Bus coupler 3 serves as an interface between the KNX bus and an application module. When the KNX bus receives telegrams, these are forwarded to the plugged-in module via the connection outlet and evaluated there. Conversely, the bus coupler converts the electrical signals of the module into KNX telegrams. Without an application module plugged in, the bus coupler has no independent function - it forms the "basic hardware" for KNX system extensions. Connection of KNX modules: Connects, for example, automatic control switches to the KNX system. Modular system integration: A functional unit is only formed in combination with an application module. Flush-fitting: Planned installation in device plugs in accordance with DIN 49073. Flexible configuration: The application program is stored in the module and not in the bus coupler - facilitates parametrisable use and exchange. Robust and reliable: Ideal for smart home, residential and commercial KNX installations.