Which statement about impedance matching is true?

• A. It is never necessary if the cable is shielded.
• B. Impedance mismatches are ideal for short runs.
• C. Impedance must be maintained only at the source.
• D. Impedance matching should be achieved with correct terminations to minimize reflections.

Answer: (D)

Impedance matching is about making the source, the transmission line, and the load all present compatible impedance so signals aren’t reflected along the run. When the line isn’t matched, some energy reflects back toward the source, causing distortions and potential data errors, especially at higher speeds or longer distances. The best way to prevent that is to terminate the line with a resistor (or network) that equals the line’s characteristic impedance at the appropriate ends, so energy is absorbed rather than reflected. Shielding alone doesn’t guarantee this, and mismatches can still cause reflections even on short runs if terminations or impedances aren’t correct. So using the correct terminations to match the line and load minimizes reflections and preserves signal integrity.