Allied Telesis AT-3012SL Installation Manual page 39

AT-30xxSL Multiport Repeaters
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).
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 RJ-45 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 device.
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.
MEDIUM DEPENDENT INTERFACE (MDI)—The mechanical and electrical
interface between a hub and a transceiver (MAU). MDI-X is another version of the
interface that enables hubs to connect using different pin-outs, thereby avoiding
conflicts that occur when receiving and transmitting packets use the same pin-out.
N-SERIES—A barrel shaped, threaded connector used on 10Base5 (thick Ethernet)
coaxial cable.
PATCH PANEL—A 10Base-T patch panel may be used between a punch-down block
and UTP workstation. The patch panel generally has a female RJ-45 connector on the
front for each workstation and a Telco (RJ21) connector on the back, which is wired to a
punch-down block. This provides a convenient way for the installer or network manager
to connect the hub 10Base-T ports into the desired building locations.
POLARITY CORRECTION—Many 10Base-T UTP ports have a polarity correction
function. If the UTP wiring has RD- and RD+ inadvertently crossed, the polarity
correction function will sample the signal and electrically swap the wires. If the TD- and
TD+ wires are crossed, the correction would occur at the MAU on the other end of the
UTP link. This occurs within a single pair and should not be confused with the crossover
cable.
PROPAGATION DELAY—The time it takes a signal to travel from the input of a
system component to the output. Usually measured in nanoseconds. IEEE 802.3 has
specific propagation delay maxima for computing propagation budgets when designing
a LAN. Cable length plays a major role in propagation delay; for example, a 50-meter
(164-foot) AUI cable has a maximum allowable propagation delay of 257 ns. The
propagation delay of cable depends on the length and velocity factor of the cable type.
There are also propagation delays associated with electronics attached to the system.
PUNCH-DOWN BLOCK—The punch-down block is the wiring panel where the house
wiring from the building's offices terminates. This is where many
10Base-T hubs would be located. Wiring installers use a special punch-down tool to
insert the UTP wire for data and voice applications.
REPEATER—A device used to extend the length, topology, or interconnectivity of the
physical medium beyond that imposed by a single segment, up to the maximum
allowable end-to-end trunk transmission line length. Repeaters perform the basic
actions of restoring signal amplitude, waveform and timing applied to normal data and
collision signals.
RJ-45—This connector is a 10Base-T standard for connecting UTP cabling. It is
inexpensive and easy to install onto UTP cable.
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