In telecommunications, signal reflection happens when a signal is transmitted along a transmission medium and part of it is reflected back toward the source instead of reaching the end. This reflection is caused by imperfections or physical variations in the cable that lead to impedance mismatches. These mismatches disrupt the signal and cause some of it to bounce back. In radio frequency (RF) systems, this is typically measured using the voltage standing wave ratio (VSWR), with a device called a VSWR bridge. The amount of reflected energy depends on the degree of impedance mismatch and is mathematically described by the reflection coefficient.