Siren Wiki (EN)
What is a siren?
A siren is a noisemaking device typically used to warn of impending disasters, usually tornadoes but also tsunamis, nuclear disasters, etc. They come in many sizes and shapes, however the most common is the mechanical siren. A good example of an mechanical siren is the Federal Signal 2T22.
There are also electronic sirens which utilize speakers and soundcards, amongst the mountain of electronics to function. A good example is the American Signal Corporation (ASC) I-Force.
The photo to the left depicts the basic parts of an outdoor warning siren.
Air is sucked into the rotor, which spins rapidly, often around 3450 RPM. Sound exits through the stator, and as a result, produces sound from the air being sucked and therefore chopped by the stator.
The ports are the holes that the air/sound exits from. The lower the amount of ports, the lower the sound and the higher the amount, the higher the pitch goes. The siren in the photo is a basic 8 port siren that I 3D modeled. 8 port sirens typically produce 460 HZ on 60HZ, 3450 RPM.
RJ. Zievers Scream Master
Produced: 1950s.
Port ratio: 9, 6/8
Motor horsepower: 7.5, 10
Origin: California, USA
RJ. Zievers was a company based in La Verne, CA. They made machines, ranging from sirens (of course) to crop defrosters, and others. However, they were most well known for their siren line.
They were almost exclusively installed in California. They especially dotted the SoCal, Bay Area and Sacramento region. They were used primarily during the Cold War period, due to a heightened sense of paranoia of a Soviet nuclear attack.
Such attacks however never came to fruition and they eventually sat abandoned following the Cold War.
RJ. Zievers went bankrupt and eventually ceased to exist in the late 50s due to extreme competition from Federal Sign and Signal and Sterling, which dominated the market at the time.
Pictured here is a unit in San Lorenzo, California that I photographed on Christmas 2023.
Partially sourced from the Civil Defense Siren wiki, though 95 percent of the info was from my memory, I had to use the wiki to rebuild my memory.