Verilink QUAD DATA (880-503319-001) Product Manual - Manual (Page 40)

Diagnostics
4-6 Verilink QUAD DATA User Manual
2. Follow the logic in the figure below:
3. If a local DPL resolves the error, the local DTE and cabling are
OK. Try to establish a far-end loopback.
4. If a local DPL does not clear a local problem, the defect is local.
Verify cabling to the QUAD DATA module. Verify that the
correct interface type has been selected. Try changing the
clock option (if the port is not set for X.21). Consider the
possibility that the local DTE or QUAD DATA module is
defective.
5. If a local loopback clears a problem and a far-end loopback
also clears the problem, the problem exists in the far-end DTE,
the far-end QUAD DATA module or DSU, or the configuration
of some device at the far end. Try changing the selection for
the clock option (ST vs Inverted ST) in the far end DSU or
QUAD DATA module. If the far end DCE is sampling near the
edge of each bit presented by the far-end DTE, the local DTE
would receive errors. These errors would clear during
loopbacks if the local DCE is sampling correctly.
6. If a local loopback clears a problem but a far-end loopback
does not clear the problem—the trouble exists in a portion of
the local node outside the QUAD DATA module (less likely) or
in the network (more likely). If the network facility on which
the troubled circuit leaves the local site is used only for this
circuit (an entire T1 for one application), do a local loopback
on the network port. If this clears the problem it is in the
Local Data Port
Loopback—clears
trouble?
Yes
No
Go to Step 3
Go to Step 4
Far-end loopback—
clears trouble?
Yes
No
Trouble is at far end.
Go to step 5
Trouble is in node
or network.
Go to step 6