Glossary O-P

Offline: The condition of being disconnected from a device or network. Offline: applies to the intentional disconnection from the device or network, as well as the disconnection that follows a system fault or failure.

Online indicator (See also, in-use light, busy indicator or busy light.) This accessory makes it very easy for people to tell when you're on a call-even when you're using a discreet headset. It lights up, so they can see at a glance that you're busy. It's a simple way to prevent interruptions, and it's helpful for the folks who monitor group phone activity. The indicator works whenever you're on the phone, with or without a headset.

Operator Services: A group of telephone services provided by a phone company’s live operator. Common operator services include: directory assistance, assisted collect calls, assisted 3-way calling and emergency line intercept (allows the operator to reach someone by interrupting a call in progress).

Optical Cable Also known as fiber-optic cable, optical cable is a telecommunications cable that uses visible light pulses over glass or plastic fibers as the transmission medium. Optical cable transports considerably more data than standard copper cable does. It is lighter in weight, and is resistant to electromagnetic and radio interference.

PABX (Private Automatic Branch Exchange) - Differs from a PBX in that a PBX may require a live operator. Since most PBX systems are now automatic, the term is virtually synonymous with PBX and is not often used.

PBX (Private Branch Exchange) - The main switching unit in a multi-line digital phone system. The PBX routes calls to voice mail, manages Direct Inward Dial (DID), station-to-station calling, transferring, internal and external conferencing, voice mail, music-on-hold (when applicable) and other manufacturer-specific functions. PBX systems are usually digital systems designed for a large number of users, although there are exceptions.

PCM (Pulse Code Modulation) - The technology used to convert analog signals to digital coding and back again (demodulation). PCM breaks an analog signal into quantified bits based on a consistent unit of time and transmits them to the receiver. PCM is used in many cordless devices (cordless phones, for instance), in dial-up modems and on T-Carrier phone lines.

PCMCIA (Personal Computer Memory Card International Association) An international organization of companies founded to create interoperability standards for small devices called PCMCIA cards, now more commonly referred to as PC cards. PC cards are small credit-card sized devices used for a variety of applications. Common examples include laptop modems, RAM memory cards, and portable disk drives.

PCS (Personal Communications Services) - Similar to cellular service, PCS employs a digital signal, CDMA multiplexing, spread spectrum technology and specified usage bands that distinguish it from other wireless services.

PDA (Personal Digital Assistant) - A portable, handheld device that is used to store and retrieve data. Common uses of PDAs include building address books, taking notes, and scheduling activities in a calendar. Newer applications include wireless networking for information sharing between PDAs, wireless telephony (combination PDA and wireless phone), and file sharing with a desktop or notebook computer.

POP (Post Office Protocol) - A standard Internet protocol for retrieving e-mail from an e-mail server. The original version of POP was POP2, but recently POP3 has become prominent. POP is usually used in conjunction with Simple Mail Transfer Protocol (SMTP), which is the protocol that delivers messages to an e-mail server. POP periodically checks an e-mail server and forwards all new messages to the inbox. A newer protocol, called IMAP4, is also used to retrieve e-mail. IMAP4 has more features than POP3, but POP3 is still the primary message retrieval protocol.

POTS (Plain Old Telephone Service) - The basic telephone service and equipment provided by the phone company.

PSTN (Public Switched Telephone Network) - The worldwide voice network that has evolved since the advent of the telegraph. Due to its ubiquity, the PSTN has been turned to other uses. Although originally analog in nature, the PSTN has transformed into primarily a digital carrier. As a result, it has been able to increase capacity and serve as the infrastructure for virtually all telecommunications, including the Internet.

Packet A small unit of digital data that is transferred within or between networks. On the Internet, packets are created by use of the Transmission Control Protocol (TCP) and sent from one location to another via Internet Protocol (IP).

Packet Switching: Packet-switching permits the transfer of data that is broken into small data packets by Transmission Control Protocol (TCP). Each data packet is sent individually and even along different routes to a specified Internet Protocol (IP) address where it is reassembled. This permits the same pathways to be used by multiple users simultaneously. In contrast, circuit-switching, the method used in Plain Old Telephone Service (POTS), requires a dedicated connection for the duration of data transfer.

Pager Notification A function of some telephones and systems that sends a message to a numeric or text pager to notify users of a received call or fax.

Parallel A form of data processing that handles multiple data streams and/or processes simultaneously. Parallel processing is used for some peripheral devices, most notably in printers. Parallel processing contrasts with serial processing, which indicates a number of single processes occurring in a series.

Peripheral: Any device that is used with, but is not actually part of, a primary computing device. For example, printers, mice, CD-ROMs, and keyboards are all considered peripheral devices to a computer.

Position: On a telephone plug, the numbers of spaces available for copper conductors are known as positions. A standard telephone wall jack, for instance, has 6 positions available and may have 2, 4, or 6 conductors, depending on the number of lines and applications it is being used to support.

Protocol A set of programmed rules for communicating data between two or more devices. There are protocols used for virtually every telecommunication device. For example, Internet connections rely on TCP/IP protocols and the attendant Hypertext Transfer Protocol (HTTP); e-mail is sent by use of Simple Mail Transfer Protocol (SMTP).

Pulse Dial: Also known as loop disconnect dialing, this method of dialing was prevalent before the 1970s. The most common example is the rotary telephone. A user would dial from the designated number position and the telephone would successively "pulse" the number(s) selected, instructing the Central Office (CO) how to connect. Pulse dialing has been all but superseded by DTMF or touch-tone technology.

Punchdown Block: Also known as a 'terminal block,' a punchdown block is the point where all the wires that carry voice and data in an on-premises network are brought together before connecting them to the trunk (phone company carrier) lines of the Public Switched Telephone Network (PSTN). The punchdown block is normally placed near the point of demarcation—where the public phone lines physically cross into your home or office.

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