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Loopback Operation 152-402-145-02, Issue 2
28 June 16, 2000 H2TU-R-402
A2LB Test Procedures
Using the codes listed in Table 11, a network tester can activate NLOC, NRG or NREM loopbacks (or SMJK, if
enabled). A tester at the customer premises can activate CLOC, CRG, or CREM loopbacks.
To perform the A2LB test procedures:
1 Send the inband Arming and NI LPBK code 11000 to the H2TU-R-402 for at least 5 seconds.
2 Monitor the output of the H2TU-R-402 for the return of the pattern. Return of the pattern indicates one of the
following:
• The H2TU-R has looped up (if the SMJK Loopback option is enabled)
• An external NID has looped up (if the SMJK Loopback option is disabled), and the H2TU-C and
H2TU-R have been armed.
3 Verify, if possible, that the H2TU-R LBK LED is either flashing yellow at 4-second intervals (indicating that
the system is armed), or is a steady yellow (indicating that it is both armed and in SMJK loopback). The
H2TU-C Status LED also flashes yellow when the system is armed.
Table 11. Addressable Repeater Loopback Commands (A2LB)
Name Description Binary Code
(a)
(Hexadecimal Equivalent)
(a) The leftmost bit arrives first in all sequences. The detection algorithm functions reliably with a random 10
-3
BER on the facility.
The entire arming and loopback sequence can also be initiated at the remote H2TU-R location.
ARMING or NI LPBK (inband) Arming code 11000-11000 ...
ARMING or NI LPBK (ESF Datalink) Arming code 1111-1111-0100-1000 (FF48)
IR LPDN or DISARM (inband) Disarming code 11100-11100 ...
IR LPDN or DISARM (ESF Datalink) Disarming code 1111-1111-0010-0100 (FF24)
IOR LPBK (NLOC and CREM)
230-232 bit errors
229-231 bit errors
(b)
(b) The H2TU-R identifies CREM (and the H2TU-C identifies NLOC) 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. The H2TU-R and H2TU-C generate 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 H2TU-R and H2TU-C transmit for a CI and NI loopback.
H2TU-C loopup 1101-0011-1101-0011 (D3D3)
IR LPDN Loopdown (H2TU-C, H2RU, or
H2TU-R)
1001-0011-1001-0011 (9393)
IR QUERY LPBK Query loopback 1101-0101-1101-0101 (D5D5)
IR ALTERNATE QUERY LPBK Alternate query loopback 1101-0101-1110-1010 (D5EA)
TIME-OUT OVERRIDE Loopback time-out override 1101-0101-1101-0110 (D5D6)
FAR END NI ACTIVATE Unblock AIS 1100-0101-0101-0100 (C554)
IOR POWER DOWN (H2TU-C)
(c)
(c) The IOR Power Down code must remain present for the duration of the powerdown mode. When this code is removed, the
HiGain HDSL2 system returns to its normal unlooped and unarmed state.
Removes HDSL2 line power 0110-0111-0110-0111 (6767)
If the Arming code is not returned after 5 seconds, the system may be armed but there is no
active loopback.