"POTS" to FreePBX

I’m new to FreePBX and looking to set up my regular telephone line in to the system for an auto-attended voice mail type system… Hopefully I can also set it up to email me the voice mails.

But I have a beginners question: Do I need a fancy board like the “Digium® TDM410” or something like that to plug in the phone line to my computer, or would a regular voice modem work?

Yes. You do need an analog to digital converter card. I do not think a regular fax modem would work with asterisk. I would also recommend using an echo cancellation module with the TDM410 as well. Otherwise you will most likely have echo issues. There are also other card manufacturers such as Sangoma, but I have not used those before…

Here is what you need:

  • Digium TDM410 card
  • Digium FXO Ports (These are modules that plug into the card to allow a regular telco line to terminate to the card)
  • Digium Echo Cancellation module (This also plugs into the card, and provides an echo cancellation technology)

There are some “cheap” cards out there, but they’re one of the greatest sources of disappointment in an asterisk system, given the proclivity of echo, etc.

If you don’t want to spend the money for the good quality card, you might consider a SIP trunk for testing, then if you like what you see, you could have your existing POTS number ported over to the sip trunk.


You can use something like a Linksys SPA3102 voice gateway to terminate your PSTN line (and also get a FXS port to plug your old analogue phone into). This device is about £50-60 in the UK. Handy if you want to use something like a ‘media PC’ for your FPBX/Asterisk server, which generally are too small to have expansion for cards.

I’m sure there other folks will chime in with their suggestions …