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N connector - A threaded connector used to join to coax cable; N is named after Paul Neill.

N/d (neutral density) filter - A filter that attenuates light equally over the whole visible spectrum.

N-series connector - A coaxial connector (RG-8/U) used in standard Ethernet networks.

NAM - Network access method.

NAS (network attached storage) - A data storage device that is attached directly to the main data network. (Lower cost than a SAN but shares bandwidth with the data network.)

NAT (network address translation/translator) - A device, or just software on a computer, that can separate a LAN network from the Internet. Routers are often NAT routers. It translates an internal IP address to an outside public IP address.
NBR/PVC - A blend of acrylonitrile-butadiene rubber; a material with good oil and chemical resistance and polyvinyl chloride (PVC). Used for jacketing.

NBR - Butadiene-acrylonitrile copolymer rubber, a material with good oil and chemical resistance.

NBR/PVC - A blend of acrylonitrile-butadiene rubber and polyvinyl chloride (PVC). Used for jacketing.

NBS (National Bureau of Standards) - A U.S. government agency that produces Federal Information Processing Standards (FIPS) for all U.S. government agencies and network users. Now called NIST (National Institute of Standards and Technology).

NEBS (network equipment building systems) - Standards defined test levels created by Telecordia Technologies (formerly Bellcore) in 1985 for the telecommunications industry. NEBS testing is required in the U.S. for equipment operated in the carrier networks of Regional Bell Operating Companies (RBOCs) and competitive local exchange carriers (CLECs).

NEC - National Electrical Code.

Negative sequence impedance - The electrical impedance of a three-phase power cable with the phase rotation reversed as compared to normal operation. Has the same numerical value as the positive sequence impedance. “Negative sequence” refers to the phase relationship of the currents in the conductors.

NEMA - National Electrical Manufacturers Association.

Neoprene - A synthetic rubber with good resistance to oil, chemical and flame. Also called polychloroprene.

Netview - IBM’s network management product for its SNA networks. It can collect information from non-SMA environments via NetView/PC.

Netware - A popular proprietary network operating system from Novell, Inc.

Network - A series of nodes connected by communications channels.

Network channel terminating equipment - Equipment used at the customer premises to provide facility termination and signaling compatibility. Also called channel service unit (CSU).

Network facilities - In a packet-switched network, standard facilities are divided into essential facilities (found on all networks) and additional facilities (selected for a given network but which may or may not be selected for other networks).

Networking - The connection of one ISN system to other compatible local area networks or PBXs.

Network interface controller - A communications device that allows interconnection of information processing devices to a network.

Network management - Administrative services performed in managing a network, such as network topology and software configuration, downloading of software, monitoring network performance, maintaining network operations and diagnosing and troubleshooting problems.

Network protection device - A device which provides isolation between PBX circuits and CO trunks or tie lines.

Network topology - The physical and logical relationship of nodes in a network. Networks are typically of a star, ring, tree or bus topology or some hybrid combination thereof.

Newton - The derived SI unit for force; the force that will give one kilogram mass an acceleration of one meter per second: 1N=1 • (kg •m) / s-2.

Next - Near-end crosstalk. A measure of the unwanted signal coupling from a transmitter at the near-end into a neighboring (non-energized) pair measured at the near-end.

NFPA - National Fire Protection Association.

NIC (network interface card) - Also called controller card, PC expansion card, controller board, network interface controller, adapter card, adapter board, network adapter module or network interface module. Its function is to allow the workstation to be physically and electronically connected to some specific network at the physical and data link layer.

Nickel clad copper wire - A wire with a layer of nickel on a copper core where the area of the nickel is approximately 30 percent of the conductor area.

NIST - National Institute of Standards and Technology. Formerly the National Bureau of Standards.

NIU - Network interface unit.

Nm-b - A UL cable type rated 600 volts and intended for use per Article 334 of the NEC. Nonmetallic sheathed cable. For dry use, 90°C conductor rating.

Nmc-b - A UL cable type rated 600 volts and intended for use per Article 334 of the NEC. Nonmetallic sheathed cable. Wet or dry use, 90°C conductor rating.

Node - A station.

Noise - In a cable or circuit, any extraneous sounds or signal which ends to interfere with the sound or signal normally present in or passing through the system.

Nomex - DuPont trademark for a temperature-resistant, flame-retardant nylon.

Nominal - Name or identifying value of a measurable property by which a conductor or component or property of a conductor is identified and to which tolerances are applied.

Nominal voltage (national electrical code) - A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (as 120/240, 480Y/277, 600 volts, etc.). The actual voltage at which a circuit operates can vary from the nominal within a range that permits satisfactory operation of equipment.

Nomograph - A chart or diagram with which equations can be solved graphically by placing a straight edge on two known values and reading the answer where the straight edge crosses the scale of the unknown value.

Noncontaminating - A type of PVC jacket material whose plasticizer will not migrate into the dielectric of a coaxial cable and thus avoid contaminating and destroying the dielectric.

Noncontaminating pvc - A polyvinyl chloride formulation that does not produce electrical contamination through plasticizer migration.

Nonflammable - The property of a material that is not capable of being easily ignited.

Nonmigrating pvc - Polyvinyl chloride compound formulated to inhibit plasticizer migration.

NOS (network operating system) - A generic term that applies to local area network operating system software.

NRZ (non-return to zero) - The common encoding of a binary stream into two voltage levels.

NRZI (non-return to zero inverted) - In SDLCO, a binary encoding technique in which a change in state represents a binary 0 and no change in state represents a binary 1.

NT - Network termination.

NTP (network time protocol) - A protocol designed to synchronize the clocks of computers over a network.

NTSC (National Television System Committee) - The television standard for North America and parts of South America having 525 lines/60 Hz (60 Hz refresh), two fields per frame and 30 frames per second (60 fields per second).

Null modem - Same as modem eliminator.

Null modem cable assemblies - The null modem cable assembly utilized the RS-232 cable system and replaces short distance modems.

Numerical aperture - The acceptance angle of an optical fiber which determines the angle at which light can enter the fiber; expressed as a number that is equivalent to the sine of the angle.

NVP (nominal velocity of propagation) - This is a measure of how fast a signal travels along a line.

NVR (network video recorder) - A storage device on a network for storing IP video.

Nylon - An abrasion-resistant thermoplastic with good chemical resistance.

NZDSF - Non-zero dispersion shifted fiber.