New models of the AVS13 & AVS15 have a frequency detection feature. If the mains frequency strays outside an acceptable range (and thus could be damaging to your equipment) the AVS will disconnect the power and the two Red LEDs (low & high voltage) will start flashing. Once the frequency returns to normal, the AVS will reconnect automatically after the pre-set delay.
This feature is present in AVS13  & AVS15 with serial numbers equal or greater than 425940000.