Harmony Control. This voltage monitoring relay monitors single-phase supplies 20-80 VAC/DC (50-60 Hz) for exceedance or undershoot of an adjustable limit value. A relay changer is available for reporting, which can be loaded up to 5 A. An error memory can be selected and enables the error to be reported until reset even in the event of short-term faults. The limit value, the switching hysteresis and a switch-off delay can be set. The settings are made using control elements 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 (nominal voltage range 24-48 VAC/DC, 50-60 Hz). The width is 17.5 mm and it is mounted on a top-hat rail.