This is just a rough starting point. One way to test the modem is by opening the efax-gtk program and clicking "Standby." It will attempt to receive faxes. If the phone line is unavailable to it it spews out continuous red error messages. To send faxes from files they have to be in postscript format. From the man page: Printing to file from the program itself        Probably  the  simplest  way of using the program with a word processor is to print to file from the print        dialog of the word processor program concerned, and choosing a file name  in  the  $HOME/faxout  directory        which  can  then  be selected with the file selector dialog in efax-gtk.  All Unix/Linux word and document        processing programs will print to file in Postscript format, ready to be faxed by efax-gtk.  (At least, if        there is one which does not, I do not know of it). You might also want to read the whole man page. (Run "man efax-gtk" in the terminal.) Some of it is technical, but there's also plenty of clearly written information like the above quote. I don't have a phone line convenient for testing this right now, but I hope that helps.