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ASAI and Call Control
Issue 7 May 1998
4-15
For calls placed over ISDN-PRI facilities, if the ISDN ALERTing message is
received from the network, the classifier is expected to detect the “in band” ringing
and provide the “no answer” classification independent of receiving an ISDN
ALERTing message.
For calls placed to on-ECS destinations, the “no answer” classification is done by
counting the number of seconds of ringing.
The adjunct is notified of the no answer outcome in a Third Party Call Ended with
cause CS3/19 — No Answer.
Busy Condition
For calls placed to off-ECS destinations, the busy results from the call classifier
detecting either precise or imprecise busy tones or the “DISConnect/cause=user
busy” (CS0/17 — User Busy) message returned by an ISDN-PRI facility.
A Third Party Call Ended is sent in these cases to the adjunct with cause value
CS0/17 — User Busy.
For calls placed to on-ECS destinations, the busy condition is the result of the
“busy” internal feedback message. Again, a Third Party Call Ended is sent to the
adjunct with cause value CS0/17 — User Busy.
Reorder Condition
For calls placed to off-ECS destinations, the reorder condition is from the call
classifier detecting either precise or imprecise network reorder tones, or receipt of
an ISDN “progress” or “disconnect” message with cause CS3/42 —
Denial/Reorder. A Third Party Call Ended is sent to the adjunct (cause CS3/42 —
Denial/Reorder).
For calls placed to on-ECS destinations, the reorder classification is the result of
the “reorder” internal treatment. A Third Party Call Ended is sent with the following
cause: CS0/34 — No Circuit or Channel Available.
Other Conditions
When a Switch-Classified call is made to a destination that gives modem tone, the
call is dropped (ended) with cause CS0/58 — Requested Bearer Capability not
Available.
ECS-Terminated Call Conditions Prior to
Classification
Before a call is classified, some conditions will cause the ECS to terminate the call
attempt:
■ No trunks available (none administered or none idle)
(cause CS3/20 — Trunks not available)