SINGAPORE - Do not be alarmed when you hear a siren on Friday evening (Feb 15).

That sound is the "Important Message" signal which the Singapore Civil Defence Force (SCDF) will play islandwide to commemorate Total Defence Day.

The SCDF said in a statement on Wednesday that the siren will be sounded for one minute using the network of public warning system (PWS) sirens across the country.

It will be played at 6.20pm - marking the time when the British surrendered to Japanese forces on the same day more than 70 years ago, in 1942.

"The PWS sounding serves to give due significance and remembrance to this historical moment," the SCDF said.

On Feb 15, 1942, British Lieutenant General Arthur E. Percival surrendered Singapore after a week of intense fighting.

He surrendered to Japanese forces under the command of Lieutenant General Tomoyuki Yamashita at the Ford Factory in Bukit Timah.

At noon on Wednesday, Defence Minister Ng Eng Hen posted a picture of the "surrender conference room" where the British general and other senior officials made the decision to surrender.

"Great hardship followed for those living in Singapore then," Dr Ng noted.

Dr Ng said that the picture can be found at Fort Canning, and said he recorded this year's message for Total Defence Day there.

"(I) felt extra poignancy given recent events and this year's bicentennial," he added.

After hearing the "Important Message" signal on Friday, you can tune in to any local radio station or free-to-air television channel for a brief message on the PWS.

Mobile phones that have the SGSecure app downloaded and are not on silent or vibration mode will also sound the signal.

The signal will stop after 20 seconds or once the message is acknowledged. This will be followed by a brief text on the PWS sounding.

Visit the SCDF's website at www.scdf.gov.sg to know more about the PWS signals.