Bus coupler insert for KNX Features: The bus coupler is the interface between the bus and the application module for KNX, such as an Info Display, data interface RS232, or automatic control switch. The bus coupler can receive, send, and evaluate messages. The bus coupler contains the address, the system program, and user-specific programs. Programming the physical address is authorised by pressing the programming button. Status display via red programming LED. Notes : For device box with screw attachment only.