Harmony Control. This voltage monitoring relay monitors three-phase supplies (220-480 VAC) for phase failure, as well as the mains voltage for exceeding or falling below an adjustable limit value (-20--2%/+2-+20% depending on the voltage). Two relay changeover switches are available for reporting, which can handle up to 5 A. One relay is available for each over- and under-value reporting. In the event of a phase failure, both relays switch. The two limit values and a switch-off delay are adjustable. The settings are made using controls on the front, which can be protected against changes under a transparent cover. Two LEDs show the status. The device is powered by the measuring voltage. The width is 17.5 mm and it is mounted on a top-hat rail.