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The Book of Terms

The Book of TermsThe WJI Book of Wire & Cable Terms: an interactive experience of learning and sharing
This book, written by industry volunteers and containing more than 5,000 entries, is an asset for newcomers to wire and cable.

At the same time, it also represents an opportunity for industry veterans to give back by either updating or adding to the more than 5,000 entries. This is an honor system process. Entries/updates must be non-commercial, and any deemed not to be so will be removed. Share your expertise as part of this legacy project to help those who will follow. Purchase a printed copy here.


All   0-9   A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Designation sometimes used in coding wire to indicate oil resistance insulation.


Designation for Overall Width.


Designation for Overcurrent.


A term applied, in the case of metals, to the absorption or entrapment of gases.

Occupational Safety and Health Act

Specifically the Williams-Steiger law passed in 1970, it covers all factors relating to safety in places of employment. Administered by the U.S. Dept. of Labor, which establishes mandatory standards and safety requirements for all businesses.


1) Designation for the overall diameter of a cable, including conductor, insulation and jacket and concentric neutral (if used). 2) Designation for the outside diameter of a cylindrical object.


Designation for Original Equipment Manufacturer.


Designation for Oxygen-Free.

Off Center

Conductor displaced within the cross-section of its insulation; not perfectly centered within the insulation.


Percentage of a specified gas released during the combustion of insulation or jacketing material.

Offset Marker

Identification technique of marking wire and cable for irregular surface printing. It employs rubber-faced transfer rolls that conform to a wide variety of surface types and shapes. Some products that have successfully used this system are multi-colored cables, ribbon or flat cables, ropey electronic cables and tech cables.


See OFHC Copper.

OFHC Copper

Oxygen-free, high-conductivity copper. One of the general types of copper used for electrical conductors. It has no residual deoxidant, 99.95 percent minimum copper content and an average annealed conductivity of 101 percent.


Designation for an S.I. unit for measuring electrical resistance or impedance. One ohm equals one volt per ampere.

Ohm Lead Wire, 300

Television lead-in wire.

Ohms Law

The formula V = I x R (voltage equals current multiplied by resistance), used for calculating voltage drop, fault current and other values in an electrical circuit. Voltage is in volts, current is in amperes and resistance is in ohms.


Designation for Official Interpretation. An interpretation of the National Electrical Code to help resolve a specific problem between an inspector and an installer.


1) A fatty or greasy liquid obtained from plants, animals or minerals used for manufacturing. 2) A lubricant used to reduce wear in machines. 3) Substance which, along with greases and other petroleum-based products, is used for quenching in hardening and tempering and as a corrosion-preventing agent. The re­quirements which may be detailed in specifications or quenching oils are viscosity, acid value, saponification value, flash point, loss in heating (volatility) and thermal conductivity. Such oils should also be highly refined and thus free from un­stable constituents so as to improve the resistance of the oil to oxidation.

Oil Aging

To bring cable to a stage fit for use in an accelerated manner (to simulate field conditions) by placing it in an oil bath, heating it to a pre-set temperature and continuing thus for a given time. At the end of the oil bath test, the cable is subjected to physical and electrical tests to evaluate any decline in its properties.

Oil Hardening and Tempering

Thermal treating high-carbon wire in the finished size by heating above the critical range, quenched in oil and reheating or tempering. The actual tempering does not take place in oil, as the term for this process would seem to indicate. See Hardening.

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