corresponds to a packet entering a network section (from a circuit section) or a packet entering a DTE (from an access circuit section).
Packet Exit Event - A packet layer reference event that corresponds to a packet exiting a network section (to a circuit section), or a packet exiting a DTE (to an access circuit section).
Packet Filter - A type of firewall in which each packet is examined and either allowed to pass- through, or is rejected, based on local security policy.
Packet Format - The structure of, data, address, and control information in a packet. Note: The size and content of the various fields in a packet are defined by a set of rules that are used to assemble the packet.
Packet Header - A header consisting of octets 4 to 8 (inclusive) of the frame (flags excluded from the octet numbers).
Packet Internet Groper - See ping.
Packetization Interval - Defines the duration of the sampled speech of the access channel that has been collected, coded, and packetized. The packetization interval for voice is 16 ms.
Packet Layer Reference Event - The event that occurs when a packet crossing a section boundary changes the state of the packet layer interface.
Packet Mode - A mode of operating a communications network in which packet switching is used rather than message switching.
Packet-Mode Terminal - Data terminal equipment ( DTE ) that can control, format, transmit, and receive packets.
Packet Sniffer - 1. A dedicated device designed for the purpose of monitoring network traffic in order to recognize and decode certain packets of interest. 2. A software package that enables a general-purpose computer to recognize and decode certain packets of interest. Note: The packet sniffer is normally used by system administrators for network management and diagnostics, but is occasionally used by hackers for illicit purposes such as stealing a user's password or credit-card number. 3. Synonym sniffer.
Packet Stream - A collection of logical links multiplexed together onto one physical channel between two endpoints of the wideband packet network .
Packet-Switched Data Transmission Service - A service that (a) provides for the transmission of data in the form of packets, (b) switches data at the packet level , and (c) may provide for the assembly and disassembly of data packets.
Packet-switched - Communication system that chops messages into small packets before sending them. All packets are addressed and coded so they can be recompiled at their destination. Each packet can follow its own path and therefore can work around problematic transmission segments. Packet switching is best when reaching a destination is the primary concern and latency is permissible, such as sending e-mail and loading Web pages.
Packet Switching - The process of routing and transferring date by means of addressed packets so that a channel is occupied during the transmission of the packet only, and upon completion of the transmission the channel is made available for the transfer of other traffic.
Packet-Switching Network - A switched network that transmits data in the form of packets.
Packet-Switching Node - In a packet-switching network, a node that contains data switches and equipment for controlling, formatting, transmitting, routing, and receiving data packets. Note: In the Defense Data Network ( DDN ), a packet-switching node is usually configured to support up to thirty-two X.25 56-kb/s host connections, as many as six 56-kb/s interswitch trunk (IST) lines to other packet-switching nodes, and at least one Terminal Access Controller (TAC).
Packet Transfer Mode - A method of information transfer, by means of packet transmission and packet switching, that permits dynamic sharing of network resources among many connections.
Pad - A network, of fixed resistors, that attenuates signals by a fixed amount with negligible distortion. Note: The resistive network is called an attenuator if the resistance is adjustable.
PAD - Acronym for packet assembler/disassembler.
Padding - 1. In cryptography, a bit or a string of bits appended to a message either for filtering purposes or to cause the message to contain an even multiple of the number of bits required by the cryptographic algorithm. 2. One or more bits appended to a message in order to cause the message to contain the required number of bits or bytes.
Padlocking - The use of special techniques to protect data or software against unauthorized copying.
Pager - A small radio receiver designed to be carried by a person and to give an aural, visual, or tactile indication when activated by the reception of a radio signal containing its specific code. It may also reproduce sounds and/or display messages that were also transmitted. Some pagers also transmit a radio signal acknowledging that a message has been received. Synonym - beeper.
Paging - A one-way communications service from a base station to mobile or fixed receivers that provide signaling or information transfer by such means as tone, tone-voice, tactile, optical readout, etc.
Paging and Radiotelephone Service - See PARS.
Paging Receiver - See pager.
Paired Cable - A cable made up of one or more separately insulated twisted-wire pairs, none of which is arranged with another to form quads.
Paired Disparity Code - A code in which some or all of the characters are represented by two sets of digits of opposite disparity that are used in sequence so as to minimize the total disparity of a longer sequence of digits. Note 1: An alternate mark inversion signal is an implementation of a paired disparity code. Note 2: The digits may be represented by disparate physical quantities, such as two different frequencies, phases, voltage levels, magnetic polarities, or electrical polarities, each one of the pair representing a 0 or a 1.
Pair-Gain System - A transmission system that uses concentrators or multiplexers so that fewer wire pairs may be used than would otherwise be required to provide service to a given number of subscribers.
PAL - Acronym for phase alternation by line. A television signal standard (625 lines, 50 Hz, 220 V primary power ) used in the United Kingdom, much of the rest of western Europe, several South American countries, some Middle East and Asian countries, several African countries, Australia, New Zealand, and other Pacific island countries.
PAL-M - A modified version of the phase -alternation-by-line ( PAL ) television signal standard (525 lines, 50 Hz, 220 V primary power ), used in Brazil.
Palm Computer - See palm-top.
Palm-Top - A small (pocket-size), hand-held computer, often including network-access software, personal-schedule software, and a basic word processor. A hand-held personal computer, lightweight, small, battery-powered, general-purpose programmable computer . It typically has a miniaturized full-function, typewriterlike keyboard for input and a small, full color, liquid-crystal display for output. In addition to an operating system that is compatible with that of a desktop computer, a palmtop will typically contain a word processor, a spreadsheet program, and a calendar and phone book. A variety of other programs can be loaded and executed, and data can usually be transferred to and from a desktop computer. Although some palmtops are like personal digital assistants in that they accept handwritten or touch screen input, they generally differ in that the palmtop has more memory, a keyboard, and a greater variety of available programs.
PAM - Abbreviation for pulse-amplitude modulation.
PAMA - Abbreviation for pulse-address multiple access.
Panning - 1. On the viewing screen of a display device, e.g., a computer monitor , horizontal shifting of the entire displayed image. Note: The panning direction is at a right angle with respect to the scrolling direction. 2. In video technology, the use of a camera to scan a subject horizontally. 3. In antenna systems, successively changing the azimuth of a beam of radio-frequency energy over the elements of a given horizontal region, or the corresponding process in reception.
p / a r -Abbreviation for peak-to-average ratio.
Parabolic Antenna - An antenna consisting of a parabolic reflector and a radiating or receiving element at or near its focus. Note: If the reflector is in the shape of a paraboloid of revolution, it is called a paraboloidal reflector; cylindrical paraboloids and off-axis paraboloids of revolution are also used.
Parabolic Profile - In an optical fiber , a power-law index profile with the profile parameter , g, equal to 2. Synonym quadratic profile.
Parallel Computer - A computer that has multiple arithmetic units or logic units that are used to accomplish parallel operations or parallel processing.
Parallel Port - A port through which two or more data bits are passed simultaneously, such as all the bits of an 8-bit byte, and that requires as many input channels as the number of bits that are to be handled simultaneously.
Parallel Processing - Pertaining to the concurrent or simultaneous execution of two or more processes in a single unit.
Parallel-to-Serial conversion - Conversion of a stream of multiple data elements, received simultaneously, into a stream of data elements transmitted in time sequence, i.e. , one at a time.
Parallel Transmission - 1. The simultaneous transmission of the signal elements of a character or other data item. 2. In digital communications, the simultaneous transmission of related signal elements over two or more separate paths. Note: Protocols for parallel transmission, such as those used for computer ports, have been standardized by ANSI.
Parametric Amplifier (Paramp) - An amplifier that (a) has a very low noise level, (b) has a main oscillator that is tuned to the received frequency, (c) has another pumping oscillator of a different frequency that periodically varies the parameters, i.e., the capacitance or inductance, of the main oscillator circuit, and (d) enables amplification of the applied signal by making use of the energy from the pumping action. Note: Paramps with a variable-capacitance main-oscillator semiconductor diode are used in radar tracking and communications Earth stations, Earth satellite stations, and deep-space stations. The noise temperature of paramps cooled to the temperature of liquid helium, about 5 K, is in the range of 20 to 30 K. Paramp gains are about 40 dB.
Parasitic Element - Of an antenna, a directive element that is not connected to a radio transmitter or receiver either directly or via a feeder, but is coupled to the driven element only by the fields. Synonym passive element.
Parasitic Emission - In a communications system in which one or more electromagnetic sources are used, electromagnetic radiation --such as lightwaves, radio waves, microwaves, X-rays, or gamma rays from one or more of the sources--that is not harmonically related, i.e., is not coherent, with the transmitted carrier. Note: Parasitic emissions are usually caused by undesired oscillations or energy- level transitions in the sources.
Paraxial Ray - In optical systems, a ray that is close to and nearly parallel with the optical axis.
Parity - 1. In binary-coded data, a condition that is maintained such that, in any permissible coded expression, the total number of 1s, or 0s, is always odd or always even. Note 1: Parity is used in error-detecting and error-correcting codes. Note 2: For example, in the ASCII code or in the International Telegraph Alphabet 5 (ITA-5) code as usually implemented, 7 bits are used to represent each character and 1 bit is used as a parity check bit. 2. Bit(s) used to determine whether a block of data has been altered.
