external keys (-matrix)
The significance (or function) of individual keys is determined by an XML-based file.
Terminal 13 "GND" is not used.
The maximum permitted cable length is 2m, with a cross section of (0.14 to 1.5)mm2.
The maximum number of programmable keys has been restricted to 4 x 8 = 32.
In the simplest case, you connect a number of keys which you define as function keys F1 to Fn for menu control.