We use an assortment of different alerting devices such as PA Speakers, Horns, and Sirens, the PA Speakers we use are usually 12v DC PA Speakers. The Horns we use are Klaxon Horns made by the company known as Farbin Horns. The sirens we use are usually MS-490 sirens which are single tone sirens with a port ratio of 8/8 ports with a 1 and 1/2 horsepower AC motor, depending on the siren model, these sirens sounds can reach up to 1000ft, but the MS-490 can reach up to 500ft, so it is perfect for campsites or small public/private communities. we also use other MS sirens usually made by the companies Vixen Horns or YAECCC.