Term
Definition
AC
Alternating current. Electric current that alternates or reverses polarity in a cyclical manner (e.g. 60 Hertz AC power)
Alternating Current (AC)
Electric current that alternates or reverses polarity in a cyclical manner (e.g. 60 Hertz AC power)
AM
Amplitude modulation.
Ampacity
Current handling capability expressed in amperes. The maximum current a conductor can carry without being heated beyond a safe limit.
Amplitude
The magnitude of a current or voltage. It can be the maximum, minimum, average, or RMS value of an alternating current (AC) signal. These four magnitudes are the same for a direct current (DC) signal.
Analog
Representation of data by continuously variable quantities as opposed to a finite number of discrete quantities in digital.
Analog Signal
An electrical signal which varies continuously, not having discrete values. Analog signals are copies or representations of other waves in nature. An analog audio signal, for instance, is a representation of the pressure waves which make up audible sound.
Attenuation
The decrease in magnitude of a signal as it travels through any transmitting medium, such as a cable or circuitry. Attenuation is usually expressed logarithmically as the ratio of the original and decreased signal amplitudes. It is usually expressed in decibels (dB).
Bandwidth
The difference between the upper and lower limits of a given band of frequencies. It is expressed in hertz. The range of frequencies that a transmitted communications signal occupies or that a receiving system can accept. For example, it takes more bandwidth to download a photograph in a second than to download a page of text. Virtual reality and three-dimensional audio/visual presentations require even more.
Bel
A unit that represents the logarithm of the ratio of two levels. One bel equals the base 10 logarithm of the ratio of two power levels. It is also equal to the base 10 logarithm of square of the ratio of two voltage or current levels, provided the impedances are the same at the two levels. See dB.
Booster
An amplifier inserted into a cable to increase the signal amplitude in order to compensate for signal loss due to attenuation. This extends the transmission range of the cable. Transformers may be employed to boost ac voltages. The term booster is also applied to amplifiers used in television receiving antenna systems.
Breakdown Voltage
The voltage at which the insulation between two conductors will fail and allow electricity to conduct or 'arc'.
Broadband
The technique used to multiplex multiple networks on a single cable without interfering with each other. Technologies that allow you to transmit or receive higher volumes of data at higher speeds.
CAP
Carrierless Amplitude Phase Modulation.
Capacitance
The ability of a dielectric material between conductors to store energy when a difference of potential exists between the conductors. The unit of measurement is the farad. Cable capacitance is usually measured in picofarads (pF).
Capacitive Reactance
The opposition to alternating current due to the capacitance of a capacitor, cable, or circuit. It is measured in ohms and is equal to 1/(2*pi*f*C) where pi is approximately 3.1416, f is the frequency in Hz, and C is the capacitance in farads.
Capacitor
Two conducting surfaces separated by a dielectric material. The capacitance is determined by the area of the surfaces, type of dielectric, and spacing between the conducting surfaces.
Characteristic Impedance
In a transmission cable of infinite length, the ratio of the applied voltage to the resultant current at the point the voltage is applied. Or the impedance which makes a transmission cable seem infinitely long, when connected across the cable's output terminals.
Circuit
A system of conducting media designed to pass an electric current.
Coil Effect
The inductive effect exhibited by a spiral-wrapped shield, especially above audio frequencies.
Conductivity
The ability of a material to allow electrons to flow, measured by the current per unit of voltage applied. It is the reciprocal of resistivity and is measured in siemens (S) or mhos.
Corona
The ionization of gasses about a conductor that results when the potential gradient reaches a certain value.
Coupling
The transfer of energy (without direct electrical contact) between two or more cables or components of a circuit.
CPS
Abbreviation for cycles per second. This term has been replace by hertz is common usage.
Current Carrying Capacity
The maximum current a conductor can carry without being heated beyond a safe limit. Ampacity.
Current, Alternating (ac)
Electric current that alternates or reverses polarity in a cyclical manner (e.g. 60 Hertz AC power).
