An experimental 9000-watt airborne sound system

An experimental 9000-watt speech announcing system AN/AIC-11(XA-1) was developed for installation in a B-26 aircraft. The system was used for studies of direct communication through the atmosphere to ground personnel from aircraft operating at relatively high altitude. The equipment consisted of a turbine generator type of auxiliary power unit; three 3000-w amplifiers, each driving a separate twin-horn loudspeaker; signal preparation, control, and monitoring units; a loudspeaker mounting frame which rotates the loudspeakers and supports two of the twin horns outboard from the fuselage; and magnetic tape recorders.