Question : Trixbox Trunk Sequence in FREEPBX

In my outbound routes I have 3 providers listed in the order I want them used.  I need to know the below regarding its operations.   Please limit your answers to fact or actual 1st hand usage.  I've read conflicting information about this and some just pass on what they read without knowing what it really does.

Here is an example of our setup.

 Trunk Sequence:  ZAP-T1 is 1st, VOIP-PROVIDERA, VOIP-PROVIDERB

1.   In what situations will the 2nd and 3rd trunk be used.
      - when the ZAP T1 24 lines are all in use?
      - If the ZAP T1 is down.  Carrier having problems?
      - If the all circuits are busy message comes up?

2.   How long is the delay before the 2nd, and 3rd trunks are used.
     - a few seconds, 20-30 seconds, a minute or longer?

3.   Is there a way to change some file in Trixbox to mimiize the delay in question 2 above.  Lets say I want it to rollover to trunk 2 within 5 seconds of a failure?

4.   Is there another way to provide rollover of trunks to handle all situations where a trunk is not useable if trixbox doesn't do it already?

Please provide as much detail to all the above 4 points and I will award the 500 points ASAP.

Thanks

Answer : Trixbox Trunk Sequence in FREEPBX

1.  "Rollover" detection is when the trunk reports circuit busy / outbusy / etc.  Basically if the call cannot proceed out that trunk the call falls to the next trunk. We have two core asterisk switches and freepbx boxes hanging off both, if on core goes down the lines roll because the IAX2 trunk for the downed box reports unavail  / busy.

2. A few seconds, normally a busy is generated within 1 second and the system fails over to the next trunk

3. I don't believe there is in the web interface, I'm not sure about editing any * config files directly because I've never had this become a issue.  If a trunk fails, failover is completed in a very reasonable timeframe.

4. The Trixbox/Freepbx method is good, it's configured so that if a trunk is unavailable *for any reason* the call will fail through to the next trunk in the sequence.

Hope that helps.
Scott