Audio, Telephone, RTI (1999-2000): Glossary: M
| MD | Mini Disc. Storage medium for digital information. Both for recording and playing. |
| MELBUS | Communication bus between Audio, CD changer, TV receiver and RTI. |
| MMI | Man Machine Interface. Joining point of communication between user and system. For example display screen in RTI system. |
| Multipath | Multi wave interference because of radio waves bouncing on obstructions. |
| Multiplex | Separating and sending a message in a number of sections or at the same time sending one or two messages on one wire. |