Loopback Operation | 152-402-145-02, Issue 2 |
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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.
Table 11. Addressable Repeater Loopback Commands (A2LB)
Name | Description | Binary Code (a) (Hexadecimal Equivalent) |
ARMING or NI LPBK (inband) | Arming code | 11000-11000 ... |
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ARMING or NI LPBK (ESF Datalink) | Arming code | 1111-1111-0100-1000 (FF48) |
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IR LPDN or DISARM (inband) | Disarming code | 11100-11100 ... |
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IR LPDN or DISARM (ESF Datalink) | Disarming code | 1111-1111-0010-0100 (FF24) |
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IOR LPBK (NLOC and CREM) | H2TU-C loopup | 1101-0011-1101-0011 (D3D3) |
230-232 bit errors | | |
229-231 bit errors (b) | | |
IR LPDN | Loopdown (H2TU-C, H2RU, or | 1001-0011-1001-0011 (9393) |
| H2TU-R) | |
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IR QUERY LPBK | Query loopback | 1101-0101-1101-0101 (D5D5) |
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IR ALTERNATE QUERY LPBK | Alternate query loopback | 1101-0101-1110-1010 (D5EA) |
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TIME-OUT OVERRIDE | Loopback time-out override | 1101-0101-1101-0110 (D5D6) |
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FAR END NI ACTIVATE | Unblock AIS | 1100-0101-0101-0100 (C554) |
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IOR POWER DOWN (H2TU-C) (c) | Removes HDSL2 line power | 0110-0111-0110-0111 (6767) |
(a)The leftmost bit arrives first in all sequences. The detection algorithm functions reliably with a random 10-3BER on the facility. The entire arming and loopback sequence can also be initiated at the remote H2TU-R location.
(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.
(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.
To perform the A2LB test procedures:
1Send the inband Arming and NI LPBK code 11000 to the H2TU-R-402 for at least 5 seconds.
2Monitor 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.
3Verify, 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.
If the Arming code is not returned after 5 seconds, the system may be armed but there is no active loopback.
