Multifiber Cable: A fiber-optic cable having two or more fibers, each of which is capable of serving as an independent optical transmission channel. [Cable Manufacturers]
National Electric Code (NEC): A standard that governs the use of electrical wire, cable, and fixtures, and electrical and optical communications cable installed in buildings.
Network Interface Card (NIC): A network interface device (NID) in the form of circuit card that is installed in an expansion slot of a computer, to provide network access. Note: Examples of NICs are cards that interface a computer with an Ethernet LAN and cards that interface a computer with an FDDI ring network. [LAN Products]
Network Interface Device (NID): A device that performs interface functions, such as code conversion, protocol conversion, and buffering, required for communications to and from a network. A device used primarily within a local area network (LAN) to allow a number of independent devices, with varying protocols, to communicate with each other. Note 1: An NID converts each device protocol into a common transmission protocol. Note 2: The transmission protocol may be chosen to accommodate directly a number of the devices used within the network without the need for protocol conversion for those devices by the NID. Synonym network interface unit.
Network Terminal Number (NTN): In the CCITT International X.121 format, the sets of digits that comprise the complete address of the data terminal end point. Note: For an NTN that is not part of a national integrated numbering format, the NTN is the 10 digits of the CCITT X.25 14-digit address that follow the Data Network Identification Code (DNIC). When part of a national integrated numbering format, the NTN is the 11 digits of the CCITT X.25 14-digit address that follow the DNIC.
Network Topologies: The structure or layout of the bus between the communication elements. There are 4 main types of bus topologies; 1. Point-to-Point, 2. Bus, 3. Ring, and 4. Star. Point-to-Point interface buses are used for very high speed interfaces. A Bus is the most normal interface found. Ring interfaces are normally token passing networks. Star topologies are normally switched fabric structures.
Non-Return-to-Zero Mark (NRZ-M): A binary encoding scheme in which a signal parameter, such as electric current or voltage, undergoes a change in a significant condition or level every time that a “one” occurs, but when a “zero” occurs, it remains the same, i.e., no transition occurs. Note 1: The transitions could also occur only when “zeros” occur and not when “ones” occur. If the significant condition transition occurs on each “zero,” the encoding scheme is called “non-return-to-zero space” (NRZ-S). Note 2: NRZ-M and NRZ-S signals are technically interchangeable; i.e., one is the logical “NOT” (inverse) of the other. It is necessary for the receiver to have prior knowledge of which scheme is being used. Without such knowledge, it is impossible for the receiver to interpret the data stream correctly; i.e., its output may be the correct data stream or the logical inverse of the correct data stream.
Non-Return-to-Zero Space (NRZ-S): A binary encoding scheme in which a signal parameter, such as electric current or voltage, undergoes a change in a significant condition or level every time that a “zero” occurs, but when a “one” occurs, it remains the same, i.e., no transition occurs. Note 1: The transitions could also occur only when “ones” occur and not when “zeros” occur. If the significant condition transition occurs on each “one,” the encoding scheme is called “non-return to zero mark” (NRZ-M). Note 2: NRZ-S and NRZ-M signals are technically interchangeable; i.e., one is the logical “NOT” (inverse) of the other. It is necessary for the receiver to have prior knowledge of which scheme is being used. Without such knowledge, it is impossible for the receiver to interpret the data stream correctly; i.e., its output may be the correct data stream or the logical inverse of the correct data stream. Contrast with non-return-to-zero mark. Synonym non-return-to-zero.
Null character (NUL): In transmission systems, a control character (a) that is used to accomplish media fill stuffing or a time-fill stuffing in storage device or in a data transmission line and (b) that may be inserted and removed from a series of characters without affecting the meaning of the series. Note: The null character may affect the control of equipment or the format of messages.
