MAC address - See medium access control (MAC) address and device address.

macrobend - Optical fiber cable bending due to installation. Such bends will increase attenuation in optical fiber cable. Contrast with microbend.

magnetic field strength - The magnitude of the magnetic field vector expressed in amperes per meter (A/m).

magnetic stripe card - An access control card with a strip of recordable magnetic material on which data is encoded.

main building ground electrode - The designated grounding point to which all utilities in a building are connected.

main cross-connect (MC) [campus distributor (CD)] - The cross-connect normally located in the (main) equipment room for cross-connection and interconnection of entrance cables, first-level backbone cables, and equipment cables. Campus distributor is the international equivalent term for main cross-connect.

main distribution frame (MDF) - See main cross-connect.

main distribution panel (MDP) - Primary electrical service entrance facility.

main path - The primary transmission path when more than one path exists.

main terminal room - See main terminal space. (TIA)

main terminal space - The location of the cross-connect point of incoming cables from the telecommunications external network and the premises cable system. (TIA)

maintenance hole (MH) (telecommunications) - 1. A vault located in the ground or earth as part of an underground duct system and used to facilitate placing, connectorization, and maintenance of cables as well as the placing of associated equipment, in which it is expected that a person will enter to perform work. (TIA) Formerly called manhole. 2. A hole through which an underground or enclosed structure may be,accessed.

managed hub - A network hub that can be monitored and controlled through network management software. See also hub.

managed personal computer (PC) - A PC having hardware and software features that allow it to be remotely monitored and configured over a network by a central computer.

management - See network management.

Manchester encoding - A digital encoding scheme where a voltage transition occurs in the middle of each binary digit sent. A high-to-low transition represents the binary digit zero and a low-to-high transition represents the binary digit one.

mandrel - 1. A rod or a shaft. 2. A mechanical device sized to fit the inside diameter of a conduit. Pulled or pushed through a duct, it ensures concentricity of the structure and frees the structure from debris 3. A cylindrical object used-to cancel high order modes during testing of multimode optical fibers.

manhole - See maintenance hole.

man in the middle - An attack on weak or nonexistent authentication mechanisms between two endpoints. The attacker inserts oneself between these endpoints, where the attacker can view information passing back and forth, which allows the ability to modify or inject data going into such a connection.

mantrap -See interlock.

master code card - An access card that grants access and exit at every card reader on the system.

MasterFormat - Jointly developed by the Construction Specifications Institute and Construction Specifications Canada, it is an organizational structure providing numbers and titles for the variety of subject matter necessary for the construction, operation, and maintenance of a facility. (CSI)

matched clad - Singlemode optical fibers produced by the outside vapor deposition process, which produces a fiber with a very low core/cladding concentricity error rate.

material safety data sheet (MSDS) - Information system describing hazardous chemicals and materials.

materials list - A complete list of all materials to be ordered and received for the project. This includes all capital items and miscellaneous materials.

matrix - See switch matrix.

measured tape - A calibrated tape used to measure and pull lengths of conduit.

measurement accuracy - The possible difference between the measured value and the actual value of the parameter.

measurement resolution - A setting on the optical time domain reflectometer to determine the spacing of data points.

mechanical room - An enclosed space serving the needs of mechanical building systems. (TIA)

mechanical splicing - The joining of two optical fibers through mechanical means to enable a continuous signal.

mechanical transfer registered jack (MT-RJ) connector - A small form factor multiple fiber, optical fiber connector.

media (telecommunications) - Wire, cable, or conductors used for telecommunications. (TIA) See also transmission media.

media interface connector (MIC) - The fiber distributed data interface connector used to link devices to the network cabling.

medium - 1. The transport media through which network devices communicate with each other. 2. A material (e.g., magnetic disk) on which data may be stored.

medium access control (MAC) address - A hexidecimal identifier, unique to each device on a LAN.

medium dependent interface (MDI) - The connector used to make a physical and an electrical connection between a medium attachment unit and a media segment.

megohmmeter - An instrument used to measure resistance. A portable instrument used to measure insulation resistance.

membrane penetration - An opening through only one surface or side of a barrier. (TIA)

mesh grip - A device attached to the end of a cable to facilitate pulling the cable. Also called cable sock. See also wire mesh grip.

mesh topology - A topology where each device or network is connected to all other devices or networks by multiple paths.

metal oxide varistor (MOV) - An electronic component used as a transient voltage (surge) suppression device on communication and power circuits.

metes and bounds - A description of a parcel of land by reference to the course's bearings and distances (usually measured in feet or chains) of the straight lines that form its boundary, with one of the comers tied to an established point.

method of procedure - A step-by-step process of principles, procedures, and . standard practices for the design toward the installation or maintenance of network components.

metric In routing - a value assigned to a path that is used as the criteria to choose routes through an internetwork.

metropolitan area network (MAN) - A data communications network that covers an area larger than a campus area and smaller than a wide area network.

microbend - Cable bend associated with the manufacture or construction of optical fiber cable. May also be associated with compression of optical fibers. Contrast with macrobend.

