I put this mp3 on my desktop to use with my caller ID to help me stop telemarketers from repeat calling. I keep my music player loaded with the file. Then when I see an 800 number on my caller ID or a number that says OHIO CALL, or PENNSYLVANIA CALL, I pick up the phone, hold it by my speaker, play the file and hang up. The 3 tones in the mp3 file tells the computer that is making the annoying calls that this number is no longer in service.