Abstract: A telephone line tester comprises a bipolar LED which has coupled thereto two wires which terminate in a modular plug of the type used on a telephone subset. In this manner the plug is inserted into a telephone jack or receptacle, and if the telephone line is operating properly, one of the diodes will illuminate depending upon the polarity of the telephone lines. The illumination of the diode presents a visual indication to the consumer that the telephone line is operating correctly. In this manner the consumer may save a service call by locating the difficulty in telephone service with the telephone subset on the line.