3-6 D-channel handler
297-2521-106 Standard 23.01 March 2001
format, but only one D-channel (either primary or secondary) can be active
in layer 3 at any one time. The other D-channel is active in layer 2.
Figure 3-2 shows the basic nonassociated signaling of a PRI interface that
contains three DS-1 facilities. It also shows the primary D-channel (D1), and
a secondary D-channel (D2).
Figure 3-2
Nonassociated PRI interface with D-channel backup
Network
User
PRI interface
DS-1
DS-1
DS-1
Primary D-channel (D1)
Secondary D-channel (D2)
MAP commands for D-channel maintenance
PRI D-channel backup extends the existing MAP terminal PRADCH-level
commands to handle the backup D-channel maintenance functions in both
• the ISDN central controller
• the ISDN multiprocessor system extended peripheral module (XPM)
The command function under PRADCH-level handles primary and
secondary D-channel maintenance. The SWACT command supports the
manual switch of activity of D-channels.
D-channel back-up interactions
The following features interact with the D-channel backup:
• universal tone receiver on PRI—calls in the digit receiving state are
cleared
• basic PRI calls—calls not in the active state are cleared
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