The UOA series offers protection to single phase equipment that is required to operate above a certain voltage minimum. Operation: With operating voltage applied above the preset Pick-Up voltage, the internal relay will energize. When the voltage falls below the preset Drop-Out voltage for a period longer than the release delay, the output relay will de energize. When line conditions return above the preset Pick-Up voltage, the UOA series automatically resets and the internal relay energizes. The Hysteresis in each unit provides a differential between the Pick-Up and Drop-Out trip points.