M-50 50/C high-speed modem cable - The 50/C cable assembly has the same function as the V.35 but allows for more circuit capability.
mA (milliampere) - One-thousandth of an ampere.
MAC (media access control) - The method by which network stations gain access to the network media and transmit information as part of the second layer of the OSI model.
Magnet wire - Insulated wire used in the windings of motors, transformers and other electromagnetic devices.
Magnetic field - The field created when current flows through a conductor; especially a coiled conductor.
Main cross-connect - A cross-connect for first level backbone cables, entrance cables and equipment cables.
Main distribution Ethernet - See STANDARD ETHERNET.
Main ring path - The party of the ring made up of access units and the cables connecting them.
Main trunk - The major link(s) from the headend or hub to downstream branches.
MAN (metropolitan area network) - A data network linking together terminals, memories and other resources at many sites within a city area. Each site may have its own local area network (LAN). Links between sites are usually on digital circuits rented from the local telephone company using a bit-rate appropriate to traffic requirements.
Manchester code - A means of coding a single bit of data with two signaling pulses in the same time slot (0, 11, 1, 00), so there is a signal event for every bit of data, whether a 1 or a 0. This simplifies the clocking needed to interpret the bit stream at the receiving end.
Manual iris lens - A lens with a manual adjustment to set the iris opening (f-stop) in a fixed position. Generally used for fixed lighting applications.
MAP (Manufacturing Automation Protocol) - The OSI profile championed by General Motors Corporation to provide interconnectivity between plant hosts, area managers and cell controllers over a broadband token-passing bus network.
MAP (multiservice access platform) - Like a DSLAM they can provide service over copper wire using DSL technology but MAPs carry additional capabilities by also supporting FTTH and other types on interfaces out of the same platform. It has Quos capabilities also.
MAP/TOP (Manufacturing Automation Protocol/Technical Office Protocol) - MAP originally developed by General Motors, defines OSI protocols and application utilities for use in the manufacturing environment. TOP, originally developed by Boeing, performs the same function for the office.
Mark - 1. In single-current telegraph communications, represents the closed, current-flowing condition. 2. In data communications, represents a binary 1; the steady state, no-traffic state for asynchronous transmission. 3. The idle condition.
Marker tape - A tape laid parallel to the conductors under the sheath in a cable, imprinted with the manufacturer’s name and the specification to which the cable is made.
Marker thread - A colored thread laid parallel and adjacent to the strand in an insulated conductor that identifies the manufacturer and sometimes the specification to which the wire is made.
Mastic - A meltable coating used on the inside of some shrink products that when heated flows to help create a waterproof seal.
MAT - Metropolitan area trunks.
Matrix switcher - A switcher able to route any of its (camera) inputs to any of its (monitor) outputs, they often include telemetry control.
MATV (master antenna television system) - A small, less expensive cable system usually restricted to one or two buildings such as hospitals, apartments, libraries, hotels, office buildings, etc.
MAU (media access unit) - Circuitry used in LANs to enable data terminal equipment to access the transmission medium.
Maximum cable diameter - The largest cable diameter that a high-voltage cable termination is designed to accommodate.
Maximum design voltage - The maximum voltage at which a high-voltage cable termination is designed to operate continuously under normal conditions.
Mbps (megabits per second) - A unit of data transmission speed.
MC - Main cross connect.
MDF - Main distribution frame.
MDPE (medium-density polyethylene) - Usually used as cable jacketing.
MDU (multiple dwelling units) - Apartment buildings and condominiums.
Mechanical focus (back-focus) - The mechanical aligning of the imaging device with the focal point of the lens; it is most important on zoom lenses to be sure the image stays in focus throughout the zoom range.
Mechanical water absorption - A check of how much water will be absorbed by material in warm water for seven days (mg/sq. in. surface).
Medium frequency - The band of frequencies between 300 and 3,000 kilohertz.
Medium voltage - A class of nominal power system voltage ratings between 2.4 and 46 kV.
Medium-and hard-drawn wire - As applied to copper wire, having tensile strength less than the minimum for hard drawn wire, but greater than the maximum for soft wire.
Mega - Prefix meaning million.
Megahertz (MHz) - One million cycles per second.
Megger - A special ohmmeter for measuring very high resistance. Primarily used for checking the insulation resistance of cables; however, it is also useful for leakage tests.
Melinex - ICI trademark for polyester. See MYLAR.
