OA&M

　　operation administration & maintenance

　　OCC

　　other common carriers

　　Ohms Restriction

　　Ohms Restriction is the same as Ohms resistance. Ohms are measures of resistance. A resistance of one Ohm allows one Ampere of current to pass at the electric potential of one Volt.

　　Open Systems Interconnection (OSI) standards

　　OSI standards are standards for the exchange of information among systems that are "open" to one another by virtue of incorporating ISO standards. The OSI reference model segments communications functions into seven layers. Each layer relies on the next lower layer to provide more primitive functions and, in turn, provides services to support the next higher layer.

　　Operating Telephone Company

　　An operating telephone company is any Bell-operating company or independent telephone company (termed exchange carrier in the MFJ) operating in North America.

　　Optical Fiber(s)

　　Optical fibers are light guides for electromagnetic waves in the infrared and visible light spectrumcomposed of concentric cylinders made of dielectric materials with different indices of refraction (i.e., velocity of propagation normalized to the velocity of light in free space). At the center is a core comprising the glass or plastic strand or fiber in which a light wave travels. A low index of refraction clad surrounds the core and is itself enclosed in a light-absorbing jacket that prevents interference among multi-fiber cables. Multi-fiber cable can be purchased with between 2 and 136 fibers.

　　OPX

　　off-premises extension

　　OSC

　　operating system control

　　OSI

　　open systems interconnection

　　OSS

　　operations support systems or operational support system

　　Out Of Band Signaling

　　Out of band signaling uses the same channel path as the voice traffic but signaling is in a frequency band outside that used for the voice traffic. In digital systems, out-of-band signaling may take the appearance of an allocated bit position or a dedicated channel or time slot.

P-MAC

　　packet media access controller

　　PAD

　　packet assembler-disassembler

　　PCB

　　printed circuit board

　　PDS

　　premises distribution system

　　Personal Communications

　　Personal communications provides at least one human operator with direct terminalaccess and real time or near real time interactive communications with a remote human opera tor or an information system resource. Personal communications can refer to a broad range of services, systems and equipment, e.g., facsimile machines, landline telephones, cellular tele phone systems and emerging personal communication system (PCS) adjuncts, and a variety of radio systems including pagers, hand-held remote data entry terminals, and autonomous citizen-band- like radio systems.

　　PHY

　　physical-layer protocol

　　PMD

　　physical-layer media-dependent

　　Point-of-presence (POP)

　　A POP is a physical location within a LATA that an IXC establishes for the purpose of gaining access to BOC/LEC networks within the LATA using LEC provided access services. An IXC may have more than one POP within a LATA and the POP may support public and private, switched and non switched services.

　　POP

　　point-of-presence

　　POT

　　point of termination

　　PPSN

　　public packet switched network

　　Premises Distribution System (PDS)

　　PDS is the transmissionnetwork inside a building or among a group of buildings, for example an office park or a campus. PDS is used in this book as a generic term although AT&T used it to describe a specific product offering. The PDS connects desktop and other station equipment with common host equipment, (e.g., switches, computers and building automation systems), and to external telecommunications networks.

　　Private Branch Exchange (PBX)

　　A PBX is a premises switching system, serving a commercial or government organization, and usually located on that organization's premises. PBXs provide telecommunications services on the premises or campus, (e.g., internalcalling and other services), and access to public and private telecommunications network services.

　　Private Network

　　A private network is a network made up of circuits and, sometimes, switching equipment, for the exclusive use of one organization.

　　PRI

　　primary rate interface

　　Protocols

　　Protocols are strict procedures for the initiation, maintenance and termination of data communications. Protocols define the syntax (arrangements, formats and patterns of bits and bytes) and the semantics (system control, information context or meaning of patterns of bits or bytes) of exchanged data, as well as numerous other characteristics (data rates, timing, etc.).

　　PSN

　　packet switched network

　　PSPDN

　　packet switched public data network

　　PSTN

　　public switched telecommunications network

　　PTT

　　postal, telephone, and telegraph

　　Public Switched Telephone Network (PSTN)

　　A Public Switched Telephone Network (PSTN) denotes those portions of the LEC and IXC networks that provide public switched telephone network services.

　　PUC

　　public utility commission

　　Pulse Code Modulation (PCM)

　　Pulse Code Modulation (PCM) is a modulation scheme involving conversion of a signal from analog to digital form by means of coding. See also modulation.

　　PVC

　　permanent virtual circuit

　　Partner＊s Program - An indirect sales channel that offers smaller businesses in the TDS Telecom service areas an opportunity to promote and sell TDS Telecom products and services.

　　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.

　　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.

　　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.

　　Peering - The arrangement of information sharing between Internet Service Providers at various NAPs.

　　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.

　　Pipeline - An extremely high-speed, large capacity bandwidth connection.

　　Point of Presence (POP) - A location where a you can connect to a network through local telephone lines.

　　Point-to-Point Protocol - A program that allows a computer to use a telephone line and modem to make TCP/IP connections.

　　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.

　　POP - See Point of Presence and Post Office Protocol

　　Post Office Protocol (POP) - A system that allows hosts to get e-mail from a server.

　　POPs (Population equivalents) - The population of a market multiplied by the percentage ownership of that market.

　　PPP - See Point to Point Protocol
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