On October 3 at 2:18 p.m. EDT, cell phones across America will ring twice with an unusually loud tone, letting their owners know President Donald Trump has just texted them about an emergency.

The Emergency Alert System (EAS) is a public warning system run by FEMA, the U.S. disaster response agency, that lets the president alert the public in times of national emergency via a network of wireless providers, cable systems and radio and television broadcasters. This will be the fourth test of the system, following two under President Barack Obama and one last year under Trump.

The idea of the sitting president being able to directly text nearly every cell phone in the nation has inspired mockery on social media, with many online commentators imagining that the alert system will become an outlet for the messages Trump usually disseminates via Twitter.

That scenario, however, is unlikely to happen. First, using the system for any purpose other than notifying the public of imminent dangers like natural disasters or terrorist attacks is illegal.

“Except to the extent necessary for testing the public alert and warning system, the public alert and warning system shall not be used to transmit a message that does not relate to a natural disaster, act of terrorism, or other man-made disaster or threat to public safety,” says the Integrated Public Alert and Warning System Modernization Act of 2015.

Second, the process of activating the EAS involves plugging a large amount of very specific data into a long and complicated code.

The text message that cell phone users will receive next month is not likely to be written by the president either. The message will be several lines long, containing specific information about the alert system itself and multiple reassurances that it is only a test.