Telecommunications Techniques Corporation interceptor 147, Reference Manual, Page: 55 / 280

3-13
3
INTERCEPTOR 147 2 Mbit/s and Data Analyzer
Setup Categories
UNFRAMED
Configures the test instrument to operate in an
unframed mode. An unframed 2 Mbit/s signal contains
no frame alignment or other overhead bits. Unframed
test patterns are often used to perform out-of-service
tests on 2 Mbit/s lines. (The UNFRAMED selection
is available only when Test Mode is set to 2048K.)
FAS
Configures the test instrument to operate using the
Frame Alignment Signal (FAS), or 31-timeslot,
framing format. In this format, 8-bit timeslots are
organized into frames of 32 timeslots each. Timeslot
0 in each frame is reserved for overhead functions
including transmission of the FAS and NFAS.
FAS-CRC
Configures the test instrument to operate using the
FAS-CRC framing format. This format is identical to
the FAS format, except that a 4-bit cyclic redundancy
check (CRC-4) code is added. The CRC-4 code is
inserted into the first bit of Timeslot 0 in odd-numbered
frames.
MFAS
Configures the test instrument to operate using the
Multiframe Alignment Signal (MFAS) framing
format. As in the FAS format, timeslots are grouped
into frames of 32 timeslots each. However, with
MFAS framing, 30 of the 32 timeslots are available
for customer data, and the other two timeslots are
used for framing and signaling information. Timeslot
0 of every frame is used for FAS and other overhead
functions. Timeslot 16 of every frame is reserved for
additional overhead functions including transmission
of channel associated signaling (CAS).