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9-2 DATA COMMUNICATIONS CONFIGURATIONS
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DSC AND PSC CONNECTIONS
The dedicated switched connection (DSC) is a feature that provides a dedicated path using circuit-switched
facilities on the System 85 (R2V4) and Generic 2 communications system; the permanent switched
connection (PSC) offers a similar capability on the System 75 and Generic 1.1 communications systems.
DSC and PSC are implemented through communications system administration. No extra hardware is
required.
DSCs and PSCs provide a clear channel through the communication system to connect two ports when
dialed number signaling is not provided on the incoming port. The channel runs at rates up to 64 kbps. A
variety of ports types may be connected through the dedicated communications-system path. They include:
• Analog line and trunk ports
• DCP ports (digital-line ports on the System 75 [R1V2 and later] and Generic 1 communications system
and GPP ports on the System 85 [R2V4] and Generic 2 communications system)
• EIA ports
Note: For EIA connections on the System 85 (R2V4), the bearer capability must be set to 2 on the trunk
group used for the connection. Set the bearer capability through PROC 103, field 15.
• DS0 channels of DS1 ports
Figure 9-1 depicts some typical DSC and PSC configurations. Other configurations are possible.
Note that:
• 24th-channel signaling and B8ZS line coding are required for certain dedicated (PSC and DSC) data
connections through the communications system.
• When a dedicated connection must be implemented between a System 75 or Generic 1 endpoint, and a
System 85 or Generic 2 endpoint, the connection should be implemented as a PSC on the System 75 or
Generic 1 communications system. Because PSCs can be established across communications systems,
no DSC is necessary on the System 85 or Generic 2 communications system when the PSC is defined
on the System 75 or Generic 1.
• On the System 75 and Generic 1 communications system, PSCs can be defined at either of two
administration screens: the Permanent Switched Connection screen or the Interface Link screen. PSCs
established through the Interface Link screen are more properly called software connections, rather than
PSCs.