Loopback Operation
150-431-115-01, Revision 01
44
September 22, 1998
HLU-431 List 1E
A3LB and A4LB Test Procedures
The HLU-431 can be looped back by sending the Addressable Office Repeater (AOR) LPBK activation code
1111(F) 1111(F) 0001(1) 1110(E) for at least 5 seconds. This causes the HLU-431 to enter the NLOC state. The
Loopback Time-out option can be set by the user to:
•
NONE (0 minutes)
•
20 minutes
•
60 minutes
•
120 minutes
These selections determine the duration of this loopback, unless it is overridden by the reception of a second
identical 16-bit loop-up command before the timer expires. When this time-out override state exists, the only way
to loop the HLU-431 down is to issue one of the three loopdown commands listed in Step 2. The automatic
time-out mode is restored during subsequent loopback sessions.
Table 14.
Addressable 1, 2, 5 (A1LB, A2LB, A5LB) Repeater Loopback Commands
Name
Description
Code
a
a The left most bit arrives first in all sequences. The detection algorithm functions reliably with a random 10
-3
Bit Error Ratio
(BER) on the facility. The IOR POWER DOWN code must remain present for the duration of the power down mode. When this
code is removed, the HiGain system returns to its normal unlooped and unarmed state. Note that the entire arming and
loopback sequence can be initiated at the remote HRU location.
ARMING or NI LPBK (in-band)
Arming code
11000 11000 …
ARMING or NI LPBK (ESF Data Link)
Arming code
1111(F)
b
1111(F)0100(4)1000(8)
b This is the HEX number for the 4-bit group.
IR LPDN or DISARM (in-band)
Disarming code
11100 11100 …
DISARM (ESF Data Link)
Disarming code
1111(F)1111(F)0010(2)0100(4)
IOR LPBK (NLOC and CREM 229-231 bit errors)
c
c The HRU identifies CREM with 231 bit errors, including the frame bits. When framed data is being sent in the AUTO framing
mode, the number of the 231 bit errors detected by the test set varies from 229 to 231, depending on whether or not the test
set counts frame errors as bit errors, and on the number of frame bits contained in the block of 231 error bits.
HLU Loopup
1101(D)0011(3)1101(D)0011(3)
ILR-1 LPBK (NDU1 and CDU1 10 bit errors)
d
d The HRU generates this bit pattern in a series of discontinuous bursts containing 20-bit errors each, including frame bits.
Those test sets that do not count frame error bits as data bit errors will indicate fewer bits than the HRU transmits for this CI
loopback.
DOUBLER-1 Loop up
1100(C)0111(7)0100(4)0001(1)
LR-20 LPBK (NDU2 and CDU2 200 bit errors)
DOUBLER-2 Loop up
1100(C)0111(7)0101(5)0100(4)
ILR-2 LPBK (NREM and CLOC 20 bit errors)
HRU Loop up
1100(C)0111(7)0100(4)0010(2)
IR LPDN
Loopdown (HLU or HRU)
1001(9)0011(3)1001(9)0011(3)
IR QUERY LPBK
Query loopback
1101(D)0101(5)1101(D)0101(5)
IR ALTERNATE QUERY LPBK
Alternate Query loopback
1101(D)0101(5)1110(E)1010(A)
TIME-OUT OVERRIDE
Loopback Time-out Override
1101(D)0101(5)1101(D)0110(6)
FAR END NI ACTIVATE
e
e Not supported by A5LB.
Unblock AIS and pass 2-in-5
1100(C)0101(5)0101(5)0100(4)
IOR POWER DOWN (HLU)
Removes HDSL line power
0110(6)0111(7)0110(6)0111(7)
