Sirens still form the core element in the overall system for alerting and warning the population, even though the authorities can now disseminate messages via the internet or app. Especially at night, the “wake-up function” of the sirens remains central. The alerting with sirens is guaranteed at all times, even in the event of a power blackout lasting several days. In the event of an incident, sirens can reliably alert, provided they function properly. That is why the annual siren test takes place throughout Switzerland today.

In Switzerland, about 5000 stationary sirens are operated for the general alarm. Around 600 of these can be used simultaneously for the water alarm. The Federal Office for Civil Protection FOCP, in cooperation with the cantons, communes and operators of dams, ensures that the sirens are kept up to date and operational.

The general alarm is sounded at 1.30 p.m.: a regular ascending and descending wail lasting one minute. If necessary, the siren test can be continued until 14:00. Parallel to the first sounding of the general alarm, all cantons will also disseminate a test alarm message via the Alertswiss app. From 2.15 p.m. until 3 p.m. at the latest, the water alarm signal will be tested in the near zones below dams. It consists of twelve low continuous tones of 20 seconds each at intervals of 10 seconds. During the siren test, the population does not have to take any measures.

But what to do in an emergency?

If the population is at risk and the alert readiness is established, the responsible authorities order the alert and the dissemination of the behavioural instructions. In case of high urgency, the National Emergency Operations Centre (NEOC) orders the alert on its own authority. If the wail of the “General Alarm” sounds outside an announced siren test, this means that a danger to the population is possible. In this case, the population is requested to listen to the radio or to inform themselves via the Alertswiss app, to follow the instructions of the authorities and to inform their neighbours. If the “water alarm” sounds with twelve low continuous tones, the population must leave the endangered area immediately, go to the assembly points described in the information sheets and follow the instructions of the authorities.

Why sirens still play an important role today?

Sirens are used as an effective warning system all over the world, in densely populated areas with special warning needs due to dams, chemical plants, harbours, power plants, defence installations and in areas at risk of tsunami or volcanic eruptions.

Switzerland has a dense network of 5,000 stationary sirens and 2,200 mobile sirens. Mobile sirens are used in remote areas and are ideal for informing the population and disseminating behavioural instructions by means of voice announcements. This practically complete coverage, coupled with radio messages, now forms the backbone of the system for alerting and informing the population in the event of disasters and emergencies, such as landslides, water pollution or industrial accidents. Today, the authorities also have the possibility of alerting and informing the population via monitors, the Internet and smartphones (push messages via the Alertswiss app). These communication channels represent a very important function for people with a hearing impairment.

However, the stationary and mobile sirens remain a central and important element of alerting and warning the population, for example in the event of a breakdown of commercial networks or the internet. In many cases, the “wake-up function” of the sirens also remains central, because smartphones and mobile phones do not remain switched on overnight everywhere.