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1-34 MULTIPLEXED COMMUNICATION
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Note that the Digital Access and Cross-Connect System (DACS) takes input multiplexed up to the DS1
level. Therefore, communications multiplexed above this level must be demultiplexed before they can be
processed by the central office.
STATISTICAL MULTIPLEXING
Statistical multiplexers assign a high-speed (56- or 64-kbps) channel for utilization by several lower-speed
(subrate data) devices. Statistical multiplexers do not require signal modulation or switching. The most
common configuration places a multiplexer on one end (putting the inputs from multiple devices onto a
single line) connected by a direct line to a demultiplexer on the other (sending the channels from processing
at different devices or computer ports). (See figure 1-11.) The signal can be switched through a System 75,
System 85, or DEFINITY communications system, however, if it is channeled over a dedicated switch or
permanent switch connection in the switch and it travels through an modular processor data module
(MPDM) upon entering and exiting the switch.
HOST
B
HOST
A
718
718
719 719
718
718
718
PRIVATE
LINE
Figure 1-11. Statistical Multiplexing
Currently, the 718 Stat Mux and the 719 Networker are recommended for use in statistical multiplexing
applications. The 719 Networker functions as network node, while the 718 is the DCE at the terminal or
host site. Both the 718 and 719 use byte interleaving.