Electrical Glossary



Auto ranging:
A DMM that automatically selects the range with the best resolution and accuracy in response to the application.

Amps alternating current

A switch designated for use with either Alternating Current (AC) or Direct Current (DC).

AC Only:
A switch designated for use with Alternating Current (AC) only.

AC Power:
AC stands for alternating current, which is an electrical current that frequently reverses direction. AC electricity is measured according to its cycles, with one complete cycle being counted each time a given current travels in one direction and then doubles back on itself. An electrical current is able to complete many cycles per second, and is then given its frequency rating based on that number; for example, the typical frequency in North America is 60 hertz (Hz), which indicates that the current is performing 60 cycles per second. AC power is the type of electricity most commonly used in homes and offices, and is extremely versatile because its voltage can be changed through a transformer to suit a variety of transmission needs.

Data converting from analog to digital format.

30A, 50A or 60A receptacles designated for use with aluminum or copper circuit conductors, identified by "AL/CU" stamped on the device. Receptacles without this designation must never be used with aluminum circuit conductors.

Active Power:

Also known as ‘Real Power’ or simply ‘Power’. Active power is the rate of producing, transfer or using electrical energy. Measured in watts and often-expressed in kW or MW.

An accessory used for interconnecting non-mating devices or converting an existing device for modified use.

Ampere (Amp):
The ampere, or amp, is the measure of an electrical current in a given circuit. A single amp is equal to 6,280,000,000,000,000,000 electrons passing a specific point in one second.

A non-negative scalar measure of a wave's magnitude of oscillation, that is, the magnitude of the maximum disturbance in the medium during one wave cycle.

Analog Meter:
A mechanical measuring device using a needle moving across a graduated scale or dial.


A plug or connector that allows the attached flexible cord to exit at right angles.


Arc Fault:
Arcing faults are one of the major causes of these fires. When unwanted arcing occurs, it generates high temperatures that can ignite nearby combustibles such as wood, paper, and carpets. Arcing faults often occur in damaged or deteriorated wires and cords. Some causes of damaged and deteriorated wiring include puncturing of wire insulation from picture hanging or cable staples, poorly installed outlets or switches, cords caught in doors or under furniture, furniture pushed against plugs in an outlet, natural aging, and cord exposure to heat vents and sunlight.


Arc Fault Circuit Interrupter (AFCI):
AFCIs are newly-developed electrical devices designed to protect against fires caused by arcing faults in the home electrical wiring.
Annually, over 40,000 fires are attributed to home electrical wiring. These fires result in over 350 deaths and over 1,400 injuries each year1. Arcing faults are one of the major causes of these fires. When unwanted arcing occurs, it generates high temperatures that can ignite nearby combustibles such as wood, paper, and carpets. Arcing faults often occur in damaged or deteriorated wires and cords. Some causes of damaged and deteriorated wiring include puncturing of wire insulation from picture hanging or cable staples, poorly installed outlets or switches, cords caught in doors or under furniture, furniture pushed against plugs in an outlet, natural aging, and cord exposure to heat vents and sunlight.
Conventional circuit breakers only respond to overloads and short circuits; so they do not protect against arcing conditions that produce erratic current flow. An AFCI is selective so that normal arcs do not cause it to trip. The AFCI circuitry continuously monitors current flow through the AFCI. AFCIs use unique current sensing circuitry to discriminate between normal and unwanted arcing conditions. Once an unwanted arcing condition is detected, the control circuitry in the AFCI trips the internal contacts, thus de-energizing the circuit and reducing the potential for a fire to occur. An AFCI should not trip during normal arcing conditions, which can occur when a switch is opened or a plug is pulled from a receptacle. Presently, AFCIs are designed into conventional circuit breakers combining traditional overload and short-circuit protection with arc fault protection. AFCI circuit breakers (AFCIs) have a test button and look similar to ground fault circuit interrupter (GFCI) circuit breakers. Some designs combine GFCI and AFCI protection. Additional AFCI design configurations are anticipated in the near future. It is important to note that AFCIs are designed to mitigate the effects of arcing faults but cannot eliminate them completely. In some cases, the initial arc may cause ignition prior to detection and circuit interruption by the AFCI. The AFCI circuit breaker serves a dual purpose – not only will it shut off electricity in the event of an “arcing fault”, but it will also trip when a short circuit or an overload occurs. The AFCI circuit breaker provides protection for the branch circuit wiring and limited protection for power cords and extension cords. Single-pole, 15- and 20- ampere AFCI circuit breakers are presently available.


Title – Standard Test Methods for Pressure-Sensitive Adhesive-Coated Tapes Used for Electrical and Electronic Applications.
ASTM International
SCOPE: These test methods cover procedures for testing pressure-sensitive adhesive-coated tapes to be used as electrical insulation. These tapes are classified as follows:
Class 1 - Non-elastomeric backings made from materials such as: Paper, flat or creped; Fabric, uncoated or coated; Cellulose ester films; Polyethylene terephthalate (polyester) films; Fluorocarbon polymer films; Composite filament films; Polyamide films; Polyimide films, and Combinations thereof.
Class 2 - Elastomeric backings that are characterized by both high stretch and substantial recovery. These backings are made from materials such as:
Vinyl chloride and co-polymers; Vinylidene chloride and co-polymers, and Polyethylene and co-polymers.

Laminates of Class 1 and Class 2 backings should be tested according to Class 1 test methods. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazards see Section 3.
The procedures appear in the sections indicated below and in alphabetical order:
NOTE 1 - These procedures apply to both Class 1 and Class 2 tapes except as noted above. The values stated in SI units are the standard, unless otherwise noted. If a value for measurement is followed by a value in inch-pound or English units in parentheses, the second value may only be approximate and is for information only. The first stated value is the preferred unit.
NOTE 2 - These test methods are similar to IEC 60454-3, but may differ sometimes in some details.
This is a fire - test response standard.

Automatic Reset:
A starter that automatically restarts a new replacement fluorescent lamp after the circuit is energized.


The abbreviation for American Wiring Gauge, the United States’ standard for measuring the diameter of non-ferrous (non-iron-containing) wire, which is most often applied to household electrical and telephone wiring. Lower-gauge (thicker) wires are capable of carrying more data and energy for longer distances than those with smaller diameters.


a. Also called ballast resistor a device, often a resistor, that maintains the current in a circuit at a constant value by varying its resistance in order to counteract changes in voltage.
b. a device that maintains the current through a fluorescent or mercury lamp at the desired constant value, sometimes also providing the necessary starting voltage and current.


