Shimano Positron shifters

[The Fixer]

Had a bloke in at the Shed the other day - old 27" Viscount (a Pommy job) with
a twin-cable Positron setup fitted, probably from new.

It's in working condition, but I managed to talk him into replacing it with some-
thing more modern and easier to set up (he's clueless) and to get parts for.

And so now it's in my shed, along with a single-cable Positron system, just wait-
ing for a suitable machine to fit them to.

Yes I know they suck, and why, so I don't think we need to go there.

But they ARE different, and a bit unique nowadays.

[Duck!]

For the benefit of anyone wondering, Positron was Shimano's original gear indexing system. Unlike modern systems, the indexing was in the derailleur rather than the shifter, and used a fairly rigid single-strand "piano wire" cable to both push and pull the derailleur between gears. Yes it sucks compared to modern systems, but in 1980-ish it was groundbreaking.

I've only ever seen one single-wire system in the wild; I didn't know there was a two-wire version until now.