You can track down the location of a mobile to a vague area which appears as a big green circle on the map -- this isn't precise enough to send an ambulance to, although it does help if someone gives a road name but doesn't know which area they are in. (Also, the LAS's beloved postcode areas aren't written on the map, so it helps if we know them off by heart) For Vodaphone and Orange mobiles it's done automatically but for other mobiles we have to get the information from the operator at the telephone exchange, who will come on the line after the caller hangs up.