The framer interfaces to a 2.048 Mbit/s backplane and provides selectable rate data link access with optional HDLC controllers for Sa bits and channel 16. The LIU interfaces the framer functions to the PCM 30 transformer-isolated four wire line. The MT9075B meets or supports the latest ITU-T Recommendations including G.703, G.704, G.706, G.732, G.775, G.796, G.823 for PCM 30, and I.431 for ISDN primary rate. It also meets or supports ETSI ETS 300 011, ETS 300 166 and ETS 300 233 as well as BS 6450.