The Swiss authorities online
What sirens are used to alert the population of dangers in Switzerland? There are two types of alarm signals: the general alert signal and the water alert signal.
Stationary sirens are sounded with a regularly ascending and descending tone, lasting one minute and repeated once in the following five minutes. Behaviour to adopt when the general alert is raised:
People living downhill from dams are alerted by special sirens and the "water alert" alarm signal. The water alert signal consists of low continuous twenty-second tones at ten-second intervals. Behaviour to adopt when the water alert is sounded: