6.8 Glossary
ANSI
Acronym for American National Standards Institute; devises and proposes
recommendations for international communications standards.
asynchronous
A method of data transmission which allows characters, that are preceded by a start bit
and are followed by a stop bit, to be sent at irregular intervals.
bandwidth
A range within a band of frequencies, or an amount of data, that can be transmitted in a
preset amount of time. The bandwidth determines the rate at which information can be
sent.
bridge
A connectivity advice that operates at the OSI Data Link Layer; it filters and forwards
packets by physical addresses. See also router.
CD
Acronym for Carrier Detect; it is a signal generated by a modem or DSU/CSU and
indicates the presence of a carrier signal on a communications link.
CSU
Acronym for Channel Service Unit; a device used to connect a digital phone line, from
the phone company, to a multiplexer, channel bank or directly to another device
producing a digital signal. A CSU performs line-conditioning and equalization functions,
responds to loop-back commands sent from the central office, regenerates digital
signals and monitors them for problems and provides a way of testing a digital circuit.
CLASS features
Acronym for Custom Local Area Signaling Services; consists of number-translation
services, such as call-forwarding and caller identification.
clock
An oscillator-generated signal that provides a timing reference and generates periodic
signals for the timing of certain functions in a transmission link.
CPE
Acronym for Customer Premise Equipment; it includes all telecommunications terminal
equipment located on the customer premises, including telephone sets, PBXs, data
terminals and customer-owned coin-operated telephones.
CTS
Acronym for Clear To Send; a signal on the DTE interface indicating that the DCE is
clear to send data.
dB
An abbreviation for decibel, a logarithmic unit used to measure sound level or signal
strength.
DCE
Acronym for Data Communications Equipment; a device that provides all the functions
required for connection to telephone company lines and for converting signals between
telephone lines and DTE. Also see DTE.
DSR
Acronym for Data Set Ready; a signal on the EIA-232 interface that indicates a
connection and readiness to start handshaking control signals for communication to
begin.
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