It sounds like the cable has been damaged. The Alarm System will not indicate a Tamper when the lid is removed because a PA fault is still present and needs to be reset (the wire needs to be repaired and hence the circuit will be cleared and the system will reset).
1 Find the damaged cable and repair.
2 Ensure that the PA buttons have been reset, usually with a key.
3 Replace the control panel lid.
4 Press Reset
5 The system should give you a double beep and be ready to be used again.
Liam
August 2007