NAM (Number Assignment Module) - The NAM is the electronic memory in the cellular phone that stores the telephone number and electronic serial number. Phones with dual- or multi-NAM features offer the user the option of registering the phone so that it will have two or more phone numbers.

Nanosecond - One-billionth of a second.

Narrowband - An imprecise term meaning to some people sub-voice grade channels capable of carrying only 100 to 200 bits per second, and to others meaning circuits able to carry up to 2400 bits per second.

Narrowband Channel - Sub-voicegrade channel with a speed range of 100 to 200 bps.

National Electrical Code  - Rules for the installation of electrical and telephone cabling published by the National Fire Protection Association. This code has the force of law only when enforced by municipalities or states.

National Electrical Safety Code - A code of safety rules for the installation and maintenance of electric supply and communications lines and published by the National Bureau of Standards. This code has been adopted as law by many states and municipalities.

Native Address - An address that matches one of a given node's summary addresses.

NBMA (Non-Broadcast Multi-Access) - Another way of saying ATM or Frame Relay.

NC (Normally Closed) - A relay contact that is closed when the relay coil is not energized.

NCC - (1) Network Control Center, a central location on a network where remote diagnostics and network management are controlled; and (2) National Computer Conference, the largest annual conference of the computer industry.

Near-End - In a relationship between two devices in a circuit, the near-end device is the one that is local.

Negative - (1) Voltage source to which the conventional DC current returns; and (2) battery terminal with an excess of electrons. 

Negative Battery - The negative terminal of a battery. Most central offices use a 50V storage battery with the positive side grounded. The negative side is then usually called simply "battery."

Negative Resistance - Property of some specialized circuits by means of which current increases as voltage is decreased.

Negative Terminal - (1) Terminal from which electrons flow; and (2) the negative output terminal of a DC power source.

Neighbor Node - A node that is directly connected to a particular node via a logical link.

NEMA (National Electrical Manufacturers Association) - An organization of electrical equipment manufacturers set up to establish uniform standards and nomenclature throughout the industry.

Network - (1) Devices connected by communications circuits. The public switched network is the network of lines used for publicly dialed telephone calls. A private network is a network whose use is restricted to a specific customer or group of customers. (2) The wiring block found in most telephone sets. The wiring block that all the wires are hooked into is call the Network.

Network Layer - Layer three In the OSI model, the layer that is responsible for routing data across the network.

Network Management - A set of procedures, equipment and operations designed to keep a network operating near maximum efficiency when unusual loads or equipment failures would otherwise force the network into a congested, inefficient state.  

Network Management System - A comprehensive system of equipment used in monitoring, controlling, and managing a data communications network. Usually consists of testing devices, CRT displays and printers, patch panels, and circuitry for diagnostics and reconfiguration of channels, generally housed together in an operator console unit.

Network Module - ATM port interface cards which may be individually added or removed from any ForeRunner ATM switch to provide a diverse choice of connection alternatives. Each network module provides between one and six full-duplex ATM physical connections to the ForeRunner switch.

Network Redundancy - Duplicated network equipment and/or data that can provide a backup in case of network failures.

Neutral - The common, current carrying conductor in an electrical distribution system, often grounded. Examples: (a) in a single phase, 3 wire system (i.e. 240/120 volts), it is the center conductor common to both hot wires; (b) in a wye connection, it is the common point in the wye; (c) in a grounded delta connection, it is the grounded point, either one corner of the delta or a center tap in one phase.

Neutral Ground - An intentional ground applied to the neutral conductor or neutral point of a circuit, transformer, machine, apparatus or system.

NFS (Network File System) - A client/server distributed file service that provides transparent file sharing for network environments.

NHC (Next Hop Client) - A client device running NHRP software.

NHRP (Next Hop Resolution Protocol) - NHRP was developed by the ROLC and is the protocol on which MPOA routing is based (it is now in its 12th draft).

NHS (Next Hop Server) - Transmits NHRP (Next Hop Resolution Protocol) queries and replies between IP subnets.

NI - No Increase bit used to prevent a source from increasing its ACR.

NIC (Network Interface Card) - A card you insert into a computer that enables it to be connected to a network. NICs are designed for a particular type of network and/or protocol. (i.e. Token Ring, ATM, etc.)

