This little noise box is based on 2 square oscillators with 2 control by oscillator: one for the tone and a other to adjust the duty cycle.
You can switch between 2 mode, a drone mode with constant sound and a push it mode with release via the button on the left side.
The pot on the right side is use for degrade the voltage input, it can create very space effect on the release of the sound.
This box run with battery or with Dc 9v adaptator.
The price is 50 euros.