What do deflections indicate to the time domain reflectometer user?

Question

Options

• AThey indicate splices, water in the cable, split pairs, and discontinuities or faults.
• BDo not connect live circuit cables to the input of the time domain reflectometer.
• CUpward deflections indicate high-impedance mismatches or opens, and downward deflections
• DThey are used to select the I/O impedance of the time domain reflectometer.

• A
  7% (4)
• B
  4% (2)
• C
  87% (48)
• D
  2% (1)

Explanation

Option C is correct because TDR deflections carry directional meaning: upward deflections signal high-impedance faults (like opens or breaks where impedance spikes), while downward deflections signal low-impedance faults (like shorts where impedance drops). This directional behavior is a core operating principle of how a TDR interprets reflected waveforms on a cable.

Why the distractors are wrong:

• A describes what a TDR can detect (splices, water, faults), but doesn't answer what the deflection direction specifically indicates - it's partially true but misses the key concept of up vs. down.
• B is a safety warning about not connecting live circuits, which is unrelated to interpreting deflections.
• D describes impedance matching for input/output configuration, not deflection interpretation.

Memory tip: Think "Up = Unbroken (open/no connection = high impedance)" and "Down = Dead short (low impedance)." The waveform deflects in the direction your impedance goes - up for too much, down for too little.

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