Sirens Built within the Framework of SEHIS – The Slovak National Early Warning and Notification System – Protecting the Old Town of Bratislava

Sirens Built within the Framework of SEHIS – The Slovak National Early Warning and Notification System – Protecting the Old Town of Bratislava

The Old Town of Bratislava includes the historic centre and adjacent areas that formed its immediate suburbs in the Middle Ages. The cosy atmosphere of the Old Town of today with its narrow streets and picturesque buildings lures thousands of tourists every year. Its area covers 9.59 km2 (3.703 sq. miles) and its population is almost 42 thousand inhabitants. Neither permanent resident caught up in their daily routines nor visitor enjoying the beauty of carved facades, ornamented walls of apartment buildings, and popular monuments may know what is above their heads, installed on top of these buildings.

The Pavian electronic siren has become an indispensable part of the Bratislava Old Town. The siren has been installed in the most vulnerable area of the city within the framework of one of the biggest projects in the world – SEHIS, the Slovak National Warning and Notification System. The system consists of almost 3,000 Pavian electronic sirens that were installed all over the Slovak Republic. Almost 160 of these sirens are placed in Bratislava, the capital of the Slovak Republic. The unique system has already proven its reliability and technological advantage, optimising the functionality and minimising the risks of its failure. It uses only fully electronic sirens with robust, weather-resistant horns, digital technology, two-way wireless communications units, and 72-hour power backup in case of power supply failure. The operator of the system can run a siren test easily and very quickly, obtaining all most important parameters of the siren status, and they can make sure that the device is fully operational whenever necessary. Telegrafia’s devices have always been developed with a view to making their operation interactive, seamless and user-friendly. By pressing a single button, all electronic sirens installed within the SEHIS system in Slovakia will send feedback to the operators, regarding the:

    • status of acoustic drivers,
    • amplifiers status,
    • battery voltage measurement,
    • power supply/charger status,
    • status of aerials and RF cabling (Return Loss, RF signal strength, RF signal level (uV),
    • speaker’s impedance measurement,
    • input voltage,
    • AC/DC converter voltage,
    • current consumption measurement,
    • temperature inside the siren box,
    • asynchronous notification – unauthorised entry, local activation of the control unit, etc.
Pictures with descriptions

1. The 600W Pavian siren placed on top of the building. A view from Bezrucova Street. The siren contains four 150W horns that are arranged in the opposite direction. This arrangement pattern is suitable for alarms to cover an approximately circular area.

2. The 600W Pavian siren placed as close as 30 metres away from the famous Michalska Gate.

3. The 300W Pavian siren located on the roof of the main building of Comenius University in Bratislava. The electronic siren has two horns with a total output of 300W, generating a sound of 103dB (A)/30m. Thanks to the arrangement of its horns, the siren can direct the whole acoustic power to the most vulnerable area and is loud enough to transmit the necessary warning signal or live voice messages to people in danger. On the other hand, the siren is not too loud to annoy the passers-by.

4. The 1200W Pavian siren can generate a sound of 115dB (A)/30m, the loudest sound recommended for urban areas by Telegrafia. Any louder siren could unnecessarily harm human hearing, especially when there are numbers of sirens mounted on multi-storey buildings in densely-populated areas. 8 horns with 150W drivers mounted on an 8’9 mm thick pole are shown in the picture.