ACA Allertor 125

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Watch an ACA Allertor 125 in alert and attack. Credit: Ben Franske on YouTube.

The ACA Allertor 125 is an outdoor warning siren made by Alerting Communicators of America from 1944 until 1980. It has a distinctive design with the chopper in the bottom horn and the noise coming out of the top horn.


The ACA Allertor was designed around the early 1960s as a 125dB siren with a metal horn. It came in four port ratios: 8, 9/12, 8/12, and 10/12, which sounds very much like a Biersach and Niedermeyer Co. Mobil Directo, an early version of the Allertor, and in fact, the 9/12 and 10/12 rotors were derived from Federal Signal. It had many changes throughout its production run, the most notable being the horn changed to fiberglass around 1968, then to a larger design, as seen in the video. The most common port ratio is 9/12. The Allertor was a popular choice for various communities in the Midwest from the late 60's, to the late 70's, and served as one of ACA's most popular sirens during that time. The design was unique, as it used a top horn design, with the air intake below the horn, near the bottom of the siren head. The first Allertors had a short bottom horn (similar to the B&N Mobil Directo horn) so the design changed to a bigger bottom horn. Despite being an efficient design, it was expensive to build the fiberglass horn. The Allertor was finally discontinued around 1980, and replaced with the more-efficiently designed Penetrator 10. The Penetrator 10 used a bell horn and cone intake that was much cheaper to produce. The Allertor was once a popular siren for outdoor warning purposes, however, they are becoming more uncommon due to their age.


The Allertor had the chopper in the bottom “horn” which sucked air through the bottom intake & blew it through the top horn. Allertors had chain-driven rotators which often broke, this often leads to their removal or failure.

In popular culture[edit]

The Allertor has been hailed by many people as the most popular siren ever produced. Some people have thought the sound comes from both the actual horn & the air intake. (the bottom horn)