@RIVA, yes it might be a good method for sure .. This method is still used in some industries ..
I meant that the receiving arduinos do not pick phone up off hook and simply transmit the info via the ringing of the phone .. only the sending arduino dials but the call should be free because it is not picked up at other end ..
This means you could use the phone system without using the phone system ..
An interesting concept .. I wonder if the same concept can be used on internet systems .