david.barker@LIGO.ORG - posted 11:36, Tuesday 28 March 2017 (35140)
Timing glitch on EX comparator unit, rack work most probably the cause
both channels on the EX comparator went out of nominal (by a very large margin) at 17:04:40 UTC (10:04:40 PDT) for just one second. It looks like the reference signal went bad at this time, which is coincidence with cable pulling activities at EX. Signals recovered after the one second glitch, with no re-occurence.