Fluke TS 1200, User Manual

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4-3
Potential Failures in the Copper Loop
If the exhibited bit rate is significantly better at the NID, then inside wiring or bridged taps are
most likely the problem, and installing a splitter may help (Figure 4-1). G.lite requires the
connection of bridged taps, or laterals from the main line for voice service, whereas G.DMT
isolates data from the voice service.
Potential Failures in the Copper Loop
If problems at the customer premises can be ruled out, and the test set fails to synchronize with
the DSLAM at the NID, the problem is probably in the outside plant. Perform a modem
emulation test with the test set terminated on the line at the next upstream access point on the
loop (i.e., probably a cross-connection box, a pedestal, or an MPOLE). Continue to the next
upstream access point until a successful connection is acquired. At the point where a successful
connection is established, check the downstream portion of the loop for loading, bridged taps,
resistive faults, or unbalanced capacitance pair.
When all else fails, and the decision is made to cut over another line to repair the problem,
ensure that the line has been prequalified for bridged taps and other required conditions, and
that load coils are not present. Basic conditioning and supervision tests should then be run on
the new line.
As a rule of thumb, run a modem emulation test with the test set at the customer site before
closing the repair ticket. This will ensure the line has been properly terminated for service.
Poor POTS Performance on an ADSL Line
If the telephone service is inactive, but the ADSL service is working properly, verify the dial tone
with a portable ADSL splitter and the TS1200 at the next upstream access point. Reduce the
trouble area and look for continuity on the pair. In the case of one open line, the ADSL service
may still be functioning. The DSLAM and the ADSL modem are self-powered, unlike POTS
service, which relies on power from the CO (typically 48V DC) and requires the Tip and Rings to
be grounded. The short range TDR can be used to locate the fault.