It is built into a tough aluminum die cast enclosure painted matte green. With two 1/4" inputs and a 1/4" output. The circuit is completely passive so it does not require power.

Please note although the outcome can be quite satisfying it can also be a bit unexpected. For tamer results use a more simple waveform for one of the inputs. Also be aware the modulated output will often have less volume than the input signal. This was designed and hand-built in Oakland, California.