Pnuematic Sirens

A Pneumatic siren is a siren that is similar to an electromechanical siren ,except it has a rotor that has no vanes ,requiring an external air source to feed air to the chopper in order to be loud. The rotor can either be a disc with four slots ,or a chopper like an electromechanical siren that has no vanes. Examples of this type of siren include the Hormman F-71 ,Hormman HLS-273 ,Rickmers Werft ,Pintsch Bamag ,and Model 120.