PBX to PBX remote connections over FXO ports

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Mar 22nd, 2008
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Hi experts I am new to VoIP. We have three sites and are connected via 2801 routers on ecah site Over T1. All sites have PBX. If I install 2 port FXO card into all three routers, can I establish the phone connection between each sites. If yes Can I have some configuration examples.



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Overall Rating: 5 (2 ratings)
paolo bevilacqua Sat, 03/22/2008 - 16:11
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Hi, if you only use FXO ports on the router, you will have much trouble, because the router can't know when the remote has disconnected and the port will remain stuck. The workaround would be to configure tone based disconnect supervision but that is also complicated and doesn't work all the time. Beside that, with FXO you have to do two-stage dialing, that is dial, wait for another dialtone, then dial again the remote PBX extension.

In summary, it is a very poor design.

So it is recommended that you connect the PBX in order of prefeence with:


2. analog E&M

3. both FXS and FXO ports. In this latter, router places calls on FXO port, and receive calls on FXS.

Hope this helps, please rate post if it does!

modipremal Sun, 03/23/2008 - 07:06
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Thanks for your reply. How can I use analog E&M and how it be connected to PBX.

paolo bevilacqua Sun, 03/23/2008 - 11:30
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You need E&M interface on the PBX, and help from the PBX technician to configure it. So if you've to add an interface anyway, the preferred one is ISDN BRI. Write back when you've got one of the three choices mentioned above on your PBXs.


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