EXFO FTB/IQS-88000 Series Power Blazer for FTB-2/2Pro/500/IQS-600 - Manual (Page 630)

Glossary
618 FTB/IQS-88000 Series
SONET/DSn/SDH/PDH

L: the TUG-2 are numbered within the TUG-3 0 or from 1 to 7

M: the TU-2, TU-12, TU-11 are numbered within the TUG-2 1, 1 to 3, 1 to
4 respectively
Examples for AU-4 (3 level convention)
TU-3: [K,0,0]
TU-2: [K,L,0]
TU-12:[K,L,M] where M = 1 to 3
TU-11:[K,L,M] where M = 1 to 4
Example for AU-3 (2 level convention)
TU-2: [L,0]
TU-12: [L,M] M is numbered 1 to 3
TU-11: [L,M] M is numbered 1 to 4