M-Bus, or Meter-Bus, is a European standard (EN 13757-2 for physical and link layer, EN 13757-3 for application layer) developed for the remote reading of utility meters. As such, M-Bus is designed to facilitate the monitoring and measurement of energy consumption to assist with energy conservation. The M-Bus interface is designed to use two wires, though there is also a wireless version (EN 13757-4).
M-Bus uses a hierarchical system controlled by a master (e.g. a PC) and a number of slaves (meters) that are connected in parallel using the M-Bus two-wire cable. Use of two-wire cable minimises wiring requirements and installation cost.
The transfer of information from master to slave uses voltage level shifts, whereas that from slave to master is by modulation of the current consumption by the slave.
An M-Bus system can comprise several ‘zones’, each having its own group address. Interconnection can be by zone controllers and higher level networks. Each zone consists of segments, which in turn are connected by remote repeaters. Normally however, an M-Bus system consists of only a single segment, which is connected via a local repeater to a PC acting as master.