Ask HN: How Do Emergency Alerts on Phone Work?

I’m now in UAE which is affected by war. Woke up to an alert yesterday night and was wondering how this works. Any good write ups on its technical side?

5 points | by rishikeshs 19 hours ago

2 comments

david_allison 9 hours ago
Might as well start with the source code[0] and dig deeper:
* CMAS https://en.wikipedia.org/wiki/Wireless_Emergency_Alerts
* ETWS Earthquake and Tsunami Warning System
[0] https://cs.android.com/android/platform/superproject/main/+/...

WarOnPrivacy 19 hours ago

     Delivery Method: WEA utilizes a one-to-many alert delivery service
     called SMS-Cell Broadcast (SMS-CB), rather than SMS Point-to-Point
     (SMS-PP). 

     SMS-Cell Broadcast (SMS-CB) is a method for sending short text messages
     simultaneously to multiple mobile phone users within a specific geographic
     area. It is a feature within the GSM (Global System for Mobile
     Communications) standard and is sometimes referred to as Cell Broadcast.

ref: https://www.etsi.org/deliver/etsi_ts/144000_144099/144012/07...

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rishikeshs 19 hours ago
Is this a universal standard? How does it override my phone’s volume!
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- Jeremy1026 13 hours ago
  Typically there are laws dictating how emergency alerts have to be delivered, and your phone's OS will follow that. So "it" doesn't override your phone's volume. Your phone's OS will override it's volume when it receives the alert.