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Loopback Tests
A number of different loop-backs can be invoked locally from
the front panel, by T-WATCH Pro commands, or remotely by
using special in-band codes (AT&T D4 network loop-up and
loop-down codes). Additionally, the loop-backs can be
remotely controlled by means of out-of-band commands by the
T1 ESF FDL or from T-WATCH Pro by a modem connection.
Network Interface Loopbacks
Network interface loop-backs affect the entire T1 data stream.
See Figure 7-2. There are two types of network loop-backs, line
loop-back and payload loop-back.
Line loop-back
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 loop-back
Similar to line loop-back, except that the framing is extracted
from the received data and then regenerated for the transmit-
ted data.
NI CSU
DS1
61202052L1-1
TSU 100
Payload Loopback
Line Loopback
Figure 7-2. Network Loopback Tests
TSU 100 User Manual
Chapter 7. Test Menu
Secondary
Interface
7-3
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