Directional coupler
<communications> (tap) A passive device used in cable systems to divide and combine radio frequency signals.
A directional coupler has at least three ports: line in, line out, and the tap.
The signal passes between line in and line out ports with loss referred to as the insertion loss.
A small portion of the signal power applied to the line in port passes to the tap port.
A signal applied to the tap port is passed to the line in port less the tap attenuation value. The tap signals are isolated from the line out port to prevent reflections.
A signal applied to the line out port passes to the line in port and is isolated from the tap port.
Some devices provide more than one tap output line (multi-taps).
