CentreCOM 3600 Series Hub/Repeaters
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DIX CONNECTOR
—See D-Sub Connector
FOIRL
— A fiber optic standard that allows up to 1,000 meters (3,280 ft.) of
multimode duplex fiber optic cable in a point-to-point link.
HARMONICA ADAPTER
—This adapter provides a simple way to convert the
50-pin Telco connection to RJ45 connections. See AT-Adapt-2.
HEARTBEAT
—See SQE
HOT SWAPPING
— The process of replacing a hub module without bringing
down the network. This process occurs by sliding an active module into a fully
powered up concentrator, replacing a failed module.
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 RJ45 receptacle at the hub would wire pin-to-pin
to the RJ45 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.
LINK SEGMENT
—The link segment of coaxial cable is a segment that has no
MAU devices, but links together two LAN devices 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 that is
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).
