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Comment by bombcar | Hacker News Reader

Does it still show bars in SOS mode? Or is SOS just “I dunno can’t see no cell towers but maybe it’d work?”

I wonder if the MVNOs that piggyback on AT&T are showing down also. If not, it’s some AT&T service authorization system that exploded.

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SOS mode means it can see towers of other providers you aren’t authenticated with, but no signal to authenticated cell towers

Emergency only means 911 calls through whatever provider is available.

Mine says SOS Only, shows no bars.

On the latest iPhones, SOS mode is the emergency fallback to satellite service. It's really meant to be used in situations where you're well outside of any sort of service area but you have a clear, unobstructed view of the sky.

Your iPhone will instruct you on where to point and help you track an emergency satellite that is manned by live humans who will take your emergency request and relay it to the proper people.

More specific info here: https://support.apple.com/en-us/104992

Won't that only activate if it can't see or communicate with any towers at all?

I’m pretty sure that “SOS only” can also mean the phone seeing networks it can’t register with but which it could make an emergency call on if required. This predates satellite SOS.

SOS means it has cell service and you can call 911.

If there is no cell service then it's SOS with a little picture of a satellite next to it.

Except SFFD is reporting that (some) AT&T customers are unable to call 911.

SOS mode typically means that your phone is connected to a carrier other than one you have a contract with.

I wonder if some devices bungle their failover. The exact failure mode state of AT&Ts network might cause some devices to hang onto AT&T’s RF.

Not sure why the downvotes but this is cool I wasn’t aware of this technology, thanks!

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