Category:Three-Signal Sirens

While most mechanical sirens are simply two-signal sirens, there are several sirens that make use of a mechanism to perform a special third signal. These include hi-lo, pulse, or a variety of other signals. Three-signal sirens make use of solenoids, dampers, sliding stator rings, or other mechanisms to perform these signals. Three-signal sirens are usually used at fire stations as a special signal for fire calls, as well as for other purposes such as in industrial plants where a distinct signal is needed. Three-signal variants of existing sirens tend to be rarer than their standard two-signal variants. Three-signal sirens often require more maintenance and regular use, or their coding mechanisms will fail. This, along with the need for three-signal sirens being replaced by pagers, has led to active sirens with working and active mechanisms having become very uncommon.

Not to be confused with coded sirens, which are specifically meant to blast a specific number of coded blasts corresponding to a fire zone or district and are not meant for general use.