R - Symbol for resistance.

R-F - Radio-frequency.

Radio Frequency (RF) - Radio-frequency. Usually considered to be frequencies ranging from 1 MHz to 3GHz. Used to transmit information from point to point over the airwaves or down coaxial cable.

RAM - Random Access Memory.

Rated Temperature - The maximum temperature at which an electric component can operate for extended periods without loss of its basic properties.   

Rated Voltage - The maximum voltage at which an electric component can operate for extended periods without undue degradation or safety hazard.

RDC - Regional Data Center.

Reactance - A measure of the combined effects of capacitance and inductance on an alternating current. 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.

Receiver - An electronic package that converts light energy to electrical energy in a fiber optic system.

Receptacle - A female housing with male or female contacts.

Reference Edge - Edge of cable or conductor from which measurements are made. Sometimes indicated by a thread, identification stripe, or printing. Conductors are usually identified by their sequential position from the reference edge, with number one conductor closest to this edge.

Reflection - The change in direction (or return) of waves striking a surface. For example, electromagnetic energy reflections can occur at an impedance mismatch in a transmission line, causing standing waves.

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

Repeater - A receiver and transmitter combination used to regenerate an attenuated signal.

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

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.

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

RJ-45 - Modular telecommunications connector.

Round Conductor Flat Cable (RCFC) - A cable made with parallel round conductors in the same plane.

Routing - The path followed by a cable or conductor.

Rubber (Wire Insulation) - A general term used to describe wire insulations made of thermosetting elastomers, such as natural or synthetic rubbers, neoprene, Hypalon, butyl rubber, and others.


SDSL - Symmetric Digital Subscriber Line.

Semiconductor - In wire industry terminology, a material possessing electrical conductivity that falls somewhere between that of conductors and insulators. Usually made by adding carbon particles to an insulator. Not the same as semiconductor materials such as silicon, germanium, etc. Used for making transistors and diodes.

Separator - Pertaining to wire and cable, a layer of insulating material such as textile, paper, Mylar, etc., which is placed between a conductor and it s dielectric, between a cable jacket and the components it covers, or between various components of a multiple-conductor cable. It can be utilized to improve stripping qualities, flexibility, or can offer additional mechanical or electrical protection to the components it separates.

Sheath - Pertaining to wire and cable, the outer protective covering (may also provide additional insulation).

Shield - A tape, serve or braid (usually copper, aluminum, or other conductive material) placed around or between electric circuits or cables or their components, to prevent signal leakage or interference.

Shield Coverage - The optical percentage of a cable actually covered by shielding material.

Shield Effectiveness - The relative ability of a shield to screen out undesirable interference. Frequently confused with the term shield coverage.

Shield Percentage - The percentage of physical area of a circuit or cable actually covered by shielding material.

Shielded Armored - Types of Shield: Aluminum, Aluminum/Steel, Gopher, and Copper. Cables that require some sort of shield.

Signal - Any visible or audible indication which can convey information. Also, the information conveyed through a communication system.

Signal Conductor - A conductor in a transmission cable or line that carries electrical signals.

Single Mode Fiber - A fiber wave guide in which only one mode will propagate. The fiber has a very small core diameter of approximately 8 micro meters. It permits signal transmission at extremely high bandwidths and is generally used with laser diodes.

Single-ended - Unbalanced, such as grounding one side of a circuit or transmission line.

Skew Rays - A ray that does not intersect the fiber axis. Generally, a light ray that enters the fiber core at a very high angle.

Skin Effect - The tendency of alternating current to travel only on the surface of a conductor as its frequency increases.

Snake Cable - A name given to individually shielded or individually shielded and jacketed, multi-pair audio cables. Used in the connection of multi-channel line level audio equipment.

SNMP - Simple Network Management Protocol.

SNR - Signal to Noise Ration. Commonly used interchangeably with ACR - the difference between attenuation and crosstalk, measured in dB, at a given frequency (acronym for Attenuation Crosstalk Ratio). Important characteristic in networking transmission to assure that signal sent down a twisted pair is stronger at the receiving end of the cable than are any interference signals imposed on that same pair by crosstalk from other pairs.

SONET - Synchronous Optical Network.

Source - The device (usually LED or laser) used to convert an electrical information-carrying signal into a corresponding optical signal for transmission by an optical wave guide.

Spacing - The distance between the centers of two adjacent conductors. Pitch.

Span - The distance between the center of the first conductor and the center of the last conductor in a flat cable.

Spectral Bandwidth - The difference between wavelengths at which the radiant intensity of illumination is half its peak intensity.

Spectrum - Frequencies that exist in a continuous range and have a common characteristic. A spectrum may be inclusive of many spectrums (e.g., the electromagnetic radiation spectrum includes the light spectrum, radio spectrum, infrared spectrum, etc.).

