Originally invented as an organ stop, the diaphone was reworked into a compressed air horn whose tone was found to have impressive power when used over water.  Different sizes were later produced for different uses from fire alarms to fog horns. The incredible carrying power of the type F and two-toned Type F2T made them one of the most used fog signals in the world throughout the 20th century.

Jake Heffernan will show how these horns generate their incredible power. Weather permitting, he will bring his truck mounted air compressor and sound his restored Type B diaphone for those in attendance.