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Rétrofriction
A trademark of Simplex for a very highly-regarded down-tube shift lever that appeared shortly before the successful introduction of indexed shifting.
Many cyclists consider these the finest "friction" type shift levers ever made.
With a pure friction lever, the friction has to at least equal the maximum pull of the derailer spring. When these are close, it takes almost no effort to push the lever forward (loosening the cable and the spring,) because the spring is helping you push the lever forward.
However, when you pull backward on the lever, tightening the cable, you are working against both the resistance of the friction clutch in the shift lever and the spring tension.
This creates an asymmetry of lever force between upshifting and downshifting.
With a "rétrofriction" system, a pawl-less ratchet disengages the friction clutch as you pull the lever backward, so you're only working against the spring. This gives a notably nicer feel to the shifter.
Other brands have solved this problem different ways. Shimano used to use a spring in the shifter that opposed the derailer's spring. This avoided the slightly "granular" feel created by the ratchet.
The popular Sun Tour "Power Ratchet " levers did something similar, using a ratchet and pawl system which made a slight clicking sound as you pulled back the lever.
