JBOD
Just a Bunch Of
Disks is indicates the
Fibre Channel-Arbitrated Loop (FC-AL) com-munications
standard for connecting multiple drives in a RAID.
JEDEC
Joint Electron Device Engineering Council is the consortium of manufacturers that devises standards most notably for computer memory modules. Industry Standard memory usually implies compliance with a particular group of JEDEC standard.
JFETs
They are referenced with the other transistors.
JIT
Just in time
JPEG
Joint Photographic Experts Group.
JTAG
Joint Test Action Group
Jukeboxes
Typically, these drives have a media storage magazine for 100 to 500 CDs or 10 to 25 magnetic tapes. The media is swapped, on-demand, in and out of one to four CD-ROM or magnetic tape drive mechanisms. Similar implementations include: CD and tape libraries, medium changers, and CD autochanger.
Kermit Protocol
An error-checking protocol. This text-only, file transfer protocol (from Columbia University) provides error-checking. Kermit permits PCs to interact with mini- and main frame ("host") computers (that use 7-bit characters). It uses an "8-bit quoting" to strip off the 8th bit, and send it separately. Some users use Kermit to take advantage of the host system's greater storage capacity to "upload" data files to it (even those with 8-bit characters that are otherwise unusable to the host computer).
Kodak Photo CD
File format for storing digital RGB images on a CD. Standard Photo CD images have to be converted from RGB to CYMK before they can be copied to film or imagesetter.
Ku-band
A 12 GHz signal. It is used by satellites for broadcasting live and unedited shows for satellite dish reception. This is opposite the use of the C-band. The Ku band is measured in decibels; the C-band is measured in degrees. The lower the measurement, the better the picture.
Landing Zone (LZ)
The read/write heads inside a drive move over the spinning platter surfaces, in response to a BIOS Seek command. When they reach the specified cylinder address, they stop and are stationary while reading or writing data to a specific sector address. In response to a command, the heads may move to many different addresses to perform data storage or retrieval tasks. When the tasks are completed, or drive power is lost, the head returns to (and are parked over) the Landing Zone (LZ) area on each platter. Usually, the LZ is next to the center hub. No data is stored in the landing zone to prevent its loss.
Note: PC What's The Problem? includes suggestions for "parking" the read/write heads in drives which do not automatically do so when either power is lost or in response to a power-down command.
Laser
Light amplification by stimulated emmission of radiation.
Laser printer
Black- and-white or color desktop printers which electrostatically transfer dry toner to paper which is them fixed in place by a heating element. This is the xerographic printing process.
LAT
Local Area Transport, a proprietary Digital Equipment Corp. (Now Compaq) protocol used to transfer data to and from Digital host systems.
Layer recording
The recorded information is in layers as seen from one side of a disc. There are single and dual layer discs. In the case of dual layer discs, the data is recorded on the disc using either OTP or PTP.
LBA
Logical Block Address defines the addressing mode of the drive by the linear mapping of sectors form 0 to n.
LCC
Leadless Chip Carrier.
LCD
Liquid crystal diodes are used in many kinds of displays including flat-panel monitors.
Lead In Area
The CD Lead-in area is the area on a CD-ROM disc preceding track one. The area contains the TOC data and precedes each program area. The main channel in the lead-in area contains audio or data null information. This area is coded as track zero but is not directly addressable via the command set. The Q sub-channel in this area is coded with the table of contents information.
For DVDs, it is the area comprising physical sectors 1.2 mm wide or more adjacent to the inside of the Data area. The area contains the Control data and precedes the Data area.
Lead Out Area
For CDs it is the area on a CD-ROM disc beyond the last information track. The main channel in the lead-out area contains audio or data null information. This area is coded as track AAbcd but is not directly addressable via the command set. The READ CD-ROM CAPACITY data is the first logical block address of this area minus one.
DVD Lead-out area comprises physical sectors 1.0 mm wide or more adjacent to the outside of the data area in single layered disc for PTP (Parallel Track Path) disc, or area comprising physical sectors 1.2 mm wide or more adjacent to the inside of the data area in layer 1 of OTP (Opposite Track Path) disc.
L-EC
Layered Error Correction code uses 276 bytes of the auxiliary data field in the CD-ROM data mode-one sectors. These bytes can be accessed by an algorithm in a drive's firmware to perform error correction.
LEC
Local Exchange Carrier
LED
Light-emitting Diode.
LEP
Light-emitting polymer technology, patented by Cambridge Display Technology Ltd (CDT), supports a 640 by 480-pixel flatpanel television screen.
LF
Low Frequency (30 kHZ to 300 kHz).
LGA
Land-grid array.
LIF
Low-insertion Force.
Light-dependent resistors
These are referenced with the other resistors.
Line Driver
A signal converter that ensures reliable transmission over a long distance.
Little endian
In memory, the organization of bytes within large words so that the least significant byte occupies the lowest address. Contrast this arrangement with "Big endian" where the lowest address has the most significant byte.
LNB
The amplifier located in the frontend of the satellite disk syste
LP
Low profile, this term indicates a "third-height" drive or bay within a computer case which is one-third of the standard full size.
LSB
Least significant bit
LSB
Low sideband.
LSI
Large-scale Integration multifunction chips.
LSR
Local Service Report
LUN
Logical Unit Number.
LUT
Look-up table
LVDS
Low voltage differential signaling, a digital interface primarily used for flat panel monitors.
References are samples only. Each one is presented in greater detail in the
Technical Research Assistant for 2001
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