Line coupler in a compact design. It connects two KNX segments via twisted pair, e.g. a KNX line with a KNX area. The device has an extended filter table for main group 0...31 and ensures galvanic isolation between the lines. The coupler supports long frames and is compatible with the ETS(R) software from ETS4.2. The buttons on the front allow the telegram filters to be deactivated for test purposes. The LEDs show operating states and communication errors on the bus.