Electronic Engineering Dictionary

Mean Life. Another way to say Mean Time Before Failure.

Mean Time Before Failure. [MTBF]. Component or system reliability calculated on a statistical basis from the known failure rates of various components of the system. Also refer to Calculating MTBF in Flip Flops. A basic measure of reliability for repairable items. The average number hours during which the component performs to specification, during a particular measurement interval under stated conditions.

Mean Time Between Outages. [MTBO] In a system, the mean time between equipment failures that result in loss of system continuity or unacceptable degradation.

Mean Time To Failure. [MTTF] A basic measure of reliability for nonrepairable items. The total number of hours divided by the total number of failures, for a population of components operating during a particular measurement interval under stated conditions.

Mean Time To Repair. [MTTR] The total corrective maintenance time divided by the total number of corrective maintenance actions during a given period of time.

Mechanical-Rotation Frequency. The speed in revolutions per minute of armatures in electric motors and engine-driven generators; blade speed in turbines.

Mechanical Scanning. The reflector, its feed source, or the entire antenna is moved in a desired pattern.

Mechanical Switch. A switch that uses a mechanical movement to actuate the switch, unlike a Semiconductor Switch which has no moving parts. Also refer to either Mechanical Switch Manufacturers or Semiconductor Switch Manufacturers.

Medium. The vehicle through which a wave travels from one point to the next. Air, water, and wood are examples.

Medium Frequency. The band of frequencies from 300 kHz to 3 MHz.

Mega. A prefix meaning one million, 10⁶; also MEG.

Megaohm Meter. A meter that measures very large values of resistance; usually used to check for insulation breakdown in wires.

Memory. All of the addressable storage space in a processing unit and other internal memory that is used to execute instructions.

Memristor. A semiconductor structure that has resistance and memory developed by a voltage that is applied and re-applied to its terminals, so that the resistance is switched on and off.

MEMS. An acronym that stands for MicroElectroMechanical Systems, or Micro-Electro Mechanical Systems, and is the technology related to very small machines or mechanical elements residing on a silicon substrate.

Mercury Switch. A switch in which a mercury pool is used to bridge fixed contacts when their inclosing sealed capsule is tilted.

Mercury-Vapor Lamp. A glow lamp that uses ionized mercury to produce light. An arc-discharge tube used as a lamp.

MESFET. Metal Semiconductor Field Effect Transistor [FET].

Mesochronous. The relationship between two signals such that their corresponding significant instants occur at the same average rate.

Message. One continuous transmission on a network.

Message Format. A predetermined or prescribed spatial or time-sequential arrangement of the parts of a message that is recorded in or on a data storage medium.

Metal Electrode Leadless Face. Surface Mount Components that have metallized terminals at each end of a cylindrical body. MELF components are designed to fit the same footprints as flat components, i.e.: 0805 (.08" x .05") and the 0603 (.06" x .03"). MELF devices may be Fuses, Resistors, or Diodes.

Metal Film Resistor. A resistor that uses a thin film of metal alloy as the resistive element. See Film Resistor, part of the Dictionary of Resistor Terms.

Metallic Armor. A protective covering for wires or cables. Made as a woven wire braid, metal tape, or interlocking metal cover. Types include wire braid, steel tape and wire armor. Made from steel, copper, bronze, or aluminum. Read more on Cable Armor.

Cable Metallic Armor

Metallic Circuit. A circuit in which metallic conductors are used and in which the ground or earth forms no part.

Metallic, Insulator. A shorted quarter-wave section of transmission line.

Metallic Rectifier. Also known as a Dry-Disk Rectifier. A metal-to-semiconductor, large area, contact device in which a semiconductor is sandwiched between two metal plates. This asymmetrical construction permits current to flow more readily in one direction than the other.

Metallic Voltage. A potential difference between metallic conductors, as opposed to a potential difference between a metallic conductor and ground.

Metallized Capacitor. A capacitor that has had a thin film of metal deposited onto its dielectric, which could be paper or plastic. Read more on Metallized Capacitor in the dictionary of capacitor terms.

Metallizing. The process of depositing a thin film of metal on a glass, semiconductor or some other surface.

Metal-Oxide Semiconductor. [MOS]

Metal-Oxide Semiconductor Field-Effect Transistor. See MOSFET. Also refer to a list of MOSFET Manufacturers.

Metastability. A circuit condition that could cause a digital logic IC to reside in an invalid state [not high or low]. Refer to the expanded Metastability Definition.

Meter. A device used to measure a specific quantity, such as current, voltage, or frequency. A panel mount analog meter is shown. However a digital meter may be more common these days.

Meter Movement. The part of the meter that moves to indicate some value. Obsolete reference, all equipment is digital, there are no analog meters being used, unless legacy units which have not been discarded.

Meter Shunt. A resistor placed in parallel with the meter terminals; used to provide increased range capability. Obsolete reference; a meter shunt was only required with analog meters which are in decline.

Metropolitan Area Network. [MAN] A data communications network that (a) covers an area larger than a campus area network and smaller than a wide area network (WAN), (b) interconnects two or more LANs, and (c) usually covers an entire metropolitan area, such as a large city and its suburbs.

Mezzanine. The termed used to describe a daughter card which plugs into another card [motherboard] called a host or carrier card, which is then plugged into a backplane. A mezzanine card lays on top of a host card, vertical to the main axis so the foot print of the host card remains unchanged. Also refer to Mezzanine Card Manufacturers.

MHO. Unit of conductance; the reciprocal of the ohm.