Device Test; Loopbacks; Local Loopback; Dte Loopback - Paradyne COMSPHERE
3610 User Manual

COMSPHERE 3600 Series Data Service Units

Device Test

Device (Devic) Test is an internal self-test. If a DBM is
installed, the DBM must be in Idle mode.
If a network loopback is in effect when you initiate a
Device Test, the test will not run and Abort appears on
the second line on the front panel.
If the DSU fails the test, the:
Second line displays Fail.
Alarm (Alrm) status indicator is lit.
Device H/S message appears in the DSU's Health
and Status report for the diagnostic channel (DC in
DiagConn configuration option, Table 4-3).
The Alarm status indicator stays lit and the failure
appears in the DSU's Health and Status report until a
Device Test ends with Pass. Until then, you can proceed
but you must be aware that the DSU may not function
properly.

Loopbacks

A loopback is any test that verifies a device's integrity
by connecting the device's output in one direction to the
device's input in the other direction and then checking the
received signal for errors.
Loopback (Lpbk) provides four loopback tests:
Local Loopback (LL)
DTE Loopback (DTE)
Digital Loopback (DL)
Remote Digital Loopback (RL)
Figures 3-3 and 3-4 show the direction of each
loopback on the circuit. All loopbacks are labeled based
on the control DSU. Loopbacks do not appear with a
multipoint DSU in Remote mode. Refer to the figures as
you read about loopbacks.
3-10

Local Loopback

Local Loopback (LL) is session-disruptive; performing
the test disrupts data. In Local Loopback, the DTE may
run a test to determine if the DTE to DSU connection and
the DSU itself are functioning properly. The DSU must be
connected to the DTE, but the network connection to the
DSU is not required for this test.
Once the LL loopback test begins, the message
Command Complete appears. While the DSU is in Local
Loopback, any data transmission from the DTE is
returned as received data. An operator can send a test
pattern and verify correct reception of the test. The DSU
does not monitor this testing. LL does not appear when in
Remote mode.

DTE Loopback

DTE Loopback (DTE) loops back the data path at the
DTE/DCE interface on a per-port basis without affecting
the operation of the remaining ports. Once the DTE
loopback test begins, the message Command Complete
appears. DTE does not appear when in Remote mode.

Digital Loopback

Digital Loopback (DL) allows manual testing of the
remote end of the circuit. For example, a Digital
Loopback 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 before the DTE interface, and returns it to the
network. Once the digital loopback test begins, the
message Command Complete appears.
December 1996 3610-A2-GB46-60