Thread by @frazer_HX

Myth busting #emergencyalerts
1. They are a broadcast so one-way, you cannot reply to a message.
2. They’re broadcast for a defined period e.g 1 minute, up to, but not exceeding 24 hours. They’re not a one-shot like SMS.

3. They're not subject to network congestion. Millions of handsets can receive the message within 8-10 seconds of sending the alert.
4. It won’t disable your phone or lock you out. You will have to click OK or ‘x’ to dismiss the message. There's no way to track this interaction.

5. More than 20 countries use this technology, the first operational service was in the Netherlands (2012).
6. The technology is already built into the handsets. Travelling to countries already using cell broadcast/emergency alerts enables this facility on your phone.

7. The first test in the UK was in September 2013 on the 2G EE network - this image.
8. The service is built around international standards which largely define how the service operates.

9. Overseas mobiles roaming on UK networks will also receive Emergency Alerts (if compatible and on 4/5G)
10. Cell Broadcast can support alternative languages

11. Test Alerts (excluding the one on the 23rd) are 'opt-in' and do not override a users volume settings. Many android devices allow options to opt-in to test alerts but Apple devices in the UK do not allow this facility.

12. In 2018, the USA tested their Emergency Alert service known as Wireless Emergency Alerts sending more than 200 million handsets a message. This was sent on the highest level channel (4370) for which it is not possible to opt out: bbc.co.uk/news/technolog…

13. Whilst the 'standard' Emergency Alert tone is largely universal, Japan selected a different alert sound for the ETWS (Earthquake and Tsunami Warning System)

https://twitter.com/RatZillaS/status/1370377307915968515?s=20

14. An annual national test is commonplace in countries with Emergency Alert technology. On 8 June 2020 the national test in the Netherlands reached 94% of the population of 12 years and older in <10 seconds, some 14.2 million people.

15. In addition to the reserved tone for Emergency Alerts there is also a distinctive vibrate pattern and some handsets, depending on the manufacturer, will readout the message to aid accessibility.

In this video ⬆️one phone (2nd from the left) is on a call via Voice Over LTE (VOLTE). This handset received the Emergency Alert after the call was ended as it was still within the broadcast period.

16. The maximum length of a cell broadcast message is 1395 characters which 15 'pages'. The use of special characters (e.g. unicode) uses more space and reduces this limit. However, a long message is undesirable as there is a need to convey the Alert and actions rapidly.

17. 1/2 There are three main components to a cell-broadcast based warning service. 1. The alerting or messaging platform known as the CBE (Cell Broadcast Entity) where the 'what' and 'where' are defined. 2. The CBC or Cell Broadcast Centre which is software.

2/2 For the UK, the CBC is located in each of the mobile networks. This translates the 'where' to which mast needs to broadcast the alert and for how long. 3. The mobile handsets pick up the broadcast & alert the recipient should they be in the area at the time of the broadcast.

18. There are two main types of emergency alert technologies. Location based SMS (LBSMS) and Cell Broadcast. The UK chose to implement Cell Broadcast. This table compares the two.

19. Emergency Alerts on Sunday 23 April in the UK will mostly arrive at 3pm however phones do ‘jump around’ latching onto different networks e.g 2G and 3G. This is a video from the tests in March 2021:

@LucyGoBag &@mtthwhgn you asked me about when emergency alerts might arrive. Here’s a video during the testing in March 2021.