Myomer Accelerator Signal Circuitry
A BattleMech subsystem. It boosts signals sent to foot "muscles" of a BattleMech. This usually causes slight running speed increase, but has a nasty habit of making things a bit more interesting on durability point of view (see overclocking) - for example, it may make limbs freeze, which in turn may have a certain type of undesired effect on movement.
Use with care, and only when you need to get away fast.
See also: BattleTech