The Federal Signal Thunderbolt siren is one of the most famous "older siren" in the history of sirens. The Thunderbolt siren consists of three major parts: the blower, rotator and siren chopper. The blower, which is made up of a motor-driven Roots-type supercharger, supplies the big volume of air for the siren head, It is housed inside a large rectangular box typically found at the base of the siren head. The rotator is a motor-driven gear unit which rotates the directional horn/projector to direct the sound where the horn is at. The chopper is located in the cylindrical housing that the horn/projector attaches to at the top of the siren. The Model 1003 is a dual-tone version with the added capability of producing a fire (Hi-Lo) signal with solenoid valves. (info from https://tornado-siren.fandom.com/wiki/Thunderbolt_siren) controls: group 1=stop rotator, group 2=start blower, group 3= solenoids, group 4= Rotator, group 5= tap to stop blower, group 6= open blower cover, Vtol up= Chopper Motor