This is a simple circuit showing various ways to terminate transmission lines. The characteristic impedance of these lines is 75 ohms. The top line is properly terminated, with a 75 ohm resistor at each end. As a result, the pulse travels across and is absorbed at the right end. This is the most efficient way to terminate a line, since it minimizes reflections that waste energy.
The second line is terminated with a resistor that is too large, causing the wave to be reflected, and absorbed at the other end (which is properly terminated). The third line is terminated with a resistor that is too small, causing the wave to be reflected negatively.
The fourth line is terminated improperly at both ends, causing the wave to reflect back and forth for a while.
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