DIGITAL MONITORING RELAY FOR 3-PHASE MAINS VOLTAGE FOR IO-LINK AC 50 TO 60 HZ 3X 160 TO 690V LINE PHASE SEQUENCE, PHASE FAILURE, PHASE ASYMMETRY UNDER- AND OVERVOLTAGE HYSTERESIS 1-20V NETWORK STABILITY TIME TRIGGER DELAY TIME 1 CHANGEOVER, SPRING BALANCER TECHNOLOGY