This is a very rare siren, used for Civil Defense warning. Less than 50 were made by Federal Sign & Signal, Inc in the late 1950s. Model 500-DH-TT.

Electrical Specs: 10HP, 208/240V 3 phase, 60 amps. Max OCPD: 70Amp. Branch circuit cdr: 4AWG CU Only. Original Price, approx 1,700$. Came with an AR timer to control the unit and offer 2 signals plus a manual test functon,

This siren offered a unique sound and one side has 8 ports, the other, 12. The resulting sound is very penetrating and from a distance of about a mile away, one can notice a slow high/low sound as the siren head rotates.