8
Setting the Interfaces
Setting SONET Transmit Interface
If STRUCTURED is chosen, the Payload test signal must be set-up.
See “Setting Transmit Structured Payload/Test Signal (Options UKJ
or 110)” page 43.
If INSERT is chosen, see “Inserting an External PDH Payload/Test
Signal” page 52.
8 Choose the PATTERN type and PRBS polarity.
NOTE If interfacing at STS-1 with a user word pattern chosen then a false frame
synchronization may occur. This is due to the effect of the standard ITU-T G.707
scrambling used at STS-1 when applied to a fixed payload.
The scrambler may produce a false (F628) frame synchronization from the fixed
payload. At STS-1 only a single F628 pattern is available for frame synchronization.
If the false pattern is detected by the receiver this will result in frame synchronization
being indicated but multiple alarms will occur. If this condition is suspected, change
the PATTERN choice to PRBS and check that the multiple alarms are cleared when
proper frame synchronization is achieved.
9 If required, choose 2M/DS3/34M/140M OFFSET value.
10 If 2 Mb/s framing PCM30 or PCM30CRC is chosen, set the CAS ABCD
bit value.
11 Choose the mapping required in the background (non-test) SPE’s.
Refer to Appendix A "STS-1 SPE Background Patterns " page 176 for
a table of background patterns for STS-1 SPE.
12 If VT-2 mapping is chosen for the test SPE, choose the PATTERN IN
OTHER VT-2s.
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