Hi Weeze
A tamper fault is a 24hr circuit that monitors (as the name suggests) anyone tampering with the detectors/ bell/control unit.
Unfortunately, the concept is fairly basic and only gives one indication for any one of the tamper circuits, this means to find out what is causing it you really need a multimeter and the ability to use it, though if its going externally as well as indoors there is a high possibility the fault is with the sounder, or the cable to it
If you press prog and enter your code this may stop it
Alarm systems need regular servicing to stop this sort of thing happening