Digium Interface card module question

After looking at the Digium cards, I have a question that I am not quite sure of. Theres two module slots for the AEX800 or TDM800P card, and since i need one module slot for FXO to plug the PSTN in, won’t that leave me 1 slot for FXS S400M which can only support up 4 analog phones(need 6)? Is there any solution for this matter?? or do i have get an extra card or another card?

Aside from that, I want to know if its is possible for Asterisk to handle multiple calls at once with a single phone line from the PSTN?

Thank you in advance!

yes, as far as I know the Digium 8 port card has the channels split into two blocks of four, it appears to use the same four channel modules as the TDM2400.

I use a Yeastar YSTDM800, these take four, two channel modules so they are more flexible re. the number of FXO & FXS channels. They also do a module with one of each port that connects through if the power fails, so that extension connects directly to the trunk if the power fails.

There are other makes, but I’ve only use Digium and Yeastar cards.

You could also consider digital VoIP phones for extensions, or adding phone ports using ATA boxes, which just connect via ethernet and give a normal phone socket.

One analog phone line can only handle one call.
You can get a digital line from your phone company that will allow two or more calls, but often these cost more than extra analog lines until you get to a realtively large ‘line’ count.

You can of course add VoIP / SIP ‘lines’, there are many providers that will give you a normal Dial-in number that connects to your Asterisk system via SIP. Quite often these are free for incoming calls and cheap (or occasionally free) for outgoing calls.

Thanks for the great help! that certainly cleared up my mind… =)


The TDM800P and the AEX800 have their module capability split into two banks. Each bank can accommodate either one quad module, or up to two single modules.

Using a quad module in a bank precludes you from using any single modules in that bank.

A quad module may be used in one bank, and up to two single modules in the other, thus six ports. Subtract one single module and it’s five ports.

Or, quad modules may be used in both banks for eight ports.

For four ports, either one quad module may be used, or four single modules.

Three ports requires the consumption of one bank with two single modules and the population of the other bank with one single module.

Two ports requires the usage of two single modules, one bank would be best so that you’ve left one free for adding an additional quad module or up to two single modules.