Telephone Terminology M-P

M

MCLD - Modifying Calling Line Disconnect. The parameter on the Lucent 5ESS switch that determines if CPC is active. Should be set to “Yes” if CPC is required. See CPC.

N

National ISDN (USA & Canada) - The U.S. “standardized” multi-platform ISDN protocol. The first version is National ISDN-1. As of mid-1996, National ISDN-2 has been implemented in some areas and is fully backward compatible with National ISDN-1.

NCTE – Network Channel Terminating Equipment. NCTE is a general term that can be applied to a CSU or NT1 or other equipment terminating a digital line at the customer’s premises. In many countries, the NCTE is provided by the Telco. The U.S. is not one of those countries.

Network Channel Terminating Equipment - See NCTE.

Network Termination - See NT.

NIU – Network Interface Unit, a line-powered, telephone company-owned interface card that provides a remote-controlled loopback function, some error monitoring, and signal level conditioning. Sometimes called an "NI" or "Smart Jack," it is typically a box in a locked cabinet on the wall with some lights that has at least one RJ45 jack and a cable going to either the RJ21x block or another demarc. The NIU converts the incoming 2-pair line to an RJ45 T1 or PRI line. A CSU/DSU is required between it and your equipment to handle the level conversion and provide your own loopback capability. The NIU and the cable going to it are the phone company’s property and their maintenance responsibility. Also a nice little college in Illinois.

Northern Telecom - The Canadian company which was once the manufacturing arm of Bell Canada (and formerly called Northern Electric back then). Now called Nortel Networks. See Nortel.

NT - Network Termination. The electrical and protocol specifications for the user end of an ISDN line. See also LT.

NT-1 - An alternative expression for NT1. See NT1.

NT1 (Network Termination Type 1) - The termination at the customer premises of an ISDN BRI circuit. The NT1 performs the role of line termination of the “U” interface and codes/ decodes from the line’s 2B1Q coding scheme. The customer end of the NT1 interfaces using the “S” or “T” interface. The NT1 is frequently part of the “Terminal Adapter” and is built-in to Zephyr Xstream, Zephyr, ZephyrExpress, Telos TWO, and Telos TWOx12 systems sold in the U.S. & Canada. See also NCTE.

NTBA - Network Termination Basic Access. The term used for NT1 in some countries. See NT1. See also NCTE.

O

OOS – Out of Service. An alarm light or condition on a T1 or trunk.

P

Packet Switching - Packet-switched networks are more commonly associated with Computers, Local Area Networks, and the Internet. In a packet-switched network, the raw stream of data is broken into individual pieces called packets. Each packet is routed through the data network individually. This is somewhat analogous to taking the pages of a book and sending each page as a letter through the postal system. The page numbers would allow reassembly of the book no matter what order the pages were received at the far end. The end-user does not know or care that the packets may travel a variety of routes.

If a given page did not arrive in a reasonable length of time, one could request that this page be re-sent. Most packet-switched systems allow packets to be discarded if the network capacity is exceeded (the postal system is not supposed to do this). This is accommodated by the higher-level protocol which knows to request that a packet be re-sent if it does not arrive. Therefore, the typical behavior of a packet-switched network when overloaded is that throughput decreases (i.e. the network “slows down”) as the percentage of discarded packets increases. In stark contrast to Circuit Switched networks. See Circuit Switching.

Pair Gain - A method of transmitting multiple POTS signals over twisted pairs. Traditionally used for a single traditional subscriber line in telephone systems. See SLC-96.

PBX - Private Branch Exchange. A privately owned switch. Basically, a PBX is a private “business” telephone system that also interfaces to the telephone network. In some circles, PBX implies a manual switchboard, in contrast to PABX (Private Automatic Branch Exchange) which implies a PBX that supports dialing by end-users.

PIC - Primary Interexchange Carrier. This is your default “1+” carrier used for inter-LATA calls in the U.S. In some cases, you may have two PICs, one for interLATA calls, and one for intraLATA long-distance calls; in this case, it stands for Primary Intraexchange Carrier. In some areas, intraLATA long-distance calls are still handled by your RBOC while in others, you now have a choice. You can identify who your current PIC is by dialing 700- 555-4141.

POP - Point Of Presence. The local facility where your IEC maintains a switch. This is where your long-distance calls get routed so that your IEC can handle them. Also used to describe the local access point of an Internet Service Provider. Sometimes carriers maintain “Paper POP’s”, points of interconnection that are advantageous for regulatory reasons. These are often at Co-Location facilities (COLO’s) or “Telco Hotels”, which are large hardened data centers where many carriers and customers interconnect and terminate data and voice facilities.

Port - This is a pretty general term. Newton’s Telecom Dictionary 10th edition defines a port as “an entrance to or an exit from a network”. Many phone equipment vendors refer to ports as the physical interface between a Switch and a Line or Trunk or “line equipment”. Product literature often refers to the number of ports on a phone system. In this context, it refers to the number of phones or lines (or sometimes the combination) the system supports.

POT - Plain Old Telephone. A black, rotary-dial desk phone. Usually a Western Electric model 500 set. Outdated term.

POTS – Plain Old Telephone Service. Regular old-fashioned analog loop start phone service.

PRI – ISDN Primary Rate Interface. A form of ISDN with 23 “B Channels” and one “D channel”. All 24 channels are carried on a single cable. Functionally related to T1 telephone circuits. In Europe, PRI has 30 “B Channels”, one “D Channel”, and one “Sync channel”. See also B channel and D channel.

Provisioning - The act of configuring a telecommunications service. Also refers to the complete line configuration information.