W-OP2 is a digital electronic instrument designed for AC voltage monitoring and protection in single phase system. Used in application such as under and over voltage. The relay can be used to protect motors, compressors or water pumps with a delay circuit to prevent sudden operation after the measured voltage returns to normal. When the measured voltage moves outside the set-point limit, the relay will de-energize (N/C) and count the selected time delay(0-5 Sec.). When the input voltage is raised and reduced past the set-point plus the differential (hysteresis Value), the relay will remain “Delay on”. After the selected time delay (0-15 Min.), the relay will automatically reset to energize (N/O), the display showed “On”.