PDH-Physical Address


Plesiochronous Digital Hierarchy. Developed to carry digitized voice over twisted pair cabling more efficiently . This evolved into the North American, European, and Japanese Digital Hierarchies where only a discrete set of fixed rates is available, namely, nxDS0 (DS0 is a 64 kbps rate) and then the next levels in the respective multiplex hierarchies. See also Plesiochronous. See T Carrier for hierarchy detail.


A Versit term . Personal Data Interchange, a collaborative application area which involves the communication of data between people who have a business or personal relationship, but do not necessarily share a common computing infrastructure.


A page description language (PDL) is a is a clever short-cut for transmitting bitmapped images from a PC application to a printer. They save processing time, by sending only "instructions" to a printer, rather than the entire bitmapped image. They also allow the printer to print any font, any size . PDL is the generic term. Hewlett-Packard has been the major proponent of the concept of PDLs. And they include something called PCL with all their printers. PCL stands for Printer Command Language. Postscript is also a PDL, but different to PCL. HP includes PCL with all its laser printers, but has only included

What we really meant was that HP had never built PostScript into their printers. They still haven't, really. You still have to buy PostScript as either a plug-in cartridge or an addon "SIM" chip from HP, Adobe or third parties for most of the HP line. The exception is the top-of-the-line LaserJet IIIsi, for which built-in PostScript is an option that you pay extra for.

That may change. For now, if you're using Windows applications, Windows' built-in "True Type" scalable fonts ” which do work on HP and other non-PostScript printers ” will satisfy most of your printing needs.


  1. Pulse Duration Modulation.

  2. See Personal Data Module.


  1. An ISDN Term. Primary Directory Number (7 digits for 5ESS switch; 10 digits for DMS-100 switch)

  2. Public Data Network. A public network for the transmission of data, particularly a network compatible with X.25 protocol. A public data network is to data what the Public Switched Voice Network is to voice. To access a public data network, you typically dial a local number, receive a carrier tone and then follow very specific instructions. Public data networks send their digital data in packets over high speed channels. The major reason to use a PDN is that it may be cheaper than dialing directly on a switched voice line. Also, they get you into some databases and services which are hard to get into by dialing direct. There are many public data networks in the United States. The two best-known public data networks are Tymnet and Telenet. But there are probably 30 more. Every industrialized foreign country has at least one, usually owned by the local government phone company.

  3. Premises Distribution Network. The electronics and cabling system which connect terminal equipment to the NTI (Network Terminating Interface). The PDN may be either point- to-point or multipoint, may be configured as either a bus or star, and may be either active or passive in nature. In an ADSL Asymmetric Digital Subscriber Line) implementation, for example, a PDN system would be used to connect the ATU-R (ADSL Termination Unit- Remote) to Service Modules which perform terminal adaptation functions. See also NTI, ADSL and ATU-R.


  1. See Power Distribution Panel.

  2. Plasma Display Panel.

  3. Packet Data Protocol. A GPRS (General Packet Radio Service) term for a range of protocols which support the transfer of packet data over a 3G (3rd Generation) wireless cellular network. See also GPRS.

  4. Programmed Data Processor. A family of minicomputers developed by Digital Equipment Corporation in the 1970s, the most popular of which was the PDP-11. PDP systems used the PAL (Paradox Application Language) programming language.

  5. Policy Decision Point. A network-based server that makes decisions relative to traffic priorities in an IP network running the COPS (Common Open Policy Server) protocol. See COPS.


Programmed Data Processor-11. On the last day of March , 1970 Digital Equipment Corporation (DEC) shipped its first PDP-11/20 minicomputer to a customer in Tennessee. The PDP-11 family was among the first minicomputers that incorporated open standards into its operations. And the PDP-11 software platform has continued through subsequent generations of hardware. It's now obsolete. DEC got bought by Compaq and is now effectively closed down. See also PDP.


  1. Premise Distribution System. Lucent's proprietary structured cable and wire system for intrabuilding application. Such a cabling system provides a number of options for deploying various combinations of UTP, STP, coax and fiber optic cables contained within a single cable sheath. Thereby, various media can be deployed in appropriate combination, considerably reducing overall deployment costs.

  2. Processor Direct Slot. Some non-NuBus Apple Macintosh computers have one PDS that allows for expansion cards.


Protocol Data Unit. OSI (Open Systems Interconnection) terminology for a generic "packet." A PDU is a message of a given protocol comprising payload and protocol-specific control information, typically contained in a header. PDUs pass over the protocol interfaces which exist between the layers of protocols (per OSI model). Basically, PDU is OSI (Open Systems Interconnection) terminology for "packet". A PDU is a data object exchanged by protocol machines (entities) within a given layer. PDUs consist of both data and control (protocol) information that allows the two to coordinate their interactions. The native PDU may be altered through a process of Segmentation and Reassembly (SAR) in order to achieve compatibility with a service offering. For example, an Ethernet PDU in the form of a frame becomes known as an SMDS Service Data Unit (SDU) when considered in the context of a SMDS network service. The SDU then is encapsulated with control information to become a Level 3 (SMDS) PDU, which subsequently is segmented into 48-octet payloads, each of which is preceded with another 5 octets of control data to constitute a 53-octet SMDS cell , also known as a Level 2 PDU. The cells are transported over the SMDS network, with the process of reassembly being performed on the receiving end. As a result, the receiving device is presented with the data in its native PDU format.


Path Delay Value


  1. Processing Element.

  2. PolyEthelyne. A type of plastic material used to manufacture jackets for outside plant cable systems.


That part of the business day in which customers expect to pay full service rates. For cellular customers, peak hours are generally 7:00 a.m. to 7:00 p.m. For business land- line customers, peak hours are generally 8:00 a.m. to 5:00 p.m.

Peak Emission Wavelength

Of an optical emitter, the spectral line having the greatest power.

Peak Envelope Power

PEP. The average power supplied to the antenna transmission line by a radio transmitter during one radiofrequency cycle at the crest of the modulation envelope taken under normal operating conditions.

Peak Hour

When used with an automatic call distributor, the peak hour is when the number of calls coming into your center are at their highest level. ACDs allow you to track and report on calls by hour. Some allow you to also track peak half-hours, or peak delays of the week or months of the year.

Peak Load

A higher than average quantity of traffic. Peak Load is usually expressed for a one-hour period, often the busiest hour of the busiest day of the year. See Busy Hour.

Peak Mount

An antenna mounting system (tripod or ridge mount) used for erecting an antenna at the ridge of roof. See Ridge Mount and Tripod.

Peak Position Requirements

A call center term. The maximum number of base staff required in any half hour within a given date range.

Peak Rate

The per-minute price for using a communications device in the "peak" time period. For cellular, "Peak" time generally includes hours such as evenings Monday through Friday, and all day Saturday, Sunday, and certain holidays. For normal landline phone service, peak rates will include workday days.

Peak To Average Ratio

PAR. Also known as the "crest factor." The ratio between the peak and the average power level applied to a carrier frequency (the frequency which carries the information signal) over a circuit.

Peak Power

Many phone systems use more power when more people are talking on them. You need to know peak power so you don't suddenly blow all your fuses when everybody gets on the phone.

Peaked Load

The load that results from peaked traffic.

Peaked Traffic

Random traffic that has a variance-to-mean ratio grater than one.


Within-the-hour or 'moment-to-moment" variations in traffic.


Momentary bursts of high volume traffic which occur during the busy hour.

Peanut Tubes

A name given to the smaller sizes of vacuum tubes.


PCM Expansion Bus. A digital voice bus for sending voice across different voice processing cards and components in the same PC. PEB is from Dialogic, Parsippany, NJ. It is an open platform. Many companies make voice processing products connecting via PEB. See also Dynamic Node Access.


Tech support shorthand for "Problems Exist Between Chair And Keyboard." A way of indicating there's nothing wrong with the computer or the network. The user is clueless.


Positive Emitter Logic.


See Pedestal.


  1. A small green box sits outside and houses cables coming in, cables going out and cable splices inside the box to join cables. This way a cable coming in from the telephone central office can be joined to one going to someone's house.

  2. A pedestal is also a mounting device used in pay telephone installations where the instrument is not attached to a wall.


X.435. The standard defines how EDI (Electronic Data Interchange) is handled in the X.400 world. The standard includes many advanced service features addressing security, message forwarding, etc.


When you store a number in memory you "poke" it there. When you want to read it back, you take a "peek." Peek and poke are thus instructions that view and alter a byte of memory by referencing a specific memory address. Peek displays the contents; poke changes it.


A peer is an equal in civil standing or rank. It is one's equal before the law. The word had little meaning in computing or telecommunications until PCs came along and got progressively more powerful ” in fact more powerful than early mainframes. Someone thought if you joined up a bunch of PCs together on networks their combined computing and storage capability would be big, powerful and cheap. One of the first places PCs were used in peer-to-peer computing was with the short-lived Napster music-sharing operation. With Napster there was a central database as to where all the music was. But the music was stored on remote computers joined by the telecom lines of the Internet. The original Napster was closed down because the music companies objected to people getting their hands on free music and because they could find Napster. But peer-to-peer computing has become far more sophisticated. Companies are using their employee computers to divide up complex processing and storage tasks ” perhaps using the machines only at night when employees aren't using them. See all the Peer and Peer-to-Peer definitions following, including Skype.

