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Glossary
Glossary-33550-A2-GB20-10 February 1995
Device Test
(Devic)
A test that uses an internal test pattern generator built into the DSU to verify that
the DSU (or DBM) is working properly. The generator sends a test message to the
device’s transmitter, where it is looped back to the device’s receiver. The incoming
message is then checked for errors, which are reported as Pass if there are no errors,
and Fail if an error is found.
Diagnostic Control Panel
(DCP)
The face of the DSU that continuously provides status information about the DSU’s
operation and allows an operator to manage its operation. This is a generic term
used for both the standalone and carrier-mounted DSU models. See shared
diagnostic control panel (SDCP) for the Model 3551.
Dial Backup Unit
(DBU)
An external digital or analog device, attached to the Model 3550 or 3551 DSU, that
is used for dial restoral (also see DBM).
dial string A sequence of up to 36 characters that the DBM can send into the dial network to
establish a call to a remote backup device. It consists of a telephone number and
may include other information, such as a callback directory pointer.
Digital Loopback
(DL)
A test used for manual testing of the remote end of a circuit. For example, a DL
may be required to complete an external bit error rate test (BERT) from the remote
DSU. The local DSU receives test data, loops it back to the transmitter, and returns
it to the network.
Digital Test
(DT)
A test used to test two DSUs and the circuit between them. Both DSUs must be
connected to the network before this test is run.
DIP switch Dual In-line Package switch.
DMI Data Mode Idle. Refers to a sequence of 1s transmitted or received on the DDS
network. When the General (Gen) branch configuration option RTS Cntrl is set to
FrcOn, the DSU will transmit DMI whenever RTS is Off. Data Mode Idle operation
is recommended for point-to-point applications.
DOC Canadian Department of Communication.
drop A tributary site.
DSR The state of the Data Set Ready lead.
DTE Loopback
(DTE)
A test that allows you to test each port independently. This test loops the data path
at the DTE interface.
DTR The state of the Data Terminal Ready lead.
EIA Electronic Industries Association. This organization provides standards for the data
communications industry to ensure uniformity of interface between DTEs and
DCEs.
elastic store A configuration option that is enabled in a tributary DSU to compensate for phase
differences between DDS network timing and the received timing of an analog
(dial) modem or DSU. It uses a buffer storage area of 16 bits.
End-to-End Test
(EE)
A test used to analyze a control and tributary DSU, and the circuit between them in
both directions independently. each DSU sends the same pattern and checks the
incoming pattern for errors.