Is 112 a valid emergency number in America?
When someone asks – “Is 911 a valid emergency number in Europe?” – the answer is surprisingly complicated. Technically, the answer is “no”, but in practice it should work as an emergency number on a mobile network. This nuance arises from the way emergency numbers are recognised by networks and devices.
In Europe, the number 112 is widely recognised as the emergency number, while in other parts of the world, different emergency numbers like 911, 000, 111, and 999 are used. These numbers, no matter where they are dialled, all serve the same purpose – to connect people with emergency services. You’ll find these emergency numbers displayed on emergency service vehicles, signs, life-saving equipment, and they are used extensively in legislation and technical standards governing emergency communications.
These emergency numbers are a convenient way for people to access emergency services. In fixed-line networks, they serve as the primary reference for routing emergency calls. When someone dials 112 or another local emergency number, the fixed-line network recognises it as an emergency call, prioritises it, and routes it to the most appropriate Public Safety Answering Point (PSAP) using dedicated or shared fixed line interconnects. All very straightforward: the end-user dials 112, the network identifies the emergency number and ensures the call is handled with priority, is free of charge and is routed to the most appropriate PSAP.
On mobile networks, identifying an emergency call is a bit more complex. When an end-user makes an emergency call, the mobile device doesn’t rely on the specific dialled digits (like 112, 911, or 999) to signal the call to the network. Instead, the mobile device sets the appropriate flags within the call signalling to inform the network that an emergency call is being made.
In 2G/3G, this is done using the TS.12 flags which can include the type of emergency service required as well as the type of emergency call (i.e. regular emergency call or eCall).
In 4G/5G (VoLTE and VoNR), this indication is provided in the SIP R-URI (i.e. the target address for the call) using Uniform Resource Name (URNs) defined in the 3GPP standards such as urn:service:sos (general), or urn:service:sos.police (service specific).
This enables the mobile device and network to correctly identify when the end-user makes an emergency call without relying on specific or regional emergency numbers. It also supports a variety of use cases, such as when end-users are roaming abroad, and allows for a variety of methods for initiating an emergency communication beyond dialling a specific number.
It should be noted that this approach of identifying and indicating an emergency call on mobile devices and networks currently applies only to voice calls, and in the future, it will extend to other media such as Real-Time Text (RTT) and video. However, it does not apply to Emergency SMS. There is currently no such concept as an Emergency SMS, and any SMS sent to 112 or any other emergency number is routed and prioritised like any other SMS message via the end-user’s home Short Message Service Centre (SMSC).
So, what happens when an end-user dials 112 or another emergency number from their phone dialler (as opposed to triggering an emergency communication via other means on the device)? According to 3GPP standards, the mobile device “shall identify an emergency number dialled by the end-user as a valid emergency number and initiate emergency call establishment“
Since there are many different emergency numbers in use worldwide, including service specific numbers in some jurisdictions, the mobile device must maintain a list of valid emergency numbers. This is further complicated by the fact that, although rare, numbers may change from time to time but also that the list of valid emergency numbers varies from country to country.
The ETSI/3GPP TS 122 101 Standard addresses this challenge by defining the rules and methods of maintaining the list of valid emergency numbers on a device. The list is determined by various factors, such as the subscriber’s home country ( with numbers stored on the USIM) and indeed whether or not a SIM is present in the device.
According to the standard, the active list of emergency numbers recognisable on the device includes:
- 112 & 911 (in device software)
- a) 000,08,110,999,118 & 119 active in device software if no sim present
Or
b) List of numbers on USIM provisioned by home service provider
- Other numbers downloaded on registration to the serving network.
So while 112 and 911 are always recognised and will initiate an emergency call on any mobile device, other numbers such as 000, 999, 111 etc. will depend on the end-user’s location, what has been provisioned on their SIM and, most importantly for roaming end-users, any numbers downloaded by the serving network on registration as described in point 3 above.
It is this last, and possibly overlooked, clause from the TS 122 101 standard that actually prompted this blog post and the implications of not downloading a list of regional emergency numbers to the devices of inbound roamers that may not be fully appreciated or understood.
Consider the scenario where a visitor from New Zealand is in the UK and needs emergency assistance. The end-user, roaming on a UK Mobile network, knows that the local emergency number is 999 and dials it. However, since 999 is not stored on their SIM as an emergency number, nor is it pre-configured in their device software, the call will not be treated as an emergency call on their device unless the UK mobile network downloads the local emergency numbers when the end-user connects. Instead of setting up an emergency session and addressing the message using TS.12 flags or R-URI correctly, the call will simply be placed as a regular telephone call by the device with a destination of 999.
If a device does not recognise the dialled number as an emergency number, what happens next depends on several factors including how call routing is implemented in the mobile network and the type of communications technology in use. If the serving network recognises the dialled digits as a valid local emergency number, and the call is on 2G/3G network, the mobile network may still treat it as an emergency call and route it with priority to the appropriate PSAP. In this case, while the device treats the call as a normal voice call, the network treats it as an emergency call.
If the call was made on LTE and the serving network recognises the dialled number as a local emergency number, then the serving IMS may instruct the device to perform a CS fallback for the emergency call. Alternatively, if supported, the device may perform an emergency attach/registration and set up an emergency session (emergency call). However, this process may be complicated by whether home routing (S8HR) is in use for normal voice calls, as the device might still be treating the call as a standard voice call up to that point.
Another crucial aspect of determining whether a call is recognised as an emergency call is that it must meet specific regulatory requirements. The call should be free of charge, prioritised on the network, and suppressed from appearing on the caller’s phone bill (at least in some jurisdictions). Even more importantly, when an emergency call is made from a smartphone, it must be correctly identified as such to trigger Advanced Mobile Location (AML). AML ensures that the most accurate location data is sent to the Public Safety Answering Point (PSAP), enabling responders to provide timely and effective assistance during emergencies.
So, a simple question like “does 911 work in Europe?” is significantly more complex that it would appear! In the normal course of events and for most call scenarios, everything works seamlessly and the complexity which makes it work is invisible to the end-user. When dealing with emergency communications, “most of the time” is not good enough. It needs to work seamlessly and invisibly in all possible situations.
It is recommended that particular attention is paid to the often overlooked clause 10.1.1 in TS22.101 and that providers of mobile network services ensure that where possible and appropriate they download a list of local emergency numbers to inbound roaming devices.
Ciaran Moynihan
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