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In countries where it's possible to make calls to emergency numbers (911/999, etc) from an iPhone that has no SIM inserted, how is it possible for the emergency services to track a device - would it be possible for them to call you back, even if the phone didn't show a caller ID due to one not being present?

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  1. No - when you don’t have service, they can’t call you back.
  2. Yes - you can call out and the only location data will be which cell tower data is provided to EMS / Emergency Services - not the GPS or location of the device doing the calling.

In more details:

A SIM doesn't determine if you can connect to a cell tower, the phone's antenna determines it. The SIM only has your phone number and carrier info so you can make emergency calls without it. In the case you've mentioned, the call will go thru but the phone number and location will not be sent. 1

So in this context, whether you have a SIM inserted or not is irrelevant. Calls to emergency centers are treated the same with or without a SIM.

Emergency calls are routed to a Public Safety Access Point (PSAP) for all carriers. Location data is sent with accuracy between 50 and 150 meters depending on if it's using cell tower triangulation or mobile-based location (GPS chip). 2


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    I don't have a source for this, but it's worth noting that the network would know your IMEI number for the call, so from the point of view of "tracing" the call (if it was malicious or a hoax) the authorities would have somewhere to start from – Matthew Steeples Dec 8 '19 at 23:25
  • Good edit, thanks @bmike. – fsb Dec 9 '19 at 0:17
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    The SIM card does not in general hold the phone number. Primarily it holds the ICCID and the IMSI. See en.wikipedia.org/wiki/SIM_card#Data for more details. The translation to phone number is done by the carrier's own system. This is why you can change your phone number without changing SIM card. I believe the actual answer to the question is that that presentation CLI for calls made without a SIM is a matter for the network receiving the call. I would guess it normally appears as "Unavailable". – abligh Dec 9 '19 at 6:18
  • (...) the only location data will be which cell tower data is provided to EMS / Emergency Services - not the GPS or location of the device doing the calling. Why is it so? The GPS is not related to the SIM so why not using this possibly more accurate position? – WoJ Dec 9 '19 at 11:26
  • @WoJ Not all mobile devices have a GPS so you can't rely on that info. – fsb Dec 9 '19 at 15:15

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