DSL

(pronounced: D-S-L or diesel)

a.k.a. "the T-1 killer"

A telecommunications line that provides a fast, permanent connection to the Internet. DSL uses the copper wiring found in almost every home and office. Special hardware attached at both ends of the line allows data to transmit at a far greater speed than standard telephone wiring can. It also provides a constant connection to the Internet, 24/7, so there is no need to dial-in to an ISP each time you want to get online (see: always-on). A DSL line is also convenient because you only need one line to carry both voice and data signals (in other words, you don't have to get a second phone line with DSL). DSL is similar to ISDN in that they both operate over existing copper telephone lines (POTS) and require short runs to a central office. (The reason why DSL is not yet available in many areas is because of the distance from a central office.) DSL provides higher speeds than ISDN, but with DSL, the connection speeds vary. Many people prefer the fixed speed of an ISDN (or a T1, for that matter). Connection speeds for DSL typically range from 1.544 Mbps to 512 Kbps downstream and around 128 Kbps upstream. There are several types of DSL, and xDSL refers to the family of digital subscriber line technologies:

* ADSL (Asymmetric DSL, where you can download faster than upload)

* CDSL (Consumer DSL)

* DSLAM (DSL Access Multiplexer)

* G.Lite (slightly slower than ADSL but much cheaper)

* HDSL (High bit-rate DSL)

* S-HDSL (Single Pair High bit-rate DSL)

* IDSL (ISDN DSL, which is DSL over an ISDN line)

* SDSL (Symmetrical DSL, where download and upload speeds are similar)

* RADSL (Rate Adaptive DSL)

* VDSL (Very High rate DSL)

* VoDSL (Voice-over DSL, which uses DSL for spoken telephone conversations).