Parity Bit - An extra bit that can be added to a group of "0" bits and "1" bits to make the parity of the group odd or even. Note: The parity bit is discarded when the message is received.
Parity Check - A test that determines whether the number of ones or zeros in an array of binary digits is odd or even. Note: Odd parity is standard for synchronous transmission and even parity for asynchronous transmission. Synonym odd-even check.
Parking Party - Representative of the served user who parks a call via "call park".
Par Meter - Abbreviation for peak-to-average ratio meter. A meter used to measure, calculate, and display the ratio of the peak power level to the time -averaged power level in a circuit, i.e. , the peak-to-average ratio ( p / a r). Note 1: A par meter is used as a quick means to identify degraded telephone channels. Note 2: A par meter is very sensitive to envelope delay distortion. The par meter may also be used for idle channel noise, nonlinear distortion, and amplitude-distortion measurements. Note 3: The peak-to-average ratio can be determined for many signal parameters, such as voltage, current, power, frequency, and phase.
PARS - Abbreviation for paging and radiotelephone service. A radio service in which common carriers are authorized to offer and provide paging and radiotelephone service to the general public. This service was formerly titled Public Land Mobile Service.
Partial-Dial Condition - A condition in which outpulsing has commenced, insufficient information has been received by the customer installation (CI) to process the call and no further outpulsing has been received from the network within a timed interval.
Partitioned Security Mode - [An] information - system (IS) security mode of operation wherein all personnel have the clearance, but not necessarily formal access approval and need-to-know, for all information handled by an IS.
Party ID -1. The served user 's (or controller 's) reference to a particular party within the context of a call. Note 1: Multiple parties may be associated with a given call, e.g., a conference call. Moreover, there may be multiple connections associated with a single party, e.g., a simultaneous voice and video call. Note 2: This service description assumes that there exists only one connection to a given party. 2. In a teleconference, any participant.
Party Line - A line that serves more than one subscriber or user. In telephone systems, an arrangement in which two or more user end instruments, usually telephones, are connected to the same loop. Note: If selective ringing is not used, individual users may be alerted by different ringing signals, such as a different number of rings or a different combination of long and short rings. Party lines remain primarily in rural areas where loops are long. Privacy is limited and congestion often occurs. Synonym multiparty line.
Passband - The portion of spectrum , between limiting frequencies (or, in the optical regime, limiting wavelengths), that is transmitted with minimum relative loss or maximum relative gain. Note 1: The limiting frequencies are defined as those at which the relative intensity or power decreases to a specified fraction of the maximum intensity or power. This decrease in power is often specified to be the half-power points, i.e. , 3 dB below the maximum power. Note 2: The difference between the limiting frequencies is called the bandwidth, and is expressed in hertz (in the optical regime, in nanometers or micrometers).
Passive Device - A device that does not require a source of energy for its operation. Note: Examples of passive devices are electrical resistors, electrical capacitors, diodes, optical fibers, cables, wires, glass lenses, and filters.
Passive Element - Synonym parasitic element.
Passive Satellite -1. In a satellite communications system, a satellite that only reflects signals from one Earth station to another, or from several Earth stations to several others. Note: Although the satellite acts passively by reflecting signals, it may contain active devices for station keeping. 2. An Earth satellite intended to transmit radio communication signals by reflection.
Passive Sensor - A measuring instrument in the Earth exploration-satellite service or in the space research service by means of which information is obtained by reception of radio waves of natural origin.
Passive Star: See star coupler.
Passive Station - On a multipoint connection or a point-to-point connection using basic mode link control, any tributary station waiting to be polled or selected.
Passive Threat - Of a data or information processing system, a threat of disclosure of information without changing the state of the system. Note: An example of a passive threat is one that could result in the recovery of sensitive information through the unauthorized interception of a data transmission.
Passphrase - A sequence of characters, longer than the acceptable length of a password, that is transformed by a password system into a virtual password of acceptable length.
Password - A code or word used to gain access to restricted data on a computer network. While passwords provide security against unauthorized users, the security system can only confirm that the password is legitimate, not whether the user is authorized to use the password. That's why it is important to safeguard passwords by:
- Never disclosing your password to anyone.
- Creating a password that consists of letters, numbers, and symbols.
- Changing your password frequently.
Password History - With respect to a given information system (IS) asset, a log of expired passwords, used primarily for automatic comparison with proposed new passwords. A password history is used to ensure that proposed new passwords were not used in the recent past, if ever, in connection with the IS asset in question. A password history may be limited to only a prescribed number of expired passwords (the usual case) with any overflow ( i.e., the earliest) being discarded as new ones are added; or it may retain expired passwords only for a prescribed period of time; or both. A password history represents a tool that may be used to ensure that passwords are not repeated within a period of time that is deemed consistent with the sensitivity of the protected information system asset.
Password Length Equation - An equation that determines an appropriate password length, M , which provides an acceptable probability, P , that a password will be guessed in its lifetime. Note: The password length is given by M = (log S )/(log N ) where S is the size of the password space and N is the number of characters available. The password space is given by S = LR / P , where L is the maximum lifetime of a password and R is the number of guesses per unit of time.
Password Length Parameter - A basic parameter affecting the password length needed to provide a given degree of security. Note 1: Password length parameters are related by the expression P = LR / S , where P is the probability that a password can be guessed in its lifetime, L is the maximum lifetime a password can be used to log in to a system, R is the number of guesses per unit of time , and S is the number of unique algorithm-generated passwords (the password space). Note 2: The degree of password security is determined by the probability that a password can be guessed in its lifetime.
Patch - 1. To connect circuits together temporarily. Note: In communications, patches may be made by means of a cord, i.e., a cable, known as a "patch cord." In automated systems, patches may be made electronically. 2. In a computer program, one or more statements inserted to circumvent a problem or to alter temporarily or permanently a usually limited aspect or characteristic of the functioning of the program, e.g., to customize the program for a particular application or environment.
Patch and Test Facility (PTF) - A facility in which supporting functions, such as (a) quality control checking and testing of equipment, links, and circuits, (b) troubleshooting, (c) activating, changing, and deactivating of circuits, and (d) technical coordinating and reporting, are performed.
Patch Bay - An assembly of hardware so arranged that a number of circuits, usually of the same or similar type, appear on jacks for monitoring, interconnecting, and testing purposes. Note 1: Patch bays are used at many locations, such as technical control facilities, patch and test facilities, and at telephone exchanges. Note 2: Patch bays facilitate flexibility in the use, routing or restoration of a variety of circuit types, such as dc, VF, group, coaxial, equal-level, and digital data circuits.
Patch Panel - One segment of a patch bay.
Path -1. In communications systems and network topologies, a route between any two points. 2. In radio communications, the route that (a) lies between a transmitter and a receiver and (b) may consist of two or more concatenated links. Note: Examples of paths are line-of-sight paths and ionospheric paths. 3. In a computer program, the logical sequence of instructions executed by a computer. 4. In database management systems, a series of physical or logical connections between records or segments, usually requiring the use of pointers.
Path Attenuation - Synonym path loss.
Path Clearance - In microwave line-of-sight communications , the perpendicular distance from the radio - beam axis to obstructions such as trees, buildings, or terrain. Note: The required path clearance is usually expressed, for a particular k -factor, as some fraction of the first Fresnel zone radius.
Path Iintermodulation Noise - See intermodulation noise.
Path Loss - In a communication system , the attenuation undergone by an electromagnetic wave in transit between a transmitter and a receiver . Note 1: Path loss may be due to many effects such as free-space loss, refraction, reflection, aperture - medium coupling loss, and absorption. Note 2: Path loss is usually expressed in dB. Synonym path attenuation.
Path Overhead (POH) - Overhead assigned to and transported with the payload until the payload is demultiplexed. It is used for functions that are necessary to transport the payload.
Path Profile - A graphic representation of the physical features of a propagation path in the vertical plane containing both endpoints of the path, showing the surface of the Earth and including trees, buildings, and other features that may obstruct the radio signal. Note: Profiles are drawn either with an effective Earth radius simulated by a parabolic arc--in which case the ray paths are drawn as straight lines--or with a "flat Earth"-- in which case the ray paths are drawn as parabolic arcs.
Path Quality Analysis - In a communications path, an analysis that (a) includes the overall evaluation of the component quality measures, the individual link quality measures, and the aggregate path quality measures, and (b) is performed by evaluating communications parameters, such as bit error ratio, signal-plus-noise-plus-distortion to noise-plus-distortion ratio, and spectral distortion.
Path Quality Matrix - A data bank that contains path-quality analyses used to support path selection and routing determination. Note: In adaptive radio automatic link establishment, path quality matrices contain path quality data for single-link and multilink paths.
Path Survey - The assembling of pertinent geographical and environmental data required to design a radio communication system.
Pattern Recognition - The identification of objects and images by their shapes, forms, outlines, color, surface texture, temperature, or other attribute, usually by automatic means.
Pawsey stub - A device for connecting an unbalanced coaxial feeder to a balanced antenna.
PAX - Abbreviation for private automatic exchange. See PBX.
