1558A APS
2-8
Installation
4)
Operate the Service Select switch on the 1558A to the
Path A position at both the near and far 1558A units. This
forces both units to use Path A as the receive signal source.
Once this is done, both test sets should indicate pattern sync
at both the near and far locations. Run test for 15 minutes.
Test should be error free at both ends. If errors are detected,
repeat test for another 15 minutes. If errors are still detected,
a problem exists in the T1 facility. Refer problem to appro-
priate channels for resolution.
5)
Operate the Service Select switch on the 1558A unit to
the Path B position at both the near and far 1558A units.
This forces both units to use Path B as the receive signal
source. Run test for 15 minutes. Test should be error free at
both ends. If errors are detected, repeat test for another 15
minutes. If errors are still detected, a problem exists in the
T1 facility. Refer problem to appropriate channels for reso-
lution.
6)
After completing the end-to -end testing of both Path A
and Path B, connect the DTE equipment.
This completes the end-to-end operational check for the
1558A. The unit is now ready to support automatic protec-
tion switching.
2.7
Bypass Test
The 1558A supports a “bypass” mode of operation which
allows the NET A path to be physically connected directly
to the DTE port. In this mode, all active electronics are
removed. The only components in the transmission paths
while the BYPASS mode is active are line protection com-
ponents and test access jacks. The BYPASS mode of opera-
tion is automatically implemented when either of the
following occurs:
• Power is removed from the unit (external power failure)
• CPU detects an internal operational fault. If this occurs,
the front panel ‘BYPASS’ LED (red) will be on to indicate
that the 1558A has detected a unit fault and that it is now
operating in the BYPASS mode.
During BYPASS, their is no signal regeneration. Typically,
the transmit and receive levels to/from the T1 demark and
the terminating DTE will perform satisfactorily. However,
there is the potential that the signal levels will be unusable
by either the DTE equipment or by the T1 facility equip-
ment.
To verify that the BYPASS mode will work in your particu-
lar application, perform the following steps:
1)
First, end-to-end testing must be complete. If so, pro-
ceed to step 2.
2)
Remove the external power from the 1558A unit. Note
that all front panel LED indicators go off. The 1558A will
automatically implement the BYPASS mode which connects
the NET A T1 facility directly to the DTE port.
3)
With the power still off, verify that the DTE equipment
is operating. If so, this application will support the BYPASS
mode. If the DTE is not operating, this means that the signal
levels either to the DTE or from the DTE are to low for
proper operation without signal regeneration. If this is the
case, then BYPASS mode will not be viable for this particu-
lar application.
NOTE: The bypass mode requires that the DTE port and
the DTE equipment must be set for the same framing and
line coding as the T1 facility (ESF and AMI or B8ZS).