Beryllium Copper (also High Strength Beryllium Copper):
Metal alloy of copper and beryllium.

Designed for incandescent lamps having an unthreaded metal shell with two diametrically opposite keyways that mate with the keyways on the lampholder. Pushing down on the bulb and turning it clockwise in the lampholder locks the bulb in place.


A small screw-base threaded lampholder designed for candelabra-base incandescent lamps commonly used in chandeliers, night lights, and ornamental lighting.

Cat III:
Equipment in fixed installations.
Example: Installation in buildings, from main fuse box to wall outlet.

A substance that accelerates the rate of a chemical reaction.

Zeroing of an instrument to a known standard.

Ability of a component to hold an electrical charge, usually stated in microfarads.

Electronic component which stores energy and then discharges it; blocks DC and allows AC to pass through.

1. Nautical An apparatus used for hoisting weights, consisting of a vertical spool-shaped cylinder that is rotated manually or by machine and around which a cable is woound.
2. A small cylindrical shaft used to drive magnetic tape at a constant speed in a tape recorder.

CE Rated:
About the CE marking
Marking of electrical equipment, machinery, gas appliances and heating boilers within the European Union
Electrical equipment, machinery, gas appliances and heating boilers to be marketed within the European Economic Area must bear the CE marking. It is a self declaration but mandatory. CE marking generally requires a Technical Construction File, which forms the basis for the Declaration of Conformity. The Technical Construction File indicates the product's conformity with the directives and includes the test reports for the product. The directives require that the manufacturer is capable of manufacturing products of consistent quality. SGS is a notified body and is able to support you to fulfil the requirements of the CE marking.
Advantages of the CE marking
This is a declaration by the manufacturer or by an importer located within the European Economic Area that the product complies with the essential health and safety requirements of the relevant EU directives. Products being sold in or, respectively, imported into the European Union have to comply with this EU-directive and, for confirmation, have to carry a visible CE-marking. This applies to more than 80% of all industrial and consumer products. Sale without a CE-marking within the EU is not permitted.

A four-contact, double-ended lampholder designed for use with tubular, circular fluorescent lamps.

15A or 20A receptacles designated for use with aluminum or copper circuit conductors, identified by "CO/ALR" stamped on the device. Receptacles without this designation must never be used with aluminum circuit conductors.

Clean Power - Less than 5% harmonic distortion

DMM with jaws that allow it to fit around a conductor to measure AC or DC current without breaking the circuit.

Clamping Level:
A clamping level is the highest level of voltage that a surge protector will allow an electrical device to reach, before actively diverting excess electricity to a grounding line.

Clamping Voltage:
The peak voltage that can be measured after a Surge Protective Device has limited or "clamped" a transient voltage surge.  Clamping voltage must be determined by using IEEE Standard C62 testing and evaluated by UL Standard 1449.

Clock Hanger:
A single, recessed receptacle with a specialized cover plate that provides a hook or other means of supporting a wall clock.


Cold Start:
A method of restarting a computer by turning the power back on; often necessary after a power failure or other system interruption. Also known as a Cold Boot. Some Uninterruptible Power Supply units are capable of performing a Cold Start on the computers they are providing with battery backup.

A multiple- gang wallplate with openings in each gang to accommodate different devices.


Compact Fluorescent:
A lampholder designed for the Compact Fluorescent Lamps (CFL’s) that are increasingly being used to replace incandescent lamps for energy efficiency.


Having the quality or power of conducting heat or electricity or sound; exhibiting conductivity


A connection between two conductors that allows a flow of current.

The continuous path for current flow in a closed circuit.

Cord Connector:
A portable receptacle designed for attachment to or provided with flexible cord, not intended for fixed mounting.

Corrosion Resistant:
A device constructed of special materials and/or suitably plated metal parts that is designed to withstand corrosive environments. Corrosion resistant devices must pass the ASTM B117-13 five-hundred hour Salt Spray (Fog) Test with no visible corrosion.

Cube Tap:
An adapter that converts one receptacle opening into multiple openings.

The flow of an electrical charge through a conductor; measured in amperes or amps.

Current Tap:
An adapter designed for medium base lampholders which has one or two receptacle openings. Available with or without integral switch.

C22.2 No. 1010.1:
Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory Use - Part 1: General Requirements. First edition, 1992. Second Edition, 2003.


CSA C22.2 #42:
A Canadian Standards Association document that gives safety requirements for attachment plugs, electrical receptacles, and similar wiring devices.


Data hold:
Feature of DMM that allows continued display of the last reading taken, after probes have been removed.

Data logging:
The practice of recording sequential data, often chronologically.

Wallplates with Decora-size openings for compatibility with Leviton’s entire line of Decora devices. Available in a variety of multiple-gang configurations. Screwless-design snap-on versions also available.

dB (also db and DB):
In electronics and communications, a logarithmic expression of the ratio between two signal power, voltage, or current levels.


Decibels, referenced to one milliwatt.


DC Power:
DC is the abbreviation for direct current, which is a type of electrical current that travels through a circuit in only one direction. Direct current is the type of electrical power that is produced by fuel cells, batteries, and generators equipped with commutators. While DC power was the first type of electricity to be commercially transmitted, it has been widely replaced by alternating current (AC) electricity, and is now used primarily in electrochemical and metal-plating applications.

Differential Signaling:
A method of transmitting data electronically over two separate wires, often used to eliminate EMI/RFI.

Digital Media Receiver:
A home entertainment device used to connect a home theatre system to a computer network in order to retrieve media files.

An electronic device with either a round knob, slide lever or finger-tip controlled buttons used to dim/brighten incandescent lighting. Available in a variety of wattages; fluorescent version also available.

An electronic semiconductor device that predominantly allows current to flow in only one direction.

Receptacle with a special cover plate intended for flush mounting on raised floors or walls.

digital multimeter An instrument that uses an LCD typically capable of measuring voltage, current and resistance.

A momentary contact switch, usually installed on a doorjamb, that is activated when the door is opened or closed.

Double-Contact Recessed:
Designed for high-output fluorescent lamps.

Double Insulated:
A Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth (US: ground).
The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation.
In Europe, a double insulated appliance must be labeled "Class II", "double insulated" or bear the double insulation symbol (a square inside another square).


