Withthe incidental standard of G.992.1 (G.dmt) whichisone of ADSL standard, specification in order to do SDSL of top and bottom symmetrical speedwiththe same standard as a base. Transmission speed the rising descent together the highest 3.2Mbps. As for SDSL which is actualized byAnnexH also "SSDSL (Synchronized Symmetric DSL)" is called,changesthe descent with rising in the same way as ISDN to brief and does communication.It is strong inthe interference from the ISDN circuitof the indiansystem same as Annex C, in the indiancountry the possibility of being adopted as SDSL standard is high. In the country offer of the service to which ACCA networks adopt Annex H has been begun.