AT&T DEFINITY 7200 series - Manual (Page 119)

6. DISTRIBUTED COMMUNICATIONS SYSTEM (DCS)
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The distributed communications system (DCS) is a information system that provides a messaging overlay
for main-satellite/tributary (MS/T) networks, electronic tandem networks (ETNs), or ETN-MS/T
complexes that are designed for DCS implementations. This overlay provides communication among the
network nodes so that the operation of a limited number of features is transparent across the network. That
is, the operation of certain features is the same (or nearly the same) on each network node. In addition,
DCS users can initiate calls to or receive calls from users on other DCS switches and enjoy the same feature
capabilities as those that would be associated with the call were both users on the same switch.
This feature transparency is achieved by interconnecting all the network nodes with a signaling link that
carries the information associated with a call. On the System 75 and Generic 1 communications systems,
this signaling link is called the processor interface (PI) (formerly called the switch communications
interface [SCI]) links. On the
DIMENSION , System 85, and Generic 2 communications systems, the link is
known as the data communications interface unit (DCIU) link. In addition to signaling links, analog or
digital tie trunks interconnect each pair of switches. The tie trunks carry the actual voice traffic between
switches.
"DIMENSION"
FP8
SYSTEM 85/ SYSTEM 85/
SYSTEM
GENERIC 2 GENERIC 2
DCIU
LINKS
SYSTEM
ENDPOINT
4XXXX TIE
TIE
5XXXX
NODE
3XXXX 2XXXX
TIE TRUNK
TRUNK
TRUNK
PI/SCI
LINK
TIE TRUNK
DCS-CLUSTER
DCS TANDEM DCS TANDEM
75 R1V2
SYSTEM 75/
GENERIC 1
DCS TANDEM
6XXXX
GATEWAY TO OTHER
DCS CLUSTERS, AN
ETN, OR OTHER
DEDICATED PRIVATE
NETWORK FACILITIES
Figure 6-1. Distributed Communications System (DCS) Cluster
6-1