A data telegram is triggered on the I-bus when a button is pressed. If the button is pressed longer, after a short delay time, a further data telegram "button still pressed" is sent. After the button has been released, a data telegram "button released" is sent.
The CLOCK button is designed in such a way that it can switch on while operating the on-board monitor control panel (BMBT).
When the EJECT button is pressed, in addition to the data telegram, the cassette is immediately ejected by the on-board monitor control panel (BMBT).
There is no reaction on the on-board monitor control panel (BMBT) if several buttons are pressed simultaneously.
In cassette mode, the radio buttons act as controls for the cassette drive. The button functions, however, still send the same data telegrams. The data telegrams are sent by the on-board monitor control panel (BMBT) to the radio. The radio evaluates the telegrams and responds also with data telegrams for operation of the cassette drive.
All buttons feature background lighting. The lighting is controlled directly with terminal 58g.