EXFO FTB-800 Series for FTB-1 - Manual (Page 443)

Test Functions
NetBlazer 433
OH - SONET/SDH

Signal Label
If the signal label in V5 (bits 5, 6, and 7) is 101 the contents of the
extended signal label is valid and contains in a 32 bit multiframe as
shown below. See Z7/K4 Structure shown below.
Z7/K4 Structure
Bits 5, 6, 7
of V5
Description
SONET SDH
000
a
a. These bytes cannot be selected in receive mode.
Unequipped Unequipped or
supervisory-unequipped
001 Reserved (Equipped - Non-specific)
010 Asynchronous
011 Bit Synchronous
100 Byte Synchronous
101 Extended Signal Label
110 Test Signal, ITU-T 0.181 specific mapping
111
a
VT SPE AIS (TCM) VC-AIS (TCM)