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MX2800 M13 Multiplexer User Manual Glossary, Appendix E
61200290L1-1G E-3
craft port The data communications interface between the MX2800 and the control termi-
nal. The control terminal is used to communicate commands to the unit.
CSU Channel service unit. A device used to connect a digital phone line coming in
from the phone company to either a multiplexer, channel bank, or directly to
another device producing a digital signal; for example, a digital PBX, a PC, or
data communications device. A CSU performs certain line-conditioning and
equalization functions and responds to loopback commands sent from the central
office. A CSU also regenerates digital signals. It monitors them for problems and
provides a means of testing the digital circuit.
CTS Clear to send. A signal on the DTE interface indicating that the DCE is clear to
send data.
D
data
communications
equipment See DCE.
data service unit See DSU.
dB Decibel. A unit of measure of signal strength, usually the relation between a trans-
mitted signal and a standard signal source.
DCE Data communications equipment. 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.
DDS Digital data service. A private line digital service for transmitting data end-to-end
at speeds of 2.4, 4.8, 9.6, and 56 kbps (and, in some cases, 19.2, 38.4, or 64 kbps).
The systems can use central hub offices for obtaining test access, bridging legs of
multi-point circuits, and cross connecting equipment. DDS is offered on an inter-
LATA (local access and transport area) basis by AT&T and on an intra-LATA
basis by the Bell operating companies.
delay The amount of time by which a signal is delayed. A round-trip transmission delay
measurement helps detect possible causes of protocol timeouts.
DLCI Datalink communications identifier. A unique number assigned to a PVC
endpoint in a frame relay network. Identifies a particular PVC endpoint within a
user's access channel in a frame relay network and has local significance only to
that channel.
DS1 Digital signal Level 1. Twenty-four DS0 channels make up one DS1. (Total
bandwidth is 1.544 Mbps.)
DS3 Digital signal Level 3. Equivalent of 28 DS1s and 672 DS0s. (Total bandwidth is
44.736 Mbps.)