資料來源 : WordNet®

digital subscriber line
     n : a generic name for digital lines that are provided by
         telephone companies to their local subscribers and that
         carry data at high speeds [syn: {DSL}]

資料來源 : Free On-Line Dictionary of Computing

Digital Subscriber Line
     
         (DSL, or Digital Subscriber Loop,
        xDSL - see below) A family of {digital} {telecommunications}
        {protocols} designed to allow high speed data communication
        over the existing {copper} telephone lines between end-users
        and telephone companies.
     
        When two conventional {modems} are connected through the
        telephone system ({PSTN}), it treats the communication the
        same as voice conversations.  This has the advantage that
        there is no investment required from the telephone company
        (telco) but the disadvantage is that the {bandwidth} available
        for the communication is the same as that available for voice
        conversations, usually 64 kb/s ({DS0}) at most.  The
        {twisted-pair} copper cables into individual homes or offices
        can usually carry significantly more than 64 kb/s but the
        telco needs to handle the signal as digital rather than
        analog.
     
        There are many implementation of the basic scheme, differing
        in the communication {protocol} used and providing varying
        {service levels}.  The throughput of the communication can be
        anything from about 128 kb/s to over 8 Mb/s, the communication
        can be either symmetric or asymmetric (i.e. the available
        bandwidth may or may not be the same {upstream} and
        {downstream}).  Equipment prices and service fees also vary
        considerably.
     
        The first technology based on DSL was {ISDN}, although ISDN is
        not often recognised as such nowadays.  Since then a large
        number of other protocols have been developed, collectively
        referred to as xDSL, including {HDSL}, {SDSL}, {ADSL}, and
        {VDSL}.  As yet none of these have reached very wide
        deployment but wider deployment is expected for 1998-1999.
     
        {(http://www.cyberventure.com/~cedpa/databus-issues/v38n1/xdsl.html)}.
     
        {2Wire DSL provider lookup (http://www.2Wire.com/)}.
     
        ["Data Cooks, But Will Vendors Get Burned?", "Supercomm
        Spotlight On ADSL" & "Lucent Sells Paradine", Wilson & Carol,
        Inter@ctive Week Vol. 3 #13, p1 & 6, June 24 1996].
     
        (2001-04-30)