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Tests
T1 Payload and Line Loops
A T1 Payload Loop commands the DSU to loop the received T1 signal back to the remote after the
network framer circuit. The remote site is responsible for test pattern generation and checking.
Payload loopback tests everything on the network side up to and including the unit. It re-generates
framing and corrects bipolar violations.
A T1 Line Loop commands the DSU to loop the received T1 signal back to the remote at the
network interface. The remote site is responsible for test pattern generation and checking.
These tests can be initiated from the terminal interface or by SNMP control.
Remote
Device
Figure 4-5
T1 Network Interface Loop
A T1 NI (Network Interface) Loop causes the DSU to send a loopback command to the Smart Jack
(or equivalent network terminating device) that connects it to the T1 network. The jack responds by
looping the T1 signal back to the DSU. This test can be initiated from the terminal interface or by
SNMP control. Test pattern generation and checking must be performed by equipment connected
to the local DSU, either at the front panel jacks or at the DTE interface.
DTE
or
Test Device
Figure 4-6
4-6
Cascade Interface
Analog
Receiver
Framer
TX
Driver
DTE
Interface
Payload Loopback
T1 Payload and Line Loops
SC 553 DSU
DTE
Inter-
Framer
face
T1 Network Interface Loop
SpectraComm 553 Fractional T1 DSU
Installation and Operation Manual
SC 553 DSU
Line Loopback
Network Interface
TX
Driver
Framer
Analog
Receiver
Smart
Jack
TX
Driver
Analog
Receiver
T1 Tests
Network
Network
076R155-000
Issue 7
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