DSL

Dual Slew Limiter

DSL is a Dual Slew Limiter for creating portamento and slew limiting effects.
The slew is controlled by two switches.
Switch one select the slew edge
D = Down edge (Fall)
B = Both edge
U = Up edge (Rise)
Switch two select the slew mode Lin or Log.

https://www.sfeo.fr/dsl.html