Media playback is unsupported on your device Media caption US phone users get national messageMore than 200 million US mobile phones have received a test “Presidential Alert” notification.
Some have described the test as a “Trump Alert” – but the US leader was not personally involved in the trial.
It is intended to be used to warn of major threats, including:missile attacksacts of terrorismnatural disastersThe alert produced a tone and showed a notification saying: “THIS IS A TEST of the National Wireless Emergency Alert System.
Even so, there was a last-minute effort to block the test and wider use of the Presidential Alert system.
The legal action alleged that the test could be “traumatic” to children and that the system was open to abuse.