EXFO FTB-8510B Guia Del Usuario página 1282

Glossary
SONET - VT Path Overhead
VT Payload Pointer
The VT Payload Pointer provides a method of allowing flexible and
dynamic alignment of the VT SPE within the VT Superframe.
New Data Flag
NDF is enabled when at least 3 out of 4 bits match "1001".
NDF is disabled (normal value) when at least 3 out of 4 bits match
"0110".
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FTB-8100 Series Transport Blazer