A buried perimeter loop wire break detector with a base unit and probe unit. The base unit injects different frequencies into the two ends of the loop wire and the probe unit detects the frequencies at a test location along the wire. If a signal is not detected, that indicates the direction toward the break. By halving the distance along the wire toward the break and retesting, the location is quickly determined. Both frequencies and amplitude are measured, sometimes with amplification, both earth and wired grounds may be employed, and a micro-ohmmeter measures resistance of the loop wire to indicate satisfactory operation.