Allied Telesis AT-MR815T - Manual (Page 40)

Glossary
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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.
CYCLIC REDUNDANCY CODE (CRC)—An algorithm used to check for
and correct bit errors in data transmission.
DATA COMMUNICATION EQUIPMENT (DCE)—In RS232 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 RS232 specification a module
typically at the end of a segment. The DTE could be an Ethernet workstation,
repeater or bridge.
HARMONICA ADAPTER—This adapter provides a simple way to convert
the 50-pin Telco connection to RJ-45 connections.
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.