I have an old Visonic Powermax alarm that's driving me mad, every time the battery needs changing on one of the wireless PIRs I then spend the next 2 hours trying to get rid of the "System Jammed" error message. This usually involves random combinations of changing the bettery again, shouting, swearing, changing other batteries, power cycling the CPU, swearing at the CPU, changing more batteries and eventually it starts working.

It's always triggered by changing the batteries in one of the remote units, not any particular one, but that's always the start of it.

Currently 2 hours into this round of trying to fix the problem.