Allied Telesis AT-3012SL Installation Manual page 38

Glossary
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COAXIAL CABLE SEGMENT—A length of coaxial cable sections and coaxial
connectors, terminated at each end in its characteristic impedance.
COLLISION—An unwanted condition that results from concurrent transmissions on
the physical medium.
COMPATIBILITY INTERFACE—The MDI coaxial cable interface and the AUI
branch cable interface, the two points at which hardware compatibility is defined to
allow connection of independently designed and manufactured components to the
baseband transmission system.
CROSSOVER—Wiring used when connecting a 10Base-T MAU to another 10Base-T
MAU or a 10Base-T hub to another 10Base-T hub. For example, one 10Base-T MAU has
the TD pair on the same pins as another 10Base-T MAU. If pins were wired straight,
there would be two transmitters on one pair and no receiver. As a solution, the crossover
cable crosses the TD pair with the RD pair, to connect the TD pins on one end to the RD
pins at the other end.
D-SUB CONNECTOR—The AUI cable uses 15-pin D-sub connectors. "D" refers to the
shape of the connector shell. Also called miniature D, DB15, or DIX connectors.
DATA COMMUNICATION EQUIPMENT (DCE)—In RS-232 specification, a
module, such as a modem, for connecting a DTE to other equipment. A repeater
connected to a terminal or workstation for Omega management use is wired as a DCE.
DATA TERMINAL EQUIPMENT (DTE)—In RS-232 specification, a module typically
at the end of a segment (i.e., uninterrupted length of Ethernet cable). The DTE could be
an Ethernet workstation, repeater or bridge.
DIX CONNECTOR—See D-Sub Connector
HEARTBEAT—See SQE
HOUSE WIRING—House wiring is the existing wiring inside a building. This wiring
generally originates from one or more wiring closets, such as a telephone room. Some
older buildings may have wiring unsuitable for 10 megabit data rates. In these
circumstances, it is recommended that the wiring be tested with a 10Base-T signal/wire
tester.
HUB/REPEATER—A hub is a central signal distributor. It is used in a wiring topology
consisting of several point-to-point segments originating from a central point. The term
hub is often used interchangeably with the term repeater. Multiport 10Base-T, 10Base2
and fiber optic (10Base-FL, FOIRL) repeaters are considered hubs. See Repeater.
HUB-to-HUB WIRING—See MAU-to-MAU Wiring
HUB-to-MAU WIRING—UTP cables for 10Base-T hub-to-MAU or NIC cards are wired
straight-through. An RJ-45 receptacle at the hub would wire pin-to-pin to the RJ-45
receptacle at the MAU.
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 shift of the data bit in respect to a standard clock cycle. Jitter is
undesirable and must be minimized.