Communication module for Modicon M171 / M172 PLC controllers. Expands the controller with an interface for RS485 for Modbus SL / BACnet MS/TP (B-AAC profile). Connection via two screw terminal blocks. Each controller can be expanded with a communication module. The connection is made by snapping it into place on the left side of the controller. The power supply is provided by the PLC controller. Mounted on a 35mm top hat rail.