Peer Entities

Entities within the same communications layer.

Peer-entity Authentication

The corroboration that a peer entity in an association is the one claimed.

Peer Group

A set of logical nodes which are grouped for purposes of creating a routing hierarchy. PTSEs (PNNI Topology State Elements) are exchanged among all members of the group.

Peer Group Identifier

A string of bits that is used to unambiguously identify a peer group.

Peer Group Leader

A node which has been elected to perform some of the functions associated with a logical group node.

Peer Group Level

The number of significant bits in the peer group identifier of a particular peer group.

Peer Networking.

See Peer and Peer-to-peer.

Peer Network Entities

The origin and destination of all data transmissions.

Peer Node

A node that is a member of the same peer group as a given node.

Peer Protocol

The set of rules defining the procedures for communication between like entities. The identical entities may be devices or software modules at specific layers in a layered network architecture implementation.


P-2-P. Peer-to-Peer is a fancy way of saying grid computing and communications. Peer-to-peer describes communications between two entities that operate within the same protocol layer of a system. Peer-to-peer has come to mean a bunch of smaller computers helping each other work on a larger computing task. Many computers, joined by communications lines, bring their little piece of computing and storage together to solve a big task. The most famous instance of peer-to-peer has been the music sharing sites, first Napster and then Kazaa. All computers of these sites share information as to where the music is (the directory) and where its stored (the storage). Some companies are replacing their big expensive mainframes with a collection of smaller computers. The concept is that the whole system becomes intelligent enough to use the computing and storage of those machines that are temporarily idle. See also Peer and the next six definitions.

Peer-to-Peer Communications

Communications between two entities that operate within the same protocol layer of a system.

Peer-Peer Directory Propagation

A way of updating user addresses in which changes in any post office on a LAN (local area network) are sent to all other post offices.

Peer-to-Peer Flow

Term used to describe communication flow in a protocol stack. It means that a layer in one protocol stack communicates with a peer layer in another protocol stack through a physical link.

Peer-to-Peer Network

  1. A network (typically a local area network) in which every node has equal access to the network and can send and receive data at any time without having to wait for permission from a control node. While peer-to-peer resource sharing is effective in small networks, security and reliability issues prevent its widespread use in larger networks.

  2. A new telephony term describing the relationship between a telephone system and the external computer working with it. Picture a telephone switch acting as an automatic call distributor and an outboard computer processor. The idea is to coordinate the call and the screen at the agent. Communication must take place between the switch and the computer. See also Extended Call Management.

Peer-to-Peer Protocols

Describes the relationship between a telephone system and the external computer.

Peer-To-Peer Resource Sharing

An architecture that lets any PC contribute resources to the network while still running local application programs.

Peer-to-Peer Technology

A communications model in which Peer-to-peer is a communications model in which each party has the same capabilities and either party can initiate a communication session. In recent usage, peer-to-peer has come to describe applications in which users can use the Internet to exchange files with each other directly or through a mediating server. See also Napster. There are four categories of peer-to-peer:

  1. Pure peer-to-peer: Completely decentralized network characterized by a lack of a central server or central entity. Users of a pure peer-to-peer network make direct contact with one another.

  2. Computational peer-to-peer: Uses peer-to-peer technology to disseminate computational tasks over multiple clients ; peers do not have a direct connection to one another.

  3. Datacentric peer-to-peer: Information and data residing on systems or devices that is accessible to other when users connect. It is sometimes called peer-assisted or grid-assisted delivery. Applications include distributed file and content sharing.

  4. User centric/hybrid peer-to-peer: Involves clients contacting others via a central server or entity to communicate, share data or process data. Often used in collaboration applications.


Once upon a time America's entire phone system was run by AT&T (the Bell System) and a bunch of independents who served subscribers in areas AT&T wasn't. Essentially the whole gigantic thing was a monopoly, with monies for transmission and switching changing hands under rules run by government regulators and essentially administered by one company. The Internet is different. There are many companies providing telecom and switching service. These companies have to move traffic of the Internet between them. Hence they established something they called peering. It's a relationship established between two or more ISPs (Internet Service Providers) for the purpose of exchanging traffic directly, rather than doing so through a backbone Internet provider. The traditional Internet architecture (to the extent that there is a "traditional architecture" in the amorphous world of the Internet) calls for ISPs and regional carriers to exchange traffic at Network Access Points (NAPs), using carrier-class switches and routers, of which there currently are a dozen or so around the world. Traditionally, that traffic has been exchanged between one ISP and another at no cost, although that no longer is necessarily true. Money is raising its grubby head. In order to avoid thye headaches and expenses of figuring who should get paid and for how much, many of the larger ISPs have developed peering relationships which allow them to exchange traffic directly over dedicated circuits. In some geographical regions , mostly in North America, several ISPs have formed "private peering points." These packet switching centers allow them to exchange traffic on a switched basis, once again avoiding the cost of doing so through a NAP. Peering requires the exchange and updating of router information between the peered ISPs. typically using the border gateway protocol (BGP). Initially, peering arrangements did not include an exchange of money. More recently. however, some larger lSPs have charged smaller lSPs for peering. Each major ISP generally develops a peering policy that states the terms and conditions under which it will peer with other networks for various types of traffic.

Peering Agreement

An agreement to directly interconnect two or more networks and thus carry each other's traffic. See Peering.

Peering Point

A point at which ISPs (Internet Service Providers) exchange traffic, a peering point is in the form of a switch or router. Public peering points are in the form of NAPs (Network Access Points), which include MAEs (Metropolitan Access Exchanges, or Merit Access Exchanges) and CIXs (Commercial Internet Exchanges), also known as just IXs. Private peering points also have been established by consortia of ISPs in order that they can exchange traffic at costs lower than those imposed by the NAPs. See Peering.


Equals. See also Piconet. See Peering.


Public, Educational or Government access. A cable TV term to denote the local public access channel/s.

Peg Board

Also called a mushroom board or white board. This is placed between termination blocks to support route crossing wire.

Peg Count

A raw count of some event. Because this was originally maintained by moving pegs on a board with units of 1,10s,100, 1000s it became a peg count. A count of the number of calls placed or received at a certain point or over certain lines during a period such as an hour or day or week. A peg count simply tells you how many calls you made or received. It does not tell you how long they were or where they went or anything else. In the old days before we had accurate and relatively inexpensive call accounting equipment, we relied on Peg Counts to figure out how many circuits we needed. No more. The peg count method is too inaccurate.

PEG Ratio

Price to Earnings Growth ratio. A new way of comparing the price of stocks. Let's say that your favorite stock is selling at $100 and growing at 50% a year, that means its PEG ratio (actually pronounced peg) is 2.0.


Picture ELement. A pel is the smallest area on a video screen that can be controlled by software. Pels are arranged on screens in a grid-like fashion. Depending on the screen mode selected by an application, a pel may be a single pixel or several pixels. (A pixel is the smallest visual element on a screen, which can be turned on or off or varied in intensity.) The larger the number of pixels in a pel, the greater the size of the palette of distinct colors. When a pel consists of multiple pixels, the number of colors can be quite large. The pel size determines the clarity of the image ” called screen resolution. Larger individual pels reduce the total number of available pels, resulting in lower resolution. Smaller pels increase the number of pels that can fit on the screen, resulting in higher resolution and a clearer picture. See also Pixel, Fax and VGA.


Privacy Enhanced Mail. An Internet electronic mail capability which provides confidentially and message integrity using various encryption methods . PEM was adopted by the IETF in 1985 as an Internet standard. PEM involves digital certificates which are issued by the Internet Policy Registration Authority (IPRA), which serves as the top-level "trusted authority." The IPRA signs certificates for a second level of trusted bodies, which then sign certificates for Certificate Authorities (CAs), which then issue them to the public. As PEM does not address MIME (Multipurpose Internet Mail Extension), it is seldom used. S/MIME (Secure MIME) is the preferred approach. See also Certificate Authority, Digital Signature, Encryption, MIME, and S/MIME.

Pen Register

Also called a Dialed Number Recorder (DNR). An instrument that records telephone dial pulses as inked dashes on paper tape. A touchtone decoder performs the same thing for a touchtone telephone. Pen registers and DNRs are used by law enforcement agencies to gather information about the telephone numbers that suspected criminals are calling. They also are used by toll fraud criminals to steal calling card numbers .

Pen Windows

A new Microsoft operating system for notebook size computers that uses a stylus instead of a keyboard.

Penal Colony

A place where a country sends undesirables such as thieves where a couple of generations later, organizations are formed to validate their aristocratic members' claim of descent from these founding fathers and mothers. Everybody knows that Australia started off as a British penal colony. What is not generally known is that it was the United States' fault: After the American colonies seceded to form the U.S., Great Britain could no longer send its criminals here. The author of this dictionary, Harry Newton, was born in Australia.


