Verilink AS56/56Plus (896-502588-001) Product Manual - Manual (Page 71)

ESF Statistics Definitions (T1/FT1 Mode)
AS56 and AS56 Plus User Manual 5-5
ESF Statistics Definitions (T1/FT1 Mode)
Errored Second (ES). Any occurrence of a Loss of Frame or a CRC6
error in a one-second period.
Failed Signal State (FSS). Ten consecutive Errored Seconds.
Failed Second (F S ) Each second during the occurrence of a Failed
Signal State.
Severely Errored Second (SES). Three hundred twenty (320) or more
CRC6 errors in a one-second period.
Bursty Errored Second (BES ) More than one but less than 320 CRC6
errors in a one-second period.
Loss of Frame Count (LOFC ) Quantity of times that a Yellow Alarm
has occurred.