What is a Time-Domain Reflectometer (TDR) test on copper used for?

• A. Detecting copper cable faults, measuring length, opens, and shorts.
• B. Measuring wireless signal strength.
• C. Verifying fiber optic splice quality.
• D. Testing DC power supply efficiency.

Answer: (A)

Time-Domain Reflectometry on copper is about sending a fast electrical pulse down a copper cable and watching what comes back. The pulse encounters changes in impedance along the line, such as opens, shorts, or loose connections, and reflections travel back toward the source. By measuring how long the round-trip takes, you can calculate the distance to the fault, since distance equals speed times travel time. The shape and amplitude of the reflected signal tell you what kind of fault or discontinuity is present—an open at the far end, a short near the source, or a gradual impedance change along the cable. This makes it a powerful way to detect issues, determine the cable length, and pinpoint exactly where faults like opens and shorts are located in copper runs such as Ethernet cables or coax.

It’s not used for measuring wireless signal strength, verifying fiber optic splice quality, or testing DC power supply efficiency, which involve different tests and equipment.