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Glossary
GL-4
February 2001 3160-A2-GB21-90
device
A mechanical, electrical, or electronic unit with a special purpose.
digital signal
A signal composed of only two discrete values, representing the binary digits 0 and 1.
diskette
A thin, flexible magnetic disk enclose in a protective jacket.
DL branch
Download branch of the DSU/CSU menu tree.
DLB
DTE Loopback. Loopback mode that loops the information received on the DTE T1 network
interface back to the network as close to the network interface as possible.
download
A process that transfers device firmware and software from a locally-attached PC to a
device, or allows the duplication of firmware and software from a local device to a remote
device.
downstream device
A device that is connected farther from the host computer.
drop/insert
An interconnection point for terminals, multiplexers, and transmission facilities. Individual
channels may be inserted into the aggregate stream or dropped out to accommodate
specific applications.
DSR
Data Set Ready. A signal from the modem to the DTE that indicates the modem is turned
ON and connected to the DTE.
DSU
Data Service Unit. Data communications equipment that provides timing, signal
regeneration, and an interface to data terminal equipment. A subrate DSU/CSU is normally
referred to as a DSU.
DSX-1
Digital Signal Cross Connect level 1. An interconnection point for terminals, multiplexers
and transmission facilities.
DS0
Digital Signal Level 0. A 64 kbps standard signal or channel.
DS0 channel
allocation
Assigning specific DS0 channels in the DSU/CSU to specific interfaces (network, DTE
Drop/Insert, etc.).
DS1
Digital Signal level 1. A signal of 1.544 Mbps in North America.
DS1/E1 MIB
Defines objects for managing the network and DTE Drop/Insert interfaces on the DSU/CSU.
DTE
Data Terminal Equipment. The equipment, such as a computer or terminal, that provides
data in the form of digital signals for transmission.
DTE Drop/Insert
interface
The Drop/Insert (DSX-1) interface on the rear panel of the DSU/CSU.
DTLB
Data Terminal Loopback. Loopback mode that loops the data for a particular synchronous
data port back to the port just before it is combined with the rest of the T1 data stream.
DTMF
Dual-Tone Multi-Frequency. A signaling method using two voice frequencies to designate
the tones used for touch-tone dialing, as distinguished from pulse dialing.
DTR
Data Terminal Ready. A signal from the DTE to the modem, sent via Pin 20 of the
EIA-232 interface (V.24 circuit 108/1, /2), that indicates the DTE is turned ON and
connected to the modem.
E1
A wideband digital interface operating at 2.048 Mbps, defined by ITU recommendations
G.703 and G.704. It is used primarily outside North America.
EDL
Embedded Data Link. The 8 kbps in-band performance channel that provides 4 kbps of
user bandwidth for the support of an SNMP management link.
EER
Excessive Error Rate. An error rate that is greater than the threshold that has been
configured in the device.