Tektronix NetTek YBT1E1, User Manual, Page: 87 / 122

Testing a Circuit
NetTek YBT1E1 T1 & E1 Circuit Tester User Manual
3- 19
Loopback Testing (Option T1 only)
Loopback testing is creating a loopback at the far end of the span
and using a single instrument to measure the round--trip performance
of the T1 line. Because loopback testing only requires a single test
instrument and operator, it is more convenient and more efficient
than point-to-point testing.
The downside to loopback testing is that it can only analyze the
combined performance of both transmit and receive paths at the
same time, making it difficult to distinguish on which side the
problem exists. However, loopback testing can offer enough
information to determine a general fault location, such as in
telephone company lines or the base transceiver station site.
There are several ways to set up a loopback on a T1 circuit:
H
Inserting loop plugs at a patch panel
H
Using the Channel Service Unit (CSU) or Network Interface Unit
(NIU) front panel to force the equipment into loopback
H
Logging into the network and setting the equipment to loop back
the signal
H
Sending T1-standard defined loopback codes to set the
equipment into loopback mode
You can use the YBT1E1 with any of these methods; the YBT1E1
can send loopback codes to force remote equipment into a loopback
mode.
NOTE
. You must set theNetTek YBT1E1 to Terminate configuration to
use this feature.