Payload -1. In a set of data, such as a data field, block, or stream, being processed or transported, the part that represents user information and user overhead information, and may include user-requested additional information, such as network management and accounting information. Note: The payload does not include system overhead information for the processing or transportation system. Synonym mission bit stream. 2. The interface rate minus frame overhead. This is the act capability for information transfer provided for the next lower level of the hierarchy.
Payload Loopback - A signal used to command the far-end receiver to loop back the received payload.
Payload Module: The portion of a payload that completely occupies one or more channels.
Payload Overhead - Bits that are assigned at the source and remain with the information payload until the payload reaches the sink and are used for functions associated with transporting the payload.
Payload Pointer - The pointer that indicates the location of the beginning of the synchronous payload envelope.
Pay Per Use Feature Blocking - Allows you to restricts all calls originating from your AT&T residential telephone line(s) from using any or all of the following Pay Per Use Features: Call Return, Call Trace, Repeat Dialing, or Three Way Calling.
Pay-Per-Use Features - The following features are available on a per-use or per-occurrence basis rather than on a monthly subscription basis. With the exception of Call Trace, most local phone companies will charge for up to ten pay-per-use features and the ten uses will appear on the bill. After ten paid feature uses, there is no charge for additional per-use features nor will the additional uses appear on the bill. There is a charge for all Call Trace uses and these charges will be identified on the bill. The following features can usually be ordered on a per-use basis: Call Return, Call Trace, Repeat Dialing, and Three-Way Calling.
PBER - Abbreviation for pseudo bit-error ratio. In adaptive high- frequency (HF) radio, a bit error ratio derived by a majority decoder that processes redundant transmissions. Note: In adaptive HF radio automatic link establishment, PBER is determined by the extent of error correction, such as by using the fraction of non-unanimous votes in the 2-of-3 majority decoder.
PBX (Private Branch Exchange) - An electronic multi-line telephone system, used primarily in very large applications with many extensions. The identifying feature of most PBXs is that you must dial 9 to get an outside line. PBXs generally use standard single-line telephones at extension locations. A pbx is a privately owned system for voice switching and other telephone related services. It routes calls from the public telephone system within an organization and allows direct internal calls.
PBX Tie Trunk - See tie trunk.
PBX Trunk - See trunk.
PC - Abbreviation for carrier power (of a radio transmitter ).
PCB - Abbreviation for power circuit breaker.
PC FAX Board - A circuit board that is installed in a personal computer. Like a FAX, it attaches to your telephone line and is capable of transmitting and receiving images with other FAX Boards and FAX machines. A FAX board, when used with a printer and document scanner, operates like a modern FAX machine.
PCM - Abbreviation for pulse-code modulation. Modulation in which a signal is sampled, and the magnitude (with respect to a fixed reference) of each sample is quantized and digitized for transmission over a common transmission medium. Note 1: In conventional PCM, before being digitized, the analog data may be processed (e.g., compressed), but once digitized, the PCM signal is not subjected to further processing (e.g., digital compaction) before being multiplexed into the aggregate data stream. Note 2: PCM pulse trains may be interleaved with pulse trains from other channels.
PCM multiplex equipment - See multiplexer.
PCS (Personal Communications Services) – Originally meant to describe digital service offered at a higher frequency (1900 MHz) than wireless, it is now used as a generic term for all digital (versus analog) wireless.
PCS application - From a user -identity- module (UIM) perspective, the files, commands and data used to support PCS services.
PCS number - A number that uniquely identifies a PCS user and is used to place or forward a call to that user. Synonyms personal number, UPT number.
PCS session - That part of the card session dedicated to the PCS operation.
PCS switching center - In personal communications service, a facility that (a) supports access -independent call control/ service control, and connection control ( switching ) functions, and (b) is responsible for interconnection of access and network systems to support end-to-end services. Note 1: The PCS switching center represents a collection of one or more network elements. Note 2: The term "center" does not imply a physical location.
PCS System -In personal communications service, a collection of facilities that provides some combination of personal mobility, terminal mobility, and service profile management. Note: As used here, "facilities" includes hardware, software, and network components such as transmission facilities, switching facilities, signaling facilities, and databases.
PC-to-PC Internet Phone
Free Internet phone systems such as Skype and FreeWorld Dialup can bypass the telephone system completely, allowing you to make free calls to other users within their respective networks. Some free networks have added services, such as Skype's Skypeout service, that let you call mobile and standard telephones for a metered fee.
PC-to-Phone Telephony - a type of VoIP communication that involves making phone calls directly from a computer. Calls are placed using a special piece of software, which may be downloaded over the internet. PC-to-Phone is an extremely cheap and efficient way to communicate, and can result in savings of up to 80% when compared to making calls from a traditional telephone.
PDF - An acronym for Portable Document Format, PDF is a file type created by Adobe Systems, Inc. that allows fully formatted, high-resolution documents to be easily transmitted across the Internet and viewed on any computer that has Adobe Acrobat Reader software.
PDH - Acronym for plesiochronous digital hierarchy. PDH refers to the DS1/DS2/DS3 family of signals which were developed as an asynchronously multiplexed hierarchy for transmission systems which are now more frequently encountered as payload in a SONET system.
PDM - Abbreviation for pulse-duration modulation.
PDN - Abbreviation for public data network.
PDS - Abbreviation for protected distribution system.
PDU -Abbreviation for protocol data unit.
PE - Abbreviation for phase -encoded. See phase-encoded recording.
Peak Busy Hour - Synonym busy hour. - In a communications system, the sliding 60-minute period during which occurs the maximum total traffic load in a given 24-hour period. Note 1: The busy hour is determined by fitting a horizontal line segment equivalent to one hour under the traffic load curve about the peak load point. Note 2: If the service time interval is less than 60 minutes, the busy hour is the 60-minute interval that contains the service timer interval. Note 3: In cases where more than one busy hour occurs in a 24-hour period, i.e., when saturation occurs, the busy hour or hours most applicable to the particular situation are used.
Peak Emission Wavelength - Of an optical emitter, the spectral line having the greatest power. Synonym peak wavelength.
Peak Envelope Power (of a radio transmitter) [PEP, pX, PX]: The average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle at the crest of the modulation envelope taken under normal operating conditions.
Peak Limiting - A process by which the absolute instantaneous value of a signal parameter is prevented from exceeding a specified value.
Peer Entity - In layered systems, entities in the same layer but in different systems (nodes) that must exchange information to achieve a common objective.
Peer-Entity Authentication - The corroboration that a peer entity in an association is the one claimed.
peer group - In Open Systems Interconnection (OSI)--Architecture, a group of functional units in a given layer of a network in which all the functions performed by the functional units extend throughout the system at the same layer.
Peering - The arrangement of information sharing between Internet Service Providers at various NAPs.
Peer Protocol - A formal language used by peer entities to exchange user data.
Peg Count -1. In communication systems, a count that is made of the number of times that an event or condition occurs. [From Weik '89] 2. In telephone systems, the process that provides counts of the calls of different service classes that occur during intervals of such frequency as to reliably indicate the traffic load. 3. A count of the attempts to seize, or a count of the actual seizures that occur, of various types of telephone trunks, access lines, switches, or other equipment.
Pel - In a facsimile system, the smallest discrete scanning line sample containing only monochrome information , i.e. , not containing gray-scale information.
Pen-Based Computer - A computer that uses pattern-recognition software to enable it to accept handwriting as a form of input. A stylus, which may contain special electronic circuitry, is used to write on the computer display or on a separate tablet. The earliest devices were limited to recognizing geometric shapes for computer graphics applications and neatly printed alphabetic characters. Pattern recognition has improved to the level where cursive input is now acceptable, especially in personal digital assistants , although such input is not always accurately interpreted by the software. Some software requires the use of a specially modified alphabet to enter data.
Penetration - 1. The intentional passage, through a building wall or partition, or an equipment enclosure or chassis, of a signal -bearing communications medium, e.g., a cable, metallic or optical. 2. Unintended access to the information within a communications or information-processing device via a metallic path intended for another purpose, e.g., via the primary power connection. 3. [The] unauthorized act of bypassing the security mechanisms of a system. 4. The passage of an rf signal through a physical barrier, such as a partition, a wall, a building, or earth. 5. Unauthorized access to a data processing system.
Penetration Testing - Security testing in which evaluators attempt to circumvent the security features of a system based on their understanding of the system design and implementation.
PEP - Deprecated abbreviation for peak envelope power. Either "PX" or "pX" is now preferred. See peak envelope power, power.
Per-Call Key - A unique traffic encryption key generated automatically by certain secure telecommunications systems to secure single voice or data transmissions.
Percentage Modulation -1. In angle modulation, the fraction of a specified reference modulation, expressed in percent. 2. In amplitude modulation, the modulation factor expressed in percent. Note: Percentage modulation may also be expressed in dB below 100% modulation.
