From the Help files....
Within a Small Community Network, calls to remote user are automatically routed to an IP trunk setup for connections to the appropriate remote IP Office. If the remote IP Office doesn't respond to the call attempt with the set timeout, the call is rerouted as follows:
· First the call is rerouted to any other trunk with the same outgoing group. If this is the case, that trunk must be able to route calls to the correct remote IP Office without any further dialing. This would typically require the fallback trunk to be a private leased line.
· If the call is still not connected an attempt is made to reroute the call via either LCR (IP Office 3.1 and 3.2) or ARS (IP Office 4.0+) short code matching of the original dialed number. This later method is the preferred case as the LCR/ARS short code matching allows number manipulation to make the outgoing dialing suitable for rerouting across the PSTN. To make this the preferred case, the IP trunk should be put into its own unique Outgoing Trunk Group ID.
In cases where the call is routed to the IP trunk by LCR or ARS in the first place, the timeout used for IP trunk fallback is the Timeout defined for the current LCR or ARS form being used. A value of 0 disables IP trunk fallback.
Setting the Default IP Trunk Fallback Timeout
The default timeout for IP trunk fallback is 5 seconds. This timeout can be changed for specific IP trunks and or all IP trunks. The required timeout is set through the Source Numbers tab of the NoUser user. The entry or entries take the form H323SetupTimerNoLCR line_number timeout where the line_number should be ALL for all IP trunks or the specific Line Number used for the IP trunk on its Line configuration tab, and the timeout is set in seconds.
For IP Office 4.2+ this option is now set through the IP trunk setting Call Initiation Timeout.
ACS - IP Office Implement
"I'm just off to Hartlepool to buy some exploding trousers
ial