Abstract: Two microphones, with at least one being directional and sensitive to different sound, are utilized in conjuction with a comparator circuit and a switching circuit to control electrically energized equipment such as alarm systems, machinery, safety devices and the like. The comparator circuit rectifies the output from each of the microphone amplifiers into either a positive or negative voltage, respectively. The switching circuit is set to pass current only when the voltage from the selected directional microphone exceeds the other microphone voltage by a predetermined value.