Percent Break - In pulsed telephone signaling ( dialing ), the ratio, expressed in percent, of (a) the open- circuit (break) time to (b) the sum of the open- and closed-circuit times of a single dial pulse cycle. Note: For example, at a pulse rate of 10 per second, the pulse period is 100 milliseconds. If, during each pulse period, the equipment generating the dial pulses ( e.g., a telephone set ) presents an open circuit (high impedance ) for 48 milliseconds, and a closed circuit (low impedance) for 52 milliseconds, the percent break is [48 ms/(48ms + 52ms)] = 0.48, or 48%.
Performance Measurement Period - The period during which performance parameters are measured. Note: A performance measurement period is determined by required confidence limits and may vary as a function of the observed parameter values. User time is divided into consecutive performance measurement periods to enable measurement of user information transfer reliability.
Perfect Forward Secrecy - In cryptography, of a key -establishment protocol, the condition in which the compromise of a session key or long-term private key after a given session does not cause the compromise of any earlier session.
Performance Anomalies - A discrepancy between actual and desired characteristics of an item. An anomaly may or may not affect the ability of an item to perform a required function.
Performance Management - In network management, (a) a set of functions that evaluate and report the behavior of telecommunications equipment and the effectiveness of the network or network element and (b) a set of various subfunctions, such as gathering statistical information, maintaining and examining historical logs, determining system performance under natural and artificial conditions, and altering system modes of operation.
Performance Measurement Period - The period during which performance parameters are measured. Note: A performance measurement period is determined by required confidence limits and may vary as a function of the observed parameter values. User time is divided into consecutive performance measurement periods to enable measurement of user information transfer reliability.
Performance Parameter - A quality, usually quantified by a numerical value, which quality characterizes a particular aspect, capability, or attribute of a system. Note: Examples of performance parameters are peg count and mean time between failures.
Performance Primitives - Basic error events or other performance-related occurrences that may be detected by monitoring a digital signal.
Performance Reliability - The ability of an item to perform a required function under given conditions for a given time period. Note 1: It is generally assumed that the item is in a state to perform this required function at the beginning of the time interval. Note 2: The term reliability is used as a measure of reliability performance.
Performance Standard - A statement of general criteria that define a desired result without specifying the techniques for achieving that result. Synonym performance-based standard.
Periapsis - In a satellite orbit, the point that is closest to the gravitational center of the system consisting of the primary body and the satellite. Note: In an orbit about the Earth, periapsis is called perigee. In an orbit about the Moon, periapsis is called perilune, and in an orbit about the Sun, it is called perihelion.
Perigee - Of a satellite orbiting the Earth, the point in the orbit at which the gravitational centers of the satellite and Earth are closest to one another.
Perigee Altitude - See altitude of the apogee or of the perigee: The altitude of the apogee or perigee above a specified reference surface serving to represent the surface of the Earth. Note: In technical usage, the definite article is not used with the term apogee or perigee alone. A body orbiting the Earth is said simply to be "at apogee" or "at perigee." It may, however, properly be said to be "at the point of apogee" or "at the point of perigee."
Periodic Antenna - An antenna that has an approximately constant input impedance over a narrow range of frequencies. Note: An example of a periodic antenna is a dipole array antenna. Synonym resonant antenna.
Period (of a satellite) - The time elapsing between two consecutive passages of a satellite through a characteristic point on its orbit.
Periods Processing - Processing of various levels of classified and unclassified information at distinctly different times. Under the concept of periods processing, the system must be purged of all information from one processing period before transitioning to the next. Under periods processing, the system must be purged of all information from one processing period before transitioning to the next when there are different users with differing authorizations.
Peripheral Device - See peripheral equipment.
Peripheral Equipment - In a data processing system, any equipment, distinct from the central processing unit, that may provide the system with additional capabilities. Note: Such equipment is often offline until needed for a specific purpose and may, in some cases, be shared among several users.
Peripheral Node - Synonym endpoint node: In network topology, a node connected to one and only one branch.
Periscope Antenna - An antenna configuration in which the transmitting antenna is oriented to produce a vertical radiation pattern, and a flat or off-axis parabolic reflector, mounted above the transmitting antenna, is used to direct the beam in a horizontal path toward the receiving antenna. Note: A periscope antenna facilitates increased terrain clearance without long transmission lines, while permitting the active equipment to be located at or near ground level for ease of maintenance.
Permanent Bond - A bond not expected to require disassembly for operational or maintenance purposes.
Permanent Signal (PS) -1. An extended off-hook condition not followed by dialing. 2. A connect signal from the network that has not been followed by network outpulsing within a timed interval.
Permanent Storage - A storage device in which stored data are nonerasable
Permanent Virtual Circuit (PVC) - A virtual circuit used to establish a long-term connection between data terminal equipments ( DTE ). Note 1: In a PVC, the long-term association is identical to the data transfer phase of a virtual call. Note 2: Permanent virtual circuits eliminate the need for repeated call set-up and clearing. Deprecated synonym nailed-up circuit.
Permissible Interference - Observed or predicted interference which complies with quantitative interference and sharing criteria contained in these [Radio] Regulations or in CCIR Recommendations or in special agreements as provided for in these Regulations.
Permuter - A device used in crypto-equipment to change the order in which the contents of a shift register are used in various nonlinear combining circuits.
Persistent Data - Information that endures beyond a single instance of use, e.g., longer than one call attempt.
Personal Agent - Synonym droid. See bot.
Personal Authenticating Information (PAI) - Information such as a secret password, a badge, or biometric data —or any combination of these—used to authenticate a user's identity.
Personal Communications Service - See PCS. A set of capabilities that allows some combination of terminal mobility, personal mobility, and service profile management. Note 1: The flexibility offered by PCS can supplement existing telecommunications services, such as cellular radio, used for NS/EP missions. Note 2: PCS and UPT are sometimes mistakenly assumed to be the same service concept. UPT allows complete personal mobility across multiple networks and service providers. PCS may use UPT concepts to improve subscriber mobility in allowing roaming to different service providers, but UPT and PCS are not the same service concept.
Personal De-registration - The process by which end users cancel a previous registration to a terminal.
Personal Digital Assistant - [personal digital assistant] (PDA), lightweight, hand-held computer designed for use as a personal organizer with communications capabilities. A typical PDA has no keyboard, relying instead on special hardware and pen-based computer software to enable the recognition of handwritten input, which is entered on the surface of a liquid crystal display screen. In addition to including such applications as a word processor, spreadsheet, calendar, and address book, PDAs are used as notepads, appointment schedulers, and wireless communicators for sending and receiving data, faxes, and electronic-mail messages. Introduced in 1993, PDAs achieved only modest acceptance during the remainder of the decade due to their relatively high price and limited applications.
Personal Identification Number (PIN) - A code or password, unique to or associated with, a specific user, and entered into a data-processing device for purposes of verifying the identity of a person requesting, e.g., a transaction or access.
Personal Mobility - In universal personal telecommunications (UPT), (a) the ability of a user to access telecommunication services at any UPT terminal on the basis of a personal identifier, and (b) the capability of the network to provide those services in accord with the user's service profile. Note 1: The personal mobility aspects of personal communications are based on the UPT number. Note 2: Personal mobility involves the network's capability to locate the terminal associated with the user for the purposes of addressing, routing, and charging the user for calls. Note 3: "Access" is intended to convey the concepts of both originating and terminating services. Note 4: Management of the service profile by the user is not part of personal mobility.
Personal Mobility Controller - In UPT (universal personal telecommunications), a facility that provides the control logic for user authentication, service request validation, location management, alerting, user access to service profile, privacy, access registration, and call management.
Personal Mobility Management - In PCS(personal communication service ), the capability that (a) provides authentication of user identification and maintains user location information in the service profile, (b) controls the completion of calls based on user-specified incoming call management contained in the service profile, (c) provides translation between user identification and identification of the terminal currently associated with the user for the completion of calls to the use's current location, and (d) controls the services and features available to the user based on the user's subscription and in conjunction with user-specified terminal access configurations.
Personal Number - A number that uniquely identifies a PCS or UPT user ( universal personal telecommunications service user) and is used to place, or forward, a call to that user. Note: Before the full implementation of UPT service, the use of the term UPT number may, in some contexts, be subject to misinterpretation. The personal number is a UPT number, and is the basis of the personal mobility aspects of PCS. The term is provided as an alternative term for use where appropriate to avoid such a misinterpretation. Synonym PCS number.
Personal Registration - In universal personal telecommunications, the process of associating a UPT user with a specific terminal.
Personal Station - A light-weight, pocket-sized FPLMTS terminal (Future Public Land Mobile Telecommunication Systems terminal).
Personal Terminal - In personal communications service, a lightweight, small, portable terminal that provides the capability for the user to be either stationary or in motion while accessing and using telecommunication services. Informal synonym brick.
Personalized Ringing - A phone company service that you could subscribe to where you are issued a different ring pattern for specific phone numbers that call you. For instance, you could assign a double ring to any calls that come from your mother's phone number and a triple ring for any calls that come from your daughter's phone number. When you mom calls you, your phone rings with a double ring pattern, When your daughter calls from here home phone number, it rings with a triple ring pattern and when anyone else calls, the phones ring like normal.
The phone companies advertise personalized ringing service for when you want to know if your kids, spouse or the boss is calling. With this feature all the people you need to talk to will be identified by the personalized ring or tone and you will know to answer their call.