Double-Pole, Single-Throw (DPST):
A switch that makes or breaks the connection of two circuit conductors in a single branch circuit. This switch has four terminal screws and ON/OFF markings.

Double-Pole, Double-Throw (DPDT):
A switch that makes or breaks the connection of two conductors to two separate circuits. This switch has six terminal screws and is available in both momentary and maintained contact versions, and may also have a center OFF position.

An adapter that provides two female receptacle openings when plugged into a single receptacle opening.

Dust Proof:
A device designed so that dust will not interfere with its operation. The IP Suitability Rating designates the degree of protection a device offers against the ingress of foreign objects (e.g. IP 20).

Earth / ground:
In electrical engineering, the term ground or earth has several meanings depending on the specific application areas. Ground is the reference point in an electrical circuit from which other voltages are measured, a common return path for electrical current (earth return or ground return), or a direct physical connection to the Earth.

Edison Base:
An internally-threaded lampholder, with the inner shell approx. 1" in diameter. Designed for widely-used standard medium base lamps.

Electrical Conductivity:
When a voltage is applied across a substance, an electric current will only flow if the substance conducts electricity

Electrical resistance:
is a measure of the degree to which an object opposes an electric current through it, measured in ohms. Its reciprocal quantity is electrical conductance measured in siemens. Assuming a uniform current density, an object's electrical resistance is a function of both its physical geometry and the resistivity of the material it is made from

Similar to the Edison Medium Base lampholder, but with a smaller outer diameter.

The transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in microelectronics and related structures. As the structure size in electronics such as integrated circuits (ICs) decreases, the practical significance of this effect increases.

Any of various usually thermosetting resins capable of forming tight cross-linked polymer structures characterized by toughness, strong adhesion, and low shrinkage, used especially in surface coatings and adhesives.

Epoxy Glue:
A thermosetting resin; used chiefly in strong adhesives and coatings and laminates.


Equalization :
Technique used to reduce distortion and compensate for signal loss (attenuation) over long distance communication lines.


EN 61326:1998 :
Electrical equipment for measurement, control, and laboratory use—EMC requirements.

Explosion Proof:
A device constructed to meet the requirements of hazardous locations as defined by the National Electrical Code, NFPA-70.

Fan Hanger:
A single receptacle with a specialized cover plate that provides a hook or other means of supporting a wall fan.

Farad (F):
The basic unit of capacitance.

An in-line switch that can be attached at any point on a length of flexible cord to provide switching control of attached equipment.

is an acronym for First In, First Out, an abstraction in ways of organizing and manipulation of data relative to time and prioritization. This expression describes the principle of a queue processing technique or servicing conflicting demands by ordering process by first-come, first-served (FCFS) behaviour: what comes in first is handled first, what comes in next waits until the first is finished, etc.

Thus it is analogous to the behaviour of persons queueing (or "standing in line", in common American parlance), where the persons leave the queue in the order they arrive, or drearily waiting one's turn at a traffic control signal. FCFS is also the shorthand name for the FIFO operating system scheduling algorithm, which gives every process CPU time in the order they come. In the broader sense, the abstraction LIFO, or Last-In-First-Out is the opposite of the abstraction FIFO organization, the difference perhaps is clearest with considering the less commonly used synonym of LIFO, FILO—meaning First-In-Last-Out. In essence, both are specific cases of a more generalized list (which could be accessed anywhere). The difference is not in the list (data), but in the rules for accessing the content. One sub-type adds to one end, and takes off from the other, it's opposite takes and puts things only on one end.

A priority queue is a variation on the queue which does not qualify for the name FIFO, because it is not accurately descriptive of that data structure's behavior. Queueing theory encompasses the more general concept of queue, as well as interactions between strict-FIFO queues.

FCC Part 15, Class A:
A Federal Communications Commission standard, which regulates the amount of electromagnetic interference (EMI) that is allowed to come from computers and other electronic devices used in commercial settings.


FCC Part 15 Compliance:
The Code Of Federal Regulation (CFR) FCC Part 15 is a common testing standard for most electronic equipment. FCC Part 15 covers the regulations under which an intentional, unintentional, or incidental radiator that can be operated without an individual license. FCC Part 15 covers as well the technical specifications, administrative requirements and other conditions relating to the marketing of FCC Part 15 devices. Depending on the type of the equipment, verification, declaration of conformity, or certification is the process for FCC Part 15 compliance.
Verification is a procedure where the manufacturer makes measurements or takes the necessary steps to insure that the equipment complies with the appropriate technical standards. Submittal of a sample unit or representative data to the Commission demonstrating compliance is not required unless specifically requested the Commission. Verification attached to the equipment a label showing that compliance is met.
Declaration of Conformity is a procedure where the responsible party makes measurements or takes other necessary steps to ensure that the equipment complies with the appropriate technical standards. Submittal of a sample unit or representative data to the Commissions demonstrating compliance is not required unless specifically requested. The Declaration of Conformity attaches to the equipment a label showing that the sample has been tested and found acceptable by the responsible party.
Certification is an equipment authorization issued by the Commission, based on representations and test data submitted by eh applicant. Certification attaches to the units subsequently marketed by the grantee which are identical to the sample tested an FCC ID number to show compliance.
FCC Part 15 Subpart A contains specific information regarding testing and certification. Information like, scope of the rules and legal implications, definitions, prohibition against eavesdropping, labeling, and other sections.
Some more interesting descriptions used in the FCC Part 15 as listed in Subpart A.


Flanged Inlet:
A plug intended for flush mounting on appliances or equipment to provide a means for power connection via a cord connector.


Flanged Outlet:
A receptacle intended for flush mounting on appliances or equipment to provide a means for power connection via an inserted plug.


Fluorescent Starter:
A device with a voltage-sensitive switch and a capacitor that provides a high-voltage pulse to start a fluorescent lamp. Rated in watts.


Flush Mounted:
An device intended to be installed flush with the surface of a panel or a piece of equipment.


Flux Percentage:
M.G. Chemicals Lead Free Solder utilizes a state-of-the-art automatic wire extrusion and wire drawing machines to manufacture consistent solder. The introduction of flux core in the wire extrusion process involves constant monitoring of flux percentage to ensure minimal flux voids and irregular wire. Typical flux percentage for our Lead Free Solder is 2.0-4.0%.

