Section 150-612-102
Revision 03
Page 11
TABLE 2. HRU-612 Test Procedures.
Step
Action
1
Depress the loopback LB button on the HRU front panel for at least 5 seconds.
2
Verify that the GREEN HRU front panel loopback LB NET LED turns on, indicating that the HRU is in
its (NREM) loopback state. Also verify, if possible, that the HLU displays the message ”NREM” also
indicating that the HRU is in loopback (see Figure 5).
3
Have the C.O. tester transmit a T1 test signal into the HLU and measure that the returned (looped)
signal is error free.
4
If the above test fails, remove the HRU from its loopback state by again depressing the HRU loopback
button for 5 seconds. Verify that the loopback NET LED is off.
5
Have the C.O. tester send the HLU (4 in 7) in-band loop-up (NLOC) for 5 seconds. Verify that the HLU
displays the message “ NLOC” indicating that the HLU unit is in its network loopback state.
6
Repeat step 3. If the test passes, the problem is in the cable pair or the HRU. If it fails, the problem is
in the C.O.
7
To verify that the proper ports are use for the VHDSL & DS1 pairs, use an ohm-meter to verify that the
VHDSL HRU-612 port has a 180 k T to R resistive signature in contrast to the DS1 ports which have a
15 ohm T to R resistive signature.
8
If the CPE 60 mA. switch option is set. Verify that the external NID is under power and that the voltage
across its front panel “60 mA MON” test points measures between 55 and 65 mv. This indicates that the
CPE current is between 55 & 65 mA. Note that the external NID’s LOOP POWER option must be set to
its “THRU” position when powered by the HRU.
NOTE: When T1 loopback tests are made on the HiGain-2 system with external metallic loopback connections
at either end, the DS1 code that exists at the metallic loopback interface may be different from the DS1 code
being received at the opposite end when the DS1 user option is set to AUTO. For example, if the HRU has a
metallic loopback and the HLU’s receive pattern’s code is changed from AMI to B8ZS and then the all 0 pattern
is sent into the HLU, the HRU remains in its AMI mode and thus loops all 0’s. This causes the HRU to indicate a
LOS condition which then causes the HLU to output the AIS pattern.