A DSL technology from the ITU (G.991.2) that provides symmetric transmission from 192 Kbps to 2.3 Mbps using a single copper pair, depending on distance from the central office (from 20,000 ft. to 6,500 ft.). With two wire pairs, 384 Kbps to 4.6 Mbps can be achieved. G.shdsl incorporates rate adaptability from SDSL and the TC PAM modulation technique from HDSL-2, hence the "sh" in the name. It was developed to provide interoperability with the alphabet soup of digital transmission technologies, including SDSL, HDSL, ISDL, ISDN, T1 and E1. G.shdsl's handshaking protocol (G.hs) can negotiate T1, E1, ISDN, ATM or IP framing depending on line conditions. See
DSL.