Note: If you want to have two separate phone numbers each with its own distinctive ring pattern on one line, in this case "personalized ring" is NOT what you want. You will need to subscribe to "distinctive ring" instead.
PGP - Abbreviation for pretty good privacy. A publicly available implementation of a public-key encryption system using no trusted third party. Note: PGP can be used to apply a digital signature to a message without actually encrypting the text of the message. This is normally used in public postings where the user wants all readers to be able to see the message text and also wants the reader to be able to confirm that the message is unaltered from its original form. Once a digital signature is created with PGP, it is impossible for anyone to modify either the message or the signature without the modification being detected by PGP.
Phantom Circuit - A third circuit derived from two suitably arranged pairs of wires, called side circuits, with each pair of wires being a circuit in itself and at the same time acting as one conductor of the third circuit. Note: The side circuits are coupled to their respective drops by center-tapped transformers, usually called "repeat coils." The center taps are on the line side of the side circuits. Current from the phantom circuit is split evenly by the center taps. This cancels crosstalk from the phantom circuit to the side circuits. Synonym [loosely] phantom facility.
Phantom Facility - A transmission facility derived with repeating coils from two or more pairs of wires. Synonyms phantom circuit, phantom pair. Note: The name "phantom" is derived from the fact that balanced, center-tapped transformers, called "repeat(ing)" coils in telephone parlance, can be used, e.g., in conjunction with two twisted pairs, to create a third, electrically isolated transmission path ("phantom pair") by splitting the latter's electrical signal between the two twisted pairs (called "side circuits") in such a fashion as to cancel inductive interference from the phantom circuit to the side circuits, and vice versa.
Phantom Group - Three circuits that are derived from simplexing two physical circuits to form a phantom circuit.
Phase - 1. Of a periodic, varying phenomenon, e.g., an electrical signal or electromagnetic wave, any distinguishable instantaneous state of the phenomenon, referred to a fixed reference or another periodic varying phenomenon. Note 1: Phase, i.e., phase time (frequently abbreviated simply to "phase" in informal usage), can be specified or expressed by time of occurrence relative to a specified reference. Note 2: The phase of a periodic phenomenon can also be expressed or specified by angular measure, with one period usually encompassing 360&176; (2 radians). Note 3: Phase may be represented (a) in polar coordinates by M , where M is the magnitude and is the phase angle, and (b) in Cartesian coordinates, i.e., an Argand diagram, as (a + jb), where a is a real component and b is an imaginary component such that tan = (b /a), where is the phase angle, and the magnitude, M, is (a 2+ b 2)½ 2. A distinguishable state of a phenomenon. 3. That period of time during which a specified function occurs in a sequential list of functions.
Phase Angle - Of a periodic wave, the number of suitable units of angular measure between a point on the wave and a reference point. Note 1: The reference point may be a point on another periodic wave. The waves may be plotted on a suitable coordinate system, such as a Cartesian plot, with degrees or other angular measure usually plotted on the abscissa and amplitude on the ordinate. Usually, at least one full cycle of each wave is plotted, with 360&176; (2 radians) encompassing one full cycle. The reference points may be any significant instants on the waves, such as where they cross the abscissa axis. Note 2: The use of angular measure to define the relationship between a periodic wave and a reference point is derived from the projection of a rotating vector onto the real axis of an Argand diagram. Note 3: The value of the phase angle of a point on the wave is the point on the abscissa that corresponds to the point on the wave. Note 4: The phase angle of a vector may be written as M , where M is the magnitude of the vector and is the phase angle relative to the specified reference.
Phase Bandwidth - Of a network or device, the width of the continuous frequency range over which the phase -vs.-frequency characteristic does not depart from linearity by more than a stated amount.
Phase Coherence - The state in which two signals maintain a fixed phase relationship with each other or with a third signal that can serve as a reference for each.
Phase Coherent - See phase coherence.
Phase Constant - The imaginary part of the axial propagation constant for a particular mode, usually expressed in radians per unit length.
Phased Array - A group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions. Note 1: The relative amplitudes of--and constructive and destructive interference effects among--the signals radiated by the individual antennas determine the effective radiation pattern of the array. Note 2: A phased array may be used to point a fixed radiation pattern, or to scan rapidly in azimuth or elevation.
Phase Delay - In the transmission of a single- frequency wave from one point to another, the delay of an arbitrary point in the wave that identifies its phase. Note: Phase delay may be expressed in any convenient unit, such as seconds, degrees, radians, or wavelengths.
Phase Departure - 1. A phase deviation from a specified value. 2. An unintentional deviation from the nominal phase value.
Phase Detector - A circuit or instrument that detects the difference in phase between corresponding points on two signals.
Phase Deviation - In phase modulation, the maximum difference between the instantaneous phase angle of the modulated wave and the phase angle of the unmodulated carrier. Note: For a sinusoidal modulating wave, the phase deviation, expressed in radians, is equal to the modulation index.
Phase Diagram - A graphic representation of the phase relationships between two or more waveforms. Note: A phase diagram may be represented as a vector diagram or as an amplitude-vs.- time diagram.
Phase Difference - The time interval or phase angle by which one wave leads or lags another. Synonym phase offset.
Phase-Locked Loop (PLL) - An electronic circuit that controls an oscillator so that it maintains a constant phase angle relative to a reference signal. Note: Phase-locked loops are widely used in space communications for coherent carrier tracking and threshold extension, bit synchronization, and symbol synchronization.
Phase Offset - Synonym phase difference.
Phase-Shift Keying (PSK) - 1. In digital transmission, angle modulation in which the phase of the carrier is discretely varied in relation either to a reference phase or to the phase of the immediately preceding signal element, in accordance with data being transmitted. 2. In a communications system, the representing of characters, such as bits or quaternary digits, by a shift in the phase of an electromagnetic carrier wave with respect to a reference, by an amount corresponding to the symbol being encoded. Note 1: For example, when encoding bits, the phase shift could be 0° for encoding a "0," and 180° for encoding a "1," or the phase shift could be -90 for "0" and +90° for a "1," thus making the representations for "0" and "1" a total of 180° apart. Note 2: In PSK systems designed so that the carrier can assume only two different phase angles, each change of phase carries one bit of information, i.e., the bit rate equals the modulation rate. If the number of recognizable phase angles is increased to 4, then 2 bits of information can be encoded into each signal element; likewise, 8 phase angles can encode 3 bits in each signal element. Synonyms biphase modulation, phase-shift signaling.
Phase Term - In the propagation of an electromagnetic wave in a uniform waveguide, such as an optical fiber or metal waveguide, the parameter that indicates the phase change per unit distance of the wave at any point along the waveguide.
Phone - 1. Abbreviation for telephone, telephony. 2. Loosely, the voice-operation mode in radio communications.
Phone Company Voice Mail - A phone company feature that answers calls and takes messages when you are on the phone, on the internet, sending a fax, or not at home. This feature also works when the electrical power is out. You can access your voicemail box through a local access number. You enter your PIN and follow the appropriate prompts to use the service. There is a maximum capacity for messages, minutes per message, and message retention length, as outlined in marketing information for your local phone company. Call Forwarding Busy/No Answer must be ordered but will not be billed when Voice Mail is ordered.
Phone Jack - n : a jack for plugging in a telephone [syn: telephone jack].
Phone Fax Switch - A device that allows a single phone line to be shared for multiple devices. Typically a Phone Fax Switch would allow voice (phones and answering machine) and a fax machine or fax modem to operate on a shared phone line. Other applications include any variation of voice, a fax machine, fax/modem and/or modem(s). Incomming calls are automatically routed to the proper device(s). If the call comes in and it is a fax call, the call is automatically routed to the fax machine or fax .modem. If the call is a modem call, it is routed to the correct modem. Voice calls are routes to phone(s) and/or answering machine. May require a security access code (SAC) in the dialing string to automatically switch to the modem. Synonym Automatic Line Sharing Device . Fax Switch , Automatic Fax Switch .
Phone Line Switch - - A device that allows one or more phone lines to be shared for multiple phone connected devices. A common application would allow voice (phones and answering machine) and a fax machine or fax modem to operate transparently on a single phone line thus eliminating the monthly costs associated with a dedicated phone line. Applications include any variation of voice, a fax machine, fax/modem and/or modem(s). Incoming calls are automatically routed to the proper device(s) with no human intervention. If the call comes in and it is a fax call, the call is automatically routed to the fax machine or fax modem. If the call is a modem call, it is routed to the correct modem. Voice calls are routes to phone(s) and/or answering machine. May require a security access code (SAC) in the dialing string to automatically switch to the modem. Synonym Automatic Line Sharing Device . Fax Switch , Automatic Fax Switch .
Phone Line Sharing - A technology that allows a single phone line to share incoming and outgoing access for multiple devices. Typically Phone Line Sharing Technology allows voice (phones and answering machine) and a fax machine or fax modem to operate on a shared phone line. Other applications include any variation of voice, a fax machine, fax/modem and/or modem(s).
Incoming calls are automatically routed to the proper device(s). If the call comes in and it is a fax call, the call is automatically routed to the fax machine or fax modem. If the call is a modem call, it is routed to the correct modem. Voice calls are routes to phone(s) and/or answering machine. May require a security access code (SAC) in the dialing string to automatically switch to the modem. All outgoing calls access the line from any device. Optional "barge-in protection" protects any voice or data call from being accessed by other telephone equipment on the same line.
