Technical data

www.westermo.com Theoretical and general applications 81
Higher speeds
xDSL
xDSL is a collective name for a family of technologies where digital modems are used
on a standard telephone or fixed line. The type of digital system sent over the line is
described by the letter that replaces the x. Examples of designations are: ADSL, SDSL,
SHDSL and VDSL. These technologies suit different applications. For example, VDSL
can reach transfer rates up to 52 Mbit yet only over about 300 m (984 ft), SHDSL
supports a maximum of 2.3 Mbit up to 3 km (1.86 mi) and 192 kbit/s up to approxi-
mately 6 km (3.72 mi).
HDSL
HDSL, High speed Digital Subscriber Line. Duplex communication at speeds of
2.3 Mbit/s in each direction.
ADSL
ADSL, Asymmetric Digital Subscriber Line. Duplex communication up to speeds of
8 Mbit/s to the subscriber (downstream) and 640 kbit/s from the subscriber
(upstream). The communication simultaneously uses the same line as standard tele-
phony traffic. The user installs a filter on the first jack in order to improve voice quality
on the line; this filter is called a splitter and is usually supplied with the ADSL product.
ADSL is a popular option for home users, as the technology offers a higher down-
stream transfer rate than upstream. Download times are usually more important to
the home user as upload is normally limited to e-mails.
VDSL
VDSL, Very high speed Digital Subscriber Line. Duplex communication at speeds up
to 52 Mbit/s to the subscriber (downstream) and 6.4 Mbit/s from the subscriber
(upstream). The communication uses 1 pair.
VDSL is the fastest technology available to transfer data over the standard tele-
phone network. It is an alternative to ADSL when high transfer rates are required for
applications such as:
… Streaming video.
… Video conferencing.
… Combination of video and data over the same connection.
… High data access requirements.
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