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Diagnostics
4-21
DTE Digital Loopback
The DTE Digital Loopback function provides a data path for a test
signal that is originated and checked at the remote site. The Digital
Loopback, illustrated in Figure 4-19, loops receive data back through
the transmit portion of the DTE interface.
You can command the loopback only by means of the terminal
interface DeskTop T1 Diagnostics Selection screen.
To initiate the loopback from the terminal interface DeskTop T1
Diagnostics Selection screen, select [C] Start DTE Digital
Loopback.
DeskTop T1 DSU
Network
DTE
Interface
Interface
Network
Figure 4-19 Data Path for DTE Digital Loopback
DTE Remote Digital Loopback
The data path for the DTE Remote Digital Loopback is illustrated in
Figure 4-20. You can command the loopback by means of the terminal
interface screen, the front panel switches, or a signal on the DTE
interface.
When you initiate a DTE Remote Digital Loopback the DSU
transmits a PN127 code to the remote unit. The remote unit responds
by establishing a digital loopback toward the local DSU. After the loop
is established, connect test equipment to the local DSU DTE interface.
Generate a test message. The test equipment should receive back the
same message it transmits. A problem exists if it does not. DTE
Remote Digital Loopback tests the local DSU, the line, and most of the
the remote DSU.
GDC 048R154-000
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