Since the need for to subscribe to a separate "fax line" or "modem line" from the local telephone company is eliminated, the return on investment (ROI) is very high. The initial cost of the device is returned in savings in a few months. After that you will save the monthly bills associated with fax, data or voice lines. For almost every business, phone line sharing technology is a smart investment.
Photocurrent - The current that flows through a photosensitive device, such as a photodiode, as the result of exposure to radiant power. Note 1: The photocurrent may occur as a result of the photoelectric, photoemissive, or photovoltaic effect. Note 2: The photocurrent may be enhanced by internal gain caused by interaction among ions and photons under the influence of applied fields, such as occurs in an avalanche photodiode (APD).
Photodetector (PD) - A transducer capable of accepting an optical signal and producing an electrical signal containing the same information as in the optical signal. Note: The two main types of semiconductor photodetectors are the photodiode (PD) and the avalanche photodiode (APD).
Photodiode - A semiconductor diode that produces, as a result of the absorption of photons, (a) a photovoltage or (b) free carriers that support the conduction of photocurrent. Note: Photodiodes are used for the detection of optical communication signals and for the conversion of optical power to electrical power.
Photon - A discrete packet, i.e., quantum, of electromagnetic energy. Note: The energy of a photon is h, where h is Planck's constant and is the frequency of the electromagnetic wave.
Photovoltaic Effect - The production, as a result of the absorption of photons, of a voltage difference across a pn junction. Note: The voltage difference is caused by the internal drift of holes and electrons.
Physical Layer - Layer 1. The lowest of seven hierarchical layers. The Physical layer performs services requested by the Data Link Layer. The major functions and services performed by the physical layer are: (a) establishment and termination of a connection to a communications medium; (b) participation in the process whereby the communication resources are effectively shared among multiple users, e.g., contention resolution and flow control; and, (c) conversion between the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel. See Open Systems Interconnection--Reference Model.
Physical Security - See communications security. The component of communications security that results from all physical measures necessary to safeguard classified equipment, material, and documents from access thereto or observation thereof by unauthorized persons.
PIC Freeze – Pre-subscribed Interexchange Carrier Freeze. An agreement between a customer and their local telephone company to prevent “slamming” on their long distance telephone bill.
Picture - Synonym image. In the field of image processing, a two-dimensional representation of a scene.
Pigtail - A short length of optical fiber that is permanently affixed to an active device, e.g., LED or laser diode, and is used to couple the device, using a splice or connector, to a longer fiber. 2. A short length of single-fiber cable, usually tight-buffered, that has an optical connector on one end and a length of exposed fiber at the other end. Note: The exposed fiber of the pigtail is then spliced to one fiber of a multifiber trunk, i.e., arterial, cable, to enable the multifiber cable to be "broken out" into individual single-fiber cables that may be connected to a patch panel or an input or output port of an optical receiver or transmitter. 3. A short length of electrical conductor permanently affixed to a component, used to connect the component to another conductor.
Pilot - 1. A signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes. Note: Sometimes it is necessary to employ several independent pilot frequencies. Most radio relay systems use radio or continuity pilots of their own but transmit also the pilot frequencies belonging to the carrier frequency multiplex system. 2. See palm-top.
PIN - Abbreviation for personal identification number. A code or password, unique to or associated with, a specific user, and entered into a data-processing device for purposes of verifying the identity of a person requesting, e.g., a transaction or access.
Ping - a geeky way of describing the action of one computer sending a signal to another computer, of course expecting some kind of response. Ping web services comprise only one out of several specific applications of XML-RPC web services.
Pipeline - An extremely high-speed, large capacity bandwidth connection.
Pitch - Synonym lay length. - In communications cables--including fiber-optic cables--having the transmission media wrapped helically around a central member, the longitudinal distance along the cable required for one complete helical wrap; i.e., the total cable length divided by the total number of wraps. Note 1: In many fiber-optic cable designs, the pitch is shorter than in metallic cables of similar diameter, to avoid overstressing the fibers during the pulling associated with the installation operation. Note 2: The wraps, i.e., turns, that are referred to should not be confused with the twists given twisted metallic pairs, i.e., wires, to reduce electromagnetic coupling. Pairs of optical fibers are not given such twists.
Pixel - In a raster-scanned imaging system, the smallest discrete scanning line sample that can contain gray scale information.
Plain Old Telephone Service (POTS) - Nothing more than a standard telephone line, the kind Ma Bell and then AT&T handled exclusively before the deregulation of the telephone industry. Upgrade your POTS to DSL, and you have broadband; add VoIP, and you have a system that uses POTS, the PSTN, and the Internet in one (ideally) seamless system.
Plain Text - Unencrypted information. Note: Plain text includes voice. Synonym clear text.
Planck's constant - The constant of proportionality, represented by the symbol h, that relates the energy E of a photon with the frequency of the associated wave through the relation E = h, where h = 6.626 × 10-34 joule•second.
Plane Polarization - Synonym linear polarization. - Of an electromagnetic wave, confinement of the E-field vector or H-field vector to a given plane. Note: Historically, the orientation of a polarized electromagnetic wave has been defined in the optical regime by the orientation of the electric vector, and in the radio regime, by the orientation of the magnetic vector.
Plane Wave - 1. A wave whose surfaces of constant phase are infinite parallel planes normal to the direction of propagation. 2. An electromagnetic wave that predominates in the far-field region of an antenna, and has a wavefront that is essentially in a plane. Note: In free space, the characteristic impedance of a plane wave is 377 .
Plant - All the facilities and equipment used to provide telecommunications services. Note: Plant is usually characterized as outside plant or inside plant . Outside plant, for example, includes all poles, repeaters and unoccupied buildings housing them, ducts, and cables--including the "inside" portion of interfacility cables outward from the main distributing frame (MDF) in a central office or switching center. Inside plant includes the MDF and all equipment and facilities within a central office or switching center.
Point Code (PC) - A unique address code that identifies a service provider (SP) within a signaling network.
Point of Interface (POI) - In a telecommunications system, the physical interface between the local access and transport area (LATA) access and inter-LATA functions. Note: The interface point is used to establish the technical interface, the test points, and the points of operational responsibility. Synonym interface point.
Point of Presence (POP) - A location where a you can connect to a network through local telephone
Point-to-Point Protocol - A program that allows a computer to use a telephone line and modem to make TCP/IP connections.
Polarity - A term used to describe the order of two electrical points – one positive and the other negative. On an RJ-11 female jack, the green lead should be positive with respect to the red lead to ensure proper operation with all equipment.
Polarization - Of an electromagnetic wave, the property that describes the orientation, i.e., time-varying direction and amplitude, of the electric field vector. Note 1: States of polarization are described in terms of the figures traced as a function of time by the projection of the extremity of a representation of the electric vector onto a fixed plane in space, which plane is perpendicular to the direction of propagation. In general, the figure, i.e., polarization, is elliptical and is traced in a clockwise or counterclockwise sense, as viewed in the direction of propagation. If the major and minor axes of the ellipse are equal, the polarization is said to be circular. If the minor axis of the ellipse is zero, the polarization is said to be linear. Rotation of the electric vector in a clockwise sense is designated right-hand polarization, and rotation in a counterclockwise sense is designated left-hand polarization. Note 2: Mathematically, an elliptically polarized wave may be described as the vector sum of two waves of equal wavelength but unequal amplitude, and in quadrature (having their respective electric vectors at right angles and /2 radians out of phase).
PON (Passive Optical Network) - a fiber-based network built without active electronics. Because a PON network uses optical splitters rather than costly active electronics, it is less expensive to build and maintain than a network that uses active electronics. PONs are still more expensive than copper-based networks. A PON network is usually used in a local loop to connect customers to the central office. BPON (Broadband Passive Optical Network) is a broadband PON.
Polnet 2.0® ACP 300, ACP-500, ACP-900 Product Pages
- Polnet 2.0 ACP-300
- Polnet 2.0 ACP-500
- Polnet 2.0 ACP-900
- Polnet ACP 2.0 Series
- Polnet ACP 2.0 Manual
- Polnet ACP 2.0 Manual PDF
- Polnet 2.0 ACP Brochure PDF
POP - See Point of Presence and Post Office Protocol
POPs (Population equivalents) – The population of a market multiplied by the percentage ownership of that market.
Positive Feedback - Synonym regeneration. In a regenerative repeater, the process by which digital signals are amplified, reshaped, retimed, and retransmitted.
Positive Justification - Synonym bit stuffing. - The insertion of noninformation bits into data. Note 1: Stuffed bits should not be confused with overhead bits. Note 2: In data transmission, bit stuffing is used for various purposes, such as for synchronizing bit streams that do not necessarily have the same or rationally related bit rates, or to fill buffers or frames. The location of the stuffing bits is communicated to the receiving end of the data link, where these extra bits are removed to return the bit streams to their original bit rates or form. Bit stuffing may be used to synchronize several channels before multiplexing or to rate-match two single channels to each other.