Bypassing the security mechanisms of a system.

Penetration Tap

A connection method used in installations that allows devices to be connected to cable without interrupting network operation. Penetration taps are most commonly found used with coaxial cable. A sharp, pointed probe is used to penetrate the outer insulation and grounding shield of the coaxial cable and to make direct contact with the inner conductor.

Penetration Testing

Attempting to circumvent a system's security features to identify weaknesses.

Pentium 4

In coming up with names , companies often vacillate between the technical and the poetic. Intel's first microprocessor in the early 1970s was called the 4004, and Intel kept naming its chips by numbers ” 286, 386 ” until the courts ruled it couldn't trademark them that way. Thus was born the Pentium. The Pentium 4 chip with 42 million transistors in a 217-square-millimeter die, compared to Pentium III's count of 28 million transistors in a 106-square-millimeter die.


A version of a vacuum tube. The pentode adds a suppressor grid between the screen grid and the plate. It's usually connected to ground potential in order to repel any stray electrons from bouncing back to the screen grid instead of the plate. Because the screen grid has a positive charge with respect to the cathode , it tends to attract a percentage of the electrons away from the plate, reducing the efficiency of the tube. The suppressor acts as a negatively-charged (with respect to the plate) barrier to prevent the diversion of electrons from the plate to the screen grid. This increases overall efficiency and gain of the tube by directing more of the electrons to their intended destination. See also Diode, Triode and Tetrode.

People Churner

A boss who drives away talented people.

People Meter

An electronic device on which individuals record their television viewing by touching predestinated " buttons " assigned to each individual in the household. Current people meters also have separate remote-controlled, portable handsets.


  1. Protocol Extensions Protocol. A part of the JEPI (Joint Electronics Payments Initiative) specification from the World Wide Web Consortium (W3C) and CommerceNet for a universal payment platform to allow merchants and consumers to transact E- Commerce (Electronic Commerce) over the Internet. PEP is an extension layer that sits on top of HTTP (HyperText Transfer Protocol). PEP works in conjunction with Universal Payment Preamble (UPP), the negotiation protocol that identifies appropriate payment methodology. These protocols are intended to make payment negotiations automatic for end users, happening at the moment of purchase, based on browser configurations. See also Electronic Commerce and JEPI.

  2. Packet Ensemble Protocol. A high-speed modulation method from Telebit Corporation for dial-up modems. Now obsolete.

  3. Policy Enforcement Point. An router or IP switch that enforces the traffic priority decisions made by a PDP (Policy Decision Point) in an IP network running the COPS (Common Open Policy Server) protocol. See COPS.

  4. See Peak Envelope Power.


Protocol for Exchange of PoliCy Information. A draft protocol from the IETF intended to support the exchange of policy information between the policy server and its clients. Policy-based networks manage traffic through the establishment of priorities based on parameters such as traffic type, application type, and user. See also Policy-Based Networking.

Per Call Calling Identity Delivery Blocking Feature

Allows a caller to toggle or override the value of a calling identity item's Permanent Presentation Status (PPS) for a particular call.

Percent of Interstate Usage

PIU. A Verizon definition. Refers to the amount of traffic subject to FCC authority and charged under GTOC FCC #1.

Percent of Local Usage

PLU. A Verizon definition. Verizon and the service provider provide this factor to each other each quarter or (as otherwise specified in their agreement) in order to identify the jurisdiction of each call type carried over their trunk groups.

Percentage ATB

Percentage of All Trunks Busy. Percentage of time during a reporting period that all trunks in a group or split were busy. This may be measured in two ways, actual simultaneous busies and call length per event, or backed into statistically. Neither technique is absolutely accurate as each depends on "snap shots" in a environment of random interleaved call events.

Percentage CA

Percentage of Calls Abandoned. Indicates the percentage of calls abandoned by callers after being accepted by the ACD.

Percentage HLD

Percentage of total calls HeLD in queue within a reporting group.

Percentage NCO

Percentage of total of Number of Calls Offered to a particular reporting group.

Percentage TUT

Percentage of Trunk Utilization Time. The percentage of a time during a reporting period that a trunk is in use and not idle.

Perceptual Analysis Measurement System


Perceptual Evaluation of Speech Quality


Perceptual Speech Quality Measure


Percussive Maintenance

The fine art of whacking the crap out of an electronic device to get it to work again. A joke.


An instrument for the manual preparation of a perforated tape, on which telegraph signals are represented by holes punched in accordance with a predetermined code.

Perforator, Paper Tape

An electro-mechanical device which converts electrical signals into coded holes in a paper tape. See Paper Tape Punch.

Performance Management

Measures and records resource utilization. It is one of the categories of network management defined by the ISO (international Standards Organization).


In satellite systems, the point on a satellite's orbit at which it is closest to the center of the primary body about which it is orbiting. Where Earth-based satellite systems are concerned , the term is synonymous with perigee. See also Geostationary Orbit.


The point at which a satellite orbit is the least distance from the center of the gravitational field of the Earth. The point in an orbit at which the satellite is farthest from the Earth is known as the apogee . In commercial application, the terms have most significance with respect to LEOs (Low Earth Orbiting) and MEOs (Middle Earth Orbiting) satellite constellations, which travel in elliptical orbits. See also LEO, MEO, and PERIAPSIS.

Perimeter Firewall

There are two types of perimeter firewalls: static packet filtering and dynamic firewalls. Both work at the IP address level, selectively passing or blocking data packets. Static packet filters are less flexible than dynamic firewalls. See Firewall.

Perimeter Protection System

A field disturbance sensor which uses buried leaky cables installed around a facility to detect any unauthorized entry or exit.

Period Of A Satellite

The time elapsing between two consecutive passages of a satellite through a characteristic point on its orbit.

Periodic Postings

Articles that are posted periodically to a newsgroup for the benefit of people who are new to the newsgroup. An Internet term.

Periodic Registration

A cellular term. A MSC (Mobile Switching Center) periodically sends out a broadcast message, requesting that all active cell phones register themselves . This process helps the MSC keep track of the active devices, and determine which cell sites are serving them.


Periodicity refers to the uniformly spaced variations in the diameter of the insulation of a cable system as a result of the manufacturing process. These variations cause signal reflections when the wavelength (or multiples of the wavelength) of the transmitted signal is exactly equal to the distance between the variations in the insulation.

Peripheral Device

See Peripheral Equipment or Applications Processor.

Peripheral Equipment

Equipment not integral to but working with a phone system. An example might be a printer or television screen on which calling traffic statistics are displayed. It might also be a voice mail or an automated attendant system. AT&T once called PBX peripheral equipment "applications processors," because they process specific applications. Some people now call them Adjunct Processor or Outboard Processors.


Practical Extraction and Report Language. An interpreted scripting programming language, first released in 1987 by Larry Wall to streamline the administration of a network of Sun and DEC VAX computers. Perl is a highly portable language widely used in writing CGI (Common Gateway Interface) scripts, which are the standard means of performing actions ” like searching or running applications when the user clicks on certain buttons or on parts of Web screen pages. The form Perl is preferred for the language itself; perl is used for the interpreter for the Perl language. See CGI.


Skeptical investors who would rather own gold, silver or water rights than own a blue-chip stock. Perma-bears believe that the stockmarket will always go down.


A permanent freelancer. A person hired on a per-project basis who lives a benefits-free existence.

Permanent Path

Fixed communication path between fibre channel nodes that provides guaranteed bandwidth. See Dynamic Path.

Permanent Presentation Status

PPS. A PPS has a public value of a "public" or "anonymous" and is used as the presentation status of a call if no per-call CIDB (Calling Line Identification Delivery Blocking) feature is active. A PPS should exist for each calling identity item. A Bellcore definition.

Permanent Shift Type

A call center term. A shift definition that the program gives priority to in creating schedules but uses only as long as no overstaffing results in any intra-day period (at which point flexible shift types are used). When scheduling is done for more than a week at a time, the permanent schedules are always identical from one week to the next.

Permanent Signal

A sustained off-hook supervisory signal originating outside a switching system and not related to a call in progress. Permanent signals can occupy a substantial part of the capacity of a switching system.

Permanent Virtual Circuit

  1. PVC. A virtual circuit that is "permanently" defined in routing tables in packet network switches or routers, at least until such time as it is "permanently" changed. The network path, therefore, is fixed in programmed logic, and can be exercised quickly. A PVC uses a fixed logical channel over a physical network. Once a PVC is defined, it requires no setup operation before data is sent and no disconnect operation after data is sent. PVCs are used in packet-switched networks such as Frame Relay and TCP/IP. See also Switched Virtual Circuit.

  2. PolyVinyl Chloride. A type of plastic material used in the manufacture of flame-retardant cable jackets.

Permanent Virtual Path Tunneling

See PVP Tunneling.

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. (RR) See also accepted interference, interference.


A Windows NT term. A rule tied to an object (usually a directory, file or printer) to regulate which users can have access to the object and in what manner.

