[R]

RFI - Radio Frequency Interference.

RG/U - RG is the abbreviation for radio guide, a military designation for a coaxial cable, and U stands for universal.

Ribbon Cable - A flat cable made with parallel round conductors in the same plane. Also referred to as planar and/or flat cable. Any cable with two or more parallel conductors in the same plane encapsulated by insulating material.

Ridge maker - one or more ridges running laterally along the outer surface of the plastic insulated wire for purposes of identification.

Ringing Out - The process of locating or identifying specific conductor paths by means of passing a current through selected conductors.

Rise Time - the time required for the initially zero potential existing on a transmission line (which is terminated in its characteristics impendence) to change from 10% to 90% of its full DC value after a DC potential source is instantaneously applied.

RMS or rms - Root-mean-square.

Rockwell Harness - a test for determining hardness in which a hardened steel ball or diamond point is pressed into the material under test.

Roentgen - the amount of radiation that will produce on electrostatic unit of ion per cubic centimeter volume.

Rope Lay Conductor - a conductor composed of a central core surrounded by one or more layers of helically laid groups of wire.