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Chapter 7. Test Menu
61202156L2-1 TDU 120e User Manual 7-3
Network Interface Loopbacks
Network interface loopbacks affect the entire T1 data
stream. See Figure 7-2. The two types of network loop-
backs are:
Line
Loops all of the received data back toward the network.
The transmitted data is the identical line code that was
received, including any bipolar violations or framing
errors.
Payload
Similar to line loopback, except that the framing is
extracted from the received data and then regenerated
for the transmitted data.
Figure 7-2. Network Loopback Tests
Local Loopback
There are three available choices for setting the local loop-
back:
Line On
Activates the line loopback.
Payload On
Activates the payload loopback.
TDU 120e
DS1
NI CSU
Payload Loopback
Line Loopback
Secondary
Interface