Melt index - The extrusion rate of a material through a specified orifice under specified conditions.
Member - A group of wires stranded together that is in turn stranded into a multiple member conductor.
Messenger wire - A metallic supporting member either solid or stranded which may also perform the function of a conductor.
MFD - Microfarad (one-millionth of a farad). Obsolete abbreviation.
MFT - Abbreviation for 1,000 feet. M is one thousand in the Roman numeral system.
MG - Glass reinforced mica tape insulated cable with an overall sheath of woven glass yarn impregnated with a flame, heat and moisture resistant finish. 450°C, 600 V appliance wire.
MHO - The unit of conductivity. The reciprocal of an ohm.
MHz (megahertz) - One million cycles per second.
MI - A UL cable type. One or more conductors insulated with highly compressed refractory minerals and enclosed in a liquid-tight and gas-tight metallic tube sheathing.
MIB (management information base) - A set of descriptions of manageable features, used with SNMP devices. MIBS are unique per manufacturer and assigned by the IANA (Internet Assigned Numbers Authority).
MIC - 1. Media interface connector. A FDDI fiber connector or an IBM Type 1 connector. 2. Multifiber indoor cable. A corning term.
MICA - A transparent silicate that separates into layers and has high insulation resistance, high dielectric strength and high heat resistance.
MICE (mechanical, ingress, climatic and electromagnetic) - A TIA rating system for the survivability of cabling components in varying degrees of environmental challenges.
Micro - Prefix meaning one-millionth.
Micro-bending loss - A signal loss due to small geometrical irregularities along the core cladding interface of optical fibers.
Microfarad - One-millionth of a farad (µf, µfd, mf, and mfd are common abbreviations).
Micro-microfarad - One millionth of a microfarad (µµf, µµfd, mmf, mmfd are common abbreviations). Also, a picofarad (pf or pfd).
Micron (µm) - One-millionth of a meter.
Microphone cable - A very flexible, usually shielded cable used for audio signals.
Microphonics - Noise caused by mechanical movement of a system component. In a single conductor microphone cable, for example, micro phonics can be caused by the shield rubbing against the dielectric as the cable is flexed.
Microprocessor - A computer-on-a-chip.
Microwave - A short (usually less than 30 cm wavelength) electrical wave.
Mid-split - A broadband cable system in which the cable bandwidth is divided between transmits and receives frequencies. The bandwidth used to send toward the headend (reverse direction) is approximately 5 MHz to 100 MHz and the bandwidth used to send away from the head-end (forward direction) is approximately 160 MHz to 300 MHz.
Mil - A unit of length equal to one thousandth of an inch.
MIL-DTL-16878 - A military specification covering various wires intended for internal wiring of electric and electronic equipment. Formerly MIL-C-16878.
MIL-DTL-17 - A military specification covering many coaxial cables. Formerly MIL-C-17.
Milli - Prefix meaning one-thousandth.
MIL-SPEC - Military specification.
MIL-W-22759 - A military specification for fluorocarbon insulated copper and copper alloy wire. Replaced by SAE AS22759.
Minimum cable diameter - The smallest cable diameter that a high-voltage cable termination is designed to accommodate.
Minimum object distance (MOD) - The closest distance a given lens will be able to focus upon an object. This is measured from the vertex (front) of the lens to the object. Wide angle lenses generally have a smaller MOD than large focal length lenses.
MIPS (millions of instructions per second) - One measure of processing power.
Mj (modular jack) - A jack used for connecting voice cables to a faceplate.
MMDS (multichannel multipoint distribution service) - Fixed wireless/wireless broadband.
MMJ (modified modular jack) - A jack used for connecting data cables to a faceplate.
Modem eliminator, modem emulator - A device used to connect a local terminal and a computer port in lieu of the pair of modems that they would expect to connect to; allows DTE to-DTE data and control signal connections otherwise not easily achieved by standard cables or connectors. Modified cables (crossover cables) or connectors (adapters) can also perform this function.
Modem - A contraction of modulate and demodulate; a conversion device installed in pairs at each end of an analog communications line. The modem at the transmitting end modulates digital signals received locally from a computer or terminal; the modem at the receiving end demodulates the incoming analog signal, converts it back to its original (i.e., digital) format and passes it to the destination device.
Modular plug - A series of connecting devices adopted by the FCC as the standard interface for telephone and data equipment to the public network. The most common is the RJ11, used to connect a single line phone and RJ45 for data.
