BL121ML OPC UA protocol translator supports Modbus RTU, Modbus TCP, IEC104, DL/T645, BACnet/IP, Modbus MS/TP protocols converting to OPC UA protocol. This protocol gateway is widely used in building automation management system.

| WAN | LAN | COM(RS485/RS232) | WiFi | |
| BL121ML | 1 | 1 | 2 | x |
| BL121MLW | 1 | 1 | 2 | / |
| BL121MLP | 1 | 1 | 6 | x |
| BL121MLPW | 1 | 1 | 6 | / |