Jabber Errors — A typical Ethernet error that occurs because of oversized packets with a faulty FCS (Frame Check Sequence).

Jabber Lock-Up — The MAU's ability to automatically inhibit the transmit data from reaching the medium if the transmit data time exceeds a specified duration. This duration is in the range of 20 ms to 150 ms. Jabber lock-up protects the medium from being overrun with data packets from a possibly defective device.

Jam — This term describes the collision reinforcement signal output by the repeater to all ports. The jam signal consists of 96 bits of alternating 1s and 0s. The purpose is to extend a collision sufficiently so that all devices cease transmitting.

JANET — Joint Academic Network. A university network in the U.K. With the increase in network speed in recent years, it has been renamed to "Super-JANET."

Java — A derivative of the C++ language, SunSoft's distributed programming language, offered as an open standard

JavaScript — A scripting language developed by Netscape Communications and Sun Microsystems, Inc.

Jitter — The fluctuation of the data packet in respect to a standard clock cycle. Jitter is undesirable and must be minimized.

Joint Photographic Experts Group (JPEG) — A widely accepted international standard for compression of color image files, sometimes used on the Internet

JPEG — See Joint Photographic Experts Group

Jukebox — A high-capacity storage device (typically contains one to four disks) that uses an autochanger mechanism to mount and dismount optical disks, as needed, automatically.

Jump — Text, graphics, or parts of graphics that provide links to other Help topics or to more information about the current topic. The pointer changes shape whenever it is over a jump. If you click a jump that is linked to another topic, that topic appears in the Help window. If you click a jump that is linked to more information, the information appears in a pop-up window on top of the main Help window.

Jumper — A device used to configure computer devices. Jumpers are used on network boards to set interrupts, memory addresses, and I/O ports.

Jumper Block — A group of jumper pins that can be connected to make a particular hardware configuration setting on a circuit board.

JUMPERS — A NetWare 3.1x command used to configure the IPX LAN driver to match the network board settings.