Current, Direct (dc)
Electrical current whose electrons flow in one direction only and is generally constant.
dB
Decibel.
DC
Direct current.
DC Resistance
See resistance.
Decibel (dB)
A decibel is one-tenth of a bel and is equal to 10 times the logarithm of the power ratio, 20 times the log of the voltage ratio, or 20 times the log of the current ratio. Decibels are also used to express acoustic power, such as the apparent level of a sound. The decibel can express an actual level only when comparing with some definite reference level that is assumed to be zero dB.
Delay Line
A transmission line or equivalent device designed to delay a wave or signal for a specific length of time.
Derating Factor
A multiplier used to reduce the current carrying capacity of conductors in more adverse environments, such as higher temperature, or where multiple conductors are together in one conduit.
Dielectric
An insulating (non-conducting) medium. It is the insulating material between conductors carrying a signal in a cable. In coaxial cables it is between the center conductor and the outer conductor. In twisted pair cables it is the insulation between conductors plus any surrounding air or other material.
Dielectric Breakdown
Any change in the properties of a dielectric that causes it to become conductive. Normally a catastrophic failure of an insulation because of excessive voltage.
Dielectric Constant
Also called relative permittivity. That property of a dielectric which determines the amount of electrostatic energy that can be stored by the material when a given voltage is applied to it. Actually, the ratio of the capacitance of a capacitor using the dielectric to the capacitance of an identical capacitor using a vacuum (which has a dielectric constant of 1) as a dielectric. A number which indicates the quality of a material to resist holding an electrical charge when placed between two conductors.
Dielectric Heating
The heating of an insulating material when placed in a radio-frequency field, caused by internal losses during the rapid polarization reversal of molecules in the material.
Dielectric Loss
The power dissipated in a dielectric as the result of the friction produced by molecular motion when an alternating electric field is applied.
Dielectric Strength
The voltage an insulation can withstand before it breaks down. Usually expressed as "volts per mil".
Dielectric Withstand Voltage
The voltage an insulation can withstand before it breaks down. Usually expressed as "volts per mil".
Distortion
Any undesired change in a wave form or signal.
E
Voltage (electromotive force).
Earth
British terminology for zero-reference ground.
Electromagnetic
Referring to the combined electric and magnetic fields caused by electron motion through conductors.
Electromagnetic Coupling
The transfer of energy by means of a varying magnetic field. Inductive coupling.
Electron Volt
A measure of the energy gained by an electron passing through an electric field produced by one volt.
Electrostatic
Pertaining to static electricity, or electricity at rest. An electric charge, for example.
Electrostatic Coupling
The transfer of energy by means of a varying electrostatic field. Capacitive coupling.
EMF
Electromotive force (voltage).
EMI
Electromagnetic Interference.
eV
Electron volt.
f
Frequency.
Farad
A unit of capacity that will store one coulomb of electrical charge when one volt of electrical pressure is applied.
Field
An area through which electric and/or magnetic lines of force pass.
Floating
Referring to a circuit which has no connection to ground.
FM
Frequency modulation.
Frequency
The number of times a periodic action occurs in one second. Measured in Hertz.
Frequency Response
The amplitude versus frequency characteristics of a device. Also may refer to the range of frequencies over which the device operates within prescribed performance
Frequency, Power
Normally, the 50 or 60 hertz power used to operate most AC powered equipment. The frequency of AC power supplied by electric utilities companies.
FSK
Frequency Shift Keying.
Gain
The increase of voltage, current, or power over a standard or previous reading. Usually expressed in decibels.
Giga
One billion.
Gigahertz (GHz)
A unit of frequency equal to one billion hertz.
GND
Ground.
Ground
An electrical connection between a circuit and the earth. Also refers to a conductor connected to earth. In some instances, can refer to a central metallic point designated as having "zero" potential.
Ground Conductor
A conductor in a transmission cable or line that is grounded.
Ground Loop
A completed circuit between shielded pairs of a multiple pair created by random contact between shields. An undesirable circuit condition in which interference is created by ground currents when grounds are connected at more than one point.
