One objection to the use of mineral insulated heating cable embedded in concrete floors concerns the difficulty of fault location in the event of failure. With a properly designed cable system and correct placing of the concrete, the chances of failure are extremely small. Should a fault occur, however, locating it has usually been difficult. A new electro-acoustic technique developed by the Research Division of Ontario Hydro has proved quite successful in pinpointing the location of a fault in the metallic-sheathed type of heating cable. The method is based on producing a series of high energy electric discharges at the fault point. To locate the exact source of the sound pulse, and thus of the fault, the race shown on the screen is arranged so that its left edge corresponds to the exact instant of the electrical discharge. The sonic pulse then appears as a "kick" on the oscilloscope screen at some point along the trace according to the delay caused by the time it takes the sound to propagate from the fault to the pickup device. The pickup can now be moved around on the floor until at some location the delay time, as shown by an immediate "kick" on the screen, is at a minimum. At this location the fault is directly below the pickup.