Permission Marketing

A marketing method whereby companies get their customers' permission to market products or services to them. Sign up for a email newsletter. It often asks you if it could also send you offers to sell you stuff. It asks your permission. The theory is that by consumers will pay more attention to the marketing message. These days email that is is not permissions driven is called spam. The term was coined by Seth Godin in his book, Permission Marketing.


  1. A call center term. Privileges granted to each user with respect to what data that user is allowed to access and what menu options or commands he or she is allowed to use. Permissions are under control of the System Administrator.

  2. A Northern Telecom Norstar definition to define specific characteristics that can be assigned to an individual telephone. Permissions includes Full Handsfree, Handsfree Answerback, Pickup Group, Page Zone, Auxiliary Ringer, Receive tones, and Priority Call.

Permissive Dialing

There's an area code change. Many peoples' phones now have different area codes. People calling them will have to dial a different area code. There'll be a time, perhaps three months, in which a caller will be able to reach the number by dialing the old area code or the new area code. That period is known as permissive dialing. Once the period of permissive dialing is over, the period of mandatory dialing begins.


See Dielectric Constant.


Someone who carries out an illegal or malicious act affecting information security.


  1. In a CRT, the time a phosphor dot remains illuminated after being energized. Long-persistent phosphors reduce flicker, but generate ghost-like images that linger on screen for a fraction of a second.

  2. The probability that when a device on a local area network which has the data to transmit senses a free transmission line it will attempt the transmission. 1.0 persistence indicates that there is 100 percent probability that the device will always attempt to transmit. IEEE 802.3 and Ethernet both use 1.0 persistence. A 0.5 persistence indicates that when a device senses a free line it will only attempt to transmit 50 percent of the time.


A persistent configured site will attempt to re-establish the connection in the event of an unexpected line drop. A non-persistent configured site will not.

Persistent Communication

A dialogue between an ASC (AIN Switch Capabilities) and a SLEE (Service Logic Execution Environment) that may involve a sequence of messages. Definition from Bellcore in reference to its concept of the Advanced Intelligent Network.

Persistent Information

Information for which a permanent data object exists. Definition from Bellcore in reference to its concept of the Advanced Intelligent Network.

Person Call

There will be two types of calls: person calls and place calls. I make a place call when I call a phone number which ends in one designated, fixed RJ-11 jack attached to the wall or floor. I make a person call when I call a phone number which does- n't necessarily end on a fixed place. A typical person call might be a cellular or wireless phone call. It might also be a service like MCI's Personal 800 Service. The major characteristic of a person call is that I am calling a person and I don't know where that person is. As a result, the person I called might answer my call anywhere ” from his car, from vacation home, from his wireless phone, etc.

Person To Person Call

The most expensive way to make a long distance call. Call the operator. Say "I want to speak to Harry Newton on 212-691-8215." The operator dials Mr. Newton's phone number, gets Mr. Newton on the phone. "Are you Mr. Newton?" Mr. Newton replies: "Yes, I am." The operator bows out of the conversation and sends you, the caller, a hefty bill for that personalized service. Until recently, person- to-person service was only offered by AT&T. Now it's offered by most phone companies. But prices, in the main, are not regulated . And some companies charge an arm and a leg. Please be careful.

Personal 800 Number

Several long distance companies are now offering Personal 800 numbers, which are basically party line 800 numbers with call routing. The way they work is as follows : You dial a number, e.g. 800-484-1000. A machine answers with a double beep. You punch in four or five digits on your touchtone pad. A voice response unit at the other end hears the digits, says "Thank you for using MCI" and dials out your long distance number which might be 212-691-8215 (mine). The long distance carriers are charging under $5 a month and 15 to 25 cents a minute for the service. The per minute charges are more expensive than normal 800 lines. One company, MCI, is also offering FOLLOW ME 800 which allows you to change the routing of your personal 800 number instantly with one phone line.

Personal Access System

See PAS.

Personal Agent

A personal agent is a piece of software on your personal computer that does your bidding. It may answer your emails (or at least some of them). It may find things on the web you're looking for. It may schedule appointments for you. The concept is easy: No one has a secretary anymore. So why not program your computer to do your bidding? Easier said than done. A software agent is software in the making.

Personal Area Network

See 802.15.1 and PAN.

Personal Authentication Device

P.A.D. A portable or fixed device which allows for precise identification and validation of each user. Used in fraud prevention and unauthorized access. Also called a "token".

Personal Central Office Trunk Line

Also known as a "private line." Allows a user behind a PBX to access a central office trunk line dedicated to him; also allows people to call him directly, bypassing the PBX. Such a private line can appear on a line access button on an electronic PBX phone, or can terminate on a separate phone. As the private line bypasses the PBX, the console attendants can't listen to your conversations; neither can the technicians, unless they physically tap the line. Private lines, therefore, are more secure than the typical PBX station line. They also are CO- powered ; as a result, they are not susceptible to power outages which might affect the PBX system. Senior executives use them, as do venture capitalists and others who conduct highly confidential negotiations. See also Private Line.

Personal Communications Industry Association

PCIA. The trade association of the new cellular phone providers. PCIA represents a wide range of interests, including Broadband PCS, paging and narrowband PCS, antenna site owners and managers, Specialized Mobile Radio (SMR), suppliers and manufacturers. See also PCS. www.pcia.com

Personal Communications Networks

PCN. A new type of wireless telephone system that would use light, inexpensive handheld handsets and communicate via low-power antennas. PCN is primarily seen as a city communications system, with far less range than cellular. Subscribers would be able to make and perhaps receive calls while they are traveling, as they can do today with cellular radio systems, but at a low price. There's talk that they'll put PCN antennas in communities and issue everyone in the community with a PCN phone that would hub off the PCN antenna. This would save the phone company wiring up each house. In this way, the PCN phone would resemble the common household cordless phone, but with a larger range. Dr. Sorin Cohn of Northern Telecom calls the new low-power, wireless, personal communications systems an " enabler of unplanned growth." Nice definition. See PCN and Personal Communications Services.

In the fall of 1992 MCI broadened the definition of PCN. It proposed a national consortium of local PCNs joined together by a long distance carrier (namely it). In its release, MCI said that "PCNs are the next generation of digital wireless communications technology. PCNs use less power and are less expensive than the current cellular technology and permit the use of inexpensive pocket telephones with much longer battery life than cellular portables. PCN phones will have many more features than today's cellular or conventional telephones, and unlike cellular phones, will be usable in most areas of the world. PCNs will operate in the same frequency band in most countries, (1850-1990 MHz) while cellular is operating in several different frequency bands in various countries , and thus is not portable from country to country." See also Personal Communications Services.

Personal Communications Services

PCS are a broad range of individualized telecommunications services that let people or devices to communicate irrespective of where they are. Some of the services include:

  • Personal numbers assigned to individuals rather than telephones

  • Call completion regardless of location ("find me")

  • Calls to the PCS customer can be paid for by the caller, or by the PCS customer

  • Call management services giving the called party much greater control over incoming calls.

PCS can both find and complete a call to a person regardless of location, but give that person the choice of accepting or rejecting the call or sending it somewhere else. PCS will possibly use a new category of wireless, voice and data communications ” using low power, lightweight pocket telephones and hand-held computers.

Personal Computer

PC. A computer for one person's use. That's why it was originally called a personal computer ” to distinguish it from other computers that existed at the time of the PC's invention, or 1981, the date IBM introduced its first PC. Those other computers were mainframes and mini-computers. Their main use was to be shared by many users. Airline reservations , being an example. Of course, as the PC got more powerful, things got more complex. In 1983, Novell introduced its first local area network software called NetWare. NetWare was originally introduced to allow a handful of personal computers to share a single hard disk, which at that stage was costly and scarce . As hard disks became more available and cheaper, NetWare evolved to allow sharing of printers and file servers. Networking developed in the 1980s and 1990s and gave PCs the shared- user power of mainframes and minicomputers. As a result, today some PCs are personal computers, used by one person standalone. Some PCs are PCs that sit on a local area network (LAN). For some reason, people call these PCs workstations. And there are some PCs which have become servers ” i.e. they "serve" many PCs. They may do faxing. They may do voice mail for the company. They may run the company's entire phone system. In short, meanings change as technology changes. Not all PCs are personal computers.

Personal Computer Memory Card International Association


Personal Computing Systems Architecture

PCSA. A network architecture defined and supported by Digital Equipment Corp. for the incorporation of personal computers into server-based networks.

Personal Computer Terminal Adapter

PCTA. A printed circuit card that slips into an IBM PC or PC compatible and connects the PC to the ISDN T-interface. The PCTA basically turns a normal PC into an ISDN phone and ISDN terminal, ready for voice and data communications. According to Northern Telecom, one of the manufacturers of such a device, the PCTA does:

  • Functional signaling call setup.

  • B channel for circuit switched data.

  • X.25 packet data services on the B or D channel.

  • Simultaneous operation of the B and D channels.

  • M5317T digital telephone to PC messaging for integrated voice and data operation.

  • NetBIOS interface to applications software, such as Microsoft Networks. For more, see Northern Telecom's brochure ISDN PC Terminal Adapter NetBIOS Interface Description (D307-1).

