Not every Australian heard the nationwide AusAlert test when it went off on Monday afternoon, even though phones across the country blasted the warning siren at full volume. That's because the test only reached compatible devices able to receive the new cell broadcast warning. The AusAlert test sounded on compatible devices at 2pm AEST on Monday and ran for about 10 seconds. Picture: Department of Home Affairs / Handout / NewsWireThe nationwide test marked the first major public demonstration of AusAlert, the new emergency warning system set to be rolled out from October. For those whose devices were compatible, the test went off loudly even if phones were on silent or set to do not disturb.