This module is based on the Serge Extended ADSR. In addition to the usual Attack, Decay, Sustain, Release envelope, it has an adjustable delay at the beginning of the envelope. All timings and the sustain level can be voltage controlled.
The envelope can be linear or exponential, or linear with an exponential attack.
[VC ALL] is a master CV input that allows all timings to be reduced at once. Controlling [VC ALL] with the same voltage as being used for VCO pitch, allows for shorter envelopes at higher frequencies, as happens in acoustic instruments.
Note that this design is a little unusual in that the [GATE] input will sit at "ON" when nothing is connected to its jack.