Ground Potential
The potential of the earth. A circuit, terminal, or chassis is said to be at ground potential when it is used as a reference point for other potentials in the system.
H
Symbolic designation for magnetic field intensity. Abbreviation for henrys (unit of inductance).
Henry
Unit of inductance (H) that will produce a voltage drop of one volt when the current changes at the rate of one ampere per second.
Hertz (Hz)
Unit of frequency equal to one cycle per second.
HF
High Frequency. International Telecommunication Union designation for the 3-30 MHz band of frequencies.
High Frequency
International Telecommunication Union designation for the 3-30 MHz band of frequencies.
Hum
Term used to describe noise in a audio, video, or other system that comes from 60 Hz power or its harmonic(s). So named for the low-frequency humming sound produced in audio systems. Usually hum is the result of undesired coupling from a 60 Hz source or of inadequate filtering of the DC output of an AC input power supply.
I
Symbol used to designate current.
I2R
Formula for power in watts, where I=current in amperes, R=resistance in ohms.
IDC
Insulation Displacement Connector. Type of connector where contact is made to the cable conductor(s) by cutting through the individual conductor's insulation. The conductor does not need to have its insulation removed prior to connection. Flat cable often uses IDCs to simultaneous connect all conductors.
IF
Intermediate Frequency.
Impedance
The total opposition that a circuit offers to the flow of alternating current or any other varying current at a particular frequency.
Impedance Match
A condition whereby the impedance of a particular circuit cable or component is the same as the impedance of the circuit, cable, or device to which it is connected.
Impedance Matching Sub
A section of transmission line or pair of conductors cut to match the impedance of a load. Also called matching sub.
Impedance Matching Transformer
A transformer designed to match the impedance of one circuit to that of another.
Impedance, Characteristic
In a transmission cable of infinite length, the ratio of the applied voltage to the resultant current at the point the voltage is applied. Or the impedance which makes a transmission cable seem infinitely long, when connected across the cable's output terminals.
Impedance, High
Generally, the area of 25,000 ohms or higher.
Impedance, Low
Generally, the area of 1 through 600 ohms.
Inductance
The property of wire which stores electrical current in a magnetic field around the wire. By coiling wire, the effect can be intensified. It is measured in Henrys.
Induction
The phenomenon of a voltage, magnetic field, or electrostatic charge being produced in an object from the source of such fields.
Induction Heating
Heating a conducting material by placing it in a rapidly changing magnetic field. The changing field induces electric currents in the material and losses account for the resultant heat.
Inductive Crosstalk
Crosstalk resulting from the coupling of the electromagnetic field of one conductor upon another.
Input
A signal (or power) which is applied to a piece of electric apparatus or the terminals on the apparatus to which a signal or power is applied.
Insertion Loss
A measure of the attenuation of a cable and/or component(s) by determining the output of a system before and after the device is inserted into the system.
Insulation Displacement Connector (IDC)
A mass termination connector for flat cable with contacts that displace the conductor insulation to complete termination.
Insulation Stress
The molecule separation pressure caused by a potential difference across an insulator. The practical stress on insulation is expressed in volts per mil.
Interface
The region where two systems or a major and a minor system meet and interact with each other.
Interference
Disturbances of an electrical or electromagnetic nature that introduce undesirable responses into other electronic equipment.
Intermediate Frequency
A frequency to which a signal is converted for ease of handling. Receives its name from the fact that it is an intermediate step between the initial and final conversion or detection stages.
Ionization
The formation of ions. Ions are produced when polar compounds are dissolved in a solvent and when a liquid, gas, or solid is caused to lose or gain electrons due to the passage of an electric current.
Ionization Voltage
The potential at which a material ionizes. The potential at which an atom gives up an electron.
IR
Insulation Resistance.
IR Drop
The designation of a voltage drop in terms of current and resistance. See also Voltage Drop.
IRS
Ignition radiation suppression.
