
337Operations and Maintenance in SDH
11.3.1.1 Anomaly
An anomaly is degradation in circuit performance, which does not cause an
interruption of service. These are small deviations of the achieved circuit
characteristics from the desired characteristics. The anomalies are indicated
by bit interleaved parity (BIP), remote error indication (REI), etc.
11.3.1.2 Defect
A defect is the state when the circuit is not able to perform its designated func-
tion. A defect is detected when the persistent anomalies build up to exceed a
maximum time limit. When a defect is detected, it calls for immediate atten-
tion of maintenance engineers to diagnose