Communication module for Modicon M171 / M172 PLC controllers. Expands the controller with an interface for RS232 and a relay output. Connection via a SUB-D 9 socket and a screw terminal block. 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.