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DEFINITY ECS Release 8.2
Administrator’s Guide
555-233-506
Issue 1
April 2000
Features and technical reference
1402ISDN service
20
ISDN interworking
ISDN interworking allows calls to use a combination of both ISDN and non-ISDN
trunking and station facilities. A non-ISDN trunking facility is any trunk facility
supported by the system that does not use the ITU-T recommended Q.931
message set for signaling. Non-ISDN trunking facilities include facilities such as
analog trunks, AVD DS1 trunks, and DS1 trunks with bit-oriented signaling
(robbed-bit or common channel).
DEFINITY ECS supports the conversion of ISDN signaling to non-ISDN in-band
signaling and the conversion of non-ISDN in-band signaling to ISDN signaling
for interworking purposes.
A mixture of ISDN and non-ISDN signaling is required in order to provide
end-to-end signaling when using different types of trunk or station facilities on a
call. See the figure below for an example of interworking.
In this example, a call for someone at Switch B comes into Switch A.
Interworking allows the ISDN signaling of the call to be converted at Switch A to
non-ISDN in-band signaling before the call forwards to Switch B. Even though
the call comes into Switch A on an ISDN trunk, Switch A can send the call to
Switch B over a non-ISDN trunk by converting the signaling information.
The system provides accurate CDR billing information on calls that are not
interworked. Accuracy of CDR billing information on interworked calls is
equivalent to the accuracy provided by the public network.
DEFINITY ECS supports sending a non-ISDN trunk name as the connected
name. Therefore, a non-ISDN trunk name can be sent as the connected name even
when a call starts out as an ISDN call but is interworked over non-ISDN trunks.
Figure Notes
1. Call from network to Switch B
2. ISDN trunk
3. Switch A
4. Non-ISDN trunk
5. Switch B