There will be a reason!
Is the mains power still on? If it isn't, and the panel back-up battery has failed, a bell box will sound from it's own internal battery.
If it's not the power, look for "tamper" faults or panic buttons having been pressed - but either of these should trigger the panel sounder as well.
My guess is the weather has got into connections in the bellbox - especially if it's an old bellbox.
Inglishg, December 2010
