Sharper Image Acuvibe 7006C Personal Shiatsu Computerized Kneading Massager

Sharper Image Acuvibe 7006C Personal Shiatsu Computerized Kneading Massager. Tested and works great. Shows normal signs of light use. There is a phone jack but does not come with a phone wire to plug in. It works just fine with nothing. I am unsure why it has the jack.