sonetMediumLineCoding 1.3.6.1.2.1.10.39.1.1.1.1.4

This variable describes the line coding for this interface. The B3ZS and CMI are used for electrical SONET/SDH signals (STS-1 and STS-3). The Non-Return to Zero (NRZ) and the Return to Zero are used for optical SONET/SDH signals.