The 102A is a 3-ph, auto-ranging, dual-range voltage monitor that protects 190 to 600 VAC, 50/60 Hz motors regardless of size. The product provides a user selectable nominal voltage set point and the voltage monitor automatically selects between the 200 V and 400 V range. A unique microcontroller-based voltage and phase-sensing circuit constantly monitors the 3-ph voltages to detect harmful power line conditions. When a harmful condition is detected, the output relay is deactivated after a specified trip delay. The output relay reactivates after power line conditions return to acceptable levels. The model 102 A includes advanced single led diagnostics. Five different light patterns distinguish between faults and normal conditions.