Flux Core:
A unique flux system was specifically used for high temperature lead free alloys. It provides the fluxing activity levels that promote fast wetting action and maximum wetting spread. Utilizing synthetically refined resin and very effective activator that wets and spreads like an RA type. This special activator exhibits virtually no spattering. Activator conforms to J-STD-004, REL0.Cleaning Flux core is a no clean formulation therefore the residues do not need to be removed for typical applications

Four-In-One (Quad):
A receptacle in a common housing that accepts up to four plugs. Four-In-One receptacles can be installed in place of duplex receptacles mounted in a single-gang box, providing a convenient means of adding receptacles without rewiring.

A switch used in conjunction with two 3-Way switches to control a single load (such as a light fixture) from three or more locations. This switch has four terminal screws and no ON/OFF marking.

The number of cycles per second that a wave form repeats; measured in hertz. (Line voltage is U.S. is 60 Hz.)

A term that describes the number of devices a wallplate is sized to fit (i.e. "2- gang" designates two devices).

GFCI (Ground Fault Circuit Interrupter):
A receptacle with a built in circuit that will detect leakage current to ground on the load side of the device. When the GFCI detects leakage current to ground, it will interrupt power to the load side of the device, preventing a hazardous ground fault condition. GFCI receptacles must conform to UL Standard 943 Class A requirements, and their use is required by the National Electric Code NFPA-70 in a variety of indoor and outdoor locations.

Glow Discharge:
A starter that provides a rapid lamp start-up and will continue to try to start a failed fluorescent lamp, causing the lamp to flicker until it is replaced.


A large conducting body (earth) used as a common return for current in a circuit.


Ground Fault Circuit Interrupter (GFCI):
A ground fault circuit interrupter is an inexpensive electrical device that, if installed in household branch circuits, could prevent over two-thirds of the approximately 300 electrocutions still occurring each year in and around the home. Installation of the device could also prevent thousands of burn and electric shock injuries each year. The GFCI is designed to protect people from severe or fatal electric shocks Because a GFCI detects ground faults, it can also prevent some electrical fires and reduce the severity of others by interrupting the flow of electric current.


Ground Impedance:
The ground resistance and the inductance/capacitance value of the grounding system. Also called dynamic surge ground impedance.

An adapter that converts a two-wire receptacle opening into a two-pole, three-wire grounding receptacle opening.

A signal with a frequency which is a multiple of the fundamental frequency (60Hz); may damage or degrade the performance of electrical devices. RS-232 (Recommended Standard 232) is a standard for serial binary data signals connecting between a DTE (Data terminal equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. A similar ITU-T standard is V.24.

Harmonic Distortion:
Diminishes power quality; caused by non-linear loads such as variable speed motor drives, electronic lighting ballasts and computers.

Hertz (Hz):
One cycle per second; the unit of frequency.

Electronic components that can be removed or exchanged while power is being supplied.

Horsepower Rated:
A switch with a marked horsepower rating, intended for use in switching motor loads.


Hospital Grade:
A device designed to meet the performance requirements of high-abuse areas typically found in health care facilities. These connectors are tested to the Hospital Grade requirements of Underwriters Laboratories Inc. Standard 498.


The International Electrotechnical Commission (IEC) is a not-for-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology". IEC standards cover a vast range of technologies from power generation, transmission and distribution to home appliances and office equipment, semiconductors, fibre optics, batteries, solar energy, nanotechnology and marine energy as well as many others. The IEC also manages conformity assessment schemes that certify whether equipment, systems or components conform to its International Standards. The IEC publishes standards with the IEEE and develops standards jointly with the ISO as well as the ITU.

IEC 1010:
IEC 1010 is an internationally recognized standard of design, manufacture and test to which all good manufacturers adhere. This gives the end user confidence when buying IEC 1010 compliant products that the product is the best available and complies with the very latest safety standard.

IEC 61010-1:
Safety requirements for electrical equipment for measurement, control, and laboratory use - Part 1: General requirements. First Edition was published in 1990 with CSA publishing their version (C22.2 No. 1010.1) in 1992. UL published three versions: UL 3101-1 to cover Electrical Equipment for Laboratory Use, 3111-1 to cover Electrical Measuring and Test Equipment and 3121-1 covering Process Control Equipment.  See IEC 61010-1 2001

IEC 61010-1:
Safety requirements for electrical equipment for measurement, control and laboratory use.

IEC 61010-2-032 Part 2-032:
Particular requirements for hand-held and hand-manipulated current sensors for electrical test and measurement


Abbreviation for the Institute of Electrical and Electronics Engineers (pronounced “eye-triple-e”), the largest non-profit technical professional organization in the world. The IEEE is international, with 360,000 members in 175 countries, and works toward the advancement of electricity-related technology. IEEE establishes standards for Ethernet and other protocols.

Designed for use with all manufactured incandescent lamps, most of which have threaded bases.

A device or combination of devices with a common mounting dimension that may be installed on a single or multiple-opening mounting strap.

A lampholder with a threaded screw shell designed for intermediate base lamps that have a 13/32" threaded base (smaller than the standard 1" dia. medium base). Mostly used in decorative lighting.


An IP (Ingress Protection) number is used to specify the environmental protection of enclosures around electronic equipment. These ratings are determined by specific tests.The IP number is composed of two numbers, the first referring to the protection against solid objects and the second against liquids. The higher the number, the better the protection.

First Number

  • 0 - No protection (sometimes X)
  • 1 - Protected against solid objects up to 50mm³
  • 2 - Protected against solid objects up to 12mm³
  • 3 - Protected against solid objects up to 2.5mm³
  • 4 - Protected against solid objects up to 1mm³
  • 5 - Protected against dust, limited ingress (no harmful deposit)
  • 6 - Totally protected against dust


Second Number

  • 0 - No protection (sometimes X)
  • 1 - Protection against vertically falling drops of water (e.g. condensation)
  • 2 - Protection against direct sprays of water up to 15 degrees from vertical
  • 3 - Protection against direct sprays of water up to 60 degrees from vertical
  • 4 - Protection against water sprayed from all directions - limited ingress permitted
  • 5 - Protected against low pressure jets of water from all directions - limited ingress permitted
  • 6 - Protected against low pressure jets of water, limited ingress permitted (e.g. ship deck)
  • 7 - Protected against the effect of immersion between 15cm and 1m
  • 8 - Protected against long periods of immersion under pressure


Isolated Ground:
Receptacles intended for use in an Isolated Grounding system where the ground path is isolated from the facility grounding system. The grounding connection on these receptacles is isolated from the mounting strap.

