Telephone Line Tester is a new kind of line fault tester with safety & multi-functions capabilities. Besides the functions as a common Tel Line Tester, it also has the functions of high voltage protection and dangerous voltage warning. A phone line tester is used for detecting either digital or analog phone systems as well as the line polarity. Telephone line testers are good for both personal and professional use. Fiberinthebox supply some mini phone line tester, and other Telephone line tester. For more information about our optical fiber tester tools, please contact our sales representative right now. Save your time & money for your business or project!