The DS3/EC1 3-Port Tributary Module, Enhanced (DS3M3T) maps and demaps three DS3s or EC1s into the STS-1s of an STS-3 link between the DS3M3T module and the Optical Multiplexer (OMM) Module. The DS3M3T module interfaces to three transmit and three receive DS3/EC1 facilities via the BNC connectors on the back panel of the OPTI-6100 chassis.