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I worked on wireless infrastructure software about 20 years ago - some of the stuff that counted as 3G. The phone does not "dial" the emergency phone number.
by OrangeMango 7y ago
I worked on wireless infrastructure software about 20 years ago - some of the stuff that counted as 3G.
The phone does not "dial" the emergency phone number. It tells the tower that it needs to initiate an emergency call. At that point, the infrastructure bypasses all authentication/authorization/billing checks and connects to what the infrastructure knows as the local emergency service. It's a standard voice connection, made over the same channels as a normal call, with one exception: if there is no available channel, it drops a normal call to make room.
In this case, some of the potential situations could be occurring:
1) There is still backbone (backhaul) availability, but perhaps the connection to the subscriber database has been severed. No normal calls can be authenticated, but emergency calls don't get authenticated and are thus not impacted.
2) Everything is working normally but at drastically reduced capacity. With the normal load of emergency calls, there is simply not enough capacity for normal calls. If this is the case, it is possible that not all emergency calls are being completed - the emergency operations center would not have the ability to know if this was the case.
- hapidjus 7y agoWould it be possible to flood the mast with emergency calls to drop all other calls?
- numpad0 7y agoYeah and that’s a way to get some sentences. IIRC cell towers generate temporary phone numbers and session IDs so a person in distress may use even sketchy phones without SIM or legit serial numbers to make a call for help.
- kevin_nisbet 7y agoThis is correct. But IIRC (it's been awhile), the device also sends it's programmed hardware id to the network, which in theory would allow the device to be tracked to some extent after flooding the network. The emergency call itself doesn't require a sim or active account (atleast in Canada). I do have a recollection of watching a network outage ticket once years ago, where someone dropped their phone in a puddle which apparently caused the device to put out interference which some techs managed to track down. There is also this case from Florida: https://www.techtimes.com/articles/161146/20160526/florida-man-gets-48k-fine-from-fcc-for-using-cell-phone-jammer.htm https://www.techtimes.com/articles/161146/20160526/florida-m...
- jvm_ 7y agoSo, if I go to California with my NY cell phone and dial 911... I get the emergency services of the tower I connected to? Was always curious who I'd get when I'm not near home.
- RL_Quine 7y agoYes. You can always make an emergency call, without service from your actual provided, and without a SIM card.
- jvm_ 7y agoBut who answers? California 911 - because that's where I'm physically located. or NY 911 because that's where my phone is from?
- munk-a 7y agoCalifornia 911 - the fact that your phone is from NY is not only ignored but never referenced in the process - this isn't a great analogy but you could think of your cellphone as having a built-in walkie-talkie that it uses for emergency calls. All the mechanisms for making a normal phone call are discarded when you dial an emergency number. So, nowhere on the state diagram of making an emergency phone call, is the box that says "Tell the user to dial 1 before a long distance number" - they are two separate systems.
- anticensor 7y agoRouting code + emergency number does work in some countries as a normally billed emergency call. Some countries silently redirect emergency call into billing infrastructure too.
- deleted 7y ago[deleted]
- Keverw 7y agoBased on your location, but I know that there's stories about location not being accurate, remember seeing a report that some Pizza app and ride sharing apps can be more accurate. Someone told me on their cell phone 911 went to state's highway patrol instead of the city police, not sure if true or not since haven't had to dial 911 from a cell phone. However if you have VOIP, not all VOIP providers support 911 but the ones that do want you to set a 911 address on your account itself, phone number or for a specific Analog telephone adapter - ATA Device from my understanding. I know our cable company provides phone service and the old modem had a sticker warning about VOIP and E911, not sure if the new one does or not since haven't looked at it too much.
- bonyt 7y agoIs this still true in the days of VoLTE and packet switching for LTE cell networks?
- gregmac 7y agoAre you saying the phone sends some type of flag "emergency call" rather than the actual dialed digits? The interesting implication of this is if I'm travelling in a country with another emergency number, I can "dial" the one from my home country (which is really just the sequence to initiate "emergency call") and be connected to local services. I can see some references to 911 working on the UK phone system where the emergency number is 999 -- but this seems to be a separate mechanism (the phone company explicitly routes this number, as well as the EU emergency number 112).
- goodcanadian 7y agoYes, that is my understanding. Dialling 911, 999, 112, or 000 on your mobile phone will all work regardless of where you are.
- OrangeMango 7y agoYes, that is exactly what happened back then: it was in the ratified spec. I can't believe that newer systems would be any different.
- xxpor 7y agoI've explicitly dialed 112 (when I actually had a reason to call 911) just to see if it worked. It worked perfectly fine.