Heat Sink - A heat sink (or heatsink) is an environment or object that absorbs and dissipates heat from another object using thermal contact (either direct or radiant). Heat sinks are used in a wide range of applications wherever efficient heat dissipation is required; major examples include refrigeration, heat engines, cooling electronic devices and lasers.

Total opposition to current flow; includes resistance, capacitance and reactance.

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A joule is a unit of electricity named after British physicist James Prescott Joule, and is defined by the International System as being equivalent to the amount of work done when a one-ampere current passes through a one-ohm resistance for the time duration of one second.

Joule Rating:
Joule Ratings
are often applied to surge protectors and power distributors, and are an indication of how much energy a given product is capable of absorbing. (See Joule, above entry.)

(on PCB boards) - The jumpers are flat, stand-alone copper plated traces with sized pads and holes matching the circuit boards.


The abbreviation for a kilo-circular mil, or 1000 circular mils (roughly equal to 0.5067 mm). The measurement "kcmil" is also known as MCM, and is often used in wire gauging and cable sizing. The circular mil (on which the kcmil - or MCM - is based) is a unit of measure that describes the area of a circle-shaped cross-section that has a diameter of 1/1000 of an inch. The circular mil is an American measurement, and is hardly ever used outside the United States.

A lampholder with a flat or round "key" knob that operates an internal switching mechanism ("Keyless" lampholders do not provide an internal switching mechanism).

A device with contacts that establishes mechanical and electrical connection to an inserted lamp. A threaded adapter that converts the thread size of the lampholder in which it is inserted so that the lampholder can accept an incandescent lamp bulb of a different size thread.

Let-Through Voltage:
Maximum voltage a surge suppression/protection device allows to reach any attached electronic devices after a power surge occurs.

Lighted (Illuminated):
A receptacle with a face that becomes illuminated when the device is connected to an energized electrical circuit.

Lighted Handle:
A switch with an integral lamp in its actuator (toggle, rocker or pushbutton) that illuminates when the switch is connected to an energized circuit and the actuator is in the OFF position.

Any device which consumes power in a circuit.

A device designed to lock an inserted plug with a matching blade configuration when the plug is rotated in a clockwise direction. The plug can only be removed by first turning it in a counter-clockwise direction.

Low Voltage:
A switch rated for use on low-voltage circuits of 50 volts or less.

L Rated:
A switch specially designated with the letter "L" in its rating that is rated for controlling tungsten filament lamps on AC circuits only.

A specially designed lampholder for tubular Lumiline-type incandescent lamps, typically used in bathrooms and retail display cases.

Maintained Contact:
A switch where the actuator (toggle, rocker, pushbutton or key mechanism) makes and retains circuit contact when moved to the ON position. The contacts will only be opened when the actuator is manually moved to the OFF position. Ordinary light switches are maintained contact switches.

Manual Motor Controller:
A switch designed for controlling small DC or AC motor loads, without overload protection.

Manual Ranging:
DMM that requires the user to manually select the range, using the meter's dial

Manual Reset:
A starter that automatically deactivates a failed fluorescent lamp to eliminate flickering. A reset button provides a means of activating the circuit after lamp replacement.

Mpa: MegaPascal = 1 Million Pascals


Max Hold:
Captures maximum reading displayed during the measurement


Maximum (Peak) Surge Current:
The peak surge current a Surge Protective Device can withstand, based on IEEE Standard C62.45 test waveforms.


Medium Base:
Same as the Edison base lampholder. An internally-threaded lampholder, with the inner shell approx. 1" in diameter. Designed for widely-used standard medium base lamps.


Medium Bi-Pin:
A fluorescent lampholder with two contacts, used in pairs. For type T-8 tubular fluorescent lamps, approx. 1" in diameter.


A type of switch that uses mercury as the contact means for making and breaking an electrical circuit.


A device designed with a smaller body diameter than standard connectors with a similar rating.


Wallplates that are approx. 3/8" higher and wider than the standard size that can be mounted onto larger volume outlet boxes and/or used to hide wall surface irregularities. These wallplates are approx. 1/4" deep to ensure a proper fit when used with protruding devices.


One thousandth (10-3) of a ohm; abbreviated as mΩ.

Feature that allows a meter to capture and store the highest and lowest readings during a specific measurement.

Designed for the smallest available incandescent lamps with a screw-in base, approx. 3/8" dia. Widely used in flashlights and toys, etc.

Miniature Bi-Pin:
Similar to medium bi-pin lampholders, but designed for type T-5 tubular fluorescent lamps, approx. 5/8" in diameter.

An abbreviation denoting the measurement 1000 circular mils (equal to approximately 0.5067 mm²). Often used in reference to wire gauge and cable sizing, MCM is also known as the Kcmil, or "kilo-circular mil.

The acronym standing for metal oxide varistors, which are components found in surge protection devices that absorb excess voltage, and then channel it away from electrical appliances and into the ground.

Individual-section wallplates with different openings that can be configured into a multi-gang plate.


The largest screw-in type lampholder, designed for mogul incandescent lamps with a screw base of approx. 11/2" dia. Used in street lights and numerous commercial/industrial applications.


An device that is factory molded to a length of flexible cord.


Momentary Contact:
A switch that makes circuit contact only as long as the actuator (toggle, rocker, pushbutton or key mechanism) is held in the ON position, after which it returns automatically to the OFF position. This is a "Normally Open" switch. A "Normally Closed" switch will break circuit contact as long as it is held in the OFF position, and then automatically return to the ON position. Available in "Center OFF" versions with both Momentary ON and Momentary OFF positions.


A wallplate that has two or more gangs.


MPD 1506:
A standard that gives requirements for polytetrafluoroethylene (PTFE) insulated electrical wires.

Mean time between failures (MTBF) is the mean (average) time between failures of a system, and is often attributed to the "useful life" of the device.


The National Electrical Manufacturers Association, which develops and publishes technical standards rating the safety and performance of electrical products.

Non contact voltage indicator - used to check if a wire is live before shock occurs.

Ohm (Ω):
The basic unit of resistance, specified as equal to that of a conductor, in which one amp of current is produced by one volt of potential across its terminals.

