Interface converter


  • Transparent conversion of serial and Ethernet interfaces into M-Bus interface
  • Readout up to 20 M-Bus slave devices
  • RS-232, RS-485 and Ethernet interface
  • Ethernet parameters setup through web interface
  • Short circuit protection of M-Bus line
  • LED indications
  • Galvanic isolation of Ethernet line
  • Wide power supply range 10-28Vdc
  • 35mm DIN rail mounting


MM20 is interface converter intended for feeding and transparent reading of M-Bus slave devices. Converter has RS-232, RS-485 and Ethernet interfaces, where the lowest priority is dedicated to RS-232 and the highest to Ethernet interface. It is designed to withstand short circuit on M-Bus line. LED indicators show status and activity of M-Bus line, slave devices and Ethernet port. Power supply has wide range, from 10 up to 28Vdc. Device is suitable for 35mm DIN rail mounting.


DECODE MM20 acts on M-Bus line as standard M-bus master device which can sustain up to 20 M-Bus slave devices. It can be used for local or remote reading of calorimeters, water meters, electricity meters and other devices which fulfill M-Bus protocol. Converter is fully adjusted for industrial communications, automation processes and telemetry. For increasing system capacity, it is possible to connect more than one MM20 converter in parallel.


M-Bus interfaceM-Bus master, up to 20 M-Bus slave devices, transparent protocol, speed 300-9600Baud; 
Connection: Pluggable screw clamp, RM 5mm, 2.5mm2
Serial interfaceRS-232 DCE, RS-485; Connection: DB9 female
Ethernet interfaceIEEE 802.3, 10/100 Base-T, UDP and TCP/IP; Connection: RJ45
LED indicatorsON, Short, Slave, Ethernet
Overvoltage protectiontranzorb on RS-485 line and M-Bus line
M-Bus portquiescent current: 0-30mA, overcurrent: 50-70mA with restart, line voltage: 30.5V  5%, internal resistance <100Ohm
M-Bus line lengthmax 12km@300Baud, min 1km@9600Baud, cable JYSTYnx2x0.8
Power supply10 – 28VDC, 6Wmax
Power supply connectionPluggable screw clamp, RM 5mm, 2.5mm2
Working temperature0 do 55°C
Mounting35mm DIN rail



MM20-24E10324Interface converter with RS-232, RS-485 and Ethernet interfaces€255
MM20-2410325Interface converter with RS-232 and RS-485 interfaces€179

*Minimum functionality kit needs to include the device and an appropriate power supply. Please note that all accessories are sold separately.


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Product Documents