Post-Detection Combiner - A diversity combiner in which (a) the signals from each channel are added together, (b) the gain of each channel is made proportional to the rms signal level and inversely proportional to the mean square noise level in that channel, and (c) the same proportionality constant is used for all channels. Synonym maximal-ratio combiner.
Post Office Protocol (POP) - A system that allows hosts to get e-mail from a server.
POTS (Plain Old Telephone Service) - Nothing more than a standard telephone line, the kind Ma Bell and then AT&T handled exclusively before the deregulation of the telephone industry. Upgrade your POTS to DSL, and you have broadband; add VoIP, and you have a system that uses POTS, the PSTN, and the Internet in one (ideally) seamless system.
Power - 1. The rate of transfer or absorption of energy per unit time in a system. 2. Whenever the power of a radio transmitter etc. is referred to, it shall be expressed in one of the following forms, according to the class of emission, using the arbitrary symbols indicated:
For different classes of emission, the relationships between peak envelope power, mean power and carrier power, under the conditions of normal operation and of no modulation, are contained in CCIR Recommendations which may be used as a guide. For use in formulae, the symbol p denotes power expressed in watts and the symbol P denotes power expressed in decibels relative to a reference level.
Power Density - Deprecated synonym for irradiance. Radiant power incident per unit area upon a surface. Note: Irradiance is usually expressed in watts per square meter, but may also be expressed in joules per square meter.
Power-Law Index Profile - For optical fibers, a class of graded-index profiles characterized by
where n (r) is the nominal refractive index as a function of distance from the fiber axis, n 1 is the nominal refractive index on axis, n 2 is the refractive index of the homogeneous cladding (n (r) = n 2 when r ), is the core radius, and g is a parameter that defines the shape of the profile. Note 1: is often used in place of g. Hence, this is sometimes called an alpha profile. Note 2: For this class of profiles, multimode distortion is smallest when g takes a particular value depending on the material used. For most materials, this optimum value is approximately 2. When g increases without limit, the profile tends to a step-index profile.
PPP - See Point to Point Protocol
Precedence - In communications, a designation assigned to a message by the originator to indicate to communications personnel the relative order of handling and to the addressee the order in which the message is to be noted. [After JP1] Note: The descending order of precedence for military messages is FLASH, IMMEDIATE, PRIORITY, and ROUTINE.
Precise Time - A time mark that is accurately known with respect to an accepted reference time standard. Note: Current uncertainty among international standards is approximately 1 part in 1014 as of 1995.
Predetection Combining - A diversity combiner in which (a) the signals from each channel are added together, (b) the gain of each channel is made proportional to the rms signal level and inversely proportional to the mean square noise level in that channel, and (c) the same proportionality constant is used for all channels. Synonym maximal-ratio combiner.
Preemption - The seizure, usually automatic, of military system facilities that are being used to serve a lower precedence call in order to serve immediately a higher precedence call.
Prefix - In telephone communications, an indicator consisting of one or more digits, that allows the selection of different types of number formats (e.g., local, national or international), transit networks and/or the service. Note 1: Prefixes are not part of the number and are not signaled over internetwork and international boundaries. Note 2: When prefixes are used, they are always entered by the user or by automatic calling equipment.
Presentation Layer - Layer 6 of the See Open Systems Interconnection--Reference Model. This layer responds to service requests from the Application Layer and issues service requests to the Session Layer. The Presentation Layer relieves the Application Layer of concern regarding syntactical differences in data representation within the end-user systems. Note: An example of a presentation service would be the conversion of an EBCDIC-coded text file to an ASCII-coded file. See Open Systems Interconnection--Reference Model.
Primary Coating - The plastic overcoat in intimate contact with the cladding of an optical fiber, applied during the manufacturing process. Note 1: The primary coating typically has an outside diameter of approximately 250 to 750 m, and serves to protect the fiber from mechanical damage and chemical attack. It also enhances optical fiber properties by stripping off cladding modes, and in the case where multiple fibers are used inside a single buffer tube, it suppresses cross-coupling of optical signals from one fiber to another. Note 2: The primary coating should not be confused with a tight buffer, or the plastic cladding of a plastic-clad-silica (PCS) fiber. Note 3: The primary coating, which typically consists of many layers, may be color-coded to distinguish fibers from one another, e.g., in a buffer tube containing multiple fibers. Synonyms primary polymer coating, primary polymer overcoat.
Primary Polymer Coating - Synonym primary coating.
Primary Polymer Overcoat - Synonym primary coating.
Primary Power - The source of electrical power that usually supplies the station main bus. Note 1: The primary power source may be a Government-owned generating plant or a public utility power system. Note 2: A Class A primary power source assures, to a high degree of reliability, a continuous supply of ac electrical power.
Primary Radar: A radiodetermination system based on the comparison of reference signals with radio signals reflected from the position to be determined.
Primary Rate Interface (PRI) - An integrated services digital network (ISDN) interface standard (a) that is designated in North America as having a 23B+D channels, (b) in which all circuit-switched B channels operate at 64 kb/s, and (c) in which the D channel also operates at 64 kb/s. Note: The PRI combination of channels results in a digital signal 1 (T1) interface at the network boundary.
Priority - 1. Priority, unless specifically qualified, is the right to occupy a specific frequency for authorized uses, free of harmful interference from stations of other agencies. [NTIA] 2. Synonym priority level. 3. In DOD record communications systems, one of the four levels of precedence used to establish the time frame for handling a given message. 4. In DOD voice communications systems, one of the levels of precedence assigned to a subscriber telephone for the purpose of preemption of telephone services.
Priority Level - In the Telecommunications Service Priority system, the level that may be assigned to an NS/EP telecommunications service, which level specifies the order in which provisioning or restoration of the service is to occur relative to other NS/EP or non-NS/EP telecommunication services. Note: Priority levels authorized are designated (highest to lowest) "E," "1," "2," "3," "4," and "5" for provisioning and "1," "2," "3," "4," and "5" for restoration. Synonym priority.
Privacy - 1. In a communications system or network, the protection given to information to conceal it from unauthorized persons having access to the system or network at large. Synonym segregation. 2. In a communications system, protection given to unclassified information, such as radio transmissions of law enforcement personnel, that requires safeguarding from unauthorized persons. 3. In a communications system, the protection given to prevent unauthorized disclosure of the information in the system. Note 1: The required protection may be accomplished by various means, such as by communications security measures and by directives to operating personnel. Note 2: The limited protection given certain voice and data transmissions by commercial crypto equipment is sufficient to deter a casual listener, but cannot withstand a competent cryptanalytic attack.
Privacy Screener with Caller ID, Name and ACR - Privacy Screener is a phone company feature that works with Caller ID (required feature) to stop unwanted telemarketers. Privacy Screener automatically intercepts unavailable, unknown, blocked or private calling telephone numbers. Interception occurs before the phone rings. Privacy Screener requires the callers to identify themselves. The caller can hang up when prompted to identify themselves; but if they choose to identify themselves, the phone rings, the Privacy Screener displays on the Caller ID unit and the caller's name is heard when the phone is answered. You then choose whether or not to accept the call. Additionally, if it is a telemarketer, the touch of a button instructs the Privacy Screener service to tell the caller to remove your name from the calling list.
Private Branch Exchange (PBX) - An electronic multi-line telephone system, used primarily in very large applications with many extensions. The identifying feature of most PBXs is that you must dial 9 to get an outside line. PBXs generally use standard single-line telephones at extension locations.
Private Exchange (PX) - A private telecommunication switch that usually includes access to the public switched network.
Private Line - 1. In telephone industry usage, a service that involves dedicated circuits, private switching arrangements, predefined transmission paths, or combination thereof, whether virtual or physical, and which provide communications between specific locations. 2. Among subscribers to the public switched telephone network (s), a one-party switched access line.
Private Line Service - 1. A service for communications between specified locations for a continuous period or for regularly recurring periods at stated hours. 2. A service whereby facilities for communication between two or more designated points are set aside for the exclusive use or availability for use of a particular customer and authorized users during stated periods of time.
Private Prime Factors - In cryptographic applications, the two prime numbers, namely p and q, whose product pq is the modulus n.
Processor - In a computer, a functional unit that interprets and executes instructions. Note: A processor consists of at least an instruction control unit and an arithmetic unit.
Profile Dispersion - In an optical fiber, that dispersion attributable to the variation of refractive index contrast with wavelength. Profile dispersion is a function of the profile dispersion parameter.
Profile Parameter (g) - In the power-law index profile of an optical fiber, the parameter, g, that defines the shape of the refractive-index profile. Note: The optimum value of g for minimum dispersion is approximately 2.
Program - 1. A plan or routine for solving a problem on a computer. Note: Processing may include the use of an assembler, a compiler, an interpreter, or a translator to prepare the program for execution, as well as the execution of the program. The sequence of instructions may include statements and necessary declarations. 2. A sequence of instructions used by a computer to do a particular job or solve a given problem. 3. To design, write, and test programs.
