AT&T 555-230-520 manual Tandem Switch Operation, LAI Using a Tandem Switch

Look-Ahead Interflow

INCOMING

CALLS

SENDING SWITCH

MAIN

SPLIT

ISDN - PRI	TANDEM	ISDN - PRI
	SWITCH

BACKUP

SPLIT

FAR END SWITCH

ALTERNATE

BACKUP

SPLIT

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-tocommand that routes the call over an ISDN facility before call acceptance, the route-tocommand is performed on a “look ahead” basis in the same man ner 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:

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

Figure 8-5. Tandem Switch Vector

8-10Issue 4 September 1995