When a motor start signal is applied to pin 3 of the the AutoMeg electric motor winding insulation monitor, a yellow LED will show that 500VDC is being applied to the motor winding. If the winding is good, the unit completes the megging operation, and the motor start signal is then connected from pin 3 to pin 4. If the winding is bad, the low meg red LED comes on, and the motor start signal will not be available to engage the motor starter. A test button is provided to verify that the unit will lock out under a low meg condition.