The NSL-32 is a DC coupled VCA using a Vactrol for the control element. The input to the VCA is the jack on the upper left of the panel (input to triangle) and the output is the jack on the upper right of the panel (output of triangle). The control port is the bottom left jack and has a response that is close to linear. When +5V is applied to the control port the output will be unity (same as the input). Control voltages of less than 5V will attenuate the signal and 0V will be full off. Control voltages greater than +5 will generate a modest positive gain.
The Vactrol in the NSL-32 has a unique response that can be nice for percussive elements. When struck by a gate on the CV port the VCA’s response is relatively fast on and fairly slow off. The response will vary greatly from Tile to Tile but a typically NSL-32 will have attack times of less than 100mS and decay times of more than 200mS.