1-24. TD-754 Mux/TD-754 Demux Options.
a. Certain TD-1337(V)/G models have the capability
to perform multiplexing and demultiplexing functions
normally accomplished by a TD-754/G. Use of these options eliminate the need for a TD-754/G to be
located in the same terminal as the TD-1337(V)/G.
The VI model has both TD-754 mux and TD-754 demux option capabilities.
The V2 model has only a TD-754 demux option capability.
b. The TD-754 mux function is performed in the demultiplexer section of a V1 model. Two separate
576 kb/s groups are demultiplexed out of a received SG and then combined (TD-754 mux function) into
a 1152 kb/s output. A maximum of two pairs of 576 kb/s groups can be demultiplexed and so combined.
These outputs are in a balanced NRZ format and use output ports 5 and 7.
The TD-754 demux function is performed in the demultiplexer section of a V1 or V2 model. A
1152 kb/s group is demultiplexed out of a received SG and presented in parallel, in unbalanced NRZ
format, at output ports 1 and 2 or 3 and 4.
d. The facing page illustration shows an example of use of the TD-754 mux and TD-754 demux
options. In this example, two TD-660/G's at one end of the communications link are remoted from a VI
model. At the other end of the link, two TD-660/G's are co-located with the other V1 or V2 model. Each
pair of TD-660/G's are operated in a master/slave arrangement. Note that each master has its transmit
timing slaved to its receive timing. This synchronizes the TD-660/G's with the V1 or V2 model. For simplicity,
this figure only shows the input/output ports associated with the above described TD-660/G's. Other in-
put/output ports could be processing data for other users.
The remoted TD-660/G's each supply
a 576 kb/s data stream
to the TD-754/G which interleaves
these two inputs into a single output (true data rate of 1152 kb/s). The TD-754/G has the capability of
driving a cable system with restorers placed at appropriate intervals. Rate of transmission over the cable
system is 2304 kb/s. Therefore, the TD-754/G transmits each data bit twice to achieve the cable rate.
The MD-1026( )(P)/G receives the TD-754/G dipulse output and converts it into a balanced NRZ format
at a true data rate of 1152 kb/s. Associated timing at 1152 kHz is also provided. This data and timing
f. At the other V1 or V2 model, SG F1 is received and the 1152 kb/s group is demultiplexed out
of the SG. This 1152 kb/s group is then presented at output ports 1 and 2 in parallel and in a unbalanced
NRZ format (TD-754 demux function). Timing of 576 kHz is also supplied. Separation of the 1152 kb/s
group data into two 576 kb/s groups is accomplished by the co-located TD-660/G's.
g. In the return direction, each co-located TD-660/G supplies a 576 kb/s data input. These data inputs,
at input ports 1 and 2, are multiplexed into SG F2 as two separate 576 kb/s groups.
h. At the V1 model receiving SG F2, the two separate 576 kb/s groups are demultiplexed out of
the received SG. These two 576 kb/s groups are then combined into a 1152 kb/s group (TD-754 mux
function) that appears at output port 5. The MD-1026( )(P)/G converts the balanced NRZ output at port
5 into a dipulse format for routing over the cable system to the TD-754/G. In turn, the TD-754/G supplies
1152 kb/s data to the remoted TD-660/G's for separation into two 576 kb/s groups.