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Glossary M


A magnet is an object that has a magnetic field. It can be in the form of a permanent magnet or an electromagnet.


Wikipedea's Matrix entry
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.
Wikipedia's entry
See also TBs: G19/01, G19/02, G22/01, G23/01 & G23/02.


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).

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.


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)


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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. 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').


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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.

glossary/glossary_m.txt · Last modified: 2021/08/11 11:57 by WortingUK

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