Learning Asterisk ! Soekris net5501-70

Hello, I am Pietro, and this is the frist time that I writhing in this forum, and before to start to ask some questions, I just want to say thanks to this beautiful and big community :smiley: Ok, so, I have got an soekris net5501-70 which is running on freebsd 6.3 that I am using as firewall with pf . so, I am very interested in a VOIP, and I am studying and trying to learn Asterisk, but, I am still confused about what to do and also which FXS/FXO card to get … I am having trouble to understand the difference between FXS/FXO, or better, which is better for me … I just want an cheaper FXS/FXO card compatible with zaptel and freebsd to make test and work on, and, I also would like to read something about how to get start with Asterisk, about hardware etc etc …


If you want to connect an analog phone to Asterisk you need a card with one fxs port, if you want to connect an analog line to Asterisk you need a card with one fxo port; Digium’s cards like TDM41XX are manufactured with both type of modules, so in one card you can have fxs and fxo ports, see digium.com/en/products/analog/tdm410.php .


Marco Bruni

that’s exactly what I don’t understand, could seem stupid, but I still don’t understand the difference between analog phone and analog line … could you explain me this ? Thanks

Well Pietro, since no one replied to you, I’ll try to explain it to you.

It really isn’t that hard. It has to do with the power that is supplied over the lines. This site has a nice image explaining the difference: http://www.x100p.com/voip/fxo_fxs.php

The reason analog phone lines still work when the power in your house goes out, is because the phone company supplies power over the phone line to power your telephone (when there is no PBX).

An FXS interface provides power (battery) to FXO equipment and generates ring signals. An FXO interface receives power (battery) and receives ring signals. (Your phone company uses FXS equipment to power your FXO phone)

Now if we bring the PBX into the picture, we see that we need both types of equipment if the PBX sits between the phone company and the phone(s) in your house.

The PBX needs an FXO port (acts like a phone to the phone company) for every outgoing line. The FXS ports inside the PBX (acts like a phone company to your phones) connect to the devices you have internally. E.g. if you have a fax, a work phone and a private phone, you might consider 3 FXS ports if you want to ring these 3 ‘devices’ seperately.

I’m looking at using the same Soekris net5501 for my gateway / router /firewall /pbx.
Do you have it installed already? Or have you found other reports of it being used? This thread on the soekris mailinglist explains the setup needed to power a TDM400 board.