EXFO FTB-800 Series for FTB-1 - Manual (Page 322)

Test Results
312 FTB-700G/800 Series
Performance Monitoring
For M.2100 ISM: Gives the count of the seconds within which
anomalies (frame bit errors, CRC block errors, etc.) are  Y or at least
one defect occurred. Y depends on the type of DSn/PDH signal as
described in the following table.

BBE (Background Block Error) (G.826, G.828, G.829, and M.2101):
Gives the count of Errored Block not occurring as part of a SES.
Signal SES Threshold
DS1 (SF) 8 frame bit errors (Near-End)
DS1 (ESF) 320 CRC-6 block errors (Near-End) 320 CRC-6 block errors
(Far-End, if FDL enabled)
E1 (Framed without CRC-4) 28 frame bit errors (Near-End)
E1 (Framed with CRC-4)
805 CRC-4 block errors (Near-End) 805 E-bit errors
(Far-End)
DS3 (M13) 2444 P-bit errors (Near-End) or 5 F-bit errors (Near-End)
DS3 (C-bit Parity) 2444 P-bit errors (Near-End) or 5 F-bit errors
(Near-End) 2444 FEBE errors (Far-End)
E2 (Framed) 41 frame bit errors (Near-End)
E3 (Framed) 52 frame bit errors (Near-End)
E4 (Framed) 69 frame bit errors (Near-End)