M

Management Information Base (MIB) The structure of the database in an power system.

Manual Bypass Switch (MBS) A manually operated transfer switch used to bypass the major electronics in the UPS, so the UPS can be serviced without power interruption.

Mapping The process of assigning physical entities to logical entities, e.g. when a particular analogue channel (internal or external) is assigned to be the channel used for measuring the bus voltage.

Maximum System Current (MSC) The maximum current that can be supplied by or from a power system (excluding batteries) under all conditions. The MSC is normally 120% of the systems rated current.

MCB A Miniature Circuit Breaker is a precisely rated, re-settable circuit protection device.

MDV A Metal Oxide Varistor is a non-linear semiconductor device used for surge protection or voltage limiting.