This attribute indicates whether a Physical AIS alarm state is
entered. A Physical AIS alarm state is entered when a Physical AIS
defect is observed and accumulated for a period of 2.5 seconds +/-
0.5 seconds. A Physical AIS defect is declared when the incoming
signal has two or less zeros in a sequence of 3,156 bits (0.5 ms). If
the physical AIS defects are intermittently occurring, the physical
AIS defect accumulator is decremented at a rate of 1/10 of the
incrementing rate (alarm integration ratio of 1/10), with all
measurements based on a 200 ms polling cycle.
A Physical AIS alarm is cleared when the Physical AIS defect is
absent for a period of 10 seconds +/- 0.5 seconds. The port goes
into an operationalState of disabled until the AIS alarm condition is
cleared. While the port is in the Physical AIS alarm state, the node
also transmits the far-end RAI defect indicator on the out-going JT2
line.