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Look-Ahead Interflow
8-10 Issue 4 September 1995
Figure 8-4. LAI Using a Tandem Switch
Sending Switch Operation
The sending switch is unaware that its Look-Ahead Interflow call is being
tandemed to an alternate switch. The operation of the sending switch in the
tandem switch configuration is the same as that in the two switch configuration.
Tandem Switch Operation
If the receiving switch executes a
route-to
command that routes the call over an
ISDN facility before call acceptance, the
route-to
command is performed on a
“look ahead” basis in the same manner as a sending switch. If the call is
accepted at the far end switch, acceptance is passed to the sending switch, and
call control is passed to the far end switch, along with tandeming of the original
calling party information and the original DNIS name. If the call is denied, the
next step of the tandem switch vector is executed.
Here’s an example of a tandem switch vector:
Figure 8-5. Tandem Switch Vector
SENDING
SWITCH
TANDEM
SWITCH
FAR END
SWITCH
ISDN - PRI
INCOMING
CALLS
ALTERNATE
BACKUP
SPLIT
ISDN - PRI
BACKUP
SPLIT
MAIN
SPLIT
1. goto step 6 if calls-queued in split 30 pri h > 5
2. queue-to main split 30 pri h
3. announcement 200
4. wait-time 2 seconds hearing silence
5. stop
6. route-to number 4000 with cov n if unconditionally
7. busy