micro cell - A base station with a very small coverage area designed to provide service in areas having a very high density of mobile subscribers. Micro cells are traditionally used in convention centers, airports and similar areas.

microprocessor-based controller - A controller that uses a microprocessor to perform logic and control functions in a building automation system network. Typically controls or monitors a specified building area through wired devices and resident software, but also has the ability to communicate with other controllers via a communications bus.

microsegmentation - The technique used to divide a network into multiple small networks to improve performance. Ultimately, each device can have its own dedicated LAN through an exclusive connection to a switch port.

microwave - An electromagnetic wave having a wavelength from 300 mm to 1 mm (1 GHz to 300 GHz). Wireless communication systems employing microwave signals generally require line-of-sight between transmitting and receiving antennas.

microwave flange connector - A style of connector that uses screws to hold two mating pieces together.

mid-span powering - Placement of an external power over Ethernet (PoE) source unit between a non-PoE capable switch and a PoE-capable access point.

Mie scattering - A phenomenon related to free space optics that describes light scattered by particles the size of the optical wavelength (e.g., fog).

millimeter wave - An electromagnetic wave having a wavelength from 1 mm to 0.1 mm (300 GHz to 3000 GHz). Millimeter waves exhibit many of the properties usually associated with waves in the optical regime.

minimum point of entry (MPOE) - Either the closest practicable point to where the carrier facilities cross the property line or the closest practicable point to where the cabling enters a mufti-unit building or buildings. (TIA)

mirroring - A technique used to increase the fault tolerance of a system. A backup device is configured identically to the primary device and can replace the primary device if it fails. See also disk mirroring.

mixing - The process of mathematically multiplying one ratio frequency signal by another to obtain a new signal with a distinct relationship with the original two. Mixing is a fundamental concept used in wireless transmitters and receivers to obtain signals of a desired operating frequency. It also can be the unintentional consequence of two signals passing through a nonlinear device, resulting in a spurious signal that disrupts communication and producing an effect known as intermodulatioti-interference.

mixing segment - An Ethernet segment connecting more than two medium dependent interfaces.

mobile access - A form of resource access where connection to a LAN is made from a remote station using a temporary telecommunications link.

mobile application part (MAP) - A protocol using the lower level layers of the Signaling System 7 protocol stack for communication between the various location registers and other mobile switching centers.

mobile assisted handoff (MAHO) - A handoff technique involving feedback from the mobile station as part of the handoff process. The feedback is usually in the form of signal level and quality measurements on the downlink and signal level measurements from neighbor cells.

mobile identification number (MIN) - Usually the mobile station number assigned to a cellular user.

Mobile Internet Protocol (IP) - An IP designed to support the mobility of a user (host). Host mobility is becoming important because of the recent proliferation of laptop computers and the increased need for continuous network connectivity at any location.

mobile station (MS) - The term used to describe the customer terminal in a wireless network.

modal dispersion - 1. Dispersion resulting from the different optical path lengths in a multimode fiber. Also called modal distortion. 2. A characteristic of transmission in an optical fiber that results from different lengths of the light paths taken by the many modes of light as they travel down the fiber from source to receiver.

mode Loosely - a possible light path followed by light rays, as in multimode or singlemode. Strictly, a distribution of electromagnetic energy that satisfies Maxwell's equations and boundary conditions in guided wave propagation.

mode field diameter (MFD) - The diameter of one mode of light propagating in a singlemode optical fiber. The mode field diameter replaces core diameter as a practical parameter in singlemode optical fiber.

modem - See modulator and demodulator.

moderate frequency base motion - A period of movement due to strong winds (expressed in seconds).

modification (contract) - A document issued after a contract has being awarded that alters, adjusts, or limits the terms or requirements of the agreement (contract).

modifications - Contract modifications include modifications after the construction agreement has been signed and additions to, deletions from, or modifications of the work to be done are accomplished by change orders, construction change directives, work change directives, field orders, architect's supplemental instructions, orders for minor changes, and written amendments. These can be issued at any time during the contract period. (CSI)

modular connector - See modularjack and modular plug.

modular jack - A female telecommunications connector(socket) that may be keyed or unkeyed and may have six or eight contact positions. (TIA)

modular patch panel (MPP) - A facility connecting hardware device enabling the terminating of cable elements on insulation displacement connector modules and their connections by means of a patch cord.

modular plug - A male telecommunications connector (plug) for cable or cords that may be keyed or unkeyed and may have six or eight contact positions. (TIA)

modulation - 1. Any of several techniques (e.g., AM and FM) used to modulate a carrier signal with an information bearing signal. 2. The process of coding and decoding information for transmission.

modulator - An electronic device that modulates baseband video, audio, and data signals to specific carrier frequencies for insertion into the broadband radio frequency distribution system.

module - Units installed in the distribution device to support communications functionality.

monolithic pour - The single, continuous pouring of a concrete floor or columns of any given floor of a building structure. (TIA)

monolithic slab - The result of a monolithic pour. (TIA)

monopole - A resonant antenna that can be thought of as being one arm of a dipole antenna, with the other arm having been removed. The optimal length of a monopole antenna is one quarter of the wavelength of the signal being received or transmitted by the antenna. A monopole antenna is a narrowband antenna, operating efficiently in only a narrow band of frequencies. See also dipole.

monopole antenna - An antenna consisting of one pole or mast.

motor control center (MCC) - Electrical unit typically located in the main electrical room primarily used to control mechanical equipment (e.g., motors, pumps, compressors).

