Guys, I really appreciate your ideas, but either I do not understand what you mean or we are talking about slightly different things.
Please have a look in this diagram, showing the steering wheel layout (mine is 3-spoke instead of 4, but it works similar):
http://www.pelicanparts.com/911/911_Parts/1974-75/4-3-1.JPG
I cannot identify a central horn switch (sorry). Only the cable at part #28 is attached to the horn pad #32. When the pad is pressed, little contacts close the loop.
What am I missing ?
Jens