Outlet Box:
Medium-base incandescent lampholder designed for mounting in 31/4" or 4" electrical boxes. Available with or without pull-chain mechanism, and with or without built-in receptacle.

Pertaining to a device, process, or channel involved in the production of data by a computer or by any of its components.

Overload (OL):
Signal amplitudes of frequencies above the specified limits of the instrument; typically displayed as "OL" on the display of a DMM.


Wallplates that are approx. 3/4" higher and wider than the standard size and are used to conceal greater wall irregularities than those hidden by Midway wallplates. These wallplates are approx. 1/4" deep to ensure a proper fit when used with protruding devices.


Pascal (symbol: Pa)
A measure of perpendicular force per unit area. ie. equivalent to one newton per square meter or one joule per cubic meter.

Peak Hold:
Feature of DMM that allows retention of highest reading in a series of measurements.

A type of switch designed for installation at the end of a length of portable cord or cable.

Phase Angle:
In electronic signaling, phase is a definition of the position of a point in time (instant) on a waveform cycle. A complete cycle is defined as 360 degrees of phase as shown in Illustration A below. Phase can also be an expression of relative displacement between or among waves having the same frequency. Phase difference, also called phase angle, in degrees is conventionally defined as a number greater than -180, and less than or equal to +180. Leading phase refers to a wave that occurs "ahead" of another wave of the same frequency. Lagging phase refers to a wave that occurs "behind" another wave of the same frequency. When two signals differ in phase by -90 or +90 degrees, they are said to be in phase quadrature. When two waves differ in phase by 180 degrees (-180 is technically the same as +180), the waves are said to be in phase opposition. Illustration B shows two waves that are in phase quadrature. The wave depicted by the dashed line leads the wave represented by the solid line by 90 degrees. Phase is sometimes expressed in radians rather than in degrees. One radian of phase corresponds to approximately 57.3 degrees. Engineers and technicians generally use degrees; physicists more often use radians. The time interval for one degree of phase is inversely proportional to the frequency. If the frequency of a signal (in hertz) is given by f, then the time tdeg (in seconds) corresponding to one degree of phase is:

tdeg = 1 / (360ƒ)
The time trad (in seconds) corresponding to one radian of phase is approximately:
trad = 1 / (6.28ƒ)

Pilot Light:
A switch with an integral lamp in its actuator (toggle, rocker or pushbutton) that illuminates when the switch is connected to an energized circuit and the actuator is in the ON position.


Pin and Sleeve:
A device with hollow, cylindrical sleeve-type contacts.


A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system. The plenum space is used typically to house communication and fiber optic cables for the building of computer and telephone networks.


A device with male contacts intended for insertion into a receptacle to establish electrical connection between the attached flexible cord and the conductors connected to the receptacle.


Polarity is a term used in electricity, magnetism, and electronic signaling. Suppose there is a constant voltage, also called an electric potential or electromotive force (EMF), between two objects or points. In such a situation, one of the objects or points (poles) has more electrons than the other. The pole with relatively more electrons is said to have negative polarity; the other is assigned positive polarity. If the two poles are connected by a conductive path such as a wire, electrons flow from the negative pole toward the positive pole. This flow of charge carriers constitutes an electric current. In physics, the theoretical direction of current flow is considered to be from positive to negative by convention, opposite to the flow of electrons. The movement of electric charge carriers inevitably produces a magnetic field. Conversely, any magnetic field is the result of the motion of charge carriers. In a permanent magnet, a magnetic field is produced by the composite motions of electrons in geometrically aligned atoms. A magnetic field is characterized by poles called north and south. Magnetic polarity refers to the orientation of these poles in space. In digital communications, data is composed of short-duration pulses called bits (binary digits). There are two possible states for each bit: logic 0 (also called low) and logic 1 (also called high). In a closed circuit, these logic elements are represented by direct current voltages. A high-speed data signal varies rapidly between the low and high states. Common values are approximately +0.5 volts for low and +5 volts for high. In some cases different values are used, for example, -3 volts for low and +3 volts for high, or -5 volts for low and -0.5 volts for high. If both voltages have the same polarity, the signal is called uni-polar; if the voltages have opposite polarity, the signal is called bipolar.


Power Factor:
Watts divided by volt amps, KW divided by KVA. Power factor: leading and lagging of voltage versus current caused by inductive or capacitive loads, and harmonic power factor: from nonlinear current.

Power Distribution Unit (PDU):
A device that works to break down high-voltage electricity into usable levels, and then distributes that electricity to other devices needing power. Power Distribution Units are most often used in data centers and offices, and operate either alone or in conjunction with an Uninterruptible Power Source (UPS).


Power Surge:
A sudden voltage spike within an electrical circuit, usually caused by a close-range lightning strike. Power surges typically last only a fraction of a second, but since they can reach up to 6000 volts, they are a leading cause of damage to electronic devices. Also known as a Power Spike.

Projection TV:
Any television where the displayed picture is not created on the viewing screen itself, but is projected onto the screen from the front or rear.


Projection Tube:
Tube within CRT and Rear Projection televisions that project images onto a television screen using color and light combinations, usually having e a short life span (depending on usage) due to phosphor burn and cathode life.


A switch where the making or breaking of contacts is controlled by pulling downward or outward on the actuator mechanism.


An incandescent lampholder with an internal switching mechanism that is activated by pulling down on a beaded chain or cord.


A switch with an actuator mechanism that is operated by depressing a button.


An incandescent lampholder with an insulated lever that is pushed from either side to activate an internal ON/OFF switching mechanism.


An enclosed channel of metallic or nonmetallic materials designated specifically for holding wires, cables or busbars.

Reactive Power:
Also called imaginary power or wattless power. It is the power value in "volt amps" obtained from the product of source voltage and source current in a reactive circuit.

An electronic device that converts a radio signal from a transmiter into useful information.

A device with female contacts designed for fixed installation in a structure or piece of equipment and which is intended to establish electrical connection with an inserted plug.

Opposition to current; measured in ohms.

A physical property of a material to resist or oppose the movement of charge through the material. Expressed in ohm-cm.

Increments in value that can be displayed by a DMM; The greater the resolution, the more precise the readout.

Response Time:
The amount of time it takes a surge suppressor to recognize a power surge and react to it, diverting potentially harmful excess electricity away from sensitive components.

