What is an asymetric digital subscriber line?

Answer 1

Short for asymmetricdigitalsubscriberline, ADSL is a type ofDSL broadband communications technology used for connecting to the Internet. ADSL allows more data to be sent over existing copper telephone lines (POTS), when compared to traditional modem lines. A special filter, called a micro filter, is installed on a subscriber's telephone line to allow both ADSL and regular voice (telephone) services to be used at the same time. ADSL requires a special ADSL modem and subscribers must be in close geographical locations to the provider's central office to receive ADSL service. Typically this distance is within a radius of 2 to 2.5 miles. ADSL supports data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate).

Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call.

· A splitter, or DSL filter, allows a single telephone connection to be used for both ADSL service and voice calls at the same time.

· ADSL can generally only be distributed over short distances from the telephone exchange, typically less than 4 kilometres (2 mi), but has been known to exceed 8 kilometres (5 mi) if the originally laid wire gauge allows for further distribution.

At the telephone exchange the line generally terminates at a digital subscriber line access multiplexer(DSLAM) where another frequency splitter separates the voice band signal for the conventional phone network. Data carried by the ADSL are typically routed over the telephone company's data network and eventually reach a conventional internet Protocol network.

ADSL standards

Version

Standard name

Common name

Downstream rate

Upstream rate

Approved in

ADSL

ANSI T1.413-1998 Issue 2

ADSL

8.0 Mbit/s

1.0 Mbit/s

1998

ADSL

ITU G.992.1

ADSL (G.DMT)

12.0 Mbit/s

1.3 Mbit/s

1999-07

ADSL

ITU G.992.1 Annex A

ADSL over POTS

12.0 Mbit/s

1.3 Mbit/s

2001

ADSL

ITU G.992.1 Annex B

ADSL over ISDN

12.0 Mbit/s

1.8 Mbit/s

2005

ADSL

ITU G.992.2

ADSL Lite (G.Lite)

1.5 Mbit/s

0.5 Mbit/s

1999-07

ADSL2

ITU G.992.3

ADSL2

12.0 Mbit/s

1.3 Mbit/s

2002-07

ADSL2

ITU G.992.3 Annex J

ADSL2

12.0 Mbit/s

3.5 Mbit/s

ADSL2

ITU G.992.3 Annex L

RE-ADSL2

5.0 Mbit/s

0.8 Mbit/s

ADSL2

ITU G.992.4

splitterless ADSL2

1.5 Mbit/s

0.5 Mbit/s

2002-07

ADSL2+

ITU G.992.5

ADSL2+

24.0 Mbit/s

1.3 Mbit/s

2003-05

ADSL2+

ITU G.992.5 Annex M

ADSL2+M

24.0 Mbit/s

3.3 Mbit/s

2008

ADSL uses standard telephone lines to transmit upstream and downstream data on a digital frequency, which sets these datastreams apart from the analog signals telephones and fax machines use. Because the ADSL signal is operating on a different frequency, the telephone can be used normally, even when Surfing the Web with ADSL service. The only requirement will probably be inexpensive DSL filters on each phone or fax line, to remove any "white noise" on the line that might be generated from ADSL service.