Recently, two federal states in Germany tested their EU-Alerting System implementation. Based on the cell broadcast mechanism that exists in all 3GPP network technologies since the the days of GSM, it makes phones emit a loud warning signal and shows a message on the screen. It definitely does wake one up, as I already discovered in 2016 in the Netherlands when they had one of their regular test runs of their system.
So while one is inclined to confirm and thus silence the alert as quickly as possible, I wondered if it would eventually stop on its own. Why? Well, every now and then I do have a phone lying around at home while I’m not there. It would be pretty unfair to the neighbors if it kept alerting indefinitely. So I collected a number of different phones and didn’t touch them once the alerts got going. And indeed, after 5 minutes, they all dropped silent simultaneously. Good for the neighbors!