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The Allertor 125 is a rotational, electromechanical civil defense siren that was produced by Alerting Communicators of America from 1968 until it was replaced by the similar Penetrator series in 1980. The Allertor was the direct successor to Biersach and Niedermeyer's Mobil Directo siren, with significant improvements to the design which simplified manufacturing and enhanced the siren's durability and performance versus its predecessor. Like the Mobil Directo, it is unique in that it sucks in air through the bottom intake horn, and then the sound comes out of the top horn of the projector.

In 1980, the Allertor was redesigned into the Penetrator-10 and 15, which replaced the giant projector with a simple horn and intake, which reduced costs and got rid of a lot of the Allertor's problems such as snow and ice building up inside the projector, and difficulty of installation. However, the Allertor's design offered superior performance. The Allertor was sold alongside the P-10 for a short time before it was finally discontinued, as can be seen in ACA's 1980 catalogue.

The Allertor 125 is driven by a dual sided 10HP AC motor, which drives both the rotor and the rotator, and was rated at 126db at 100ft. Rather than using all-metal construction like its predecessor, ACA used then-brand new fibreglass construction on these sirens, which greatly improved the siren's longevity and durability as it prevented corrosion and better protected the siren's internals. The siren was rotated as one large unit, with the siren's motor being connected to a gear reducer that then drove vertical shaft that operated a gear-driven or chain-driven rotator below. This design was quite reliable, as chains do not suffer from the same issues as belts do. A popular misconception is that the Allertor's chains were prone to snapping, but this is far from the truth. Allertors were and still are very reliable sirens due to their fibreglass construction. The Allertor's biggest flaw was that it was prone to water building up inside the projector drum if the drainage holes were blocked, which could freeze and result in the rotor getting stuck and burning up the motor. The ACA Howler would be introduced in 1972 in an attempt to combat this problem, and the Penetrator-10 would also later solve this problem at the cost of performance.

A three-signal Allertor was offered alongside the standard dual-signal model for a short time, using a special motor that could reverse polarity during operation, which would quickly bring the rotor to a halt, creating a "Yelp" signal. This was a short lived option, with no three-signal units known to exist today, nor were any known to have been sold. Single tone 8-port or 12-port were also options, though no single tone units were known to have been sold.

The Allertor 125 came in three different generations:

1st Generation[]

File:Type-1 Allertor.png

A 10/12 port Type-1 Allertor in New Hampton, IA. Note the elongated motor cover and gear-driven rotator.

The first generation Allertor is easily distinguished by its elongated two-piece motor cover that is taller than later models, and came standard in 10/12-port dual tone (with the chopper and stator being reused from the BN44E Mobil Directo), 8/12-port dual tone, and 9/12-port dual tone. The rotors on 9/12 and 10/12-port 1st generation Allertors are bidirectional, with the 9/12's rotor being very similar in design to the Federal Signal SD-10's rotor. These early Allertors did not use chain-driven rotator, instead using a rotating gear driven by the motor that rotates the siren around a very large stationary gear under the siren. These rotators are much larger in diameter than the chain driven rotators later Allertors used, and makes it very easy to spot. 1st generation Allertors also use a smaller intake borrowed from the Mobil Directo. These were produced from 1968 until sometime in the very early 1970s. The very earliest of these had a vent on the side of the motor cover, which was later removed. Some units, such as the 8/12-port units, do not have elongated motor covers, similar to Type-2 units.

While the 9/12 and 10/12-port rotors and stators on these units are bidirectional, meaning they can run in either direction with identical performance, the 8/12-port rotor and stator are unique in that they are the first of ACA's rotational sirens to use a directional rotor and stator, which greatly improves performance when wired correctly, however the siren will perform worse if running backwards. Also unique to the first generation Allertors is that the rotor spins in the opposite direction of the rotator, spinning counterclockwise while the siren rotates clockwise. 2nd and 3rd generation Allertors rotate the same direction as the rotor spins, rotating clockwise if configured correctly.

2nd Generation[]

File:Type-2 Allertor (actually).png

A Type-2 Allertor, in Florence, AL. Note the early larger chain-driven rotator and lipped horn.

The second generation Allertor was introduced in the very early 1970s, dropping both the 8/12 and 10/12-port options in favour of a redesigned directional 9/12-port rotor and stator, which improved the efficiency of the siren when spinning in the right direction. However, if it is wired backwards, sound output will be reduced. The second generation also switched from the gear-driven rotator to a smaller chain-driven rotator. Early second generation Allertors had a larger, teardrop shaped rounded rotator with a small lip at the end, with later units switching to the smaller design that would be later used in the third generation Allertors. Another way of differentiating these Allertors from the first generation models is that the second generation Allertors have a lip on the top horn, while first generation units do not. Production ended on this generation in 1972, being succeeded by the third generation. Second gen units had a very short production run, and are hard to find as a result.

3rd Generation[]

File:Type-3 Allertor.png

A Type-3 Allertor in Blue Eye, MO.

The third generation Allertor was released in 1972, and was the final redesign given to the siren. This is when the siren received the design it is most well known for, and switched to an all-fibreglass construction instead of the previous mix of fibreglass and steel. Like the previous generation, the Gen-3 Allertor came exclusively in 9/12-port dual tone, using the same directional rotor and stator as the second generation units. The intake was greatly enlarged in order to prevent snow and ice from getting into the projector, and the motor cover was redesigned from a two-piece fibreglass and steel design to a single, shorter fibreglass mould. This design decision forced ACA to add an indent into the back of the projector drum to allow it to fit onto the rotator plate. This means that projectors from previous generations are incompatible. This design would be used all the way until the siren's discontinuation in 1980, and everything except the projector from this generation would be reused for ACA's Penetrator-10 and 15.

Cities with active ACA Allertor 125s[]

Yankee Stadium The Bronx NY Home Runs

Batavia, Ohio

Bloomfield, New York - (used as a fire call siren)

Blue Eye, Missouri

Bolivar, Missouri

Brown Deer, Wisconsin

Cedar Falls, Iowa

Chaska, Minnesota

Crane, Missouri - (used as a storm siren)

Cresco, Iowa

Cumberland, Wisconsin

Elmwood Park, Illinois

Elmwood, Wisconsin

Emmetsburg, Iowa

Georgetown Township, Michigan

Grand Ledge, Michigan

Greendale, Wisconsin - (used as a tornado siren)

Big Farm, AR

Hastings, Nebraska

Knox Township, Ohio

Lee's Summit, Missouri

Mahomet, Illinois

Manitowoc, Wisconsin

Milwaukee, Wisconsin - (used as a tornado siren)

New Hampton, Iowa

Niles, Michigan - (used as a tornado siren)

Otterville, Missouri - (used as a tornado siren)

Paxton, Illinois

Prague, Oklahoma

Port Washington, Wisconsin

San Bernardino, California

Sidney, Illinois - (used as a tornado siren)

Tarrs, Pennsylvania - (used as a fire call siren)

Tipton, Kansas

Waldorf, Minnesota

Wauwatosa, Wisconsin

White Bear Lake, Minnesota (Relocated to Cumberland, Wisconsin)

Whitefish Bay, Wisconsin - (used as a tornado siren)

Woodstock, Illinois (Modified)

Richardson, Texas

Chilton, Wisconsin has two of them - (used as tornado sirens) 1 on East side & 1 on West side of the city

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