The ACA Allertor is an outdoor civil defense siren made by Alerting Communicators of America (ACA) that used to be the Biersach & Niedermeyer Co. (B&N Co.) which produced a similar, older version of this siren called the Mobil Directo. This Siren was in production from 1967 to 1981. It had a unique design have the intake chopper on the bottom, and the sound coming from the top horn.
The ACA Allertor was originally the the Mobil Directo by the Biersach & Niedermeyer Co. in the early 1940s. The Mobil Directo's main function was to warn of the event of an air-raid. The Mobil Directo was made of metal and came in 4 different port ratios: 8, 8/12, 9/12, and 10/12; 9/12 was the most common. The ACA Allertor sound would go up to 125 db at 100 feet away which is why it's called the ACA Allertor "125". In 1968, B&N changed their name to ACA and started producing Allertors.