Originally Posted by
garage sale GT
Positronic was an early Shimano index shifting system with a detent on the rear derailleur. It is not the same as Forward Freewheel which is what you describe.
I think FF came in levels of quality. The one I had looked very high quality. However, you would have to replace the freewheel if something went wrong with the cranks and vice versa.
Being a child of the '70s who rode my 'ten speed' while wearing bell bottoms, still remembering catching and ripping my pants in the chainwheel more than once, Id never ever consider a front-freewheel system.