The SD-10 was an outdoor warning siren produced by the Federal Signal Corporation. The model number stood for Special Dual Tone, 10 Horsepower.[citation needed] The siren itself is essentially identical to a Model 5T except for the housing. The SD-10 came out in approximately 1954 after the Office of Civil Defense issued a requirement that all sirens be dual tone to distinguish them from vehicular sirens. However, by the mid to late 1960s this requirement was ultimately forgotten about. The SD-10 stayed in production until at least 1987-1988. The siren was quite a popular civil defense siren as a lot of towns and cities bought them, with a notable example being Los Angeles, CA incorporating approximately 80 SD-10s into its system. Many SD-10s are still in service to this day, but some also remain silent, as a testament to the times where the people of the US lived in fear of a Soviet attack. The siren has appropriately gained the nickname the wire spool due to its shape. The SD-10 could, like pretty much any siren, be mounted on a roof or pole with the appropriate mount. The SD-10 was offered in both three and single phase (A and B respectively). As mentioned earlier, the siren was powered by a 10 HP motor. The controls used on the SD-10 typically were RC-5 cabinets, but in some cases, example being Atlanta, GA, they could be run off whatever the city had on hand. In Atlanta's case, the controls were nothing more than a General Electric traffic controller, and a Bell System phone relay, as seen on the right. The diameter of the siren's chopper assembly is approximately 46" Assembled, the height of the siren is 80". The power requirements for the respective sirens are as follows: Power requirements for SD-10A: 208/240Vac 3-phase, 28/14A, 50/60hz; Power requirements for SD-10B: 240Vac single-phase, 56A, 60hz only

Company Federal Signal Corporation
Type Electromechanical
Sound output 109[1] dBc at 100 feet
Horsepower 7.5[1]
Documentation Manual