UBZR1 contains two ADSRs to allow for two distinct contours with distinct timing and sustain levels.
ADSR1 is fixed to feed the VCAs of the three VCOs and the Noise Generator.
ADSR2 can be used for various purposes and is available via the modulation matrix. It can for example control the VCF cut-off frequency.
The ADSR is fully voltage controlled.
My design uses a 1/2 LM 13700 transconductance amplifier as a voltage controlled integrator.
Attack, sustain and release output voltage levels can be chosen freely between −5 V and +5 V. Thus you can generate any contour shape with three different levels, e.g. also an inverse contour.
I am not aware of any similar ADSR designs. Originally I designed this feature to avoid analog multiplication and to move multiplication of ADSR control voltages out to the controlling digital part.
Another unique feature is the multi-output capability: The ADSR can be easily extended having more than one outputs. Distinct ADSR outputs can have completely independent attack, sustain and release output voltage levels. They do however all share the same timing.