The following changes were made to the T1/T2 PLC control system:

- De-glitching system investigated and Tony discovered that it was programmed incorrectly:  the de-glitch time was observed only when a PV changed from bad state to good, not the opposite (meaning there was actually no de-glitching in place since system start-up in 2016!).  This was reversed and the following de-glitch times were programmed:  100ms for trip thresholds except 300ms for flow meter trips, and 2s de-glitch on all warning thresholds.  The new system was tested with the PLC in simulation mode and seems to be working correctly.  This should eliminate or significantly reduce nuisance warnings and trips from the system.

- PLC system code was modified so that the target version displays '???' when no target is installed instead of defaulting to 'MK1'  (all target positions registered as 'plugged' with no target installed, so there was no danger to the system, but this was still confusing to operators)