Modular - Equipment is said to be modular when it is made of plug-in-units that can be added together to make the system larger and improve its capabilities or expand its size. There are very few phone systems that are truly modular.
Modulate - To change or vary some parameter such as varying the amplitude of a signal for the amplitude modulation or the frequency of a signal for frequency modulation. The circuit that modulates the signal is called a modulator.
Modulation - 1. The act of modifying the amplitude, phase or frequency of a carrier to allow the transmission of information. 2. The process by which a carrier is varied to represent an information carrying signal. See AM, FM and PHASE MODULATION.
Module - 1. In hardware, short for card module. 2. In software, a program unit or subdivision that performs one or more functions.
Modulus of elasticity - The ratio of stress (force) to strain (deformation) in a material that is elastically deformed.
MOF - Metal-clad optical fiber.
Moisture absorption - The amount of moisture, in percentage, that a material will absorb under specified conditions.
Moisture resistance - The ability of a material to resist absorbing moisture from the air or when immersed in water.
Molded plug - A connector molded on either end of a cord or cable.
Mono filament - A single-strand filament as opposed to a braided or twisted filament.
Monochrome signal - In monochrome television, a signal for controlling the brightness values in the picture. In color television; the signal that controls the brightness of the picture, whether the picture is displayed in color or in monochrome.
Monochrome - Having only one color. In television it is black and white.
Monomer - The basic chemical unit used in building a polymer.
Motor lead wire - Wire that connects to the fragile magnet wire found in coils, transformers and stator or field windings.
MPEG - Motion Picture Experts Group.
MPF - Mine power feeder cables. Usually rated 5, 8, or 15 kV.
MPLS (Multiprotocol Label Switching) - A connection-oriented switching, not routing, technology, used as a mechanism for assuring QOS on IP networks.
MSDS - Material safety data sheets.
MSHA - Mine Safety and Health Administration. The Federal enforcement agency for employee safety in mines and mills. Formerly known as MESA, Bureau of mines. MSHA regulations appear in CFR (Code of Federal Regulations) Title 30, Chapter 1.
MTU - Multiple tenant units (office buildings).
MTW - Machine tool wire, a UL cable type. Thermoplastic insulated, 90°C to 105°C, 600 V. UL 1063 is the governing standard.
Multicast - The ability to broadcast messages to one node or a select group of nodes.
Multi-drop - See MULTIPOINT CIRCUIT.
Multimode - Optical fiber that allows more than one mode of light to propagate. A step-index fiber has a core of uniform refractive index while in a graded-index fiber the refractive index of the core smoothly varies with the radius.
Multiple-conductor cable - A combination of two or more conductors cabled together and insulated from one another and from sheath or armor where used.
Multiple-conductor concentric cable - An insulated central conductor with one or more tubular stranded conductors laid over it concentrically and insulated from one another.
Multiplex - The use of a common physical channel in order to make two or more logical channels, either by splitting of the frequency band (frequency-division multiplex) or by utilizing this common channel at different points in time (time-division multiplex).
Multiplexing/multiplexers - 1. Equipment that permits simultaneous transmission of multiple signals over one physical circuit. 2. The division of a composite signal among several channels; concentrators, FDMs and TDMs are different kinds of multiplexers.
Multipoint circuit - A single line connecting three or more stations.
Multipoint circuit - A single line connecting three or more stations.
Multiport repeater - A repeater that is used to connect more than two cable segments.
Multiport transceiver - Multiple transceiver connection packaged in a common rack. Provides one transceiver attachment to the trunk cable and the ability to serve up to eight stations.
Multi-segment LAN - A LAN that is composed of more than one coaxial cable segment.
Multi-station access unit - In the IBM Token-Ring Network, a wiring concentrator that can connect up to eight lobes to a ring network, the 8228. Also the four-lobe unit from General Instrument that uses Type 3 Media Cable.
Murray loop test - A method used to localize cable faults.
Mutual capacitance - Capacitance between two conductors in a cable.
MUX (multiplex) - To transmit two or more signals over a single channel.
Muxer - Multiplexer. Electronic equipment which allows two or more signals to pass over one telephone line.
MV (medium voltage) - Cables usually rated 5 to 35 kV.
mV (millivolt) - One-thousandth of a volt.
mW (milliwatt) - One-thousandth of a watt.
Mylar - DuPont trademark of polyethylene terephtalate (polyester) film. See MELINEX.