FEBE

Far End Block Error - FEBE errors are mostly seen on DS3 circuits, however they are known to be present on other types (SONET/T1s etc).Each terminating device (router or otherwise) monitors the incoming signal for CP-bit path errors. If an error is detected on the incoming DS3, the terminating elements transmit a FEBE bit on the outgoing direction of the DS3. Network monitoring equipment located anywhere along the path then measures these FEBEs in each direction to gauge the quality of the circuit while in service.
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n. Phoebe, goddess of the moon (Greek Mythology); one of the moons of Saturn