We have two office buildings connected by a WAN. Our primary office has a phone system that requires each handset to be connected to the PBX via cable (it is NOT VOIP compatible). We are setting up some offices in the second building but don't want to upgrade our phone system and I was hoping to find some way of 'mapping' a network connection over the WAN? This might be completely impossible (I'm a novice doing my best to help out with some tech stuff) but along with the server/internet traffic travelling across the WAN I want to send data from the phone port across the WAN and have it sent to the phone handset once received (please excuse lack of jargon). If I can clarify further please ask as I don't really know how to explain what I want. Thank you very much!

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  • I'm pretty sure that can't be done. Before VoIP, you usually had to have a phone system ("switch") in each building which you could then connect with trunk lines if you wanted campus dialing. You could double check that there is no VoIP add on card or module for your phone system, there might even be third party solutions. – Todd Wilcox Apr 16 '15 at 12:58

Look into Asterisk (http://www.asterisk.org - free software-based PBX, heavy on VOIP). It's possible to use a COTS computer with a PCI line card to pair with a PBX. You configure your PBX to see Asterisk as a partner system and to treat the terminal/port connecting to the line card as an outbound trunk.

At that point you can use VOIP from the Asterisk side to "bridge" your WAN connections. Possible to use ATA's (Analog Telephone Adapter) on the far end to connect "regular" telephones to the Asterisk PBX. You can also/instead connect VOIP phones fairly easily if you have them. (or use software-based phones -- anything supporting SIP will probably "work," but as always your mileage will vary)

This will require some customization in Asterisk and some finagling and it will not work perfectly seamlessly but it IS a solution that would allow you to bridge your phone system across the WAN with a minimum of expense.

Also an important consideration is QoS on your network. Newer Cisco switches can use the AutoQos feature to set this up fairly painlessly. Your WAN QoS scenario will also be a factor.


Your phone system is not VoIP. It cannot be directly bridged by IP. (every digital PBX I know of, does this by installing a VoIP module, and even there, it's a proprietary bridge between two PBX's)

If the PBX is pure POTS, then a channel bank (T1) and some circuit emulation trickery could get that T1 carried across an IP network. But such a hackish solution is a waste of time and money -- even if this stuff is in a box under your desk.


If your phone system supports extenders over T1 or the two phone systems can be linked by T1 in some fashion, you could look into using something like the Cisco NM-CEM-4TE1 module.

I was in an environment where they had an older Avaya system and wanted to install an extender at a remote location. We used Cisco routers with this module at the time which allowed the Avaya PBX to "hand off" a T1 to the routers which then encapsulated it as IP traffic to provide a T1 to the extender at the remote location over the WAN link.

You may have to do some research as it has been awhile and some of the hardware may be end of life at the point, but there should be something similar.

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