Splitter - A device that divides a high bandwidth signal into two or more lower bandwidth signals, each carrying a selected frequency range. Users connected to a DSL line, for example, may have a splitter installed at their home or business to divide the incoming signal into low frequencies to send to their phone and high frequencies for data to the computer.

Standing Wave - The stationary pattern of waves produced by two waves of the same frequency traveling in opposite directions on the same transmission line. The existence of voltage and current maxima and minima along a transmission line is a result of reflected energy from an impedance mismatch.

Standing Wave Ratio (SWR) - A ratio of the maximum amplitude to the minimum amplitude of a standing wave stated in current or voltage amplitudes.

Star Quad - Term given to 4-conductor microphone cables where the conductors are spiraled together. Which, when connected in an "x" configuration, greatly increases common mode noise rejection.

Static Charge - An electrical charge that is bound to an object. An unmoving electrical charge.

Stay Cord - A component of a cable, usually of high tensile strength, used to anchor the cable ends at their points of termination and keep any pull on the cable from being transferred to the electrical conductors.

Step Insulated - Process of applying insulation in two layers. Typically used in shielded networking cables such that the outer layer of insulation can be removed and remaining conductor and insulation can be terminated in a RJ-45 type connector.

Step-index Fiber - An optical fiber in which the core is of a uniform refractive index with a sharp decrease in the index of refraction at the core/cladding interface. STP - Shielded Twisted Pair(s).

Strain Gauge - A device for determining the amount of strain (change in dimensions) when a stress is applied.

Strand - A single uninsulated wire.

Stranded Conductor - A conductor composed of groups of uninsulated wires.

Strip - To remove insulation from a cable or wire.

Stripping Groove - The controlled thinning of the lamination between two conductors in a flat cable to allow easy hand separation. Tear feature.

Structural Return Loss (SRL) - The magnitude of internal cable reflections, measured in dB.

Surge - A temporary and relatively large increase in the voltage or current in an electric circuit or cable. Also called transient.


TCP/IP - Transmission Control Protocol/Internet Protocol.

Tear Feature - The controlled thinning of the lamination between two conductors in a flat cable to allow easy hand separation.

Teflon (R) - DuPont Company trademark for fluorocarbon resins. (FEP - Fluorinated ethylene-propylene. A thermo-plastic material with good electrical insulating properties and chemical and heat resistance.). (TFE - Tetrafluoroethylene. A thermoplastic material with good electrical insulating properties and chemical and heat resistance.). It is not suitable where subjected to nuclear radiation and does not have good high voltage characteristics. FEP Teflon is extrudable in a manner similar to PVC and polyethylene. This means that long wire and cable lengths are available. TFE Teflon is extrudable in a hydraulic ram type process. Lengths are limited due to amount of material in the ram, thickness of the insulation, and preform size. TFE must be extruded over a silver- or nickel-coated wire. The cost of Teflon is approximately 8 to 10 times more per pound than PVC compounds.

Tefzel - Fluorocopolymer thermoplastic material has excellent electrical properties, heat resistance, chemical resistance, toughness, radiation resistance, and flame resistance.

Temperature Rating - The maximum temperature at which the insulating material may be used in continuous operation without change of its basic properties.

Tensile Strength - The pull stress required to break a bare wire.

TFE - Tetrafluoroethylene. A thermoplastic material with good electrical insulating properties and chemical and heat resistance.

Thermal Rating - The temperature range in which a material will perform its function without undue degradation.

Thermoplastic - A material which will soften, flow, or distort appreciably when subjected to sufficient heat and pressure. Examples are polyvinyl chloride and polyethylene.

Thermosetting - A material which will not soften, flow, or distort appreciably when subjected to heat and pressure. Vulcanizable. Examples are rubber and neoprene.

TIA - Telecommunications Industry Association. Body which authored the TIA/EIA 568A "Commercial Building Telecommunications Wiring Standard" in conjunction with EIA.

TIA-EIA 568A - "Commercial Building Telecommunications Wiring Standard defines a generic telecommunications wiring system for commercial buildings that will support a multi-product, multi-vendor environment. It also provides direction for the design of telecommunications products for commercial enterprises.

Tinsel - A type of electrical conductor comprised of a number of tiny threads, each thread having a fine, flat ribbon of copper or other metal closely spiraled about it. Used for small size cables requiring limpness and extra-long flex life.

Topcoated Wire - Conductor produced by applying a layer of tin over a stranded bare copper conductor holding the strands together allowing easier soldering and preventing the fraying of strands.

TP-PMD - Twisted Pair-Physical Medium Dependent.

Transducer - A device for converting mechanical energy to electrical energy.

