How to use a Linux system as a land phone

I have a land line connection. I would like to receive and make calls using my computer. It is a basic land line connection which also provides broadband internet. I am not asking about VoIP.

• I would like to know whether this is possible to make land line calls using my computer hardware.
• If possible, how to do that with some software or some commands?
• This answer mentions a use of Asterix. Can we use it here?

What you need is an FXO card for your PC. This is a PCI card with a phone socket in it, and it effectively works as a PSTN (public switched telephone network) phone on a card. You plug this into your wall socket just as you would a telephone.

Then you use PBX software (such as Asterisk) to mediate the calls. You would need a way to interact with the PBX, and this is usually done with VoIP, even if the FXO card and the headset are attached to the same machine. You would use a softphone that connects to the PBX over VoIP and then the PBX would make the ongoing call over PSTN.

You will still need a splitter. The broadband connection needs to connect to your ADSL line directly and to the FXO card via a filtered splitter.

The advantage of this, over just plugging a hardware phone into the broadband line with a splitter, is that you get to take advantage of the features of a PBX like voicemail, voicemail to email, fax to emails. The advantages increase when used in conjuntion with an outgoing VoIP service.

The simple answer is no, you cannot make a typical computer into a PSTN-connected PBX without a new piece of hardware: an "FXO card". An analog modem cannot perform as a voice-service FXO as they are designed only to process data bits asynchronously (i.e., V.92 protocol) – that's why modems are much cheaper and more common than FXO cards. A LAN card's port doesn't accept analog signaling at all and cannot handle your telecom's line voltage either, so don't plug a phone line into it!

In my opinion, if you are dealing with fewer than four telephone lines coming into your premises, I would not build a PC-based PBX but rather buy a smaller embedded device to interface with it.

The Linksys SP3102, for example, will handle one phone line, and allow you to make or receive calls with it via a desktop SIP app. Bought second-hand, it is cheaper than many quality FXO cards, which you would need to build an Asterisk or FreeSWITCH PBX yourself. I have never used a USB-FXO, but I doubt call quality or latency will compare favorably to a dedicated PCI card (remember those things?).

Also, the time to set up and debug Asterisk/FreeSWITCH to work reliably with any FXO card is substantial, whereas the Linksys box can do basic call processing by itself after configuring it via a web page. Later on, you can integrate it with a separate Asterisk server if you want more configurability or voicemail storage, etc.

No additional hardware is no problem if your computer (modern notebook?) has a microphone and speaker. However, to reduce or avoid crosstalk, an earphone plugged into the audio out connector would help.

There is plenty of software that can connect your microphone and speaker to asterisk, e.g.: Ekiga, Linphone.

You don't like VoIP, but you call over voip without noticing. Remember, internet started with a digital modem over phone lines, but nowadays analog phone calls are routed over the internet. Asterisk is your friend here.