EXFO FTB-800 Series for FTB-1 - Manual (Page 365)

Test Results
NetBlazer 355
Summary (ISDN PRI)

Performance
EFS (Error Free Second) gives the number of seconds within
which no error occurred.
ES (Errored Second) gives the number of seconds in which one or
more bits are in error.
SES (Severely Errored Second) gives the number of seconds in
which bit error ratio is ≥ 1x10
-3
.
UAS (Unavailable Second) gives the count of the seconds
corresponding to the periods of unavailable time that begins at the
onset of 10 consecutive SES events, including these 10 seconds. A
period of available time shall begin at the onset of 10 consecutive
non-SES events, including these 10 seconds.

Bit Error Rate/Count graphically displays a meter representing
either the bit error rate or the bit error count depending on the
Pass/Fail Verdict selection (refer to ISDN PRI - ISDN Settings on
page 148
)
.
When the verdict is enabled, the values under the threshold are
presented in green while the values above are in red.
When the verdict is disabled, the bit error rate is displayed in blue.