Loopback Operation
150-388-125-01, Revision 01
36
September 15, 1998
HLU-388 List 2E
R
ETIRING
S
YSTEM
A
LARMS
To retire a system alarm, press the SEL button and execute an Alarm Cut Off (ACO). An ACO turns the alarm off
and replaces the
ALRM
message with an
ACO
message. The second part of the
ALRM
message, which defines the
cause of the alarm, remains. Both parts of the message remain until the alarm condition clears or another higher
priority alarm occurs. Disabling the alarm also retires the alarm.
S
ELF
T
EST
The Self Test mode that occurs when both HDSL loops are not in sync has been enhanced to include the input
DS1 transceiver chip. The Self Test procedure can cause the AIS pattern, that is normally transmitted from the
HLU-388 during these out of sync intervals, to exhibit occasional BPVs.
L
OOPBACK
O
PERATION
HiGain has a family of loopback options. The most important of these is the SmartJack (SMJK) loopback, which
enables an HRU response to the standard (2/3 in 5) SMJK in-band loopback codes in emulation of standard
Network Interface Device (NID) functions. This option can be enabled or disabled from either the front panel
MODE and SEL buttons or through the System Settings screen.
G
ENERIC
L
OOPBACK
C
ODE
(GNLB)
The HiGain generic loopback code is GNLB. The GNLB allows in-band codes to loop-up either the HLU/NLOC
(4 in 7) or HRU/NREM (3 in 7) towards the network. In addition, it allows in-band codes to loop-up the
HLU/CREM (6 in 7) or HRU/CLOC (5 in 7) towards the customer. For doubler applications, it permits looping
doubler 1 toward the network NDU1 (2 in 6) or toward the Customer CDU1 (4 in 6). Doubler #2 is looped toward
the network with NDU2 (3 in 6) or toward the Customer with CDU2 (5 in 6). Either loop-up condition is
terminated (looped-down) with the 3-in-5, loop-down code. Both in-band codes must be present for five seconds
before the HiGain system responds. See
“GNLB Loopback Test Procedures” on page 41
for the test procedures
that apply when using the GNLB mode.
