LITERATURE REVIEV

2.1 EARLY STAGES

Sometime before 1799, the first siren was invented by the Scottish natural philosopher (physicist) John Robison Robison’s sirens were used as musical instruments; specifically, they powered some of the pipes in an organ. Robison’s siren consisted of a stopcock that opened and closed a pneumatic tube. The stopcock was apparently driven by the rotation of a wheel.

In 1819 an improved siren was invented and named by Baron Charles Cagniard de la TourDe la Tour’s siren consisted of two perforated disks that were mounted coaxially at the outlet of a pneumatic tube. One disk was stationary, while the other disk rotated. The rotating disk periodically interrupted the flow of air through the fixed disk, producing a tone. De la Tour’s siren could produce sound under water, suggesting a link with the sirens of Greek mythology; hence the name of the instrument.

2.2 MODERN ELECTRONIC SIREN REQUIREMENTS

Siren application and to a large extent siren technical requirements are defined directly by law in many countries. Even though the requirements in questions are similar, from the technical point of view they are so different that they cannot be met by a single version of a siren alone.

Not only are the requirements related to acoustic announcements hut also those are related to control methods and siren status control. Great attention is also paid to siren backup in the case of a power failure. That is the reason why a modern siren or a modular device with many firmware versions from the hardware point of view, normally backed up by batteries and designed in such a way that electric power supply is used at a minimum when it is not active and the conversion of electric power into acoustic power is at peak efficiency when the siren is active.