The Model A is a Small Siren By Federal Signal. Despite Being Discontinued in 2007 Many are Still Sold today..
On the FedSig Website it Says:
Model A is a general-purpose electro-mechanical siren that produces a distinctive sound and tonal quality for industrial applications. It has a high maximum pitch which provides excellent contrast to industrial ambient noise. Introduced in 1918, Model A is still used today in many rugged and extreme environments and applications...