Personal Data Interchange

PDI. A format for exchanging information, such as electronic business, cards via wired or wireless connections.

Personal Data Module

A removable module, unique to the ROLM Cypress and Cedar, which stores all information entered by the user. Such items as phone numbers, terminal profiles and log-on sequences are stored in the PDM, which also features battery backup to protect the memory in the event of a power failure. The user can take his personal data module with him, plug it into another Cypress or Cedar and get all his speed dial and other personalized programming on his phone he just moved from.

Personal Digital Assistant

PDA. A consumer electronics gadget that looks like a palmtop computer. Unlike personal computers, PDAs will perform specific tasks-acting like an electronic diary, carry-along personal database, personal communicator, memo taker, calculator, alarm clock. The communications will take place through the phone, through a cable attached to your PC or through infrared. See also Windows CE.

Personal Identification Number

PIN number.

  1. An AT&T term meaning the last four digits of your AT&T, MCI Bell operating company Credit Card ” the card you use for making long distance numbers.

  2. Some banks and financial institutions issue credit cards for machine, teller-less banking. These machines, called Automated Teller Machines, ask you for a password consisting of several numbers or characters. These are not on your credit card. These numbers or characters , called PIN numbers, are designed to make sure the right person is using your card. It's not a good idea to use your birthday as your PIN number.

Personal Intelligent Communications

What General Magic calls the products and services its alliance members will create using General Magic technologies that will help people remember, communicate and know things in new and powerful ways. According to General Magic, "the alliance's shared long-term vision is to bring personal communications to people who may not use a computer today, to people whose personal technology is a car, a television set and a telephone."

Personal Information Assistant

Tandy's name for what Apple calls a Personal Digital Assistant. See PDA.

Personal Information Manager

PIM. Software application which allow the user to organize personal information. similar to an appointment book but personalized and programmed into the PC. PIMs now support Caller ID. When the phone rings, the phone system passes the calling number to the PC, which does a lookup in the PIM on the phone number and throws information about the caller up on screen. See PIM.

Personal IVR

An Interactive Voice Response system running on your own personal PC and designed to serve the needs of only one person. See IVR.

Personal Line

A feature which allows specific key telephones to have their own private Central Office line. Sometimes called an AUXILIARY LINE. You can typically receive and make calls on this line. No one else can answer it, since it does not appear on any other phone instrument in the office. You can give this number to your wife or girlfriend. It is not a good idea to give it to both.

Personal Name

An X.400 term for a standard attribute of an O/R (Originator/Recipient) Address form that identifies a person relative to another attribute (e.g., an organization name). The personal name may include surname , given name, initials, and generation qualifier. Initials consists of the first letter of all the user's names except the user's surname.

Personal Productivity Tool

Another term for a computer. John Perry Barlow thinks the expression was created by the "druids" who run Microsoft and Apple. Mr. Barlow is a cattle rancher, computer hacker, poet, and a lyricist for the rock band The Grateful Dead.

Personal Scanners

Personal scanners are tiny devices that read bar codes off ads in magazines and newspapers and allow us to go directly to the spot on the web where there's more information about the product or service. Early personal scanners were the CueCat, the Gamut and the CS 2000. They haven't been very successful so far. I threw my three CueCats out. Some people are predicting a big future for them.

Personal Speed Dial

Simplified ways of dialing. You do them by dialing a couple of digits. Or you punch in a button at your phone. Personal Speed Dial codes are programmed for each telephone, and can only be used at the telephone on which they are programmed. System Speed Dials, in contrast, can be used from every phone in the system.

Personal System/2

PS/2. IBM's current family of microcomputers some of whom sport one major difference from its predecessors, namely the existence of a 32-bit micro-channel bus. This "bus" serves the same purpose as a PBX's backplane ” namely to move information from the printed circuit cards and to other printed circuit cards, which may contain their own individual microprocessors (computers on a chip) and which may communicate with the outside world through their own communications ports.

Personal Telephone

The category of cellular telephones pioneered by Motorola's Pan American Cellular Subscriber Group with the introduction of the MicroTAC Digital Personal Communicator Telephone. Weighing less than one pound , they are so compact and lightweight, they fit comfortably into a shirt pocket or purse making them "body friendly."

Personal Video Recorder

See PVR.

Personal Wireless Telecommunications

PWT. Also known as Personal Wireless Telephony. A U.S. cordless telephony standard for in-building wireless communications systems, PWT is a variant of the DECT (Digital European Cordless Telecommunications) standard. PWT is an air interface which operates in the unlicensed PCS (Personal Communications Services) 1.9 GHz radio band. PWT(E) is an enhanced version which operates in the licensed PCS bands. See also Air Interface, DECT, and PCS.

Personality Module

A small motherboard added to a voice board to give it the "personality" of a proprietary electronic PBX telephone. "Personality" means electrical characteristics and the same button configuration and responsiveness, all of which can be recreated on the screen of a PC which has the voice board installed.

Personalization Technology

Software that lets suppliers of information to "nonintrusively" (their word, not mine) learn the individual interests of their customers in order to deliver personalized Web content, targeted advertising, and product recommendations.

Personalized Ring

  1. A telephone feature which allows you to select different ringing sounds for your telephone. This feature is useful if you work in a big room with lots of other people and it's hard to tell whose phone is ringing.

  2. A cell phone feature which allows you to customize the ring on your cell phone. You can customize that ring with one of the various ringtones that the manufacturer gives you or which you download from a web site. You can get a bunch from www.yourmobile.com.


A Java platform optimized for the requirements and constraints of mobile devices.


Project Evaluation and Review Technique. A variation on the Critical Path Method of organizing the completion of projects. Projects are examined for the their worst, best, average completion times. A critical path is determined and overall standards for completion times are created. The PERT technique was created by the military. It is used for organizing complex tasks.

Pervasive Computing

A form of computing that involves ubiquitous access to information through the use of portable computers and extensive networking.


  1. Packetized Elementary Stream. In MPEG-2 (Moving Pictures Experts Group) compression, once the media stream has been digitized and compressed, it is formatted into a stream of packets. The resulting PES then is multiplexed into either a Program Stream or Transport Stream. See also MPEG-2.

  2. Packet over Ethernet over SONET. A technique by which IP (Internet Protocol) packets are encapsulated within Ethernet frames to transit an Ethernet LAN segment, which is connected to another Ethernet segment across an network based on a SONET optical fiber transmission system. A developing PES application is that of 10GbE (10 Gigabit Ethernet). See also Ethernet, IP, PEW, and SONET.


Perceptual Evaultion of Speech Quality, currently under review by the ITU, with expected approval as P.862 in 2001. It is widely anticipated that PESQ will eventually replace previous methods (like PSQM and PAMS) for objective speech quality testing. PESQ is directed at narrowband telephone signals. It is applicable to systems with speech coding (including low bit-rate vocoders), variable delay, filtering, packet or cell loss, time-clipping, and channel errors. PESQ scores predict listening quality scores for ACR (Absolute Category Rating) listening tests. PESQ leverages the best featurs of PAMS and PSQM99. It combines the robust time-alignment techniques of PAMS with the accurate perceptual modeling of PSQM99, and it adds new methods including transfer function equalization and a new method for averaging distortion over time.


P. A prefix that denotes 10 to the 15th power or one quadrillion. In computer terms, however, peta- is actually equal to 2 raised to the 50th power , or 1,125,899,906,842,624, the power of 2 that is closest to one quadrillion.


Pb. A petabit is literally equal to 2 50 bits, or 1,125,899,906,842,624 bits, but is often calculated with a base of 10, making it equal to 10 to the 15th or one quadrillion bits. See Petabyte.


PB. A combination of the Greek "pente," meaning "five," and the English "bite," meaning "a small amount of food." A unit of measurement for physical data storage on some form of storage device ” hard disk, optical disk, RAM memory etc. and equal to two raised to the 50th power, i.e. 1,125,899,906,842,600 bytes.

KB = Kilobyte (2 to the 10th power)

MB = Megabyte (2 to the 20th power)

GB = Gigabyte (2 to the 30th power)

TB = Terabyte (2 to the 40th power)

PB = Petabyte (2 to the 50th power)

EB = Exabyte (2 to the 60th power)

ZB = Zettabyte (2 to the 70th power)

YB = Yottabyte (2 to the 80th power)

One googolbyte equals 2 to the 100th power.

Peter the Great of Russia

Peter the Great of Russia had his wife's lover beheaded, pickled the head in a jar of alcohol and had her keep it in her bedroom.

Petition for Reconsideration

A Petition for Reconsideration is a written request submitted to the FCC for review of an action it has previously taken. Applicants have 30 days after a Report and Order is published in the Federal Register to file comments with the FCC. The agency will consider public comments, replies, and industry concerns before finalizing its initial decision. As a result of the review process, the FCC will either issue a Memorandum Opinion and Order amending its initial decision, or deny the Petition for Reconsideration.


