Which tool is used to determine the physical distance to a fault along a cable by sending a signal and analyzing reflections?

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Time Domain Reflectometry (TDR) is used to locate faults along a cable by sending a fast electrical pulse into the line and analyzing reflections that occur when the signal meets impedance changes. The time between sending the pulse and seeing a reflection, together with the cable’s propagation velocity, lets you calculate how far away the fault is. Since the pulse travels to the fault and back, you use half the round-trip time to get the one-way distance (distance = round-trip time × velocity / 2). This is like a sonar test for cables, revealing opens, shorts, or bad connections wherever the impedance changes along the run. The reflection shows up as a spike on a TDR trace, with its position indicating where the fault lies. Other tools don’t provide this distance-to-fault capability: a cable tester checks continuity and mapping but not fault location, toner and probe helps trace physical paths rather than electrical faults, and a multimeter measures voltage, resistance, or current without locating reflections along a line.