Editing Civil defense siren (section)

===Mechanical===

==== Basic design ====
[[File:ACA Allertor 125 video.ogv|thumb|left|175px|An ACA Allertor 125 in Alert and Attack modes (video)]]
[[File:3T22 Sandy, Oregon.jpg|thumb|left|175px|An older and damaged 3T22 at a fire station in Sandy, Oregon, that has now been restored and hung from the ceiling of the entrance lobby]]
[[File:IsraeliAirRaidSiren.jpg|thumb|left|175px|A Hormann HLS F-71 Pneumatic air-raid siren in [[Haifa]], Israel. Sirens of this type are common in Israeli towns and cities, and until 2012<ref>{{Cite news|last=זיתון|first=יואב|date=2012-02-20|title=שקל אחד, וכל הצופרים הישנים יורדים מהגגות|language=he|work=Ynet|url=https://www.ynet.co.il/articles/0,7340,L-4192091,00.html|access-date=2023-10-08}}</ref> were used to warn against air raids and missile attacks.]]

A mechanical siren uses a [[Rotor (electric)|rotor]] and [[stator]] to chop an air stream, which is forced through the siren by radial [[wikt:vane|vane]]s in the spinning rotor. An example of this type of siren is the Federal Signal 2T22, which was originally developed during the [[Cold War]] and produced from the early 1950s to the late 1980s. This particular design employs dual rotors and stators to sound each pitch. Because the sound power output of this type of siren is the same in every direction at all times, it is described as omnidirectional. The Federal Signal 2T22 was also marketed in a three-signal configuration known as the [[Federal Signal 3T22]], with the capability for a ''high–low'' signal.<ref>{{Cite web|title=2T22 and 3T22|url=https://wiki.airraidsirens.net/2T22_and_3T22|access-date=2021-10-08|website=Air Raid Sirens Wiki|language=en}}</ref> 

While some mechanical sirens produce sound in all directions simultaneously, other designs produce sound in only one direction, while employing a rotator mechanism to turn the siren head through 360 degrees of rotation. One rare type of mechanical siren, the Federal Signal RSH-10 ("Thunderbeam"), does not rotate or produce equal sound output in all directions. It instead uses a slowly rotating angled disc below the siren which directs the siren's output throughout 360 degrees.<ref>{{Cite web|url=https://wiki.thesirenboard.com/RSH-10|title=RSH-10}}</ref>

==== Supercharged ====
A variation of the electromechanical siren is a ''supercharged'' siren. A supercharged siren uses a separate source, usually a [[supercharger]]-like [[Blower fan|blower]], which forces air into the rotor assembly of the siren. This increases the [[Pressure|air pressure]] in the rotor assembly, causing the sound output of the siren to increase heavily, which in return increases the sound range by a large amount. The blower is generally driven by an electric motor, but in rare cases it is driven by an [[engine]]. [[Federal Signal Corporation|Federal Signal]] took advantage of this design and created their [[Thunderbolt (siren)|Thunderbolt Siren Series]], utilizing [[Sutorbilt]] [[Roots Blower]]s of different varieties and outputs.<ref>{{Cite AV media|title=Sutorbilt 4M Blower Test|date=30 July 2021|url=https://www.youtube.com/watch?v=zwE0w7jQkPE|access-date=2023-09-02|language=en|via=[[YouTube]]}}</ref><ref>{{Cite AV media|title=Testing a Thunderbolt siren C-series blower|date=6 September 2009|url=https://www.youtube.com/watch?v=D04jpC2hr8Q|access-date=2023-09-02|language=en|via=[[YouTube]]}}</ref><ref>{{Cite AV media|title=My Thunderbolt 1000BT Blower Test|date=24 February 2020|url=https://www.youtube.com/watch?v=KnDOO9UyDwE|access-date=2023-09-02|language=en|via=[[YouTube]]}}</ref><ref>{{Cite AV media|title=Series A1 (6M) Thunderbolt blower run|date=25 June 2014|url=https://www.youtube.com/watch?v=IbkVQgk1ro4|access-date=2023-09-02|language=en|via=[[YouTube]]}}</ref>

A very early model called the Thunderbolt 2000. The difference between the Thunderbolt 2000 and later editions is that its blower is driven by an [[Cummins|Onan]] two cylinder gas engine.<ref>{{Cite web|title=Thunderbolt Siren Series|url=https://wiki.airraidsirens.net/Thunderbolt_Siren_Series|access-date=2021-10-08|website=Air Raid Sirens Wiki|language=en}}</ref> Another example of a siren that has a separate blower is the [[Alerting Communicators of America]] (ACA) [[ACA Hurricane|Hurricane]]. One more example of a siren with a blower is the [[Southern California|SoCal]] Edison Model 120, utilizing a Centrifugal Style Blower, built specifically for the [[San Onofre Nuclear Generating Station]]. The SoCal Edison Model 120 is no longer standing out in public, as only one exists, and is owned privately.<ref>{{Cite web|title=Model 120|url=https://wiki.airraidsirens.net/Model_120|access-date=2021-10-08|website=Air Raid Sirens Wiki|language=en}}</ref>

[[File:SoCal Edison Model 120.jpg|thumb|A SoCal Edison Model 120 illuminated by a spotlight in the night sky in 2003. They were manufactured in-house by SoCal Edison and were installed in 1982 for use with the [[San Onofre Nuclear Generating Station]] Community Alert Siren System. The blower is located in the middle just above the mounting plate hidden within the mesh bird screen between the frame support structure for the horns.]]

==== Pneumatic ====
Another variation on the electromechanical siren is the [[pneumatic]] siren. Similar to supercharged sirens, pneumatic sirens also force air into the rotor assembly of the siren. However, these sirens use a pressurized air reservoir instead of a motor-driven blower.<ref>{{Cite AV media|title=Classic Siren Recordings – HLS 273 on the ground|date=3 November 2021|url=https://www.youtube.com/watch?v=oVFQ04kBDRU|access-date=2023-09-02|language=en|via=[[YouTube]]}}</ref> {{lang|de|hochleistungssirene}} (HLS), first produced by the German firm [[Pintsch-Bamag]] and later by the German firm [[Hörmann]]. Soon afterward, Hörmann improved on the design to create the HLS 273, which did away with the massive siren head of the original in favor of a more compact head and cast aluminum exponential-profile horns. These sirens stored a reservoir of [[compressed air]], recharged periodically by a [[diesel engine]]-driven [[gas compressor|compressor]] in a vault in the base of the massive siren unit. The later HLS 273 placed the large (6,000 liter) air tank underground beside the machinery vault, instead of in the mast itself as in the earlier HLS units.