LOS（Loss Of Signal）
A LOS defect at 2048 Kbit/s,6312 Kbit/s,8448 Kbit/s,34 368 Kbit/s and 139 264 Kbit/s interfaces is detected when the incoming signal has "no transitions",i.e.when the signal level is less than or equal to a signal level of Q dB below nominal,for N consecutive pulse intervals,where 10<=N<=255.
AIS（Alarm Indication Signal）
An AIS defect at a 2048 Kbit/s interface is detected when the incoming signal has two (2)or less ZEROs in each of two consecutive double frame periods(512 bits).
The defect is cleared when each of two consecutive double frame periods contains three(3)or more ZEROs or when the Frame Alignment Signal(FAS)has been found.
