It is at my son's day nursery in a residential street so that is very strange and the fact that it only happens on that particular day. Could it be coming from someone else's car? Last week i changed the battery in it as i thought it was that but obviously not. The stupid handbook didn't say to have another battery ready so i took the battery out at 8am and got another at lunchtime and then, of course, the thing had forgotten the frequency so had to take to the garage to get re-done!