Asymmetric digital subscriber line ( ADSL ) & Digital subscriber line (DSL )

Asymmetric digital subscriber line (ADSL) is a
type of digital subscriber line (DSL)
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 (the last mile),
Note :- 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 (Asymmetric Digital Subscriber Line)
uses an ordinary phone line to deliver a
high-speed Internet connection. It does this
by converting the data from your computer
into high-frequency signals. These high-
frequency signals can travel along a
telephone cable at the same time as a voice
call because the ADSL and voice signals use
different frequency ranges
Digital subscriber line (DSL; originally digital
subscriber loop) is a family of technologies
that provide internet access by transmitting
digital data using a local telephone network
which uses the Public switched telephone
network. In telecommunications marketing,
the term DSL is widely understood to mean
asymmetric digital subscriber line (ADSL), the
most commonly installed DSL technology.
DSL service is delivered simultaneously with
wired telephone service on the same
telephone line. This is possible because DSL
uses higher frequency bands for data. On the
customer premises, a DSL filter on each non-
DSL outlet blocks any high frequency
interference, to enable simultaneous use of
the voice and DSL services.
The bit rate of consumer DSL services
typically ranges from 256 kbit/s to over 100
Mbit/s in the direction to the customer
(downstream), depending on DSL technology,
line conditions, and service-level
implementation. Bit rates of 1 Gbit/s have
been reached in trials. In ADSL, the data
throughput in the upstream direction, (the
direction to the service provider) is lower,
hence the designation of asymmetric service.
Note:- In symmetric digital subscriber line
(SDSL) services, the downstream and
upstream data rates are equal.
Researchers at Bell Labs have reached
broadband speeds of 10Gbps, while
delivering 1Gbit/s symmetrical ultra-
broadband access services using traditional
copper telephone lines. These speeds can be
achieved with existing telephone lines and
can be used to deliver broadband where
fiber optic cables can't be installed to the
premise.
A 2007 book described DSL as "the most
globally prolific broadband access
technology, yet it is only available to around
60–75 percent of the population in many
developed countries." A 2012 survey found
that "DSL continues to be the dominant
technology for broadband access" with 364.1
million subscribers worldwide