The air raid siren on display here was originally installed on Grapeview Drive in St. Catharines and was dismantled in the 1980’s and donated to the Museum in 2002.

This siren was made by CLM Industries in Scarborough and is model type 92763CP.

CLM started off as a small steelwork company in Scarborough, Ontario, part of the larger McGraw-Edison company, producing electrical equipment such as lightning arresters. Early on into the company’s history, CLM was commissioned by the Canadian government to create air raid sirens for civil defense. CLM made several different sirens, both rotational and omnidirectional. All CLMs were designed with the harsh Canadian winter in mind, and as such, measures were taken to protect them from the elements. All CLM siren controllers were equipped with a special mode that would operate the siren’s rotors at all times at a very low speed, between 60-75RPM, in order to prevent ice from building up and potentially jamming the rotors and burning up the motor. All CLM sirens use directional rotors, which allows the siren increased performance as long as the rotors are spinning in the right direction. (source: https://civil-defense-sirens.fandom.com/wiki/CLM_Sirens#:~:text=CLM%20started%20off%20as%20a,raid%20sirens%20for%20civil%20defense.)

How Does it Work?

This is a 3HP vertical omnidirectional siren which came exclusively in 10/12 port dual tone. They were available only in 220V single phase AC. These were a vertical option that were designed to be used as part of a wider system, often supplementing Type 927xxDP rotational sirens by filling coverage gaps, although they were also occasionally used in their own systems. These used two curved surfaces to help project the sound outwards, rather than using horns. Unlike CLM’s other sirens, this used a single 10/12 port rotor and stator rather than two split rotors. The siren has two intakes, with the top intake having a very large rain shield above it which also acts as the upper projector, while a second intake is located below the rotor. A large skirt is included under the stator, which serves to complete the two projector surfaces. The 12-port side is fed by the top intake while the 10-port side is fed by the lower intake. The siren uses a rotor-over-motor configuration, with the siren’s bare motor being located underneath the siren, unprotected from the elements. A mesh screen is included on both intakes to protect the rotor. 

This air raid siren has a second part – the transformer which you can see in this photo. The transformer was located on the pole with the siren and was connected to the larger warning system which was controlled by the Civil Defense Committee.

Watch this! Check out this short video about Air Raid Sirens in Canada during the Cold War to hear the sounds of air raid sirens from that era.