500XP Pair Tracing ProbeCat No: 500XP. Water resistant (floats) and tough, combined with all the very best digital signal processing filtering 500XP will help identify signals buried in the worst of noiseSimple two-button operation with dual signal strength indicating LEDs can work with any tone generatorHeadset allows discrete use in quiet environments and can help in acoustically noisy areasoption to enable acAlert. which helps warn users if brought near hazardous ac power voltages which may be inaudible if using the advanced filteringPatented – Patent #6946850, 8754629