LTPH-UM-1049-02, Issue 2 Testing
H2TU-C-319 List 4E January 9, 2002 61
A2LB Test Procedures

Using the codes listed in Table 23, a network tester can activate NLOC or NREM loopbacks (or SMJK, if

enabled). A tester at the customer premises can activate CLOC or CREM loopbacks. All loopbacks shown in

Table23 can also be in itiated from the H2TU-C front-panel MODE and LBK pushbuttons (see “Setting Options

through MODE and LBK” on page10).

Table 23. Addressable Repeater Loopback Commands (A2LB)

Loopback Binary Code (a)
(Hexadecimal Equivalent)
(a) The leftmost bit arrives first in all sequences. The detection algorithm functions reliably with a random 10-3 Bit Err or Rate (BER)
on the facility. The entire arming and loopback sequence can also be initiated at the remote H2TU-R location.
Description
ARMING or NI LPBK (in-band) 11000-11000... Arming code
ARMING or NI LPBK (ESF Data Link) 1111-1111-0100-1000 (FF48) Arming code
IR LPDN or DISARM (in-band) 11100-11100... Disarming code
IR LPDN or DISARM (ESF Data Link) 1111-1111-0010-0100 (FF24) Disarming code
IOR LPBK (NLOC or 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, excluding 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, excluding 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.
1101-0011-1101-0011 (D3D3) NLOC—DSX-1 signal is looped back to the network at
the H2TU-C.
CREM—Signal from customer is looped back to the
customer at the H2TU-C.
ILR-2 LPBK (NREM or CLOC)
20 bit errors (c)
(c) The H2TU-R is assigned the ILR-2 loopback code. It responds with 20 bit errors (excluding the frame bits).
1100-0111-0100-0010 (C742) NREM—DSX-1 signal is looped back to the netwo rk at
the H2TU-R.
CLOC—Signal from customer is looped back to the
customer at the H2TU-R.
IR LPDN (except SMJK) 1001-0011-1001-0011 (9393) Loopdown (H2TU-C or H2TU-R)
IR QUERY LPBK 1101-0101-1101-0101 (D5D5) Query loopback
IR ALTERNATE QUERY LPBK 1101-0101-1110-1010 (D5EA) Alternate query loopback
TIME-OUT OVERRIDE 1101-0101-1101-0110 (D5D6) Loopback time-out override
FAR END NI ACTIVATE 1100-0101-0101-0100 (C554) U nblock AIS
IOR POWER DOWN (H2TU-C) (d)
(d) The IOR Power Down code must remain present for the duration of the powerdown mode. When this code is removed, the
HiGain system returns to its normal unlooped and unarmed state.
0110-0111-0110-0111 (6767) Removes HDSL2 li ne power