Emergency alarm: the return of the sirens

Ka connection under this number: early in the morning on November 11, 2021, numerous control centers of the police (110) as well as the fire brigade and rescue service (112) could no longer be reached due to failure of the telephone emergency call. The disruption affected regions across Germany, and it took over an hour to resolve the problem, apparently caused by new software. It was the second major disruption to the emergency call infrastructure within a few weeks. The last time there were significant problems was on September 29, 2021.

Such situations highlight the importance of communication channels for emergencies. Because the intuitive and quick accessibility of control centers via memorable abbreviations is a prerequisite for short response times and thus the efficiency of the operations. In the Federal Republic of Germany, the emergency numbers that are common today have been established for large cities since the late 1940s. On September 20, 1973, the Prime Minister and the Federal Chancellor decided to introduce it across the board. This was made possible by the committed lobbying work of the Björn Steiger Foundation. Today the 112 is valid in more than 30 countries, including all states of the European Union since 1991.

However, communication usually runs in at least two directions, which also applies to emergencies: In addition to the possibility of emergency calls, reliable information technology is required for contact between the helpers (alerting and communication during the deployment via radio networks for authorities and organizations with security tasks – BOS radio) as well as to inform the population through the public sector. The nationwide warning day on September 10, 2020, which is characterized by technical breakdowns, made it clear that there is an urgent need to catch up in Germany on the last point. The next warning day should take place in 2022. Then it will show what one has learned from the error analysis from two years ago.

A finding that was as banal as it was critical in 2020 was that there are too few sirens in Germany to provide reliable, comprehensive warnings. The network is currently being expanded again, with start-up funding from the Federal Office for Civil Protection and Disaster Aid (BBK) amounting to around 90 million euros. In Bavaria, where the existing network of warning systems is to be almost doubled, the first new sirens from the program are to be put into service this year.

The topic of siren warning became even more explosive when the affected citizens were informed too late about the risk during the floods triggered by heavy rain in summer 2021 – with particularly serious consequences in the Ahr valley. Early siren alarms might have avoided fatalities here. The event is currently being dealt with by an investigative committee of the Rhineland-Palatinate state parliament.

From a technical point of view, mechanical sirens have a comparatively simple structure: air is passed through a rotating blade (rotor) and a stationary element with outlet openings (stator). The air flow is generated either by the rotor itself (motor siren) or by compressed air held in a tank (pneumatic siren or high-performance siren). The interruption of the current creates the characteristic howling sound with frequencies between 384 and 420 Hertz.

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