The Model 180 is 100% discrete transistor core dual channel A/D A/H/D function generator (envelope). A trigger or gate signal greater than 2.5v at the “trigger” input causes the output CV to linearly ramp up to its maximum value at a speed set by the “attack time” pot. Once reaching the maximum CV output (set from the factory at 5v but easily adjustable via trimmer) the module will hold at this level for a static duration set by the “note duration” pot, or will hold at its maximum level as long as the trigger input is high. This behavior is selected with the “controlled internally” vs. “controlled by trigger length” switch. At the end of the “hold” period the CV output will ramp back down to approximately 0v at a rate set by the “decay time” pot.
Like many “west coast” function generators, the envelope cannot be retriggered until the attack phase is complete, allowing for some function as a clock divider etc..). The attack, hold, and decay times can be set very fast, and the module can easily create percussive blips as well as longer drawn out envelope shapes.