The present invention is a technique for locating and identifying a failed filter/arrester in an underground conveyance such as a fiber optic cable. A sensor is installed in the filter/arrester housing to sense grounding of a cable locating frequency. The sensor will monitor the cable locating signal that is normally on the cable and blocked by the filter arrester to ground. A small radio frequency oscillator (85 to 88 Hz), also installed inside the filter housing, is activated by the sensor. The RF signal is detected above ground with standard cable locating equipment. A warning indicator such as an indicator light may also be installed on the outside of the filter housing. The indicator is also activated by the sensor. In that way, the particular failed filter can be identified if multiple filters are installed at that location. The power that will be required to operate the RF transmitter and indicator will be obtained from the voltage passing through the cable.