Abstract: A low-cost transmission line fault detector visually indicates the nature and location of transmission line failures. A current detection circuit inductively coupled to the transmission line produces an output signal when current is flowing through the line. A voltage detection circuit directly coupled across the transmission line monitors the relative potential across the line and produces an output signal when the relative potential is within predefined limits. By observing the states of the outputs of the current and voltage detection circuits (e.g., through visual indications provided by light emitting diodes), one can tell if the transmission line has shorted or open-circuited, and if it has, the location of the failure (e.g., between the source and the detector coupling point or between the detector coupling point and the load).