500 Series

500 Series
Company	Federal Signal Corporation
Type	electromechanical

The 500 Series was a line of electromechanical sirens produced by Federal Sign & Signal. It went through a lot of prototyping, ranging from a coded unit that allows it to make a "pulsed" signal, along with variants of single and dual tone models, even different phase motors were tested. They finally settled on one design that was compact, yet effective. This model unfortunately was advertised as a "mid-range" siren by Federal, which in turn caused their Thunderbolt siren to outsell it by a long shot. The most powerful unit they made was the 10/12 port, 3-phase 500SHTT, meaning single head two tone. This model packed a punch and performed well past their advertised 120dBc rating, pushing 128 or more.