Telecom Dictionary

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MAAP 
maintenance & administration panels

MACSTAR 
multiple access customer station rearrangement

MAC 
media access control or moves, adds, and changes

Main Cross-Connects
In a premises distribution system, main cross-connects are the cross connects located in an 
equipment room.

MAN 
metropolitan area network

MCU 
mobile control unit

Media
See transmission medium; yielded media; unguided media.

Message Telecommunications Service (MTS)
MTS is a non-private-line intrastate and interstate long-distance that uses in whole or in part the 
public switched telephone network (PSTN).

MFJ 
Modification of Final Judgment

MFOTS 
Military Fiber-Optic Transmission System

MF 
multiple frequency

MHS 
message handling system

MIB 
management information base

MIC
Material Identification Code

Microwave
In telecommunications, microwaves are frequencies above 1 GHz.

MIPS 
million instructions per second

Modems (MOdulator/DEModulators)
Modems are devices that transform digital signals generated by data terminal equipments (DTEs) 
to analog signal formats, suitable for transmission through the extensive, world-wide connectivity 
of public and private, switched (dial up) and non-switched telephone voice networks.

Modification Of Final Judgment (MFJ)
MFJ is a ruling issued by U.S. District Court Judge Harold Greene which concluded the U. S. 
Justice Department's antitrust suit against AT&T by modification of an earlier (1956) consent 
decree's final judgment.

Modulation
Modulation is the process of varying certain parameters of a carrier signal i.e., a signal suitable 
for modulation by an information signal by means of another signal (the modulating or 
information bearing signal).

MPEG 
Moving Pictures Experts Group

MSS 
metropolitan switching system

MTSO 
mobile telephone switching office

MTS 
message telecommunications service

Multiline Telephone
A multiline telephone is a telephone that incorporates visual displays and switches (keys) that 
permit the station user to access more than one central office or other line and to perform other 
desired functions. Typical functions include answering or originating a call on a selected line, 
putting a call on hold, operating an intercom feature, a buzzer, etc. Displays can indicate busy, 
ringing and message waiting status.

Multimode Optical Fiber(S)
Multimode fibers, with much wider cores than single mode fibers, allow light to enter at various 
angles, and reflect (bounce off of) core-clad boundaries as electromagnetic (light) wave 
propagates from transmitter to receiver. From a technical performance trade-off point of view, 
single mode fiber exhibits bandwidths of up to 100,000 MHz (MHz = 1,000,000 hertz or cycles 
per second = one megahertz) while multimode band width is in the range of 1,000 to 2,000 MHz 
(1,000 MHz = one billion hertz = one gigahertz = 1 GHz). See optical fiber(s); single 
modefiber(s).

Multiplexing
Multiplexing is a technique that enables a number of communications channels to be combined 
into a single broadband signal and transmitted over a single circuit. At the receiving terminal, 
demultiplexing of the broadband signal separates and recovers the original channels. Multiplexing 
makes more efficient use of transmission capacity to achieve a low per channel cost. Two basic 
multiplexing methods used in telecommunications systems, are frequency division multiplexing 
(FDM) and time division multiplexing (TDM).