Packet over Ethernet over WDM. A technique by which IP (Internet Protocol) packets are encapsulated within Ethernet frames to transit an Ethernet LAN segment, which is connected to another Ethernet segment across an network based on a DWDM (Dense Wavelength Division Multiplexing) optical fiber transmission system. A developing PEW application is that of 10GbE (10 Gigabit Ethernet). See also DWDM, Ethernet, IP, and PES.

PF Xfer

Power Failure Transfer.


PK-E is a suffix to an FCC registration number, indicating the function of a system in accordance with its FCC registration. A PF-E is a Fully Protected PBX Telephone System, with "PF" denoting "PBX Function," and "E" denoting that the system will accept both rotary and tone signaling. See also KF-E, MF-E, PBX, and Registration Number.


Pure F...ing Magic. A term to indicate that it works but the software engineer has no real idea how it works. It works by PFM. Sort of like an accidental winning shot in tennis. Looks great. The hitter won the point, but he had no idea how he did it. See PFTS.


Pending the Firm Order Commitment.

PG Peer Group

A set of logical nodes which are grouped for purposes of creating a routing hierarchy. PTSEs are exchanged among all members of the group.


  1. Programmable Gain Amplifier, a part of the Analog Front End.

  2. Pin Grid Array. A silicon chipset in which all of the connecting pins are arranged in concentric squares. See also DIP, SIMM, and SIP.


Peer Group Leader: A single real physical system which has been elected to perform some of the functions associated with a logical group node.


Pretty Good Privacy. PGP is a cryptography program for computer data, electronic mail and voice conversations. PGP was written in 1991 by Philip R. Zimmermann, who gave the software away. It was posted on a public computer on the Internet, and thousands downloaded copies. Originally, PGP was just used for the transmission of computer data and electronic mail. Then it got extended to voice conversations on the phone, called PGPfone. The idea is that you use modems to dial. Then the PCs "shake hands" and jointly agree on a complex number that is plugged in a scrambling algorithm equation. This notoriously complex scrambling algorithm, called Blowfish, recalculates the digital ones and zeroes of the sampled voices into a stream of numbers unintelligible even to highly sophisticated eavesdroppers. Finally, PGPfone unscrambles the stream to provide intelligible ” though not great quality ” sound. In February 1993, the U.S. government notified Zimmerman that he was being investigated for violating its restriction on the export of encryption technologies. The case was dropped in 1996, leaving Zimmerman free to found PGP, Inc. The company later was acquired by Network Associates. See also Encryption.


The name of the protocol used for voice conversations on Pretty Good Privacy. See PGP for a full explanation.


  1. Packet Handler, or Packet Handling function.

  2. The Ph system allows you to look up directory information, usually including e-mail addresses at universities, research institutions, and some governmental agencies throughout the world. You need a program that lets you use Ph. Tell that program which Ph server to use, and then enter a name you would like to search for.

Phantom Circuit

A 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 phantom.

Phantom Directory Number

Also called a virtual DN. A directory number with a voice mailbox, but not a phone on it. Calls are then transferred to this number. The mailbox user can dial into the system, enter the extension number, security information and retrieve their messages.

Phantom Load

The electricity consumed by a device when it is not doing its main function and may be theoretically turned off. Studies show that about 6 per cent of the electricity used in typical homes is by devices that consume power even when turned off.


The relationship between a signal and its horizontal axis, also called zero-crossing point. A full cycle describes a 360 degree arc. A sine wave that crosses the zero-point when another has attained its highest point is 90 degrees out of phase with the other. See Phase Shift Keying.

Phase 1

Phase 1 Environmental Site Assessment. Investigation to determine the condition of the land at the proposed site location. Soil contaminants , pollution etc. To be done at any site where equipment will be touching the ground. See SHPO ” State Historic Preservation Officer.

Phase A

Phase A is the first part of a fax machine's call process. It is the call establishment. It occurs when transmitting and receiving units connect over the phone line, recognizing one another as fax machines. This is the start of the handshaking procedure. See Phase B.

Phase B

Phase B is the second part of a fax machine's call process. It is the premessage procedure, where the answering machine identifies itself, describing its capabilities in a burst of digital information packed in frames conforming to the HDLC standard. See Phase C.

Phase C

Phase C is the third part of a fax machine's call process. It is the fax transmission portion of the operation. This step consists of two parts C1 and C2 which take place simultaneously . Phase C1 deals with synchronization, line monitoring and problem detection. Phase C2 includes data transmission. See Phase D.

Phase D

Phase D is the fourth part of a fax machine's call process. This phase begins once a page has been transmitted. Both the sender and receiver revert to using HDLC packets as during Phase B. If the sender has further pages to transmit, it sends an MPS and Phase C recommences for the following page. See Phase E.

Phase Displacement Antenna

An antenna constructed from a driven element and a group of reflectors, the secondary radiation from which produces an antenna with directivity. The Yagi-Uda array is a member of this family.

Phase Delay

See Envelope Delay.

Phase Distortion

An unwanted modification of a transmitted signal caused by the non-uniform transmission of the different frequency components of the signal. Same as Delay Distortion.

Phase E

Phase E is the fifth part of a fax machine's call process. This phase is the call release portion. The side that transmitted last sends a DCN frame and hangs up without awaiting a response.

Phase Hit

In telephony, the unwanted and significant shifting in phase of an analog signal. As defined by AT&T: any case where the phase of a 1004 Hz test signal shifts more than 20 degrees. Also, error- causing events more severe than phase jitter, especially for data transmission equipment using PSK modulation.

Phase inversion

The condition whereby the output of a circuit produces a wave of the same shape and frequency but 180 degrees out of phase with the input.

Phase Jitter

In telephony, the measurement, in degrees out of phase, that an analog signal deviates from the referenced phase of the main data-carrying signal. Phase jitter is often caused by alternating current components in a network.

Phase lock

The phase of a signal follows exactly the phase of a reference signal.

Phase Locked Loop

PLL. Phase Locked Loop is a mechanism whereby timing information is transferred within a data stream and the receiver derives the signal element timing by locking its local clock source to the received timing information.

Phase Modulation

One of three ways to change a sine wave (or L signal) to let it carry information. In this case, the phase of the sine wave is changed as the information to be carried is changed. See Phase Shift Keying and Modulation.

Phase Roll

Variations in the phase of a transmitted signal and its echoed back modem verification. Phase roll is encountered most often in international systems.

Phase Shift

A change in the time or amplitude that a signal is delayed with respect to a reference signal.

Phase Shift Keying

Also known as PSK and Phase Modulation. Used by relatively sophisticated modems for transmitting digital signals over analog phone lines. Picture an electromagnetic sine wave. In its natural state, the sine wave is a continuous and uninterrupted waveform of a certain amplitude and carrier frequency. If we want to place a digital signal on it, it is necessary that we cause the signal to change in some way to reflect the presence of a "1" or the absence of a one, i.e., a zero. In phase shift keying, we simply change the phase of the carrier signal to reflect a change in value of the adjacent bits. The receiving device looks for the phase shift of the signal in absolute, rather than relative terms. Differential Phase Shift Keying (DPSK) is a more sophisticated technique, involving the comparison of the signal shift to the carrier frequency, with the latter being used as a reference. Compare with Differential Phase Shift Keying. Contrast with Amplitude Modulation and Frequency Modulation. See also BPSK and QPSK.

click to expand

Phase Shift Modulation

Another way of saying Phase Shift Keying. See above.

Phased Array Antenna

A phased antenna system consists of two or more active antennas ” called antenna elements ” arranged (also called arrayed) so the electromagnetic fields effectively add in some directions and cancel in other directions. This produces enhanced transmission and reception in the directions where the fields add, and reduces the strength of radiated and received signals in the directions where the fields cancel. A phased array antenna is used in certain satellite, wireless TV, and WLL (Wireless Local Loop) applications. Phased Array Antennas are typically small (e.g., 4.5 inches square), flat antennas which mount on the side of your building or on your rooftop. Inside the thin flat box is an array (i.e. several) of chip-based radio receivers which lock in on the desired transmission frequency on a dynamic basis. That is to say that they have sufficient intelligence to direct and redirect their focus in order to maximize the strength of the incoming or outgoing signal. As neither the device nor its components, are physically dynamic (i.e., they cannot be repositioned physically, in the moving kinetic sense of the word), this capability is critical. These devices have the appearance of a pizza box. The term "pizza box" sometimes is applied to them. Many AM (amplitude-modulation) broadcast stations use sets of two, three, or four phased vertical antennas. This results in a directional pattern that optimizes coverage, so the station can reach the greatest possible number of listeners in its designated area. The nulls in the pattern reduce or eliminate interference with other AM broadcast stations . Some new wireless 802.11b transmission systems used phased array antenna, thus effectively getting around limitations on the strength of the signal they can emit. Using phased array antennas gives them greater range and reliability. In two-way radio communications, several vertical dipole antenna can be placed end-to-end and fed in phases. This is known as a collinear antenna and is a specialized type of phased array. At low elevation angles, the radiation and response are enhanced relative to a single vertical dipole. This gain occurs at the expense of radiation and response at higher elevation angles, increasing the range of communication for surface-to-surface communications. See also WLL.


