Harmony Control. This voltage monitoring relay monitors a measuring circuit for exceedance or undershoot of the set limit value (15-500 VAC/DC). You can choose between exceedance, undershoot and overshoot and undershoot in window mode. An error memory is optionally available, which holds the error message until a reset. Two relay changeover switches are available for reporting, which can be loaded up to 8 A. The mode of operation, the limit value, the switching hysteresis and a drop-out delay can be set. The settings are made using control elements on the front, which can be protected against changes under a transparent cover. An illuminated scale arrow makes it very easy to see the setting of the potentiometers, even from a distance. The diagnostic switch on the front enables the output relays to be switched off to test the entire application. When the transparent cover is closed, the diagnostic switch is automatically reset. The wide-voltage power supply (24-240 VAC/DC) enables universal use. Two LEDs show the status. The width is 22.5 mm and it is mounted on a top hat rail. The cable connection is made via screw terminals.