Littelfuse 201A Three-Phase Voltage MonitorLittelfuse 201A Voltage Monitor Product Description The 201A is a 3 phase, auto ranging, dual range voltage monitor that protects 190 480 V ac, 50 60 Hz motors regardless of size. The product provides a user selectable nominal voltage setpoint and the voltage monitor automatically selects between the 200 V and 400 V range. The 201A includes advanced single LED diagnostics, where color and light patterns distinguish between faults and normal