After going crazy figuring this out I thought I'd pass it on. This module attaches to an XR gate the can shut down and envelope generator when it's output is 60 db down. The objective was to shut the envelope generator down when the release phase reached -60 db. Regardless of whether the input midi gate was on or off.
As shown the feedback from the operators z-1 fbk enters into the middle input. The sensing circuitry for it produces a 0 at FBG when the output of the env gen falls -60db, or .001.
The bottom On Off is a master switch from a panel button 0 off 1 on. Simple enough.
The top input "from midi in gate" attaches to a midi gate.
The logic is setup to hold the external XR gate on once the gate is turned on or initiated by the midi gate. But once the external XR gate is triggered it must not be stopped with a note off. If you do stop it there is no release phase. That's what made this a tough one right there.
This a broader view of the system.
See the 3 inputs labeled G FBgate and OP2. This is the above module. The external z-1 is on the output on the top right. In reality the FB gate is internally attached the sensing gate (GT) as shown below. I only put it inside the top picture for clarity.
There's no point explaining this module, only to show that the z-1 fbk is attached to the env gen final output. The system works the same with or without the Dup Filter or the latch.
This is the actual front module, The actual gate (GT) is shown above.
When the XR gate shuts the system down the final output is .001 or -60 db. As a side note the external Clk Gen underclocks the entire system. That's a different story but it works well when a fast attack is not needed. So it also save's cpu when it's not needed. Just another way of battling CPU. Hope it makes sense
One final note, the XR gate on/off travels further downstream into the final audio output to a multipliers which switches the final .001 value to 0. Personally I can't hear 60 db down and the click is transparent. Also in this system there is a final low pass filter at the end that further slows the transition down from -60db to off.