The M3311 and M3425A devices use the COM1 (RS-232) front port to perform an exclusive communication with BECO 2200 protocol. The COM2 (RS-232) and COM3 (RS-485) rear ports are for exclusive use of Modbus RTU protocol.

The RS-232 serial interface of these devices supports communication rates from 300 up to 9600 bps, 8 (eight) data bits, no parity, and 2 (two) stop bits.