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The Alarm Indication Signal (AIS), also known as the blue alarm, is a continuous stream of binary 1s transmitted in all timeslots of the T1 digital signal. The AIS is an unframed signal and results in an out-of-frame (OOF) condition. If Blueworx Voice Response receives the AIS for more than two seconds, a Remote Alarm Indication (RAI), also known as a yellow alarm, is transmitted to the terminating equipment (CSU, PABX, channel bank and so on). AIS is normally sent to keep a T1 digital line open while making the line unusable for traffic.