For a few months I made an alarm for my house, it is very simple: it is based on magnetic sensors DC-1561 (for windows and exterior doors), a few PIR sensors for rooms, buttons, LEDs and (of course) an ArduinoNano v3. Something simple!
The question is that lately I do not spend much time in my house and I would like it when I'm away from home the alarm calls me (when is activated) to my cell phone using the public switched telephone network (PSTN) because I live in Cuba and it's the easiest way and cheaper (the GSM modems/modules are very expensive for me). I do not want to leave any message or sound record, just call me and receive the call on my cell phone, using the RJ-11 connector (in my country only 2 pins are used) to connect it with the Arduino/some_IC.
I have been investigating since yesterday and have found quite a bit of information. The most recommended/successful that I found (remember that I want to continue using the system that I already have, I just want to add to the Arduino the ability to use the mark through the PSTN) is to use an IC (HT9200B) that is a generator of DTMF codes (as see in the figure) with serial AND parallel connection, aparently, compatible with the electronic logic of the Arduino (5V).
But of all the information that I found is to connect to this IC (HT9200B) a speaker and reproduce the DTMF codes. This is not what I want, what I want is to connect directly to the phone line and be able to "call" from it.
Anyone have any ideas, links, projects in progress, or anything that can help me?