TDM400P "knockoffs" vs genuine cards

Hi everybody,

I’m looking for a card to provide an FXO port for my PBX which is currently running Asterisk 1.8 and FreePBX 2.8 + the DAHDi Config module. I basically want to connect my Bell telephone line to the PBX so I can run the legacy bell phone line at the same time as my new VOIP provider for a few months and make sure everything is working smoothly.

I figured out fairly quickly what I need is a TDM400P with at least 1 FXO port. Maybe I’ll get 2xFXO and 2xFXS just to have some flexibility.

But when I go on eBay, I see a lot of different options. I’m wondering which ones are “legit” digium cards that will work with relatively few tears, and which ones are China knockoff cards that will give me grief.

This looks legit:

But this looks tempting as well:

What is this new “version 2” TDM400P card? I like the failover support the ebay article suggests that it has, but I wonder if it actually a legitimate, supported card, or is it some knockoff may not work properly in a vanilla Asterisk installation.

What do you guys think?

The problem is that some (more than a few) ads on fleabay use a recognizable manufacturer’s name and model number to advertize products that are not made by that manufacturer. Look at digium’s site and try to find any reference to a version 2 of their very popular TDM card, it isn’t there. And there is no product there that looks like the one featured in the ad you referenced.

That is not to say that the advertized product is bad, just that it isn’t a digium product. When it comes to analog TDM cards, you pretty much get what you pay for. If you want HWEC (hardware echo cancellation) then you can expect to pay hundreds more than one without HWEC. The first ad you reference is an older digium offering that is not HWEC capable.

The Openvox cards or the only inexpensive cards I would recommend.

I purchase mine through Adam Huebner at Bullzeye, a long time supporter of the FreePBX project.

I figured that was the case - you’re right I don’t see any “version 2” of the TDM400P cards anywhere on Digium’s website.

Is hardware echo cancellation really that important? Shouldn’t Bell / my PSTN provider be handling that stuff? I suppose I shouldn’t get into that debate, lol.

Thank you for recommending Bullzeye Networks! I just sent them an email asking for details for shipping to Canada. All their products look reasonably priced and if you guys say that they are legit products I’m more than happy to spend an extra couple bucks over there and not take a chance.

“Is hardware echo cancellation really that important?”

All I can say is when you need it, you need it. I did some initial testing with a cheap OpenVox card, and it worked pretty well, but not perfectly. Sofware EC goes a long way, but it doesn’t always do the trick. I never did replace it, but once in a while I am reminded that I need HWEC.

I never did find a good retailer in Canada, with pricing comparable to what is available in the US.


The other poster is right, occasionally you find line conditions with horrific impedance mismatches the only hardware echo cancellation can address. I have seen very few of these cases.

As far as the “you guys” recommendeding Bullzeye and OpenVox my opinions in no way are official recommendations of the FreePBX team. I am only sharing my personal experience with the product and the owner of Bullzeye.