AP234 monitors 3 Phases only, AP235 monitors 3 Phases and NeutralProtection of phase failure & incorrect phase sequenceDIN rail mount.Fail-to-safe design.Combined overvoltage and undervoltage monitoring with phase failure or sequence detectionMonitoring of own supply voltage (3 phase).Separately adjustable setpoints: over-voltage, (5 to 20%) and, under-voltage (-5 to -20%).Separately adjustable response times on trip & recovery (0.1 to 10 seconds).Fixed hysteresis: 2%.Adjustable start-up delay for disabling latching 0.1 to 10 sec.Selectable latching (ie manual or auto reset).LED indication of Relay ON and fault type.2 x 10A SPDT relay outputs (1 for Overvoltage, 1 for Undervoltage)