Fire siren

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A fire siren is another name for an air raid siren or outdoor warning siren used to summon volunteer firefighters for emergencies. While fire sirens were the primary means of alerting firefighters for many years, more modern means of notification have now been implemented to replace the fire siren. As there can be problems with modern communications, many fire departments (typically in smaller communities) still sound the siren as a backup or auxiliary to these devices (for example, pagers and radios). Many fire sirens also pull double duty as tornado or civil defense sirens, alerting an entire community of impending danger. Most fire sirens are either mounted on the roof of a fire station, or on a pole next to the fire station. Fire sirens can also be mounted near government buildings, on top of tall structures such as water towers, as well as in systems; where several sirens are sporadically placed around a town for better sound coverage. Most fire sirens are single tone and mechanically driven by electric motors with a rotor attached to the shaft. Some newer sirens are electronically driven by speakers, though not as common. The most common types of sirens include the Federal Signal Model 5, Model 2, STH10, and the Sterling (now Sentry) siren Model M. Fire sirens are often called "fire whistles", "fire alarms", "fire horns" even though the nomenclature is incorrect. There is no standard signaling of fire sirens. Civil defense sirens pulling double duty as a fire siren often can produce an alternating "hi-lo" signal (similar to a British police car) as the fire signal, or a slow wail (typically 3x) as to not confuse the public with the standard civil defense signals of alert (steady tone) and attack (fast wavering tone).

1 History
2 Other types of outdoor alerting
3 Siren activation and control
4 Sirens on vehicles
5 See also
6 Links and references

[edit] History

The earliest way of summoning volunteers was by ringing of a bell, either mounted atop the fire station, or in the belfry of a local church. As electricity became available, the first fire sirens were manufactured. Two early manufacturers of fire sirens where Federal Signal and Sterling Siren. Both started manufacturing fire sirens around 1905.

Also, many communities that have deactivated their fire sirens in the past due to noise complaints, have reactivated them due to post 9/11 security concerns and for increased reliability in notifying firefighters.

[edit] Other types of outdoor alerting

Steam whistles were also used as a warning device if a supply of steam was present, such as a sawmill or factory. These were common before fire sirens became widely available. Fire horns, large compressed air horns, also were and still are used as an alternative to a fire siren. Many fire horn systems were wired to fire pull boxes that were located around a town, and thus would "blast out" a code in respect to that boxes location. For example, pull box number 233, when pulled, would trigger the fire horn to sound a two blasts, followed by a pause, followed by there blasts, followed by a pause, followed by three more blasts. In the days before telephones, this was the only way firefighters would know the location of a fire. The coded blasts were usually repeated several times. This technology was also applied to many steam whistles as well. Also, some fire sirens are fitted with brakes and dampers to enable them to sound out codes as well. These units tended to break down a lot, and thus, aren't common or produced anymore. Other bizzare methods of alerting firemen have been incorporated as well.

[edit] Siren activation and control

Fire sirens today are usually activated with the same radio signals that are sent to activate pagers as well. In the past, sirens were manually activate by either someone in the fire station, or many times in smaller communities, a "nearby neighbor" would run over to the station to cut the siren on, as the local emergency calls would be directed to him or her. Switches were, and still are in many cases, mounted outside of the fire station for passersby to activate the fire sirens. Telephone relays also were used to set off fire sirens from dispatch centers prior to the days of reliable radio technology. A voltage applies across a pair of leased telephone wires would trip the motor starter relay of the siren remotely.

A typical fire siren setup includes the siren, an activation unit of some sort, and a motor starter (used to take the low voltage of the activation unit and close a contact switch that completed the high voltage circuit the siren motor needs)

[edit] Sirens on vehicles

Many people refer to fire sirens as the mechanical or electronic sirens found on fire engines. For this description on vehicular sirens, please see siren.