The process of ensuring that both sending and receiving facsimile machines start at the same position on a page.

Phasing Orbit

A temporary satellite orbit which is used prior to putting the satellite into its final orbit.


Temporary buffer storage that compensates for slight differences in data rate between TDM I/O ports and devices.


Per-hop-behavior; also described in RFCs 2597 and 2598 (also describes "Expedited" PHB).

Phenolic Insulating Materials

A type of insulating materials, one of which is bakelite. Now no longer used.


A slang use of the word phenomenon used to mean a prodigy, for example: John Elway at 18 or Serina Williams at 17.


Packet Handling Function. The switching capability that processes and routes X.25 virtual calls.


PBX-to-Host Interface. The same as CPI (Computer to PBX Interface) but it puts the PBX first, which is the way many telephone manufacturers prefer to see it. It refers to a connection between a telephone system and a computer, such that the computer can signal the telephone system to switch calls and the telephone system can signal the computer when it has switched them. There are major advantages in joining a telephone system to a computer. For a much greater explanation, see OAI, which stands for Open Application Interface.

Phi Phenomenon

A theory developed by psychologist Hugo Munsterberg, it explains the illusion of motion created by rapid presentation of a series of still images. Munsterberg suggests that the brain hallucinates, effectively filling in the voids between the images. At 30 fps (frames per second), the brain processes the images as fully fluid motion. See Frame Rate.

Phiber Optik

See Master of Deception


MCI's ill-fated order entry system that never rose from the dead, i.e. never worked.


A simpler way of saying the word "telephone." See Telephone.

Phone Bomb

A phone bomb is a booby-trapped cellular phone. I saw the term first used on the front page of the January 6, 1996 New York Daily News. The story read: "'The engineer,' an extremist Palestinian bomb maker which was No. 1 on Israel's most-wanted list was killed on the Gaza Strip yesterday when his head was blown up by a booby-trapped cellular phone. The phone was rigged with about two ounces of explosives." No one admitted to killing the man.

Phone Centric Users

These are knowledge workers for whom the telephone plays a key role in the success of their business ”, e.g. salesmen , stock brokers .

Phone Farm

A place where you prepare cell phones for giving to the ultimate user. The theory is that a good specialist will not hand you a product that has not been activated, tested, or charged for immediate use. A reader wrote me "When I order several phones I get a surge-protected strip and connect all the chargers up to the phones and charge the phones. This also works with digital phone testing and can work with most landlines when many phones have to be tested ."

Phone Freak

See Phone Phreaks.

Phone Ladies

Women in Bangladeshi villages who buy cheap cell phones from the country's leading provider, then sell time to phoneless fellow villagers for a profit, building a cottage industry in the process

Phone Phreaks

Communication hobbyists. People, usually kids , who like to figure out how the telephone network works and sometimes make free calls on the network by figuring a way to bypass billing mechanisms. Phone Phreaks have become Computer Phreaks with the advent of PCs and the advent of out-of-band signaling, making it a lot more difficult to make long distance calls for free. See Phreak.

Phone Services Database

A Bluetooth term. The portion of the BT implementation that stores information about device services, both local services and remote services.


A phone-in promotion uses the telephone as a key element in its communication to and/or obtaining response from its target audience. Phone-ins can be used with most types of sales promotion. The key to success depends upon the effectiveness with which the phone-in number is communicated to the customer.


A ROLM term for Voice Mail. Rolm's PhoneMail is a voice messaging system that provides telephone answering (with the user's own greeting), the capability to store and forward voice messages and the capability to turn on a message waiting light or message on the recipient's phone. PhoneMail can be used positively to speed the flow of information. It can also be used negatively to allow the user to "hide behind" the system and avoid the outside world and anyone in the outside world who might actually want to buy something. See also Voice Mail.


A voice recognition term. The minimal significant structural unit in the sound system of any language that can be used to distinguish one word from another. For example, the p of pit and the b of bit are considered two separate phonemes, while the p of spin is not. These minimal sound units comprise words.


Farallon's twist on Apple's local area network called LocalTalk. PhoneNet uses standard one pair UTP ( unshielded twisted pair) wiring for networking. PhoneNet is compatible with LocalTalk.

Phonetic Alphabet

A list of standard words used to identify letters in a message transmitted by radio or telephone. The following are the authorized words, listed in order, for each letter in the alphabet: Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliet, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu.


Substance which glows when struck by electrons. The back of a picture tube face is coated with phosphor.

Photo Diode

Also spelled photodiode. The basic element that responds to light energy in a solid state imaging system. It generates an electric current that is proportional to the intensity of the light falling on it. Photo diodes are the light source or detector in a fiber optic transmission system. Light sources and light detectors are paired: LEDs (Light Emitting Diodes) as light sources, and PINs (Photo INtrinsic diodes) as light detectors in the slower systems; Laser Diodes and APDs (Avalanche PhotoDiodes) in the high-bandwidth systems such as SONET. See also APD, Laser Diode, LED, PIN and SONET.

Photo Electric Cell

A light activated switch frequently used to turn lights on at dusk or off at sun rise. Sometimes they are also used to dim lights at night.

Photo Etch

The process of forming a circuit pattern in metal film by light hardening a photo sensitive plastic material through a photo negative of the circuit and etching away the unprotected metal.

Photoconductive Effect

Some non-metallic materials exhibit a marked increase in electrical conductivity when they absorb photon or light energy. This is called the photoconductive effect. The conductivity increase is due to the additional free carriers generated when photon energies are absorbed in electronic transitions. The rate at which free carriers are generated and the length of time they persist in conducting states (their lifetime) determines the amount of conductivity change.


The conductivity increase exhibited by some nonmetallic materials, resulting from the free carriers generated when photon (i.e. light) energy is absorbed in electronic transitions. The rate at which free carriers are generated, the mobility of the carriers, the length of time they persist in conducting states (their lifetime) are some of the factors that determine the extent of conductivity charge. See Photoconductive Effect.


  1. Any transducer that produces a current which varies in accordance with the incident light energy. A fiber optic communications term.

  2. Photoconductor is also material, available in many forms (sheets, belts, and drums), which changes in electrical conductivity when acted upon by light. Electrophotography (a form of facsimile machine printing) relies on the action of light to selectively change the potential of a charged photoconductive surface, creating areas receptive to an oppositely charged toner, thus making the latent charged-image visible.


The current that flows through a photosensitive device (such as a photodiode) as the result of exposure to radiant power. Internal gain, such as that in an avalanche photodiode, may enhance or increase the current flow but is a distinct mechanism.


In a lightwave system, a device which turns pulses of light into bursts of electricity.


See Photo Diode.

Photoelectric Effect

An effect explained by Albert Einstein which demonstrates that light seems to be made up of particles, or photons. Light can excite electrons (called photoelectrons in this context) to be ejected from a metal. Light with a frequency below a certain threshold, at any intensity, will not cause any photoelectrons to be emitted from the metal. Above that frequency, photoelectrons are emitted in proportion to the intensity of incident light. The reason is that a photon has energy in proportion to its wavelength, and the constant of proportionality is the Planck constant. Below a certain frequency ” and thus below a certain energy ” the incident photons do not have enough energy to knock the photoelectrons out of the metal. Above that threshold energy, called the work function, photons will knock the photoelectrons out of the metal, in proportion to the number of photons (the intensity of the light). At higher frequencies and energies, the photo- electrons ejected obtain a kinetic energy corresponding to the difference between the photon's energy and the work function.


Photomasks are typically quartz plates several inches thick and six inches across. They transfer chip designs onto silicon wafers in a process called optical lithography. An advanced mask set can include two-dozen or more plates, or reticles. Each imparts specific design elements or layers of the chip onto the silicon. In the 1990s, mask makers were able to do extraordinary things with light to etch shrinking chip designs onto wafers. Ordinary light produces wavelengths about 0.6 microns wide, or about 1/200th the width of a human hair. By the mid 1990s, when mask makers came into their own by providing a key enabling technology for the chip industry, they used ultraviolet light and then deep-ultraviolet light, which has a wavelength of 0.248 microns. That cleared the way for ships at the 0.25-micron node. Those mask sets cost about $100,000 initially, and the price has dropped somewhat since then. On their inexorable march toward tighter design rules, leading makers of integrated circuits soon designed chips at the 0.18-micron node, or 1/500th the thickness of a human hair. Ics at the 0.13-micron node are ramping now, with the 90-nanometer node next in the coming cycle. To keep up, mask makers have figured out how to exploit predictable behavior of light.


The Photon is a particle of light. For hundreds of years light was thought of solely as a wave. In 1905 Einstein discovered that under certain circumstances the energy of a light wave only came in specific amounts or quanta. These quanta are called photons.

Photonic Band Gap

See Photonic Crystals.

