REFRACTION - Deflection from a straight path undergone by a light ray or energy wave in passing obliquely from one medium (as air) into another (as glass) in which its velocity is different.
REFRACTIVE INDEX - The ratio of the speed of light in a vacuum to the speed of light in a material. Also called Index of Refraction.
REPEATER - A device that receives signals in one circuit and automatically delivers corresponding signals to one or more other circuits, usually amplifying the signal.
RESIN - A solid or semi-solid organic substance, originally of plant origin but largely synthesized now. It may be clear, yellowish, or brown, ranging from transparent to translucent; typically a nonconductor of electricity and soluble in organic solvents but not in water. Consequently, resins are widely used in insulating, potting, and encapsulating. Resins are broadly classified as thermoplastic or thermosetting according to whether they soften or harden with the application of heat.
RESISTANCE - The tendency of a material to resist the passage of an electric current and to convert electrical energy into heat energy. Symbol R. It is the ratio of the applied potential difference across a conductor to the current flowing through it (see Ohm’s law). If the current is an alternating current, the resistance, measured in ohms, is the real part of electrical impedance,
Z, given by the formula:
Z = R +iX
where
i equals
and
X is the reactance.
RESISTANCE WIRE - Wire constructed from a material, such as Nichrome® or constantan, that has a high resistivity and low temperature coefficient of resistance. It is used for accurate wire-wound resistors. Nichrome® is a trademark of the Driver Harris Company.
RESISTIVITY - An intrinsic property of a material equal to the resistance per unit length and unit cross sectional area. Reciprocal of conductivity. The lower the resistivity of a material the better conductor it is. Materials can be classified as conductors, semi-conductors, or insulators according to their resistivity. Conductors have a resistivity of 10-6 to 10-8 ohms per meter, semi-conductors have a resistivity of 10-6 to 10-7 ohms per meter, and insulators have a resistivity of 10-7 to 10-23 ohms per meter.
RESPOOL - To rerun material from one package spool to another for various purposes, such as to verify lengths, inspect for defects, or to a specified packaging by customer.
RETRACTILE CORD - A cord in which the insulation and/or jacket has been specially treated so that it will return to its original contracted form from an extended condition.
REV. - Abbreviation for revision.
RF - a) Abbreviation for radio frequency. b) Tinned copper conductors, rubber insulation, cotton braid saturated with moisture resisting, flame-retarding compound, smoothly finished in white, black, red, green, blue, and yellow for identification. The lubricated surface finish of the wire permits easy pulling through conduits.
RF CONNECTOR - Connector used for connecting or terminating coaxial cable.
