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Tests
Remote
Device
Figure 4-12
T1 Local Test
The Local Test loopback condition isolates the DSU from the network by connecting the transmit
logic circuits to the receive logic circuits. The loopback provides a path through the DSU for an
externally generated test signal.
During Local Test:
•
The DTE interface remains active.
•
The DSU loops transmit data from the DTE back as receive data.
•
Either the DTE or a bit error rate tester (BERT) connected either to the DTE interface or the
front panel Line jacks can supply and check a test signal.
•
The device supplying the test signal is responsible for error detection and reporting.
The Local Test function can be commanded by means of the terminal interface, by SNMP control,
or by means of front panel switches.
Note
Tests cannot be performed by means of front panel switches when the front panel has been inhibited by
an SNMP controller or by the terminal interface. Front panel enabled is the default condition.
076R155-000
Issue 7
Cascade Interface
Analog
Receiver
Framer
TX
Driver
DTE
Interface
T1 Local Test with Self Test, Cascade Interface
SpectraComm 553 Fractional T1 DSU
Installation and Operation Manual
SC 553 DSU
TPC
Network Interface
TX
Driver
Framer
TPG
Analog
Receiver
TPG = Test Pattern Generator
TPC = Test Pattern Checker
T1 Tests
4-11
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