Photonic Crystals

Photonic crystals are microscopically patterned materials that might be used to produce the true optical equivalent of the electronic integrated circuit (IC) ” but at much higher speeds. The idea is that when electronic ICs (integrated circuits) run out of speed, photonic crystals will take over. To produce a photonic crystal involves micromachining arrays of very small holes into a planar wafer. The diameter of each hole (they're usually circular) is actually smaller than the wavelength of light used for telecommunications. The easiest way to understand the behavior of light in a photonic crystal is to compare it to the movement of electrons and holes in a semiconductor. Take a deep breath . This stuff is complicated. In a silicon crystal, the atoms are arranged in a diamond-lattice structure, and electrons moving through this lattice experience a periodic potential as they interact with the silicon nuclei via the Coulomb force. This interaction results in the formation of allowed and forbidden energy states. For pure and perfect silicon crystals, no electrons will be found in an energy range called the forbidden energy gap or simply the band gap. However, the situation is different for real materials: electrons can have an energy within the band gap if the periodicity of the lattice is broken by a missing silicon atom or by an impurity atom occupying a silicon site, or if the material contains interstitial impurities (additional atoms located at non-lattice sites). Now consider photons moving through a block of transparent dielectric material that contains a number of tiny air holes arranged in a lattice pattern. The photons will pass through regions of high refractive index ” the dielectric - interspersed with regions of low refractive index ” the air holes. To a photon, this contrast in refractive index looks just like the periodic potential that an electron experiences travelling through a silicon crystal. Indeed, if there is large contrast in refractive index between the two regions, then most of the light will be confined either within the dielectric material or the air holes. This confinement results in the formation of allowed energy regions separated by a forbidden region ” the so-called photonic band gap. Since the wavelength of the photons is inversely proportional to their energy, the patterned dielectric material will block light with wavelengths in the photonic band gap, while allowing other wavelengths to pass freely . It is possible to create energy levels in the photonic band gap by changing the size of a few of the air holes in the material. This is the photonic equivalent to breaking the perfect periodicity of the silicon-crystal lattice. In this case, the diameter of the air holes is a critical parameter, together with the contrast in refractive index throughout the material. With photonic crystals, it's possible to make a so-called "perfect mirror." This is formed from a regular hexagonal array of holes, giving the appearance of a honeycomb. The holes must be identical in size. In practice, the holes are quite shallow because they are drilled into the surface of a thin wafer, but this doesn't stop them from working. The perfect mirror can reflect light incident from any angle in the plane of the wafer (unlike the edge of a standard waveguide, the properties of which change with angle) for a selected band of wavelengths. Take two perfect mirrors, put them side by side with a narrow gap in between, and the result is a waveguide. Unlike today's waveguides, which leak out light when angles get tight, a photonic crystal waveguide can guide light around 90 bends with zero loss ” at least that's the theory. But making and measuring these things has proven fairly challenging. To make this idea work in reality, the light has to be confined in the vertical direction; otherwise it gets radiated out of the top of the wafer. That's because the photonic crystal is a two-dimensional structure ” it controls light in the plane of the wafer, but can't stop it from escaping out of the top or bottom.

Two teams of researchers have made breakthroughs that could lead to a big leap forward in making optical integrated circuits. One project at Sandia National Laboratories in the U.S., promises to yield optical waveguides that can guide light around tight bends with zero losses. Currently, optical waveguides rely on small differences in refractive index to channel light. To get light around a corner with no losses requires a bend radius of several centimeters in some cases ” not good news for making compact optical circuits. Sandia's technology has huge potential for overcoming this limitation. In a separate but related development, scientists at Kyoto University in Japan have made the integrated equivalent of an optical add-drop multiplexer ” though at the moment it only performs the drop function. The device is based on microcavities, which select a specific frequency of light from a waveguide (as a fiber Bragg grating does) and spew it out of the top surface. But unlike Bragg gratings, which need to be several centimeters in length, the microcavity is less than one micrometer wide. The number of manufacturers working on optical integration is an indicator of how important a direction this is considered to be. And there are many. However, most of these companies ” for example Bookham Technologies Ltd. and the newest, Sparkolor Corp. ” take components made in separate processes and then glue them onto a substrate. Intense Photonics Ltd. and a few others are attempting to make monolithic chips, but they're at a very early stage, and the number of components they can integrate is small. Making large numbers of components at the same time on the same chip will require a radically different approach. In that sense, the integrated optics industry is at the same stage that the electronics industry was 30 years ago, when people thought that six transistors was the most they would ever squeeze onto a chip. I believe I stole much of the above explanation from the Economist.

Photonic Ethernet

A high-speed networking technology based on Polymer Optical Fiber (POF) cabling that can deliver gigabit networking speeds for a fraction of the cost of conventional fiber cable, even though the new POF has the same optical characteristics as glass. With this new technology, Gigabit Ethernet can be delivered to the desktop cost- effectively ” about $200 per port (Summer of 1998) ” making it potentially interesting for bandwidth-constricted workgroups.

Photonic Layer

The lowest of four layers of Sonet capability, which specifies the kind of fiber to be used including sensitivity and laser type. See SONET.

Photonic Switch

A switch which switches photonics, or light signals. See Lambda Switch and Photonic Cystals.


The technology that uses light particles (photons) to carry information over hair-thin fibers of very pure glass. See also Photonic Cystals.


In 1880 (four years after he invented the telephone) Alexander Graham Bell and his assistant, Charles Tainter, invented the photophone, which Bell felt was his greatest invention. In fact, Bell was so proud of it that he wanted to name his daughter Photophone. A cooler head prevailed, with that head sitting on his wife's shoulders. Consisting of a set of specially ground and shaped mirrors, and associated electrical gear, the photophone was capable of voice transmission over short distances, using sunlight. It was, in fact, the first optical transmission system, preceding fiber optics by nearly 100 years. It also was highly impractical , relying on fragile mirrors and sunny days. The Nazis experimented with a variation on the theme for application in W.W.II tank warfare ” the results were not positive. See also Bell, Alexander Graham.


A transistor that detects light and amplifies the resulting electrical signal. Light falling on the base-collector junction generates a current, which is amplified internally.


Photovoltaics is the name of the science that uses a semiconductive device to convert sunlight into electricity. The photovoltaic effect was first discovered by a French Physicists by the name of Edmond Becquerel in 1839. It is the only area of work that Einstein received a Nobel Prize in. It was commercially developed in the 1950s but did not expand into a significant industry until the 1990s.

Photovoltaic Effect

Using light to produce electricity. Shine light on a device, typically a "cell." If the device produces electricity, that's called the photovoltaic effect.


  1. Personal Handy Phone. Japan's standard for digital cordless phones.

  2. Initially known as Personal Home Page Tools and now officially called PHP: Hypertext Preprocessor, PHP was developed in late 1994 by Rasmus Lerdorf. Its aim is to make it easy to write dynamic Web pages. PHP code is embedded into standard HTML Web pages. www.informationweek.com/769/devlop.htm


A phone phreak (also known as a Phreaker) is to the phone network community what the original hackers were to the computer revolution. These were the hobbyists who couldn't get enough information about the telephone from reading published works or taking one apart; rather they learned how the touchtone frequencies worked to route calls. Granted, one aspect of what they did was making illegal phone calls, but the larger picture was a hunger for information that they couldn't get elsewhere. See also Cracker, Hacker, Phone Phreak, Script Kiddies, and Sneaker.


Personal Handyphone System, or Personal Handyphone Service. Also known as PDC (Personal Digital Cellular), PHS previously was known as PHP (Personal HandyPhone) and Japanese Digital Cellular. PHS is the Japanese version of the U.S.'s PCS (Personal Communications Service, with two key differences. It's not as powerful as PCS. You can't use a PHS phone in a rapidly moving vehicle, since there is no cell- handoff , i.e. it won't move you from one cell to another. And thus, if you move outside your cell with PHS, you lose connection. PHS is a perfect mobile phone for pedestrians in high density cities like Tokyo, as long as they don't move around a lot during the course of a call.


PHYsical, as in physical specifications. OSI Physical Layer: The physical layer provides for transmission of cells over a physical medium connecting two ATM devices. This physical layer is comprised of two sublayers : the PMD Physical Medium Dependent sublayer, and the TC Transmission Convergence sublayer. See Physical Layer, PMD and TC.

Physical Address

  1. A number of digits which identifies the physical location of a communications channel or port within a system. In the old Rolm CBX, for instance, the number was in the form of xxyyzz, where xx=shelf, yy=slot and zz=channel.

  2. The address where something physically resides. A physical addresses is translated from a logical address. Allow me to illustrate . When someone dials your telephone number, they are dialing a logical address; in other words, the series of numbers means nothing until they are translated into a physical address. The physical address is the port to which your local loop is connected to which your telephone is connected. Similarly, your postal address is a logical address. It has meaning only when translated by the post office into the plot of earth on which your house sits. A logical address, on the other hand and just to confuse you, may have no fixed physical address. For example, your e-mail address has no fixed physical address. Rather, it is translated into an IP (Internet Protocol) address which is associated with your e-mail server, which can be moved from place to place. Ultimately, your e-mail address actually is associated with you, and you and your computer can move all over the world without losing access to your e-mail. Rather, you gain access to your e-mail by going on a network connected to the Internet ” e.g. dialing a telephone number (logical address) which connects you to your e-mail server which has a physical address which can change as the server is moved from one location to another.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net