US Patent 7135996 Multispeed communications device

A physical layer device for a network device comprises a converter module that selectively converts an n-bit input to an m-bit output based on first and second mapping functions. A scrambler module selectively scrambles the m-bit output. An encoding module receives the m-bit output from the scrambler module and selectively maps the m-bit output based on the first mapping function to three level output signals and the m-bit output based on the second mapping function to four level output signals.