Chapter 5. Configuration Menu
61200410L1-1
ESU LT User Manual
5-3
FRAMING
The ESU LT can operate in three different framing modes:
Common Channel Signaling (CCS), Channel Associated
Signaling (CAS), or unframed.
CCS
CCS uses a 7-bit pattern called the Frame Alignment Signal
(FAS) in order to establish and maintain frame
synchronization. The FAS word is located in timeslot 0 of
even frames. Odd numbered frames may contain the Not
FAS word (NFAS) in timeslot 0. The ESU LT can be
configured to require the NFAS word for frame sync.
In CCS mode, there are 31 channels (timeslots 1-32) available
for user data. Timeslot 16 cannot be used to carry signaling
information in this mode.
CAS/TS16
CAS, also known as timeslot 16 multiframing, requires a
multiframe alignment signal to be present for frame sync.
The Multiframe Alignment Signal (MFAS) is inserted into the
16th timeslot of frame 0 of the 16-frame multiframe. The
MFAS word consists of four zeros, an unused bit, the
multiframe alarm bit and two more unused bits. Frames 1
through 15 carry the A,B,C and D bits for timeslots 1-15 and
17-32.
The ESU LT is designed for data transmission; therefore, the
signaling bits used for voice traffic are set to
all ones
.
In CAS mode, there are 30 channels available for user data. If
timeslot 16 is included in the unit’s mapping, it will be
disregarded. For example, if the starting TSO is set to 1 and
the number of TSOs is set to 20. User data will be mapped to
timeslots 1-15 and 17-21.
UNFRAME
The ESU LT can operate in unframed mode. In this mode,
user data is inserted into all 32 channels of the E1 stream.
Since the object of running without framing is to utilize the
full bandwidth of the E1 line, the starting TSO and number of
TSOs option settings are ignored.
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