R
Symbol for electrical resistance

Radio Frequency
The frequncies in the electromagnetic spectrum that are used for radio communications. A band of frequencies between 10 kilohertz and 100 gigahertz

Random Winding
A winding in rotating equipment wherein wires do not lie in an even pattern

REA (Rural Electrification Administration)
A federally supported program to provide electrical service to rural areas

Reactance
The opposition offered an alternating electron flow by a capacitance or inductance. The amount of such opposition varies with the frequency of the current. The reactance of a capacitor decreases with an increase in frequency; the opposite occurs with an inductance

Recovered Diameter
Diameter of shrinkable products after heating has caused it to return to its extruded diameter

Red Plague
A powdery, brown-red growth sometimes found on silver-coated copper conductors and shield braids

Redraw
The consecutive drawing of wire through a series of dies to reach a desired wire size

Reel
A revolving flanged device made of wood or metal, used for winding flexible cable

Reference Edge
See preferred term Index Edge

Reference Junction
The junction of a thermocouple which is at a known reference temperature. Also known as the 'cold' junction, it is usually located at the emf measuring device

Reflection
(1) The change in direction (or return) of waves striking a surface. For axample, electromagnetic energy reflections can occur at an impedance mismatch in a transmission line, causing standing waves
(2) Change in direction of a light wave or ray in an optical fiber

Reflection Loss
The part of a signal which is lost to reflection of power at a line discontinuity

Reflow Soldering
The process of connecting two solder-coated conductive surfaces by remelting of the solder to cause fusion

Refraction
The bending of lightwaves or rays as they go from one material to another due to the difference in velocities in the materials

Reinforced Sheath
The outer covering of a cable which has a reinforcing material, usually a braided fiber, molded in place between layers

Reliability
The probability that a device will function without failure over a specified time period or amount of usage

Resin
A solid or semisold organic substance, originally of plant origin but largely synthesizes now. Resins are broadly classified as thermoplastic or thermosetting according to whether they soften or harden with the application of heat

Resistance
In DC circuits, the opposition a material offers to current, measured in ohms. In AC circuits, resistance is the real component of impedance, and may be higher than the value measured at DC

Resistive Conductor
A conductor with electrical resistance

Resistivity
A material characteristic which opposes the flow of electrical energy through the material. It is affected by temper, temperature, contamination, alloying, etc. The unit of volume resistivity is the ohm-cm. The unit of surface resistivity is ohms/m²

Resistor
An electronic component designed to have a specific value of resistance

Resistor Color Code
A method of indicating resistance value and tolerance. The first color represents the first significant figure of the value. A second color represents the second significant figure, and the third is the multiplier or the number of zeros that follow two significant figures. When there is a fourth color band. It indicates the tolerance

Resonance
An AC circuit condition in which inductive and capacitive reactances interact to cause a minimum or maximum circuit impedance

Retractile Cord
A cord having specially treated insulation or jacket so that it will retract like a spring. Retractability may be added to all or part of a cord's length

Return Wire
A ground wire or the negative wire in a direct-current circuit

RFI
Radio Frequency Interface. The disruption of radio signal reception caused by any source which generates radio waves at the same frequency and along the same path as the desired wave

RF Modem
Radio Frequency Modem. A device used to covert digital data signals to analog signals (and from analog to digital), then modulate/demodulate them to/from their assigned frequencies

RG/U
"RG" is the military designation for coaxial cable, and "U" stands for "general utility"

RHH
Rubber-Insulated, heat-resistant building wire, 90ºC. A UL cable type

RHW
Rubber-insulated building wire, heat and moisture-resistant, 75ºC dry or wet. A UL cable type

RHW-2
Rubber-insulated building wire, heat and moisture-resistant, 90ºC dry or wet. A UL cable type

Ribbon Cable
A flat cable of individually insulated conductors lying parallel and held together by means of adhesive or woven textile yarn

Ridge Marker
One or more ridges running laterally along the outer surface of a plastic insulated wire for purposes of identification

Rigid Coaxial Cable
Nonflexible coaxial cable, usually a metal tube armored coaxial cable. Sometimes called "hardine"

