An artificial reverberation device made for the home by the Radio Craftsmen in the 1950’s. Basically it was a box about the size of a bookshelf loudspeaker that contained a small speaker and about 50 feet of tubing with a microphone at the other end. This produced a time delay of about 50 milliseconds and this reverb was mixed in with the original signal and radiated in the room through a separate amp and speaker. The Xophonic may have been the very first signal processor designed for home use. It was popular for a short time before falling into oblivion with the advent of stereophonic sound reproduction.