The TQ8105/TQ8106 are SONET/SDH transceivers that integrate multiplexing, demultiplexing, SONET/SDH framing, clock-synthesis PLL, and enhanced line and clock diagnostic functions into a single monolithic device. The TQ8106 is a pin-compatible upgrade of the TQ8105 that includes a Clock and Data Recovery (CDR) function. The TQ8105 and TQ8106 allow maximum flexibility in the selection of internal/external Clock and Data Recovery, Opto-Electronic (O/E) Module, and Reference Clock Sources.