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Each module has a DSE to interface codecs or digital
transceivers to the TDM bus. The actual digital switching
occurs when the DSE is programmed by the system I/O
bus to place (transmit) data or retrieve (receive) data on
the TDM bus in specific time slots. This process also
involves time slot interchanging so that an available slot in
the TDM cycle can be filled with a talk (transmit) or listen
(receive) slot. The DSE provides dynamic conferencing
ability by allowing up to 16 time slots to be conference
together and sent out to a single port (station).
408 Module
CODEC
008D Module
D/A
converter
DSE
i
n
t
e
r
f
a
c
e
DSE
Interface
circuity
A/D
converter
Analog
voice
terminal
TDM Bus
256 Time slots in one TDM cycle
0 1 2 3
…
60 61 62 63
…
150
…
160
…
200
…
220
…
225
Time
Time slots
for control
signals.
Time slots
for tones.
Analog station
talks on time
slot 150 and
listens on time
slot 160. The
conversation
is continuous.
Digital station
sends data on
time slot 200
and receives
data on time
slot 220.
FIGURE 1-10 Time division multiplexing.
Theory of Operation 1-43