Table of Contents
Advertisement
Testing
L
O
OOPBACK
PERATION
HiGain HDSL4 has a family of loopback options for analyzing circuit functionality. The loopback signal is
transmitted and returned to the sending device for comparison. This allows you to verify the integrity of the
HDSL4 channels to the H4TU-R remote unit and H4D doublers (if present), the H4TU-C DSX-1 interface, and
the H4TU-R DS1 channels to the customer.
The HDSL4 system is enhanced to support a multiple set of loopback commands without changing any loopback
configuration setting. The following three sets of loopback commands can be initiated simultaneously:
•
Generic Loopback (GNLB) commands, including the SmartJack (SMJK) loopback commands (see
on page
45)
•
A3LB Addressable Repeater Loopback commands (see
•
A5LB Addressable Repeater Loopback commands (see
Loopback commands can be initiated by:
•
Entering the loopback code into the test equipment connected to the H4TU-C or H4TU-R.
•
Selecting and activating the loopback type from the Monitor menu when connected to the craft port of the
H4TU-C or H4TU-R (see
•
Using the loopback pushbuttons (LLB and RLB) on the H2TU-R (see
Front-Panel Pushbuttons" on page
•
HiGain supports multiple loopbacks, but a single loopback is the preferred method. HDSL4
automatically rejects activation of closed loop loopbacks. For example, an NREM and CREM
cannot be activated at the same time.
DSX-1
Activate loopback using
one of the following:
NLOC
•
Maintenance terminal
• Test set
Network
42
"Loopback Testing Using a Maintenance Terminal" on page
50).
Span 1
CREM
NDU1
CDU1
H4TU-C
H4D1
Downstream
*
When enabled, TLOS is an automatic loopback
that occurs with an LOS at the remote DS1 input.
Figure 27. Loopback Summary
October 15, 2003
Table 18 on page
Table 19 on page
"Loopback Testing Using Remote Unit
Span 2
Span 3
NREM
NDU2
CDU2
SMJK
TLOS*
H4D2
Upstream
LTPH-UM-1253-01
Table 17
47)
48)
50).
Activate loopback using
one of the following:
• Loopback pushbuttons
CLOC
• Maintenance terminal
• Test set
H4TU-R
Customer
Premises
H4TU-C-231 List 5AA
Advertisement
Table of Contents
