The Homematic IP contact interface flush-mounted - 1-way enables the uncomplicated integration of a conventional switch, button or contact into the Homematic IP smart home system. In combination with Homematic IP actuators, existing lamps or roller shutters, for example, can be intelligently controlled and flexibly automated wirelessly via the Homematic IP system. Alternatively, the contact interface can also be used to activate or deactivate the Eco mode in conjunction with Homematic IP room climate products. The installation is extremely simple, as only the supplied cables of the contact interface have to be connected and thanks to the long-lasting lithium battery power supply, no external power supply is required for operation.