Transfer Impedance - For a specified cable length, transfer impedance relates to a current on one surface of a shield to the voltage drop generated by this current on the opposite surface of the shield. Transfer impedance is used to determine shield effectiveness against both ingress and egress of interfering signals. Cable shields are normally designed to reduce the transfer of interference - hence, shields with lower transfer impedance are more effective than shields with higher transfer impedance.

Transmission Line - An arrangement of two or more conductors, a coaxial cable, or a waveguide used to transfer signal energy from one location to another.

Transmission Line Cable - Two or more conductors placed within a dielectric material in such a way as to control the electrical characteristics.
Transmitter - The electronic package that converts electrical energy to light energy in a fiber optic system.

Triad Cable - Cable with three twisted conductors.

Triaxial Cable - A cable construction having a conductor, and two isolated braid shields, all insulated from each other.

Triboelectric Noise - Noise generated in a shielded cable due to variations in capacitance between the shield and conductors as the cable is flexed.

Trunk Cable - In a CATV system, the transmission cable from the head end (signal pickup) to the trunk amplifier. Also called a feeder cable.

Twin-lead - A transmission line having two parallel conductors separated by insulating material. Line impedance is determined by the diameter and spacing of the conductors and the insulating material and is usually 300 ohms for television receiving antennas.

Twinax Cable - Cable with two twisted conductors with established electrical properties (one pair=twinax).

Twisted Pair - Two lengths of insulated conductors twisted together. the traditional method for connecting home and many business computers to the telephone company. Gets its name because two insulated copper wires are twisted together, both of which are needed for each connection. In commercial environments, performance of data transmission can be improved by adding a composite tape to the wire. This is known as shielded twisted pair.

Two pair premise wiring - Refers to the two pairs of voice grade (low bandwidth) twisted pair wire installed in most homes since the 1950s. The extra pair makes it possible for you to add another line when you need it.


- Abbreviation for Underwriters Laboratories, a nonprofit organization which tests and verifies construction and performance of electronic parts and equipment, including wire and cable.

UM - Unsoldered Mechanical Protection - Additional steel and polyethylene over inner polyethylene jacket. Provides additional mechanical protection.

Unbalanced Line - A transmission line in which voltages on the two conductors are unequal with respect to ground. A coaxial cable is a common type of unbalanced line.

Unilay - A conductor with more than one layer of helically laid wires with the direction of lay and length of lay the same for all layers.

UTP - Unshielded Twisted Pair(s). 



V - Volt.

VA - Volt-ampere. A designation of power in terms of voltage and current.

VC/MTM Variable Constellation/Multi - Tone Modulation.

VDSL - Vary high bit-rate Digital Subscriber Line.

Velocity of Propagation (VP) - The transmission speed of electrical energy in a length of cable compared to speed of light in free space. Usually expressed as a percentage.

Video - Pertaining to picture information in a television system.

VLF - Abbreviation for very low frequency, 10 to 30 kHz.

Volt - A unit of electromotive force.

Voltage - Electrical potential of electromotive force expressed in volts.

Voltage Drop - The voltage developed across a component or conductor by the current flow through the resistance or impedance of the component or conductor.

Voltage Rating - The highest voltage that may be continuously applied to a cable construction in conformance with standards or specifications.

Voltage Standing Wave Ratio (VSWR) - The ratio of the transferring signal voltage as compared to reflected signal voltage measured along the length of a transmission line.

VSWR - Abbreviation for voltage standing wave ratio.

VW-1 - A flammability rating established by Underwriters Laboratories for wires and cables that pass a specially designed vertical flame test, formerly designed FR-1.


W - Symbol for watt or wattage.

Wall Thickness - The thickness of an insulation or jacket.

WAN - Wide Area Network.

Watt - A unit of electrical power.

Wave Form - A graphical representation of a varying quantity. Usually, time is represented on the horizontal axis, and the current or voltage value is represented on the vertical axis.

Wavelength - The distance between positive peaks of a signal. As the frequency increases, and waves get closer together, the wavelength decreases.

Wire - A conductor, either bare or insulated. 




X - Symbol for reactance.

XLPE - Crosslinked polyethylene is a thermoset and is crosslinked by radiation, thermally, or by moisture. XLPE offers a wide range of operating temperatures, excellent deformation, abrasion, and flame resistance. XLPE can be formulated with halogenated or non-halogenated flame retardant packages. Some grades are also rated XHHW-2 which offers excellent wet electrical properties.

XLR - A multi-pin audio Connector (typically 3 pins) used in microphone, line level and snake cable connections.

XPE-PVC Expanded Polyethylene - Polyvinyl Chloride. Fire retardant.






Z - Symbol for impedance

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