Font A+ A-

Civil Defence Shelter

Public Warning System


The Public Warning System (PWS) is a network of sirens that the SCDF has placed at strategic points throughout the island. The purpose of this system is to warn the public of imminent threats that could endanger lives and property.



The Public Warning System (PWS) Various Signals & Meanings

The Public Warning System will be used to warn of attacks from the air, land or sea, as well as natural and other man-made disasters. The table below shows what the various signals mean. It would be a good idea to memorise them.


Signals How It Sounds* Situation What It Means
"Alarm" Signal


Click for audio

(wav, 307.09KB)

This is sounded when an air raid or shelling is imminent. Move to a shelter immediately.
"All Clear" Signal


Click for audio

(wav, 331.59KB)

This is sounded when the threat is over. You can leave the shelter.
"Important Message" Signal


Click for audio

(wav, 307.08KB)

This is sounded to alert the population to an important broadcast on the radio. Tune in immediately to any local FM radio station or TV channel.

*NOTE: To hear the audio recording of the various Public Warning Signals, click on the image under "How it Sounds" in table above.



Annual Island-wide PWS Sounding


Annually, the SCDF will be sounding the “Important Message” signal through the island-wide network of PWS sirens on 15 February at 6.20 pm and 15 September at 12.05 pm. Do not be alarmed by the minute-long sounding exercise.


The signal will also sound for all smartphones that have the SGSecure Mobile App downloaded, and are not on silent or vibration mode. The signal will stop once the message is acknowledged or cease after 20 seconds. This will be followed by a brief text on the PWS sounding.


When you hear the “Important Message” signal, tune in immediately to any local radio station for a brief message on the PWS.


The annual sounding and radio broadcast message are part of the SCDF’s continuous efforts to familiarise the public with the PWS signals and to raise awareness on how the public should react upon hearing the signal.



Find out more information on Civil Defence Shelter.


Contact us for more public education materials on the Public Warning System.

back to top

Last updated on 4th Oct 2017