It may be required for specific applications that the voltage remains within certain limits. This can be necessary to avoid performance problems or damage to the equipment. Examples of such applications include material handling, pump control, generator control, water/wastewater plants and packaging facilities. Macromatic voltage monitor relays are designed to detect these potential problems if they arise. These relays can be divided into two main groups: Over/undervoltage relays and voltage band relays.

Over/undervoltage relays are designed for applications that need to operate above or below a specific level. Depending on how the relay is used, the relay will either energize and shut down the load when a maximum level is reached, or will remain energized unless the voltage drops below a minimum level, thereby de-energizing and shutting down the load. These relays feature adjustable pick-up settings with either fixed or adjustable drop out levels. A time delay is used for the drop out, which can be fixed or adjustable. Voltage band relays are made for operations that need to stay within a certain voltage range. In this case the relay continues to be energized, unless the voltage goes above or below the set limit. Voltage band relays have adjustable over and under voltage limits, with either a fixed or adjustable time delay.

All of the different series of voltage monitor relays feature LED indicators to show the current status. Certain models check only for AC single phase voltage, while others are made for DC voltage. Most of the units feature plug-in housings, with 8 pin octal sockets, while the VWKE series has a DIN rail mount housing.