EXFO FTB-800 Series for FTB-1 - Manual (Page 262)

Test Results
252 FTB-700G/800 Series
Alarms/Errors
DS3
Alarms

AIS (Alarm Indication Signal)
RX: The M-frame contains zeros (0) for C-bits, ones (1) for X-bits,
1010... repeating sequence with a one (1) immediately following any of
the control bit positions for the information bits.

Idle (DS3 Idle)
RX: Subframe 3 of the M-frame contains zeros (0) for the three C-bits,
ones (1) for X-bits, 1100... repeating sequence with the first two bits
following each control bit set to 11 for the information bits.

OOF (Out-OF-Frame)
RX: Four consecutive frame bit errors are detected.

RDI (Remote Defect Indicator)
RX: Both X-bits of the M-Frame are set to “0”.
Errors

CP-Bit (Control-Bit)
RX: The three C-bits reserved to control bit stuffing are different of
“111” and “000”.

F-Bit (Framing-Bit)
RX: The frame alignment pattern received is different of “1001”.

P-Bit (Parity-Bit)
RX: The P-Bits does not match the parity of all the information bits
following the first X-Bit of the previous DS3 frame.

FEBE (Far-End Block Error)
RX: The three FEBE bits reserved for framing or parity error detection
contain the “000” pattern.