150-412-181-01
March 31, 1998
Revision 01
HRU-412 List 8A
PairGain Engineering - Plant Series
31
All HRU-412 List 8A loopbacks toward the network (NREM and SMJK) are
metallic/logic (AIS/ENA) or metallic only (AIS/DIS). The TLOS loopback is
a logic loopback.
The SMJK and NREM loopbacks perform the same functions; their initiation
differs. The SMJK identifying label indicates that the loopback was initiated
by the 2-in-5 in-band command. NREM initiates by any in-band command
except the 2-in-5 command. These other in-band commands include 3-in-7
command, 16-bit addressable repeater commands, or activation using the
front panel MODE and SEL buttons.
When T1 loopback tests are made on the HiGain system with
external metallic loopback connections at either end, the DS1
code at the metallic loopback interface may be different from the
DS1 code at the opposite end when the DS1 user option is set to
AUTO. For example, if the HRU-412 List 8A has a metallic
loopback and the HLU receive pattern code is changed from AMI
to B8ZS, an all 0s pattern is sent to the HLU. The HRU-412
List 8A remains in AMI mode and loops all 0s causing the
HRU-412 List 8A to indicate an LOS condition. The result is that
the HLU outputs an AIS pattern.
Summary of Contents for 150-1103-81
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