ADTRAN 1200060L1, User Manual

Page: 28 / 78

Chapter 1. Introduction
1-12 TSU User Manual 61200060L1-1
Network Loopbacks
There are two types of network loopbacks; see Figure 1-7 .
• Line Loopback : 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 Loopback : similar to Line loopback, except that
the framing is extracted from the received data and then
regenerated for the transmitted data.
Figure 1-7. Network Loopback Tests
TSU
DS1
NI CSU
Payload Loopback
Line Loopback
Interface
V.35