Snowpix

I think this community will enjoy this song lol

A 1952 advert from Federal Enterprises advertising their Thunderbolt 1000 and Model 2 outdoor warning sirens. The Model 2 is still in production today, while the Thunderbolt was made until 1990. Both can still be found in service across the North America, though many Thunderbolts are starting to be replaced with newer sirens.

Federal Enterprises now runs as Federal Signal Corporation, and many of the listed cities still use old and new Federal sirens.

This ad was released roughly around 1948, advertising the Mobil Directo air raid siren. I've posted an ad for this siren previously, which only featured the Mobil Directo's gas engine-driven BN52 model. This ad introduced a new variant of the Mobil-Directo, driven by a 10HP electric motor instead of the 25HP Wisconsin aircooled engine. This new electric model proved extremely successful, as engines require significantly more maintenance and are far less practical for siren use than a motor.

The new model, known as the Mobil Directo BN44E, saw widespread use across the United States and Canada. Rated at 126 dB @ 100ft for 10/12-port dual tone models to nearly 128 dB for 8-port single tone models, the BN44E was louder than most other sirens during the time of its production. The engine-driven BN52 would see sales dry up quickly after the BN44E's release, being discontinued in 1953. The BN44E would be sold until 1967, when BNCO was forced to stop making sirens due to stiff competition from Federal Sign & Signal.

BNCO would create a new division, known as Alerting Communicators of America (ACA) who would redesign the Mobil Directo into the Allertor 125, which saw the steel projector replaced with a fiberglass projector, and the dual belt-driven pulleys on the rotation drive replaced by a single chain-drive rotation mechanism under the siren. The Allertor 125 would be sold until 1981, when it was replaced by the Penetrator-10 which replaced the large projector with a simplified horn.

The Model M was an early electric siren first developed in 1920 by the Inter-State Machine Products Company, who would later rebrand to the Sterling Siren Fire Alarm Company based out of Rochester, NY. The Model M was perhaps the most popular and widespread fire siren sold in North America, with units being sold across the US and Canada in great numbers. It is said that nearly every volunteer fire department in the eastern US had a Sterling Model M, or Sterling's other sirens such as the Model 5VX or Little Giant.

Unlike earlier electric sirens such as the Denver sirens I talked about in a previous post, the Model M was designed from the ground up to be weatherproof. Reliability in an emergency is everything, and its designer, Merton C. Armstrong, knew this. The choppers are covered with rounded "sounders" which also direct sound downwards, the motor is protected by a cover, and the air intakes on each side had protective wire mesh to keep debris out. By 1928, the siren would be improved with metal louvres on the intakes to further protect it. The Model M used motors between 3-10 horsepower, could be single or dual headed, and were rated to roughly 115 decibels @ 100 ft.

The Model M as previously mentioned saw incredible success. As shown by a friend of mine who made a map of every known Sterling siren, these sirens found their way everywhere. Unfortunately, by the early 1970s, competition became too great as Sterling's 50 year old design became obsolete. Sterling went out of business in 1972, but its designs were bought by a new company known as Sentry Siren who produced the Model M until 1986.

Sentry Siren is still in business today, and many of its sirens are directly based on the Model M's chopper design which is a testament to how good the Model M was. Many Model Ms remain in service today, including several units which are roughly 100 years old. Van Alstyne, TX's Model M is speculated to be the oldest surviving Model M, and is currently still in service.

Video of an early single tone Model M in Van Alstyne, TX, presumably the oldest known Model M

Video of a later dual tone Model M with louvred intakes in Columbus Grove, OH

This is a 1952 ad for the engine-driven BN52 model Mobil Directo air raid siren, which used a 25HP Wisconsin air-cooled engine to drive both the chopper (the noisemaker) and two belt-driven pulleys to spin the siren around. Later BN44E models would switch the engine to an electric motor. It was one of the first rotational sirens, and would later redeveloped into the "Allertor" and "Penetrator" electric sirens.