Ringing Out
Locating or identifying specific conductive paths by passing current through selected conductors

Ring Tongue
A solderless terminal that connects wire to a stud

Rip Cord
Two or more insulated conductors in a parallel configuration which may be separated to leave the insulation of each conductor intact

Rise Time
The time it takes the voltage to rise from 0.1 to 0.9 of its final value

RIV
Radio Influence Voltage. The radio noise appearing on conductors of electric equipment or circuits

RMS
See Root-Mean-Square

Rockwell Hardness
A measure of hardness determined by resistance to indention by a small diamond or steel ball under pressure

Romex
A type of nonmetallic sheathed cable

Root Mean Square (RMS)
The effective value of an alternating current or voltages

Rope Centric
A group of stranded conductors assembled in a concentric manner

Rope-Lay Conductor
See Concentric-Lay Conductor

Rope-Strand
A conductor composed of a center group of twisted strands surrounded by layers of twisted strands

Rope Unilay
A group of stranded conductors assembled in a unilay manner

Rotating Cable
A coil of cable whose inner end is attached to a member that rotates in relation to a member to which the outer end of the cable is fastened

Round Conductor Flat Cable
A cable made with parallel round conductors in the same plane

Round Wire Shields
Shields constructed from bare, tinned, or silver-plated copper wire that include braided, spiral, and reverse spiral

Routine Tests
Tests made on each high-voltage cable or upon a representative number of devices, or parts, during production for the purposes of quality control

RS-232
An EIA recommended standard (RS); a common standard for connecting data processing devices, RS-232 defines the electrical characteristics of the signals in the cable that connect DTE with DCE; it specifies a 25-pin connector (the DB-25 connector is almost universally used in RS-232 applications); and it is functionally identical to CCITT V.24/.28

RS-232-C
A technical specification published by the EIA that specifies the mechanical and electrical characteristics of the interface for connecting DTE and DCE. It defines interface circuit functions and their corresponding connector pin assignments. The standard applies to both asynchronous and synchronous serial, binary data transmission at speeds up to 20 Kbps in fullor half-duplex mode. RS-232-C defines 20 specific functions. The physical connection between DTE and DCE is made through plug-in, 25-pin connectors. RS-232-C is functionally compatible with the CCITT Recommendation V.24

RS-232-C Serial I/O Port
A standard connection interface for computer peripheral equipment

RS-422
A standard operating in cojunction with RS-449 that specifies electrical characteristics for balanced circuits.
\ An EIA recommended standard for cable lengths that exceed the RS-232 50-foot limit. Although introduced as a companion standard with RS-449, RS-422 is most frequently implemented on unused pins of DB-25 (RS-232) connectors. Electrically compatible with CCITT recommendation V.11

RS-423
A standard operating in conjunction with RS-449 that specifies electrical characteristics for unbalanced circuits.
An EIA recommended standard for cable legths that exceed the RS-232 50-foot limit. Although introduced as a companion standard RS-422, RS-423 is not widely used. Electrically compatible with CCITT recommendation V.10

RS-432-A
Electrical characteristics of unbalanced-voltage digital interface circuits (EIA)

RS-449
Another EIA standard for DTE/DCE connection which specifies interface requirements for expanded transmission speeds (up to 2 Mbps), longer cable lengths, and 10 additional functions. RS-449 applies to binary, serial, synchronous or asynchronous communications. Half- and full-duplex modes are accommodated and transmission can be over 2- or 4-wire facilities such as point-to-point multipoint lines. The physical connection between DTE and DCE is made through a 37-contact connector, a separate 9-connector is specified to service secondary channel interchange circuits, when used

RTS
Request-To-Send. An RS-232 modem interface signal (sent from the DTE to the modem on pin 4) which indicates that the DTE has data to transmit

Rubber, Ethylene Propylene (EPR)
A synthetic rubber insulation having excellent electrical properties

Rubber Insulation
A general term used to describe wire insulations made of elastomers such as natural or synthetic rubbrs, neoprene, Hypalon, EPR, CPE, and others

Rulan®
DuPont's trade name for their flame-retardant polyethylene insulating material