Come Monday next week, almost every phone in Australia is expected to go off with a siren sound during a synchronised nationwide test of the AusAlert warning system.
The ACT Emergency Services Agency is urging Australians to prepare for the first-of-its-kind "critical alert" scheduled for 2pm on July 27.
This mass broadcast will be different from previous "priority alert" tests done in Canberra (June 10) and Queanbeyan (June 21), in that it will override a device's silent and Do Not Disturb settings.
Those who do not wish to receive the test alert or believe it may compromise their safety should switch off their devices or set them to "aeroplane mode" before 2pm on July 27, for at least one hour, according to advice from the National Emergency Management Agency (NEMA).
The 10-second siren, similar to a fire or car alarm, will be sent to compatible phones (with the latest software update), some smart watches and tablets.
Older devices may get a test alert with the heading "Presidential Alert" or "Extreme Threat Alert".
NEMA said whether people receive the alert or not, nothing needs to be done and it is "just a test".
Reasons some people may not receive the test include an incompatible or outdated device, a loss of cell network, maintenance work or an outage at your nearest mobile tower, or if the device is switched off or on aeroplane mode.
The national test follows a widespread Telstra network outage on July 8, attributed to a software glitch, which affected mobile connectivity in various jurisdictions.
Following field testing on the day of the outage, chief officer of ACT Fire and Rescue Peter Cleary confirmed the territory had not been affected by the problem and there were no confirmed reports of issues with triple zero connectivity.
Although the ACT was not affected by the Telstra outage, Commissioner Wayne Phillips said the July 27 warning test and all future emergency broadcasts relied on working cell towers.
The commissioner said NEMA had various checks in place to ensure the test would go ahead as planned.
"The Telstra incident was unfortunate and not great for us as emergency services," Mr Phillips said.
"Though we weren't affected here in the ACT directly, at the end of the day, we have an expectation that telecommunications companies have a system where people can ring triple zero because triple zero is our primary knowledge of when people need us."
Following the national test on July 27, the AusAlert system will be rolled out on October 1 ahead of the 2026-2027 bushfire season.
ACT ESA director of collaboration, Leighton Bush, said emergency services would reserve the new warning system for local and national disasters such as bushfires, and not for public alerts such as fire ban notices.
"The best way of looking at is it's one additional tool that we can reach the community with, and it's important to note AusAlert will be used in very serious situations where there's a threat to life and/or property," Mr Bush said.
