This technical report (TR) describes the physical layer of the Rate Adaptive Asymmetrical Digital Subscriber Line (RADSL) interface to metallic loops. The report should be of interest and benefit to system implementers, network providers, service providers and customers using Internet, voice, data and video services. This technical report describes the interfacing of RADSL transmission units at the remote end (ATU-R) and at the central office end (ATU-C) and the transport capability of both units. A single twisted pair of telephone wires is used to connect the ATU-C to the ATU-R. RADSL systems operate over a variety of twisted wire pairs and in the presence of typical impairments (e.g., crosstalk and noise).