The Thunderbolt is a discontinued mechanical outdoor warning siren made by

Federal Signal Corporation Federal Signal Corporation is an American manufacturer headquartered in Oak Brook, Illinois. Federal Signal manufactures street sweeper vehicles, public address systems, emergency vehicle equipment, and emergency vehicle lighting. The comp ...

. It has a very recognizable design, being a unidirectional siren with a large yellow (or other color based on buyer's choice) exponential horn.

History

The Thunderbolt siren was developed between 1949 and 1952. It was the first "supercharged" siren, which uses a

supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement. The current categorisation is that a supercharger is a form of forced induct ...

to force air into the rotor, greatly increasing the siren's volume. In the 1980s, when

civil defense Civil defense ( en, region=gb, civil defence) or civil protection is an effort to protect the citizens of a state (generally non-combatants) from man-made and natural disasters. It uses the principles of emergency operations: prevention, miti ...

fell into disuse, thunderbolts across the United States were repurposed for nuclear and storm warning siren systems. During the

Gulf War The Gulf War was a 1990–1991 armed campaign waged by a 35-country military coalition in response to the Iraqi invasion of Kuwait. Spearheaded by the United States, the coalition's efforts against Iraq were carried out in two key phases: ...

, Federal sent a number of modified Thunderbolt 1003s to

Kuwait Kuwait (; ar, الكويت ', or ), officially the State of Kuwait ( ar, دولة الكويت '), is a country in Western Asia. It is situated in the northern edge of Eastern Arabia at the tip of the Persian Gulf, bordering Iraq to the nort ...

to warn its citizens of an air raid. These were the system 7000 series and were only found in Kuwait. Later, Kuwait's sirens were all replaced with

Federal Signal Modulator Federal Signal Modulators (also known as Modulator Speaker Arrays) are electronic warning devices produced by Federal Signal Corporation that are used to alert the public about tornadoes, severe weather, earthquakes, fires, lahars, tsunamis, or a ...

s. One system 7000 is on display next to a

at the Kuwait General Administration of Civil Defense. in Kuwait City, Kuwait. Eventually in 1990, the Thunderbolt was discontinued in favor of the new 2001 Siren Series. Since then many have sat abandoned or have been replaced by newer systems. In the 21st century, many communities lacking siren coverage have purchased Thunderbolts that once sat in various towns, and have been refurbished. Many Thunderbolts are also in private and legal possession.

Design

The Thunderbolt came in several models. The Model 1000 was single tone, while the Model 1000T and Model 1003 were dual tone. The Model 1003 also included two

solenoid upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...

-operated control valves. They are used to create alternating steady, alternating wail, pulsed steady, and pulsed wail signals, which can be used as a fire warning. Otherwise, it is identical to the 1000T, but used the 5/6 rotor only. Although the 4/5 port rotor is compatible, it was never offered for the 1003. Only two 4/5 port rotor 1003's exist currently, one in

Saint Paul, Nebraska St. Paul is a city in and the county seat of Howard County, Nebraska, United States. The population was 2,290 at the 2010 census. St. Paul is part of the Grand Island, Nebraska Micropolitan Statistical Area. Geography St. Paul is located at ...

, and the other in

University Park, Illinois University Park is a village, a south suburb of Chicago mostly in Will County with a small portion in Cook County in the U.S. state of Illinois. The village is one of the region's few planned communities, was developed in the 1960s as Wood Hill, ...

. The 1003 entered production in 1962, and ceased in 1990 (However, it has been recently been believed to enter production in '61). It is noteworthy that the 1003 was the last production unit ever built. The last sirens went to a township in Michigan, however all of them were removed and replaced around 2009. Originally the Thunderbolt used a motor and an Abart gear reducer driven by pulley to drive the large spur gear which makes the projector rotate. The pulleys utilized 3 different belt slots to change the RPM in which the siren rotates, from 2, 4, and 8 RPM. In 1980, Federal wanted to make the Thunderbolt more maintenance free, doing so by turning the motor and gear reducer to face each other and attached to make a direct drive system which rotated at 4 RPM. This rotator was used only on the B-series models. B-series units were only offered in 1980.

References

External links

Thunderbolt siren manual

Listen to a single tone Thunderbolt 1000 in alert mode.

Listen to a dual tone Thunderbolt 1000T in alert mode.

Listen to a dual tone Thunderbolt 1003 in Hi-Lo mode.

Map of all Thunderbolt sirens still in existence
{{Civil defense sirens Sirens Disaster preparedness Civil defense Emergency population warning systems