Isolation
The ability of a circuit or component to reject interference, usually expressed in dB.
kB
Kilobyte.
keV
1000 electron volts.
Kilo
One thousand.
kV
Kilovolt (1000 volts).
kVA
Kilo Volt-ampere. One thousand volt-amperes (VA). See also VA.
kW
Kilowatt.
L
Symbol for inductance.
Leakage
The undesirable passage of current over the surface of or through an insulator.
Level
A measure of the difference between a quantity or value and an established reference.
LF
Low frequency. International Telecommunication Union designation for the 30-300 kHz band of frequencies.
Line Drop
A voltage loss occurring between any two points in a power or transmission line. Such loss, or drop, is due to the resistance, reactance, or leakage of the line. See also Voltage Drop and IR Drop.
Line Equalizer
A reactance (inductance and/or capacitance) connected in series with a transmission line to alter the frequency-response characteristics of the line.
Line Level
Refers to the output voltage level of a piece of electronic equipment. Usually expressed in decibels (e.g.. 0 dBV).
Line Voltage
The value of the potential existing on a supply or power line.
Load
A device that consumes power from a source and uses that power to perform a function.
Loss
Energy or signal lost without accomplishing useful work.
Lossy
Having high losses resulting in efficiency.
Low Frequency
International Telecommunication Union designation for the 30-300 kHz band of frequencies.
M
Mutual inductance. The abbreviation for mega or 1 million. And also indicates 1000 (one thousand) feet in the wire industry. Lower case m is for milli or one-thousandth. See also m.
mA
milliampere (one-thousandth of an ampere).
Megahertz (MHz)
Unit of frequency equal to one million hertz.
mfd
Microfarad (one-millionth of a farad). Modern abbreviation is uF (lower case Green mu followed by F).
Mho
The unit of conductance equal to the reciprocal of the unit of resistance (ohm).
MHz
Megahertz (see also).
Microfarad
One-millionth of a farad (uf, ufd, mf, and mfd are common abbreviations).
Micromicrofarad
One-millionth of a microfarad (uuf, uufd, mmf, mmfd are common abbreviations). Modern usage is picofarad (pF).
Modulation
Altering the characteristics of a carrier wave to convey information. Modulation techniques include amplitude frequency, phase, plus many other forms of on-off digital coding.
Multiplex
A technique for putting two or more signals into a single channel.
Mutual Capacitance
Effective capacitance between two conductors when the effects of the other conductors and shield, if present, are removed.
mV
Millivolt (one-thousandth of a volt).
mW
Milliwatt (one-thousandth of a watt).
Noise
In a cable or circuit, any extraneous signal which tends to interfere with the signal normally present in or passing through the system.
OFDM
Orthogonal Frequency Division Multiplexing.
Ohm
The unit of electrical resistance. The value of resistance through which a potential difference of one volt will maintain a current of one ampere.
Ohm's Law
Stated E=IR, I=E/R or R=E/I. The current I in a circuit is directly proportional to the voltage E, and inversely proportional to the resistance R.
Output
The useful power or signal delivered by a circuit or device.
Ozone
Extremely reactive form of oxygen, normally occurring around electrical discharges and present in the atmosphere in small but active quantities. In sufficient concentrations is can break down certain rubber insulations under tension (such as a bent cable).
Parallel Circuit
A circuit in which the identical voltage is presented to all components, with current dividing among the components according to the resistances or the impedances of the components.
Peak
The maximum instantaneous value of a varying current or voltage.
Periodicity
The uniformly spaced cable impedance variations that result in addition of the reflections of a signal. The distance between them is the half wavelength most affected. Multiples of that frequency are also affected. Even very slight variations, which appear over and over in a construction or installation, can have major effects on signal integrity because of periodicity.
Phase
An angular relationship between waves.
Phase Shift
A change in the phase relationship between two alternating quantities.
Pickup
Any device which is capable of transforming a measurable quantity of intelligence (such as sound) into relative electrical signals (e.g., a microphone).
