This trap indicates that the specified e1 channel is receiving an Alarm Indication Signal (AIS) from the far-end equipment. The Alarm Indication Signal failure is declared when an AIS defect is detected at the input and the AIS defect still exists after the Loss Of Frame failure (which is caused by the unframed nature of the 'all-ones' signal) is declared. The AIS failure is cleared when the Loss Of Frame failure is cleared.