Abstract: In acoustical sound processing equipment, a combination microphone and blow actuated keying and unkeying means. The speaking person blows a first time into a tube to key the processing equipment and blows a second time to unkey the equipment. The person also vocalizes into the tube. The tube is in fluid communication with a chamber which houses the microphone. A blow detector senses the blowing action and triggers a bistable flip-flop which in turn drives a keying relay.