I have a gasmeter from elster. There are different communication moduls available (mBus, radio, etc.). These modules can be via a 4 pin connector:
Does anybody know anything about this connector and how it can be used using own electronics?
I found out a bit about it: Electrically it is an UART interface where the counter is fed through the RX pin. In image top right pin is TX out and lower left pin is RX in. The remaning 2 Pins are GND. Protocolwise the device seems to use m-bus, for which a linux library is available.