Programmable Security Access Codes (SAC's) -Transfer of a call is executed by dialing the programmed SAC for each voice/data device connected to the fax switch. SAC's are programmable (using a touch tone phone only) up to 4 characters long-digits 0 through 9 and symbols * Touch Tone Pulse Dial (star) and # (pound). Fax switches will not detect SAC's dialed from "calling" pulse phones-only from touch tone phones. Call transfers dialed by a pulse phone are limited to phones hooked to or on the same line as the fax switch and are limited to transfer to the "FAX" port only. The pulse dial SAC for this is fixed at "2" You must also have the "Pulse Select" feature on if you use a pulse dial phone to transfer a call.
Programming Language - An artificial language that is used to generate or to express computer programs. Note: The language may be a high-level language, an assembly language, or a machine language.
Propagation - The motion of waves through or along a medium. Note: For electromagnetic waves, propagation may occur in a vacuum as well as in material media.
Proration - 1. The proportional distribution or allocation of parameters, such as noise power and transmission losses, among a number of tandem-connected items, such as equipment, cables, links, or trunks, in order to balance the performance of communications circuits. Synonym budgeting. 2. In a telephone switching center, the distribution or allocation of equipment or components proportionally among a number of functions, to provide a requisite grade of service.
Protected Hook Flash -This feature allows the fax switch to be compatible with certain multi-line KSU phone systems. Some KSU systems do not allow touch tones (DTMF tones) to be generated from a telephone key pad after an inbound call has arrived. With Protected Hook flash "on" the phone system can be "fooled" into generating touch tones by striking the flash key Calls can then be manually transferred between devices by dialing the proper security access code. Factory preset is "off."
Protection - Synonym lockout. 1. In telephone systems, treatment of a user's line or trunk that is in trouble, or in a permanent off-hook condition, by automatically disconnecting the line from the switching equipment. 2. In public telephone systems, a process that denies an attendant or other users the ability to reenter an established connection. 3. In a telephone circuit controlled by two voice-operated devices, the inability of one or both users to get through, either because of excessive local circuit noise or because of continuous speech from either or both users. 4. In mobile communications, an arrangement of control circuits whereby only one receiver can feed the system at a time. Synonym receiver lockout system. 5. An arrangement for restricting access to use of all, or part of, a computer system.
Protocol - 1. A formal set of conventions governing the format and control of interaction among communicating functional units. Note: Protocols may govern portions of a network, types of service, or administrative procedures. For example, a data link protocol is the specification of methods whereby data communications over a data link are performed in terms of the particular transmission mode, control procedures, and recovery procedures. 2. In layered communications system architecture, a formal set of procedures that are adopted to facilitate functional interoperation within the layered hierarchy. 3. A set of rules and formats, semantic and syntactic, permitting information systems (IS's) to exchange information.
Provisioning - 1. In telecommunications, the setting in place and configuring of the hardware and software required to activate a telecommunications service for a customer; in many cases the hardware and software may already be in place and provisioning entails only configuration tasks such as creating (or modifying) a customer record in a database and associating it with the service(s) and service level for which the customer has subscribed. 2. The act of acquiring telecommunications service from the submission of the requirement through the activation of service. Note 1: Provisioning includes all associated transmission, wiring, and equipment. Note 2: In NS/EP telecommunication services, "provisioning" and "initiation" are synonymous and include altering the state of an existing priority service or capability. 3. Processes that arrange and connect equipment and facilities, and create their associated software and data base translations, in response to service demands and forecasts. In this sense, provisioning does not include equipment installations, but rather the state of the equipment, i.e., in service, out of service, stand by, reserved, etc., the state of which may also be controlled by provisioning functions. 4. The act of supplying telecommunication service to a user, including all associated transmission, wiring, and equipment. 5. The process of establishing and supplying telecommunications service to a user, including an associated transmission, wiring, and telecommunications company equipment.
PSK - Abbreviation for phase-shift keying. - 1. In digital transmission, angle modulation in which the phase of the carrier is discretely varied in relation either to a reference phase or to the phase of the immediately preceding signal element, in accordance with data being transmitted. 2. In a communications system, the representing of characters, such as bits or quaternary digits, by a shift in the phase of an electromagnetic carrier wave with respect to a reference, by an amount corresponding to the symbol being encoded. Note 1: For example, when encoding bits, the phase shift could be 0° for encoding a "0," and 180° for encoding a "1," or the phase shift could be -90 for "0" and +90° for a "1," thus making the representations for "0" and "1" a total of 180° apart. Note 2: In PSK systems designed so that the carrier can assume only two different phase angles, each change of phase carries one bit of information, i.e., the bit rate equals the modulation rate. If the number of recognizable phase angles is increased to 4, then 2 bits of information can be encoded into each signal element; likewise, 8 phase angles can encode 3 bits in each signal element.
Psophometer - An instrument that provides a visual indication of the audible effects of disturbing voltages of various frequencies. Note: A psophometer usually incorporates a weighting network. The characteristics of the weighting network depend on the type of circuit under investigation, such as whether the circuit is used for high-fidelity music or for normal speech.
Psophometric Weighting - A noise weighting established by the International Consultative Committee for Telephony (CCIF, which became CCITT and, more recently, ITU-T), designated as CCIF-1951 weighting, for use in a noise measuring set or psophometer. Note: The shape of this characteristic is virtually identical to that of F1A weighting. The psophometer is, however, calibrated with a tone of 800 Hz, 0 dBm, so that the corresponding voltage across 600 ohms produces a reading of 0.775 V. This introduces a 1-dBm adjustment in the formulas for conversion with dBa.
PSTN (Public Switched Telephone Network) - The network of wires, signals, and switches that lets one telephone connect to another anywhere in the world. Some VoIP services provide a gateway from the Internet to the PSTN and vice versa.
Public Key Cryptography - 1. The type of cryptography in which the encryption process is publicly available and unprotected, but in which a part of the decryption key is protected so that only a party with knowledge of both parts of the decryption process can decrypt the cipher text. Note: Commonly called non-secret encryption in professional cryptologic circles. FIREFLY is an application of public key cryptography. 2. [An] Encryption system using a linked pair of keys. What one pair of keys encrypts, the other pair decrypts.
Public Switched Network (PSN) - 1. Any common carrier network that provides circuit switching among public users. Note: The term is usually applied to public switched telephone networks, but it could be applied more generally to other switched networks, e.g., packet-switched public data networks. 2. A switched network accessible by the public for the purpose of originating and terminating telecommunications messages. 3. Any common carrier switched network, whether by wire or radio, including local exchange carriers, interexchange carriers, and mobile service providers, that use the North American Numbering Plan in connection with the provision of switched services.
Public Switched Telephone Network (PSTN) - The network of wires, signals, and switches that lets one telephone connect to another anywhere in the world. Some VoIP services provide a gateway from the Internet to the PSTN and vice versa.
Public Utilities Commission (PUC): In the United States, a state regulatory body charged with regulating intrastate utilities, including telecommunications systems. Note: In some states this regulatory function is performed by public service commissions or state corporation commissions.
Pulse - 1. A rapid, transient change in the amplitude of a signal from a baseline value to a higher or lower value, followed by a rapid return to the baseline value. 2. A rapid change in some characteristic of a signal, e.g., phase or frequency, from a baseline value to a higher or lower value, followed by a rapid return to the baseline value.
Pulse Amplitude - The magnitude of a pulse parameter, such as the field intensity, voltage level, current level, or power level. Note 1: Pulse amplitude is measured with respect to a specified reference and therefore should be modified by qualifiers, such as "average," "instantaneous," "peak," or "root-mean-square." Note 2: Pulse amplitude also applies to the amplitude of frequency- and phase-modulated waveform envelopes.
Pulse Broadening - An increase in pulse duration. Note: Pulse broadening may be specified by the impulse response, the root-mean-square pulse broadening, or the full-duration-at-half-maximum pulse broadening.
Pulse-Code Modulation (PCM) - Modulation in which a signal is sampled, and the magnitude (with respect to a fixed reference) of each sample is quantized and digitized for transmission over a common transmission medium. Note 1: In conventional PCM, before being digitized, the analog data may be processed (e.g., compressed), but once digitized, the PCM signal is not subjected to further processing (e.g., digital compaction) before being multiplexed into the aggregate data stream. Note 2: PCM pulse trains may be interleaved with pulse trains from other channels.
Pulse Duration - 1. In a pulse waveform, the interval between (a) the time, during the first transition, that the pulse amplitude reaches a specified fraction (level) of its final amplitude, and (b) the time the pulse amplitude drops, on the last transition, to the same level. Note: The interval between the 50% points of the final amplitude is usually used to determine or define pulse duration, and this is understood to be the case unless otherwise specified. Other fractions of the final amplitude, e.g., 90% or 1/e (where e = 2.71828. . .), may also be used, as may the root-mean-square (rms) value of the pulse amplitude. Deprecated synonyms pulse length, pulse width. 2. In radar, measurement of pulse transmission time in microseconds, that is, the time the radar's transmitter is energized during each cycle.
Pulse Length - Deprecated synonym for pulse duration.
Pulse Repetition Rate: The number of pulses per unit time.
Pulse String - A series of pulses having similar characteristics. Synonym pulse train.
Pulse Train - A series of pulses having similar characteristics. Synonym pulse string.
Pulse Width - Deprecated synonym for pulse duration.
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