The system of pathways that are provided to run riser cables for one floor to another. Elevator shafts cannot be used as risers.

A switch where rotating the actuator in a clockwise direction makes the circuit connection, and then rotating the actuator in either the same or opposite direction breaks the connection.

RMS Current:
RMS is an abbreviation for the 'root mean square' mathematical process of determining the effective value of an alternating current. The RMS or effective value of a current is by definition such that the heating effect is the same for equal values of alternating- or direct-current. However, the wattage found by multiplying the average voltage by the average current is not the same as the RMS voltage times the RMS current for pulsating direct-current. The product of average voltage and average current in a pulsating direct-current circuit is sometimes called 'DC watts.'


RMS Voltage:
Consider the "120 VAC" power line coming into your home. The average voltage in this signal is zero. (So, why pay the light bill?) In fact, electricity is billed in "kilowatt hours", or the time integral of power. The power is what is important to run electrical equipment.
In general, electric power varies as voltage squared, (P=V2/R) which is strictly non-negative. The average (mean) power can be computed using the "mean squared voltage". Specifically, power is found using the square of the "root mean squared voltage" (VRMS or VRMS). This is the quantity which is important when shopping for AC signals. In fact, when talking about these signals, "120 VAC" refers to the RMS voltage of the cosine waveform delivered to your doorstep.

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Safety or Tamper-Resistant:
A receptacle specially constructed so that access to its energized contacts is limited. Tamper-resistant receptacles are required by the National Electric Code NFPA-70 in specific pediatric care areas in health care facilities.

An adapter wired in series to a flexible cord containing an in-line switch used to control electrical equipment plugged into the adapter.

Any connection that has relatively low, or any, resistance between two points below a preselected threshold.

A receptacle that accepts only one plug.

Single-phase electric power:
In electrical engineering, single-phase electric power refers to the distribution of electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors. A single-phase supply connected to an alternating current electric motor does not produce a revolving magnetic field; single-phase motors need additional circuits for starting, and such motors are uncommon above 10 or 20 kW in rating.

The generation of AC electric power is commonly three phase, in which the waveforms of three supply conductors are offset from one another by 120. Standard frequencies of single-phase power systems are either 50 or 60 Hz. Special single-phase traction power networks may operate at 16.67 Hz or other frequencies to power electric railways.No arrangement of transformers can convert a single-phase load into a balanced load on a polyphase system. A single-phase load may be powered from a three-phase distribution system either by connection between a phase and neutral or by connecting the load between two phases. The load device must be designed for the voltage in each case. The neutral point in a three phase system exists at the mathematical center of an equilateral triangle formed by the three phase points, and the phase-to-phase voltage is accordingly times the phase-to-neutral voltage. For example, in places using a 415 volt 3 phase system, the phase-to-neutral voltage is 240 volts, allowing single-phase lighting to be connected phase-to-neutral and three-phase motors to be connected to all three phases.

In North America, a typical three-phase system will have 208 volts between the phases and 120 volts between phase and neutral. If heating equipment designed for the 240-volt three-wire single phase system is connected to two phases of a 208 volt supply, it will only produce 75% of its rated heating effect. Single-phase motors may have taps to allow their use on either 208 V or 240 V supplies.

On higher voltage systems (kilovolts) where a single phase transformer is in use to supply a low voltage system the method of splitting varies. In North America utility distribution practice the primary of the step-down transformer is wired across a single high voltage feed wire and neutral, at least for smaller supplies (see photo of transformer on right). Rural distribution may be a single phase at a medium voltage; in some areas single wire earth return distribution is used when customers are very far apart. In Britain the step-down primary is wired phase-phase.

Single Pole:
A standard ON/OFF switch that controls one fixture from one location.


Single-Pole, Double-Throw (SPDT):
A switch that makes or breaks the connection of a single conductor with either of two other single conductors. This switch has 3 terminal screws, and is commonly used in pairs and called a "Three-Way" switch.


Single-Pole, Single-Throw (SPST):
A switch that makes or breaks the connection of a single conductor in a single branch circuit. This switch has two screw terminals and ON/OFF designations. It is commonly referred to as a "Single-Pole" Switch.


Sleep Mode:
Automatically shuts down unit not in use, to preserve battery life.


A switch with a slide-action actuator for making or breaking circuit contact. Dimmer switches and fan speed controls are also available with slide-action mechanisms for lighting and fan speed control


Slimline Single-Pin:
A fluorescent lampholder with a single contact designed for Slimline fluorescent lamps such as the T-12 (11/2" dia.), T-8 (1" dia.), and the smaller version T-6 (3/4" dia.).


An device with factory-assembled spring clips that securely snap into a panel cutout without requiring additional fasteners.


Fast, short duration electrical transients in voltage, current, or transferred energy in an electrical circuit.


A duplex receptacle that allows each receptacle to be wired to separate circuits. Most duplex receptacles provide break-off tabs that allow them to be converted into split-circuit receptacles.


Static Discharge:
Spark associated with static electricity caused by electrostatic discharge, as excess charge is neutralized by a flow of charges from, or to, the surroundings.


Step Bit:
A step bit, step drill, speed bit, or Unibit is a roughly conical bit with a stair-step profile. Due to their design, a single bit can be used for drilling a wide range of hole sizes. Some bits come to a point and are thus self-starting. The larger-size bits have blunt tips and are used for hole enlarging. They are now available in fractional inch and metric sizes. Step bits are most commonly used in general construction and plumbing. One drillbit can drill the entire range of holes necessary on a countertop, speeding up installation of fixtures. They are most commonly used on softer materials - plywood, particle board, drywall, acrylic, laminate, etc. They can be used on very thin sheetmetal, but metals tend to cause premature drill wear and dulling. A metal hole saw is more appropriate for large-hole applications in thicker metals. An additional use of step bits is deburring holes left by other bits, as the sharp increase to the next step size allows the cutting edge to scrape burrs off the entry surface of the workpiece. However, the straight flute is poor at chip ejection, and can cause a burr to be formed on the exit side of the hole, more so than a spiral twist drill turning at high speed.

Straight Blade:
A non-locking device into which mating plugs are inserted at a right angle to the plane of the matching device face.

Surface Mounted:
A device designed to be surface mounted on a panel or piece of equipment.

Surface Resistance:
The ratio of DC voltage to the current flowing between two electrodes of specified configuration that contact the same side of a material. This measurement is expressed in ohms.

