Example: [Collected on the Internet, 2005]
Important Number you should note
If you travel to work on the tube please note the following information: If your mobile phone has no signal (so even if you were in a tunnel) if you dial 112 it diverts to a satellite signal and puts you through to the 999 call centre.
ALL phone companies have signed up and as it is a satellite service it also gives them a trace to you if you don't know where you are.
Origins: The spate of bombings and attempted bombings in the London Underground in July 2005 have left many commuters and those who care about them feeling anxious and at risk. One way we as humans struggle to overcome the discomfiting sensations of helplessness and disquiet is to search for something, anything, that restores so much as the smallest part of our usual sense of control over events. We are used to believing we are in charge of our own lives, so we cast about desparately for that which will return things to what we see as their proper state of our directing, or at least influencing, our outcomes.
The seemingly helpful heads up about connecting to emergency services via using an alternate phone number when deep in the subway system is part of that search, in that it gives the appearance of being information those traveling in risky circumstances could put to use. However, it's all a chimera: while the need to feel safe once again (or at least capable of being quickly rescued) is real, the intelligence about an alternate phone number that will always work is not.
The global mobile emergency number, 112, is "special" in the sense that (unlike other local emergency numbers, such as 999) it will use any tower your mobile phone can contact to complete the call, regardless of whether or not your phone is authorized to relay signals through that tower. However, the 112 number has no special properties that enable callers to use it in areas where all cellular signals are blocked (or otherwise unavailable). Mobile phones do not work in many parts of the London Underground, and satellite signals cannot reach there either. While dialing 112 or 999 will put you through to emergency services in Britain when your mobile has signal, such calls will not go through when your unit does not. Many sections of the London Underground are far too deep for satellite signal to penetrate; in those areas, calls to neither 112 nor 999 will connect.
More succinctly, when there's not enough signal with which to make a call to 999, there will not be enough to make one to 112.
London Transport and mobile firms are warning people about the
"It will not divert to a satellite signal."
"Even with a satellite mobile phone (which very few people have), you would need to have a clear line-of-sight to the satellite. You would have to be outside, not in a building or a tube tunnel."
Barbara "i.c.e. capades" Mikkelson
Last updated: 28 July 2005
BBC News.   "Fake Tube Safety E-Mail Spreads." 28 July 2005.