Editing Time-domain reflectometer (section)

=== Reflection ===
Generally, the reflections will have the same shape as the incident signal, but their sign and magnitude depend on the change in impedance level.  If there is a step increase in the impedance, then the reflection will have the same sign as the incident signal; if there is a step decrease in impedance, the reflection will have the opposite sign.  The magnitude of the reflection depends not only on the amount of the impedance change, but also upon the loss in the conductor.

The reflections are measured at the [[Input/output|output/input]] to the TDR and displayed or plotted as a function of time.  Alternatively, the display can be read as a function of [[Electrical cable|cable]] length because the speed of signal propagation is almost constant for a given transmission medium.

Because of its sensitivity to impedance variations, a TDR may be used to verify cable impedance characteristics, [[Fusion splicing|splice]] and [[electrical connector|connector]] locations and associated losses, and estimate cable lengths.