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10 Glossary of terms
analog
- A continuously varying signal or wave. Telephone transmission and/or
switching that is not digital.
ADSL - Asymmetric Digital Subscriber Line
- A group of DSL technologies that are
asymmetric, thereby reserving more downstream bandwidth (coming to the user from
the Internet) than upstream bandwidth (going from the user to the Internet). This type of
DSL is advantageous for residential users that do not need the same bandwidth speed
in both directions. Also see
DSL
ATM - ATM Asynchronous Transfer Mode
- A method of data transportation whereby
fixed-length cells are sent over a switched network. Because of its uniform handling of
services, one network can meet the needs of many broadband users, for the receipt of
voice, video, and data.
bandwidth
- A measure of the width or capacity of a communications channel. Greater
bandwidth allows communication of more information in a given period of time.
Bandwidth is generally described either in terms of analog signals in units of Hertz (Hz),
which describes the maximum number of cycles per second, or in terms of digital
signals in units of bits per second (bps).
bit -
The basic unit in data communications, represented as either a one or a zero.
When discussing digital data, a small "b" refers to bits, and a capital "B" refers to bytes.
bit rate
- the number of bits of data transmitted over a phone line per second
broadband
- Broadband is the largest size bandwidth category, meaning that there are
the most channels of data moving over a single communication medium, thus
information such as data, voice, and video can be received and sent most quickly.
dedicated connection
- A communication link that operates constantly.
dial-up connection
- A data communication link that is established when the
communication equipment (e.g. a modem) dials a phone number and negotiates a
connection with the equipment on the other end of the link.
DSL - Digital Subscriber Line
- A generic name for a family of digital lines being
provided by CLECs and local phone companies to provide Internet access to their local
subscribers.
DSLAM - Digital Subscriber Line Access Multiplexer
- A device found in telephone
company central offices that takes a number of DSL subscriber lines and concentrates
them onto a single ATM line.
DMT - Discrete Multi-Tone Modulation
- A method of transmitting data on copper
phone wires that divides the available frequency range into 256 sub-channels or tones,
and which is used for some types of DSL.
