Help understanding analog hardware needed?

I’m having difficulty understanding what hardware (Analog card in particular) I would need to install to interface with my current phone system.

I have used asterisk in the past but is was an all-IP set-up. My current scenario is two analog phone lines (AT&T) one of these is also a DSL line. the lines roll over so if a call is received one one while the other is busy the free line rings. we currently use 3 analog (2-line) business style (Panasonic KX-TS3282B) phones. our primary goal for using an Asterisk box is to handle voice-mail, call recording, and call tracking.

My understanding is that I would need an analog card with 2x FXO Ports (to attach to the incoming phone lines) and (at least) 2x FSX ports (attached to the phones). Is this correct? and if so how would DSL be affected? would the Asterisk box have to be installed after the DSL modem, Would a DSL Filter need to be used? If so where?

Any recommendations,and/or clarification would be greatly appreciated. We would like to keep this as simple and low-cost as possible. We have 11 other locations all containing 5 analog lines (one being FAX/Credit Card machine and one being Voice/DSL) each that we would like to set up PBX’s also. But would like to get a better understanding of what I’m doing on this small scale project first. Thanks


For the line that’s not your DSL line, it’s going to go straight into an FXO interface on an analog card.
For the line that is your DSL line, you’re going to need to split it in two - one side to the DSL modem and the other side, with a filter, into a second FXO interface.

To handle two analog phones, you’ll need 2 FXS interfaces; to handle 3 analog phones, you’ll need three FXS interfaces.

If you’re sticking with 4 total (2 FXO + 2 FXS) then the Digium TDM410 card, with the appropriate modules, can supply what you need. The bundle you’d be looking for would be TDM422B - or TDM422E if you want DSP-based echo cancellation (generally better) instead of software-based echo cancellation. Replace “TDM” with “AEX” for those model numbers if you need a PCI-Express card instead of PCI.

If you’re wanting to drive that third analog phone, then you’d be looking at the Digium TDM800, specifically the TDM842B - or again TDM842E for DSP-based echo cancellation. Same story here, replace “TDM” with “AEX” in the model number if you need PCI-Express.

If I can be of assistance, please let me know.


Thank you ever so greatly! I you’ve cleared it all up.