This patent describes the Simplex Selematic 5. It is one of the most complex, sophisticated and interesting derailleur patents that you will find. Anyone who can understand all of its intricasies deserves a medal.
It's such a pity that the resulting derailleur was a total dog - ludicrously heavy and laughably ineffective.
If you want to the original French version of this patent, it is here.
Browse associated derailleurs.
Simplex Selematic 5 1981