Jacket

The flexible covering of a cable, used to protect the colour-coded conductors inside.

JavaScript

A programming language that is mostly used in Web pages, usually to add features that make the page more interactive. When it is included in an HTML file it relies upon the browser to interpret the JavaScript. When it is combined with Cascading Style Sheets (CSS), and later versions of HTML (4.0 and later) the result is often referred to as DHTML (Dynamic HTML).

JPEG

Joint Photographic Experts Group - JPEG is most commonly mentioned as a file format for image files. JPEG format is preferred to the GIF format for photographic images as opposed to line art or simple logo art.

Jumper

A cable unit or cable element without connectors used to make a connection on a cross-connect.