DSL


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DSL

(communications)

DSL

(communications)

DSL

(language)

DSL

(language)

DSL

(1) (Domain-Specific Language) See special-purpose language.

(2) (Digital Subscriber Line) A technology that increases the digital capacity of ordinary telephone lines (the local loops) into the home or office for Internet and TV service. Depending on the DSL version, speed is based on the distance between the customer and telco central office or telephone junction box.

DSL provides "always-on" operation. At the central office, DSL traffic is aggregated in a unit called the DSL Access Multiplexor (DSLAM) and forwarded to the appropriate ISP or data network. DSL arrived in the late 1990s with more version alphabet soup than most any other new transmission technology. See PPPoA and PPPoE.


Asymmetric: Fast Down - Slow Up



ADSL - (Asymmetric DSL)
ADSL shares ordinary telephone lines by using higher frequencies than human speech. To eliminate interference, the first DSL deployments required a technician from the phone company to install a splitter that divided the line into separate DSL and phone lines. Subsequent splitterless versions (known as G.Lite, Universal ADSL and ADSL Lite) eliminated the support visit but require the user to plug filters into every phone outlet.

ADSL is available in two modulation schemes: Discrete Multitone (DMT) or Carrierless Amplitude Phase (CAP). See CDSL, G.shdsl, ATU-C and ATU-R.


ADSL Transmission
The higher frequencies of DSL have to be filtered out for regular telephones, answering and fax machines.







The Filter
Low-pass DSL filters split the line between phone and DSL modem. When DSL is installed, every telephone and answering machine must plug into the filter.








RADSL (Rate Adaptive DSL)
RADSL is a version of ADSL that adjusts speeds based on signal quality. Many ADSL technologies are actually RADSL.


VDSL/VHDSL (Very High Bit Rate DSL)
VDSL is used as the final drop from a fiber optic junction point to nearby customers. VDSL lets an apartment or office complex obtain high-bandwidth services using their existing copper wires without having to replace them with optical fibers. Like ADSL, VDSL can share the line with the telephone.

Whereas VDSL achieves 50 Mbps transmission speed at 1,000 feet, VDSL2 extended the length of the path to 3,300 feet and delivers 100 Mbps at 1,600 feet. See Gfast.


Symmetric - Same Speed Both Ways



HDSL (High Bit Rate DSL)
HDSL provides T1 transmission over copper wires without the additional provisioning required for setting up T1 circuits, such as bridged tap removal and repeater installation. HDSL requires two cable pairs up to 12,000 feet, while HDSL-2 requires only one cable pair and spans 18,000 feet. HDSL does not allow line sharing with analog phones.


SDSL (Symmetric DSL)
SDSL is an HDSL variation that is rate adaptive, uses one cable pair and is offered in speeds from 144 Kbps to 1.5 Mbps. Like HDSL, SDSL does not share lines with analog phones.


IDSL (ISDN DSL)
IDSL is a slightly faster basic BRI ISDN service. It uses the 16 Kbps "D" channel for data rather than call setup to achieve 144 Kbps instead of 128 Kbps. It also offers the longest distance of 26,000 feet. Unlike standard ISDN, IDSL does not support analog phones, and signals are not switched through the telephone network. Since IDSL uses the same 2B1Q line coding as ISDN, ISDN customers can use existing BRI terminal adapters and routers. See ISDN.


References in periodicals archive ?
Riding high on the profound use of video streaming, broadcast video services, DSL tester service providers are eying to bolster performance stability and operational efficiency.
For example, BellSouth offers FastAccess HomeNetworking Plus, a service that enables customers to share FastAccess DSL with up to four computers over a wireless network.
The strip splitting is completed by physically splitting the DSL into two or three separate skip lists.
The most essential application for DSL is high-speed Internet access.
Relying on precedent from an Oregon Supreme Court case in 1979, the petitioner argued that DSL must make an affirmative finding that the project would serve a public need before it may issue a permit.
DSL Software, an ISO 9001/2000 and CMM Level 5 certified company, is a 2,000+ strong unit focused on Investment Banking Technology and Operations.
Companies operating in the global DSL and G-fast chips market will benefit from this technology greatly.
In terms of the number of DSL subscribers, Japan was second with 10.27 million, followed by the United States with 9.11 million and South Korea with 6.43 million.
By using a low-power spectral density in-signal transmission, Huawei's Giga DSL prototype reduces radiation interference and power consumption.
Swedish telecomms solutions provider Ericsson said on Tuesday (4 November) that it had signed an agreement with the Russian telecomms company SATEL Company Group to supply Russia's first Ethernet DSL Access network.
DSL Marries SBC's DSL service to Yahoo's customized content and features, such as a free Web page and financial tracking.
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