Pretty much every electronic device in Canada with a link to the outside world is about to ring out in a terrifying cacophony as Alert Ready prepares to conduct a nationwide emergency test alert today.

But before you panic and call up that weird doomsday prepper you know on Facebook, take a deep breath and be assured that this auditory barrage is only a test meant to keep you and everyone else safe.

REMINDER: There will be an @AlertReady test at 12:55pm today across Ontario. These alerts will be broadcast to mobile devices, television, and radio. Learn more: https://t.co/HzpABUuTSd #AlertReady@OntarioWarnings @ONgov pic.twitter.com/TheKzwWa8H

— Ministry of the Solicitor General (@ONsafety) November 17, 2021

It may only be a test, but the Canada-wide blaring of the National Public Alerting System is sure to freak out some unaware of today's test, when televisions, radios, and mobile devices send out jarring siren-like tones in unison, simulating what Canadians would hear in the event of a large-scale emergency.

The tests will be conducted at different times across the provinces and territories, with Ontario's alert to invade your ear canals at 12:55 p.m. today.

Today's the day of the #AlertReadyTest, Canada!

If you are in a participating province or territory, you will receive a test alert on your compatible wireless devices, radio, and TV at the times below 👇 pic.twitter.com/iVAhVRGXGS

— Alert Ready (@AlertReady) November 17, 2021

You'll likely be jolted out of your work trance or lunch break by an alert tone known as the Canadian Alert Attention Signal, along with a reassuring message reminding everyone that this piercing warning is only a test.

Alert Ready tests the National Public Alerting System twice a year, though it's hard to get used to these ominous warnings even with such regularity. Canadians can't opt out of the tests or alerts, but you can minimize the damage to your eardrums this afternoon by turning off or muting devices.

"Conducting regular tests allows us to better educate Canadians about the Alert Ready system and it provides an opportunity to validate that the system is working end to end," says Martin Bélanger, Director of Public Alerting at Pelmorex Corp., the company responsible for the Alert Ready system's technical infrastructure.

If you're uncertain about your device's compatibility (and actually want your phone to scream at you today), you can always contact your wireless provider or visit alertready.ca. Alert Ready also has a Twitter page where you can track ongoing updates on the latest test.