... trig type: Over, under, window trig, ROC trig; Harmonic, single phase P,Q, 3 phases P,Q, frequency, Positive sequence voltage ... , Negative sequence voltage, Zero sequence voltage, difference of phase angle etc. Protection relay trig type:Generator percentage differential ... simultaneously. When a host is being maintained, the other one would be on duty. FTR-01 Digital Fault Recorder series ...