Surge Suppressor:
A device, which helps to prevent power-surge damage to electrical equipment by shutting down – or “clamping” – voltage levels that exceed the tolerance level of a given circuit.

A device for making, breaking, or changing the connections in an electric circuit.

A wallplate with individual gangs arranged vertically one above the other.


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


THD – Total Harmonic Distortion

THHN (Thermoplastic High Heat-resistant Nylon-coated:
Designated for a specific insulation material and temperature rating for electrical wire and cable. Wires with THHN insulation are commonly used in the alternating current (AC) electrical distribution systems of buildings of all types and sizes throughout North America, usually at voltage levels (potential difference or electromotive force) ranging from 110-600 Volts. This type of insulation is used for both copper and aluminum wires which are either solid or stranded, depending on size.


Type THW is a single conductor ground wire suitable for non-grounded multi-conductor cables. Compatible with twisted, heavy-duty, jacketed, or parallel cables. These wires are manufactured to UL standard Type THW. The solid bare copper conductor is insulated with a moisture-resistant, polyvinyl chloride (PVC) insulation.

  • For installation in conduits and other raceways
  • Oil and grease resistant insulation
  • Abrasion and crush resistant
  • THW insulation is flame retardant PVC and meets the UL VW-1 flame test
  • Maximum continuous conductor temperature: 75°C Dry, 75°C wet

Three-Position, Center OFF:
A two circuit switch, either maintained or momentary contact, where the OFF position is designated as the center position of the actuator.

Three Way (3-Way):
A 3-way switch controls one fixture from two locations. For example, a light controlled from either end of a stairway or hallway. In three-way applications, two 3-way switches are required.4-Way: A 4-way switch allows you to control one fixture from three locations.

Tightsight display (at the bottom of the unit) allows users to view readings in dark, bright, or tight locations.

Time Delay:
A switch with an integral mechanism or electronic circuit that will automatically switch a load OFF at a predetermined time interval.

A switch with an integral mechanism or electronic circuit that can be set to switch an electrical load ON at a predetermined time.

A threaded version of the BNC connector with superior performance at microwave frequencies.

A switch with a lever-type actuator that makes or breaks switch contact as its position is changed.

T Rated:
A switch specially designated with the letter "T" in its rating that is rated for controlling tungsten filament lamps on direct current (DC) or alternating current (AC) circuits.

True RMS. DMM that has the True RMS feature, allowing for accurate measurement of AC voltage in environments with harmonics.

Transient Voltage Surges:
High-speed, high-energy electrical disturbances present on AC power lines and data and communication lines, generated by utility switching, motor-load switching and lightning strikes.

Transient Voltage Surge Suppressor (TVSS):
A device designed to protect sensitive electronic equipment such as computers and computer peripherals, logic controls, audio/video equipment and a wide range of microprocessor-based (computer chip) equipment from the harmful effects of transient voltage surges. Also referred to as a Surge Protective Device (SPD).

Any object (source) which sends information to an observer (receiver)

A receptacle with a common mounting means which accepts three plugs.

The abbreviation for Underwriters Laboratories, a third party, not-for-profit organization that tests and rates electrical products for consumer safety.

UL 311-1:
The latest UL standard for electrical test instruments is UL 61010B-1, which is a revision of 3111-1. It specifies the general safety requirements, such as material, design, and testing requirements, and the environmental conditions in which the standard applies. UL 3111-2-031 lists additional requirements for test probes. The requirements for hand-held current clamps, such as the current measuring portion of clamp meters, are included in UL 3111-2-032.

UL 444:
An Underwriters Laboratories standard for component electronic controls that will be factory-installed into appliances and utilization equipment with an electrical rating of 600 volts or less.


UL 498:
An Underwriters' Laboratories safety standard that discusses safety requirements for electrical receptacles, cord connectors, attachment plugs, current taps, inlets, and flatiron and appliance plugs.


Uninterruptible Power Source (UPS):
A type of battery-backup, which provides electronic devices with a brief emergency supply of electricity in the event of a power outage. Uninterrupted power sources are especially critical in preventing data loss, since they either allow time to properly power down computers, or carry electronics through until generators can be activated.


UL 1363:
An Underwriters Laboratories document, which gives standards for indoor-use relocatable power taps, which are cord connected and rated at 250 V/AC or less, and 20 A/AC or less.

UL 1449:
UL 1449 is the Underwriters Laboratories’ safety standard for surge suppressors on 50 or 60 Hz power circuits.


UL 1778:
An Underwriters Laboratories document, which gives continuity standards for Uninterruptible Power Supply (UPS) systems.

UL 61010A-1 (formerly UL 3101-1):
Electrical Equipment For Laboratory Use; Part 1: General Requirements. First edition, 2002. Second edition, 2003.

UL 61010C-1 (formerly UL 3121-1):
Standard for Process Control Equipment. First edition, 2002. Second edition, 2003.

UL Rated E210116):
Measuring, testing and signal generation equipment..

A volt is the measure of the amount of force needed to propel a single ampere through one-ohm resistance. Voltage determines the potential energy of a current.

Volts alternating current

Volts Direct Current ; Video Display Controller (in terms of audio/video devices)

(Video Graphics Array) An IBM video display standard, that originated with its PS/2 models that has become the minimum standard for PC display.

Viscosity is a measure of a fluid's resistance to flow, or property of a fluid that resists force.

Voltage Event:

Voltage events are sags, swells, transients, outages and frequency variations on line voltage at receptacles, where the most sensitive loads are connected.


W Type:
Same as "Y" type, except having three cord connectors arranged in the form of the letter "W".

A plate designed to enclose an electrical box, with or without a device installed within the box.

An inlet, or outlet, specially constructed so that water will not enter under specified test conditions. The IP Suitability Rating designates the degree of protection a device offers against the ingress of moisture and water (e.g. IP 55, IP 44).


A standard International System unit of electrical and mechanical power, which is the equivalent of one joule per second. The watt is named after James Watt, an eighteenth-century Scottish inventor. Wattage is calculated be multiplying a current’s number of amps by its number of volts.


A device specially constructed so that exposure to weather will not interfere with its operation.


Y Type:
An adapter in the form of a letter "Y", having two cord connectors on one end and a male plug on the other end.


A moderately reactive bluish grey metal that will tarnish a bright bluish-green flame, giving off zinc oxide.


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