Public Warning System (Singapore)

The Public Warning System (PWS) is a network of civil defense sirens installed by the Singapore Civil Defence Force on over 2,000 strategic points in Singapore to warn Singaporeans of impending dangers, air raids and atomic bomb blasts. Thus far, the siren network has only been used for occasional public awareness drills, monthly noon chimes and for commemorating the island's Total Defence (February 15).

Source: Wikipedia — Public Warning System (Singapore) (CC BY-SA 4.0)