Diagnostics
4-11
GDC 048R154-000
Figure 4-6
Data Path for Network Payload Loopback
Network Line Loopback
The Network Line Loopback function provides a data path for a test
signal that is originated and checked at the remote site. The Line
Loopback, illustrated in Figure 4-7, loops back the entire T1 line. The
loopback occurs at a point within the DSU at which the data has passed
through only a minimum of the network interface circuitry.
You can command the loopback by means of either the terminal
interface screen or the front panel switches:
•
On the terminal interface Diagnostic Selection screen this function
is selection
[4] Start Network Line Loopback
.
•
Figure 4-8 shows the switches and indicators that are involved
when you command a Network Line Loopback from the front
panel. The DSU also establishes a DTE Local Loopback when
DSU hardware configuration switch S10-4, LL Switch Mode, is
set to Bilateral (Off).
The line loopback can also be initiated by a loop code transmitted to
the local DSU from the remote site. Local DSU optioning determines
whether it can be commanded into the loopback by the remote. For the
DSU to accept the remote line loop code, set switches S14-5 & -6 to 5
Off, 6 On.
Network
DTE
Interface
Network
Interface
DeskTop T1 DSU
DTE or
other
signal
source
Network Payload Loopback can be commanded from
front panel by running DTE Local Loopback with DSU
optioned for bilateral loopbacks (switch S10-4).
Network Payload Loopback