NM (Network Management Entity) - The body of software in a switching system that provides the ability to manage the PNNI protocol. NM interacts with the PNNI protocol through the MIB.

NMCC (Network Management Control Center) - A central place from which the network is maintained and changed, and statistical information is collected.

NML (Network Management Layer) - An abstraction of the functions provided by systems which manage network elements on a collective basis, so as to monitor and control the network end-to-end.

NMS (Network Management Station) - The system responsible for managing a network or a portion of a network. The NMS talks to network management agents, which reside in the managed nodes.

NNI (Network-to-Network Interface or Network Node Interface) - The interface between two public network pieces of equipment. 

NO (Normally Open) - A relay contact that is open when the relay coil is not energized.

No-Answer Transfer- A sophisticated service provided by a cellular carrier that automatically transfers an incoming cellular call to another phone number if the cellular subscriber is unable to answer. Most no-answer transfer systems will automatically transfer the call on the first ring if the cellular phone is turned off, but will not make the transfer until the third or fourth ring if the phone is turned on.

Nodal Attribute - A nodal state parameter that is considered individually to determine whether a given node is acceptable and/or desirable for carrying a given connection.

Nodal Constraint - A restriction on the use of nodes for path selection for a specific connection.

Nodal Metric - A nodal parameter that requires the values of the parameter for all nodes along a given path to be combined to determine whether the path is acceptable and/or desirable for carrying a given connection.

Nodal State Parameter - Information that captures an aspect or property of a node.

Node - A computer or other device when considered as part of a network. 

Noise Level - The volume of noise energy, expressed in decibels, above a reference level.

Non-Blocking Switch Capacity - A non-concentrating arrangement where no switch connections are blocked when traffic flow is at 100% switch capacity. 

Noncritical Technical Load - That part of the technical load not required for synchronous operation.

Nonvolatile Storage - Memory storage that does not lose its contents when power is turned off.

Non-Wireline - FCC regulations restrict providers of cellular telephone service in any given market to one wireline carrier (the local telephone company) and one non-wireline carrier (any company other than local telephone company). 

NPC (Network Parameter Control) - Defined as the set of actions taken by the network to monitor and control traffic from the NNI. Its main purpose is to protect network resources from malicious as well as unintentional misbehavior which can affect the QoS of other already established connections by detecting violations of negotiated parameters and taking appropriate actions. Refer to UPC.

Nrm - For ABR, it refers to the maximum number of cells a source may send for each forward RM-cell (range of 2 to 256 cells with 32 as default).

nrtVBR (non-real time Variable Bit Rate) - One of the service types for transmitting traffic where timing information is not critical and which is characterized by the average and peak cell rates. It is well suited for long data packet transfers.

NRZ (Non Return to Zero) - A binary encoding scheme in which ones and zeroes are represented by opposite and alternating high and low voltages and where there is no return to a zero (reference) voltage between encoded bits.

NRZI (Non Return to Zero Inverted) - A binary encoding scheme that inverts the signal on a "1" and leaves the signal unchanged for a "0". (Also called transition encoding.)

NSAP (Network Service Access Point) - OSI generic standard for a network address consisting of 20 octets. ATM has specified E.164 for public network addressing and the NSAP address structure for private network addresses.

NSAP prefix - 13-byte address prefix that can be used to describe a specific location (country, system, area).

NTSC (National TV Standards Committee) - Started in the US in 1953 from a specification laid down by the National Television Standards Committee. It takes the B-Y and R-Y color difference signals, attenuates them to I and Q, then modulates them using double-sideband suppressed subcarrier at 3.58MHz. The carrier reference is sent to the receiver as a burst during the back porch. An industry group that defines how television signals are encoded and transmitted in the US. (See also PAL, SECAM for non-U.S. countries).

NuBus - A high-speed bus used in the Macintosh family of computers, structured so that users can put a card into any slot on the board without creating conflict over the priority between those cards.

Null - A value of all zeros.

nx64K - This refers to a circuit bandwidth or speed provided by the aggregation of nx64 kbps channels (where n= integer> 1). The 64K or DS0 channel is the basic rate provided by the T Carrier systems.

Nyquist Theorem - In communications theory, a formula stating that two samples per cycle is sufficient to characterize a bandwidth limited analog signal; in other words, the sampling rate must be twice the highest frequency component of the signal (i.e., sample 4 KHz analog voice channels 8000 times per second).