The DOCSIS Rec.J.112 and [ITU-T J.122] definethe requirements for the two fundamental components that comprise a high-speed data-over-cable system: the cable modem (CM) and the cable modem termination system (CMTS). This Recommendation provides physical layer requirements for CMTS transmitters in the DOCSIS architecture. It applies to head-end components built according to the M-CMTS architecture ([ITU-T J.212] and [ITU-TJ.211]) as well as integrated CMTS systems.