谢谢你写的这么好的文章。的确，手机显示没有service provider的信号时也可以打911。因为这时候，手机会自动找到那里的最强的信号。
you can make emergency phone calls without a network signal. When your phone loses signal from your provider's network, it automatically connects to the strongest network that it can find in order to allow for emergency calls to go through. However, since it is not your network, you cannot make other calls.
https://survivalfreedom.com/do-emergency-calls-work-without-signal/