Picofarad
One trillionth of a farad. A micromicrofarad. Abbreviated pF in modern usage or mmF in earlier usage.
Potting
Sealing by filling with a substance to exclude moisture.
Power
The amount of work per unit of time. Usually expressed in watts. Power equals the product of voltage and current (P=V*I).
Power Loss
The difference between the total power delivered to a circuit, cable, or device and the power delivered by that device to a load.
Power Ratio
The ratio of power appearing at the load to the input power.
Propagation Delay
Time required for a signal to pass from the input to the output of a device.
Pulse
A current or voltage which changes abruptly from one value to another and back to the original value in a finite length of time. Used to describe one particular variation in a series of wave motions.
QAM
Quandrature Amplitude Modulation.
QPSK
Quaternary Phase Shift Keying or Quadrature PSK.
R
Symbol for resistance.
R-F
Radio-frequency.
Radio Frequency (RF)
Radio Frequency. Includes frequencies from a few kilohertz to several hundred gigahertz. Used to transmit information from point to point over the airwaves or down coaxial cable.
Rated Voltage
The maximum voltage at which an electric component can operate for extended periods without undue degradation or safety hazard.
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. Also refers to a unit that converts an RF signal to another type of signal (e.g. radio, television). See also Photodetector.
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.
Resonance
An ac circuit condition in which inductive and capacitive reactances interact to cause a minimum or maximum circuit impedance.
RF
Radio Frequency.
RFI
Radio Frequency Interference.
Ringing Out
The process of locating or identifying specific conductor paths by means of passing a current through selected conductors.
RMS
Root-mean-square.
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.
Series Circuit
A circuit in which the components are arranged end to end to form a single path for current.
Signal
Any visible or audible indication which can convey information. Also, the information conveyed through a communication system.
Single-ended
Unbalanced, such as grounding one side of a circuit or transmission line.
Sinusoidal
Varying in proportion to the sine of an angle or time function. Ordinary alternating current is sinusoidal.
Skin Effect
The tendency of alternating current to travel only on the surface of a conductor as its frequency increases.
SNR
Signal to Noise Ratio (see also).
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.).
Speed of Light ( c )
Approximately 2.998 x 10^8 meters per second.
Splitter
A device that send the signal from one source to two or more receiving devices by allocating a portion of the signal to each receiver (e.g. cable TV 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. See also Standing Wave.
Static Charge
An electrical charge that is bound to an object. An unmoving electrical charge.
Structural Return Loss
Magnitude of the internal cable reflections, measured in decibels, relative to the actual cable impedance, not the system impedance. Measure of signal reflections caused by the structure of the cable without the additional reflections from any impedance mismatch between the cable and the measuring equipment. Measure of internal cable reflections using a reference impedance in the measuring equipment that is adjusted to the nominal or average impedance of the cable. See also Return Loss
Surge
A temporary and relatively large increase in the voltage or current in an electric circuit or cable. Also called transient.
Sweep Test
Testing a characteristic of a cable or device across a range of frequencies. In cable, it usually implies return loss or structural return loss (see also).
TDMA
Time Division Multiple Access.
Transducer
A device for converting one form of energy to another, such as 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. Also refers to equipment that generates RF or electrical signals for transmission through the air or space or over a transmissions line.
UHF
Ultra High Frequency. International Telecommunication Union designation for the 300-3000 MHz band of frequencies.
V
Volt (see also).
VA
Volt-ampere. Measure of apparent power in a reactive circuit found by multiplying the voltage by the current.
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.
VHF
Very High Frequency. International Telecommunication Union designation for the 30-300 MHz band of frequencies.
VLF
Very Low Frequency. International Telecommunications Union designation for the 3-30 kHz band of frequencies.
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
Ratio of maximum voltage of the standing wave to the minimum voltage of the standing wave. See also Standing Wave Ratio.
VSWR
Voltage Standing Wave Ratio.
W
Symbol for watt or wattage.
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.
X
Symbol for reactance.
Z
Symbol for impedance