Fire Fence UK

I believe a device sends an interrupt when it reaches a certain threshold before it goes into alarm, it sends an interrupt to stop the loop polling all the devices so it can put data on the loop, if there is an interrupt followed by corrupt data it sounds like a faulty device. Corrupt data that jumps around between different devices can be caused by corrosion on the cable itself, and if there is water in the device, like someone mentioned above, be careful because it can blow the loop card on an advanced, and from experience that sometimes does not put a fault on the panel at all.