The best way to record a phone call is to hook the DM-1 up to an extension OF THE SAME LINE or to use a splitter to connect both the telephone and the DM-1 up to the same extension outlet. The second technique (using a splitter) gives poorer quality than connecting the DM-1 directly to the wall extension.

For instance: I connect my DM-1 up to an extension of my office phone that's located in a bedroom.  I hit RECORD.  I then go into my home office and dial into the teleclass.  When I'm done with the teleclass, I hang up the phone, then go into the other bedroom and hit STOP.  Then I bring the DM-1 into my office and connect it to my USB port to download the recorded file from the DM-1 to my PC.  This gives me the best quality over any other configuration I've tried.  (I've been playing with recording teleclasses for four years, and I've tried a bunch of different configurations.)

I convert the .dss file into a .wav or .mp3 file.