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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 for: 1) Asphalted jute, non-metallic armor. 2) Joule Nm, work, energy, quantity of heat.

J Box

A box for joining different runs of raceway or cable, plus space for connecting and branching the enclosed conductors.


A plug-in type terminal widely used in electronic apparatus for temporary connections. A connection is made to a jack simply by plugging a probe or plug attached to a flexible insulated wire or cable into the jack.

Jack Chain

A form of un-welded bent wire chain. It is in the form of a figure eight. Widely used for light suspension work.


A rubber or synthetic covering applied over the primary insulation, braids, shields, cable components or over the cable itself. In fiber optics, a covering, frequently plastic, over a fiber, bundle of fibers or cable, which protects against the environment.

Jacket, Conducting

An electrically conducting polymeric covering over an insulation.

Jacquard Wire

A mild bright wire drawn from annealed mild steel to finish in two light drafts. Used on jacquard looms as part of the mechanism for raising and lowering the harness. At one end of a cut length, a hook loop is formed and a bend is made in the middle, the part thus formed being assembled into the harness.


The wedging of a cable such that it can no longer be moved during installation.

Jenkin’s Bend Test

An alternating bend test through 180° performed by means of a small portable machine having a con­stant radius bend.


A fixture or holding mechanism used to hold products in place while they are being worked.

Jig For Welding

See Welding, Jig.

Jockey Pulley

A pulley mounted on a spring-loaded hydraulically or pneumatically con­trolled swinging arm on a multi-hole wiredrawing machine. It is designed so that the pull of the wire moves the arm and automatically adjusts the speed of the motor driving each block, causing the block to run at exactly the speed required, without slip. The blocks are individually driven by DC motors, with the jockey pulley actuating the controls. See Dancer Arm.


When electrical drives momentarily energize the system to check on speeds and rotation. Describes the low startup speed of a drawing machine. Used for the safe start of a pointed rod end through the die during string-up.


See Splice.

Jominy Test

Hardenability test performed usually on alloy steels. An austenitized bar is quenched on its end with a water stream resulting in a cooling rate gradient and a range of steel structure that can be evaluated to assess hardenability.

Joule (J)

A measurement of energy. The joule rating on a surge protector indicates the amount of energy that a device is capable of absorbing. In general, the higher the joule rating, the better the unit is able to protect your equipment.


1) The portion of a rotating axle, shaft, spindle or roll which turns in a bearing. 2) The neck of a roll.

Jumbo Coils

In the coiling of rod, the material that results from a continuous casting operation.

Jump Test

See Upsetting Test.


1) Any length of conductor used to tie two or more points on an electrical circuit together. It usually implies a temporary condition but can be a permanent arrangement. 2) An assembly of twisted pairs without connectors used to join telecommunications circuits/links at the cross-connect.

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