Asterisk FXO

Just a few questions. I’m planning on building an Asterisk FXO box. This is a small business with 10 analog lines running in the office. I’m pretty sure that would mean I’d need to get 10+ FXO modules, I’m looking at these, ( … -1412.html ). My question, is this the only option I have if I want to use analog lines? I have the capability of changing all those analog lines into ethernet, but then purchasing phones for them all would be very expensive (I need to keep costs down). Any ideas?




But your going to need phones anyway

How many staff are you going to have ?

and how many concurrent calls?


Well I have lots of analog phones now that can handle extensions. But if I were to go with the other route, I’d of course get Phones that are ethernet powered. For concurrent calls, We were assuming to start with, about 4, which is why I assume I would need 4 FXOs for that openvox card. Staff is around 10, but all won’t be using the phones at the same time.


An FXO card will only connect your server to the lines… Your staff will still need phones, If you want to use analog sets with asterisk then you need cards with FXS interfaces. or use iP sets


Ahh, so lets just say, I want to at most have 4 simultaneous calls. I plan to have the PBX box use VoIP from some service over the internet (I don’t want to actually have an analog service from my telephone providers [Verizon]). So I’d need 4 FXO on the PBX, which are wired to those 4 analog phones in our office. Then the PBX would understand the on/off hook and route the calls in/out over the internet VoIP.

Unless you can stress to me that getting VoIP phones is better.

Almost one letter out. :smile:

You need a 4 port FXS card to connect to the 4 phones. and use voip for the trunks.

-----voip over dsl-------|  *server----fxs|----phone

Sort of like above


Ahh thank you for that clarification, I do need FXS (not FXO).

Thanks for all your help Ian.


I prefer to use ATA (analog telephone adapter) devices for FXS ports. Check out the Grandstream HT286 (single FXS port for around $30) or similar products from other vendors. There are also 4-port and 8-port devices. The ATA contains a codec and performs the analog->digital conversion using its internal dedicated processor, thus reducing the computing load on your Asterisk server.