Originally Posted by
blamester
It's the Shimano version of retrofrictions.
Spring assist.
The 7700 left shifter is unishift I believe and works beautifully.
I have a set of early Shimano bar end shifters that look similar to Suntour Barcons, but are spring-loaded to help downshift the rear derailleur against the force of the derailleur spring.
Shimano M700 "Unishift" ratchet thumbie, and Shimano spring-loaded Fingertip Control bar-end shifters
They're wonderful.
I also have M700 Deore thumbies from 1985, which are not spring-loaded, but say "Unishift" on the top of the shifter... I always thought that simply referred to Shimano's multi-layered ratchet mechanism