MPEG format - A collection of standards (MPEG-1, MPEG-2, and MPEG-4)forcompressing audio and/or video files. Various encoding and playback options are specified to accommodate available hardware and communications channel capabilities.

MPEG-1 - Digital compression standard for digital storage media (e.g., storage of vertical helix scan-quality audio and video on CD-ROMs).

MPEG-2 - Digital compression standard for the recording and transmission of studioquality audio and video (e.g., high-definition television). Four levels of video resolution are defined.

MPEG-4 - A versatile multimedia coding standard associated with interactive multimedia applications over the Internet and various types of entertainment networks.

mud ring - (plaster ring/low-voltage ring) An adapter that is designed to convert a standard electrical box to accept a single-gang faceplate and raise the faceplate attachment location so that it is flush with the drywall. See also low-voltage mounting bracket.

multi-carrier code division multiple access (MC-CDMA) - A combination of three IS-95 carriers to form one wideband carrier. It is an evolution of IS-95 for third generation systems. Also called cdma2000.

multicast - A technique for sending data, audio, or voice to a selected group of devices on a network using a single point of transmission. See also broadcast and unicast.

multicell - A group of wireless cells that overlap in a common area.

multi-dwelling unit (MDU) - Category includes apartments, townhouses, condominiums, and assisted-living facilities. These facilities may be under a single roof or consist of multiple buildings in a residential campus.

multi-dwelling unit telecommunications room (MDU-TR) - Space where backbone and auxiliary disconnect outlet cables terminate to support multiple living units.

multiground neutral(MGN)system - A utility power system where the neutral conductor is continuously present along with the phase conductors. The neutral conductor is connected to earth periodically along its path, typically, four times per 1.6 km (1.0 mi).

multihop - A system where the transmission of wireless signals is transferred through multiple sites (e.g., from Site A to Site B to Site N). Site A and Site N are known as terminal sites where the signal originates and terminates. Also called multisite.

multilayer switching (MLS) - A technology that combines Layer 2 and Layer 3 (and possibly Layer 4) switching in a single internetworking device.

multiline (complex) connector - The universal service order code (USOC) system established a series of USOC codes for interface jacks used to connect devices to the public telephone network. The designation "X" (e.g., RJ-21X) was used to define "complex" or "multiline" connectors.

multimedia - 1. An application that communicates to more than one of the human sensory receptors. (TIA) 2. Applications that communicate information by more than one means. (TIA)

multimeter - Test equipment that can be set up to perform a variety of electrical property measurements, usually including resistance, voltage, and current.

multimode optical fiber - An optical waveguide that allows many bound modes to propagate.

multimode telephone - A cellular telephone compatible with a number of air interface technologies.

multipair cable - A cable having more than four pairs. (TIA)

multipath - The propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths.

multipath fading - On a wireless network, signal fading caused by the arrival of signals from different directions, each with a different path length.

multipath propagation - On a wireless network, the arrival of signals from different directions, each with a different path length.

multiple access - 1. A scheme that allows users to share the same channel instead of each being assigned separate, unique channels 2. In satellite communications, the capability of a satellite to function as part of a link between more than one pair of satellite terminals.

multiple-aperture - Separate transmit and receive antennas within a free space optics transceiver.

multiple prime contract - When the owner divides the work among several contractors and enters into a separate contract with each.

multiplex (mux) - Combining two or more signals into a single wave (the multiplex wave) from which the signals can be individually recovered. See also multiplexing.

multiplexer (mux) - A device that combines two or more signals over a single communications channel (e.g., time-division multiplexing and wavelength-division multiplexing).

multiplexing (muxing) - The combining of two or more communications channels into a common, high-capacity channel from which the original signals may be individually recovered.

multipoint microwave distribution system (MMDS) - A wireless broadband technology for Internet access, also known as multichannel multipoint distribution system and wireless cable.

multiport bridge - See switch. multiport repeater See hub. multiprotocol label switching (MPLS) An internetworking technology that employs the use of short headers (labels) placed at the beginning of each data packet to increase efficiencies in routing. MPLS allows for the precise allocation of resources to offer specified quality of service while supporting a variety of traffic types.

multistation access unit (MAU) - A passive (unpowered) token ring concentrator to which all devices on the ring are attached.

multi-user telecommunications outlet assembly (MUTOA) - A grouping in one location of several telecommunications outlet/connectors. (TIA)

multiweave wire-mesh grip - A wirepulling grip that distributes the pulling pressure evenly over a length of the cable. Mushroom See spool.

muster report - A report for accounting for occupants within a defined space, utilized as a tool to aid in the verification that all occupants are accounted for.

mutual capacitance - Effective capacitance between the two conductors of a pair.