Want a better, more informative version of this article? Check this out! The Denver Siren is a line of mechanical sirens that was created from 1905 until 1931 by William A. Box Iron Works, also known as Dillon Box Iron Works. Various sirens were produced, including the Type A, Type B, Duplex, Quadruplex, the Center Drive Siren, and Boxco sirens. The sirens were produced until William Box's death in 1931. These sirens were the first purpose-built electric outdoor warning sirens, designed for use in mines, industrial areas, and fire departments. These are also the earliest known outdoor warning sirens to use directional rotor vanes.