"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

MAC: Abbreviation for medium access control.

Manchester code: A code in which the data and clock signals are combined to form a single self synchronizing data stream.

MARK. An interval during which a signal is present.

Mean Time Between Failures (MTBF): An indicator of expected system reliability calculated on a statistical basis from the known failure rates of various components of the system. Additional MTBF information.

Medium: In telecommunications, the transmission path along which a signal propagates, such as a wire pair, coaxial cable, waveguide, optical fiber, or radio path.

Minimum Bend Radius: The radius below which an optical fiber or fiber-optic cable should not be bent.

MODULAR JACK. A device that conforms to the Code of Federal Regulations, Title 47, part 68, which defines the size and configuration of all units that are permitted for connection to the public exchange facilities. [Telcom Connector Manufacturers]

Multifiber Cable: A fiber-optic cable having two or more fibers, each of which is capable of serving as an independent optical transmission channel. [Manufacturers of Fiber Cable]