New installation into legacy phone system

Hello everyone, I am the IT dept for a local insurance office that has 3 remote offices. the owner is looking to implement a voip solution so that all the offices can page each other without having to make a long distance phone call. So far I have installed freepbx on 2 machines and have them up and running and talking to each other via a sip trunk. Paging works great using softphones however we want to be able to use the legacy phone systems they have at each location. This is where I am getting confused. I know i will need either an FXO or FXS card for each freepbx machine to “talk” to the phone system. (The phone systems are all toshiba, main office is a dk280 and the remotes are ctx40s i believe, none of the phones are ip capable.) The main office has extensions 2xx and remote office 1 is 3xx. I know i will have to configure a dial plan in freepbx so that when a user dials 8|300 from the main of it will send the the internal call from one freepbx to the remote freepbx and then route the call to the appropriate ext. This will only be needed on 2-3 different phones in each office. Right now we are not looking to move off of our land lines, we just want inter-office calling. Can anyone help? Thanks a lot!

Your main issue on trying to do this will be setting things up so that the correct extension on the other end gets dialed. For example, a typical setup in this type of scenario would be:

User1 (201) -> PBX1 -> FXO Port on PBX1 (i.e. Line4) -> SIP ATA -> FPBX Server1 -> FPBX Server2 -> SIP FXO -> ATA on PBX2 -> PBX2 -> User 2 (301)

It’s convoluted, but for most legacy systems it’s really the only way to get it to work. The main issue is that most systems won’t let you directly ring an extension from a line port (FXO), so you need to use an ATA (that way, when you dial it can dial the target extension directly). SOME legacy systems will let you setup digit routing, but it’s not very common and can be a real pain if you’re not a legacy PBX person (I have no idea for this case as I’ve never dealt with Toshiba at that level). Also be aware that your callerID will not get passed along properly, as you have no way of identifying yourself to the legacy PBX (since you’re calling out from an ATA).

Depending on the number of extensions that you have at each site and your level/comfort in programming the existing systems you could streamline that process, but it will take a bit of work. For example, a better setup would be

User 1 (201) -> PBX1 -> FXO (line port) -> ATA -> FPBX server -> ATA registered at second site -> FXO (line Port) -> PBX2 -> User 302

The trick to this setup is that you’d have to have a voicemail/autoattendant setup on the legacy PBX2 to immediately answer the incoming call. You’d then have to have FPBX customized so that when the call is answered, it would pass along the DTMF for the final destination. The Auto attendant would then route the call based on the DTMF just as if an outside person had called and directly dialed an extension. In theory it all works, but depends on your level of comfort programming it all…


ok that makes a little more sense, lol so it looks like we will need an ata for each phone as well that wants inter-office calling. Currently all the ext for the main office are individually punched down on a block with what looks like a 50 pin cable connecting them to the toshiba system. Could I punch down on the the ext that needs inter-office and plug into a FXS card in the freepbx machine? then with a dial plan detecting the 8 first digit it would know to go through the fpbx and bypass the regular pbx entirely? I know voltage is carried through these lines to provide tone, etc so i dont want to fry anything. That may not work at all I have no clue. I have enough working knowledge of phone systems to be dangerous. Thanks for the help

Sorry I know it’s messy, what you’re trying to do is something that typically a telecomm integrator would setup, not an end user so if you’re not familiar with PBX setup its a bit tricky.

You don’t need individual ATAs, just one per system. Here’s the basic points:

  1. PBX1 needs some way of talking to your FPBX system
  2. PBX2 needs some way of talking to your FPBX system

Since PBX1 and PBX2 can’t talk SIP, so you have to let them talk to each other via analog. To do this, you need an FXO (a line port, something that accepts dialtone) and an FXS (something that generates dialtone).

The problem becomes more complicated because you need a way to dial internal extensions on PBX2 when PBX1 calls out. This is not something PBX2 ever expects to do over a regular line. (i.e. when a normal person calls a phone number, that number just rings on the PBX; a normal caller has no way of saying "Just ring the extension I want, not all of the extensions programmed for this line).

So to solve that you either have to use an auto-attendant (give the calling person a way to specify to PBX2 “just ring the extension I want”), or connect it the other way around so that PBX2 has the ATA; the ATA acts like an internal extension (rather than an external line), so it’s able to directly dial extensions on PBX2.

Realistically I don’t think this is something you should try to do based on help from this forum, as the scope is really above and beyond basic FPBX community support/assistance… This is the type of custom design/integration that you’d want a consultant to at least design (if not implement) for you.


Rob, it seems this is going to be to big of a project to take on myself. Now lets say that I talk to company into buying a few IP phones for the agents that need inter-office. Would it still be this complicated to integrate the systems this way? would the ip phones be able to page the other exts in their own office as well as the remote ip phones in the other offices?

Thanks for your help!

The problem always boils down to integrating the Legacy equipment with the IP stuff. If you get IP phones, you can set them up fairly easily to be able to call/page each other… but they will be completely separate from the legacy systems… so that means you won’t be able to make calls to the real world on them, and they won’t be able to receive inbound calls from the real world either. You could get a SIP provider and setup a trunk to give them outside world (PSTN) access, but then you’ll also have a new phone number etc so you’ll basically end up with two completely separate phone systems. This usually ends up being the migration path that companies take… setup a whole new system to give one important new feature… then once it works slowly migrate people off the old legacy equipment on to the new IP setup.

If you’re OK with that, then since you have everything else setup all you’d have to do is get some IP phones to replace those softphones you’re using; the setup on the FPBX side would be the same as what you have now.

Just to clarify something… when you say the offices want to page each other, I assume you meant call each other (i.e. intercom), not page…

If your company is really determined to have the Legacy PBXes integrated together it’s doable, but not something that you should take on yourself.


How many extensions are you talking about at each office?

IP phones are not that expensive, the features they will gain going completely IP will be a huge leap forward. Have you looked at the feasibility of this?

I have decided to work up a proposal to slowly work them off this ancient phone system in the main office, by doing so they can also drop some of the land lines for voip. The remote offices have newer ip capable systems but just do not have the interface cards needed. Speaking of anyone know a reputable vendor for such things? the local guy that did the original install seems to want to over charge.