Knowledgebase

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====== Glossary M ======


[[:glossary:start|Return to main Glossary index]]


===== Magnet =====


A magnet is an object that has a magnetic field. It can be in the form of a permanent magnet or an electromagnet.\\ 
[[wp>Magnet|Magnet]]


===== Matrix =====

[[wp>Diode_matrix|Wikipedea's Matrix entry]]\\ 
[[:helpsystem:matrix|Main article]] available to MERG Members only.

===== Memory Wire =====
Wire made from a special alloy which changes its molecular structure at a certain temperature causing it to shrink. This effect can usefully be applied to point and signal actuation. Some types require a tension spring to pull it back to its original length while others will return unaided, although a spring is still required to keep the wire tight, it can only pull when shrinking, it cannot push.\\ 
[[wp>Shape-memory_alloy|Wikipedia's entry]]\\ 
See also TBs: [[http://www.merg.org.uk/merg_tbs/download.php?fileid=919&userid=62|G19/01]], 
[[https://www.merg.org.uk/merg_tbs/download.php?fileid=920|G19/02]], 
[[https://www.merg.org.uk/merg_tbs/download.php?fileid=922|G22/01]], 
[[https://www.merg.org.uk/merg_tbs/download.php?fileid=923|G23/01]] & 
[[https://www.merg.org.uk/merg_tbs/download.php?fileid=924|G23/02]].\\ 
===== Microprocessor =====


A microprocessor (sometimes abbreviated µP) is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semiconducting integrated circuit (IC).\\ 
[[wp>Microprocessor|Microprocessor]]

microprocessor is a general-purpose name. Specialised devices:\\
A digital signal processor (DSP) is specialized for signal processing.\\
Graphics processing units (GPU) for rendering of images.\\
Microcontrollers integrate a microprocessor with peripheral devices in embedded systems..\\
System On Chip (SoC) often integrate one or more microprocessor cores with bus controllers.
===== Mobile decoder =====


A DCC decoder intended for fitting in a loco.


===== Modulation =====


Is the process of superimposing information onto a pure sine wave (Carrier wave), this process can be achieved by any of four methods, amplitude (AM), frequency (FM), Phase (PM) or Pulse (PAM, PWM, or PPM)


===== MOMS ====

MERG Online Membership System - MERG's membership management system - used by Members to manage their contact details and renew membership and by the Membership Secretary for administration purposes. Available via the MERG Forum [[https://www.merg.org.uk/forum/index.php|{{:glossary:moms-link-01.png?nolink|}}]]

===== Monostable =====
An electronic circuit that has a single (mono) stable state and an unstable state, an input will cause the circuit to assume the unstable state, when the input signal is removed and after a predictable delay the circuit will return to the stable state. This behaviour is the basis of most timer circuits.
===== MOSFET Metal-Oxide-Semiconductor Field-Effect Transistor =====

A MOSFET is a type of transistor with a Gate, Source and Drain terminals. [[wp>MOSFET|MOSFET]].
 They are the dominant type of transistor in electronics.\\
The resistance between Source and Drain (D-S) is controlled by the Voltage applied across the Gate and Source.
A Voltage across D-S causes a current to flow in the D-S resistance. There are several sub-types...\\
 - N channel uses positive Voltages or P channel uses negative Voltages \\
 - Depletion mode uses increasing Gate Voltage to increase D-S resistance or Enhancement mode uses decreasing Gate Voltage to decrease D-S resistance\\
For MERG, the common type is N channel Enhancement mode.\\
//Compapared to a Bipolar transistor, Gate = Base, Source = Emitter, Drain = Collector.//


The Gate exhibits a very high resistance (insulation) to the Source or Drain.\\
There being an insulation, the Gate has capacitance to the other pins and needs to be driven by a low impedance (AC resistance) input signal. A high impedance input signal will make the device slow. An open circuit Gate can build up a charge and results in the D-S going low resistance (turns 'ON').

===== MSAG =====

**M**ERG **S**omerset **A**rea **G**roup

===== Multiplexor =====


A communications device that multiplexes (combines) several signals for transmission over a single medium. A demultiplexor completes the process by separating multiplexed signals from a transmission line. Frequently a multiplexor and demultiplexor are combined into a single device capable of processing both outgoing and incoming signals.\\ 
A multiplexor is sometimes called a mux and also spelled as multiplexer.\\ 
[[http://www.webopedia.com/TERM/M/multiplexor.html|http://www.webopedia.com/TERM/M/multiplexor.html]]