EXFO FTB-8510B Guia Del Usuario página 1042

PDH Tabs
E4/140M RX
Alarm Analysis
Note: Only AIS is available when the framing is set to Unframed.
LOF (Loss Of Frame): The LOF alarm indicates that four consecutive
incorrect frame alignment signals have been received.
RAI (Remote Alarm Indication): The RAI alarm is declared when bit 13
of a framed E4 is set to "1".
AIS (Alarm Indication Signal): The AIS alarm is declared when an
unframed all-ones signal is received.
Spare Bits
Note: Spare Bits are not available when Framing is set to Unframed.
G.751 Bit 14, 15, 16 are reserved for national use. Possible values are 000
to 111.
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