Glossary
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IMPEDANCE—An electrical characteristic of a circuit dealing with the
combination of the AC and DC resistance and the appearance of that
resistance to attached circuits.
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 is a term used to describe 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.
JITTER—The fluctuation of the data packet in respect to a standard
clock cycle. Jitter is undesirable and must be minimized.
LINK SEGMENT—The link segment of coaxial cable is a segment which
has no MAU devices but links two LAN devices together such as repeaters.
LINK TEST—In 10BASE-T Ethernet there is a link test function that
validates the UTP link. This consists of a pulse transmitted from point A
on one pair and validated at point B. Point B also transmits a pulse on the
second pair to be validated by point A. These pulses occur during media
idle states (in between packets).
MANAGED MODULE— An intelligent repeater in a department
concentrator chassis that makes management data available to the
Master.
MANAGEMENT AGENT—Software that is used to view hub activity
and set hub variables.
MASTER—A repeater in the top-most position in a department
concentrator chassis that contains and downloads the management agent
software to Backup and Slaves. The Master contains the only active image
of the management agent and controls the management functions of the
Backup and Slaves.
MAU—See Medium Attachment Unit
MAU-to-MAU, HUB-to-HUB WIRING—10BASE-T MAU-to-MAU or
hub-to-hub wiring generally requires a cross-over cable located
somewhere along the UTP cable run. This may commonly occur at the
punch-down block or between the RJ45 wall receptacle and the
workstation.
MAU/TRANSCEIVER—An Ethernet transceiver is a MAU. A 10BASE-T
MAU interfaces the UTP media to an AUI port on a workstation, repeater,
bridge or other Ethernet devices.
MDI/MDI-X—See Medium Dependent Interface
MEDIUM ATTACHMENT UNIT (MAU)—In a LAN, a device used in a
data station to couple the DTE to the transmission medium.
