The envelope generator section is a standard ADSR envelope generator used to shape amplitude curves and/or filter CV. If you're not familiar with the operation of envelope generators, here's an overview:
When DCO-106 sees a gate voltage from a note, the envelope generator outputs a dynamically changing voltage, according to the settings of its four stages. The attack stage defines how long it takes for the output voltage to rise from 0 to 5 volts. Once the attack stage reaches 5V, it moves to the decay phase, which defines how long it takes to fall from 5V to the setting of the Sustain phase. Unlike the attack, decay, and release phases, which define times, sustain simply sets the held voltage level following the attack and decay phases - this equates to the envelope output level while holding down a key. Finally, the release slider defines the the length of time it takes for the voltage to fall back to 0V when the gate input voltage is removed, i.e. when the key is released.
"A" (Attack) slider- Defines the length of time for voltage to rise from 0V to 5V when a key is played.
"D" (Decay) slider- Defines the length of time for voltage to fall from the attack stage 5V peak to sustain stage setting.
"S" (Sustain) slider- Sets the voltage level following attack and decay phases while a note is held.
"R" (Release) slider- Defines the length of time for voltage to fall from sustain level to 0V when a key is released.