ADTRAN TSU 120, User Manual

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Chapter 1. Introduction
61200.129L1-1 TSU 120 User Manual
19
T1
Network Interface
(NI)
Port
Loopback
TSU 120
Nx56/64 Interface
Nx56/64 to
Network Control
Circuit
to DTE
Figure 1-11
Port Interface Loopback
DSX-1 Interface Loopbacks
Line Loopbacks
On the DSX-1 interface, the line loopback causes data
received at the DSX-1 to be looped back toward the
PBX achieving a local loopback.
Port Loopback
The port loopback is internal and loops all data
mapped to the DSX-1 back toward the network
interface on the controller. The loopback, when used
in conjunction with an external bit error rate tester
(BERT) to drive the network interface, exercises the
entire data path from the network interface (NI)
controller, through the DSX-1 interface, and back out
the network interface controller. See Figure 1-12.
To deactivate the loopback, select None under the
0.2 DSX-1 submenu.