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EtherExpress TPE Hubs: Wiring Information
WIRING INFORMATION
EtherExpress TPE Hubs Wiring Information
This document contains information which will help you in planning the
installation of an EtherExpress TPE Hub board. It contains information
on 10BASE-T Ethernet topology rules as they relate to hubs, 10BASE-T
wiring specifications, and cable construction and wiring.
Basic Ethernet Topology
EtherExpress Hubs can be used in situations where they are the center of
a stand-alone network, or they may be combined with other networking
devices as a component of a larger network. In the case where an
EtherExpress Hub is part of a larger network, the following Ethernet
topology rules must be abided by:
1. There may be no more than 4 repeaters between any 2 nodes on the
network.
All 10BASE-T hubs are repeaters. Each EtherExpress Hub board is a
12 port repeater, and must be treated as such when used in
conjunction with other repeaters (hubs) in the network.
Multiple EtherExpress Hub boards may be joined together with
internal daisy-chain cables to build a hub which has greater than
12 ports. A Hub constructed of multiple EtherExpress Hub boards
joined together with daisy-chain cables is considered a single
repeater.
2. There may be no more than 3 coax cable segments between any 2 nodes
on the network.
EtherExpress Hubs may be integrated with coax backbones (10BASE-5
or 10BASE-2) using the optional AUI Connector Kit (#AUI9010) and an
appropriate transceiver. When doing so, ensure that rule # 2 is
not violated.
3. The maximum length of coax cable segments are:
10BASE-5: 500 Meters
10BASE-2: 185 Meters
When adding a coax cable segment to integrate an EtherExpress Hub
into a coax backbone, ensure that rule #3 is not violated.
4. When crossing a bridge or router, repeater counts and coax cable
segment counts are reset to 0.
If an EtherExpress Hub is being integrated into a network which
contains bridges or routers, do not count repeaters or coax
segments on the other side of a bridge or router when applying
rules 1 & 2.
10BASE-T Wiring Specifications
The IEEE 802.3 standard for 10BASE-T Ethernet defines the electrical
characteristics which must be met by cabling used in 10BASE-T networks.
Most cabling vendors provide cables which they have been manufactured to
be in compliance with the IEEE specifications. Make sure you purchase
compatible cable for new installations.
When using previously installed cabling, it is highly recommended that
the end to end cabling be tested for compliance with the IEEE
specifications. This service can be performed by professional cable
installers. The following are the most important IEEE 802.3 cabling
specifications. These specifications assume a source and load impedance
of 100 ohms.
* Insertion Loss (Attenuation): No greater than 11.5 db at all
frequencies between 5 and 10 megahertz for a 100 meter segment.
* Differential Characteristic Impedance: Between 85 and 100 ohms for
all frequencies between 5 and 10 megahertz.
* Differential Near End Crosstalk (NEXT) loss between wire pairs
within the same cable:
4 pair cable: at least 30.5 db at 5 MHZ and 26 db at 10 MHZ.
25 pair cable: at least 35 db at 5 MHZ and 30.5 db at 10 MHZ.
Cable Construction & Wiring
Included with each EtherExpress Hub board is a 3 meter adapter cable.
On one end of this cable is a high density 50 pin male "D" connector
which is plugged into a corresponding connector on the EtherExpress Hub
board. On the other end of the cable is a female 50 pin Telco connector
which can be plugged into an RJ-45 harmonica, an RJ-45 patch panel, or a
punchdown-block system which terminates in RJ-45 wall jacks.
When ordering harmonicas, patch panels, or punchdown blocks which will
be used with the adapter cable, you must specify that you require male
Telco connectors. If you are connecting to pre-existing system which
provides a female 50 pin Telco connector you can use a standard feeder
cable with male connectors on each end to switch genders. It is also
possible to build your own adapter cable for custom installations.
Cable Length
The end-to-end length of all cabling between an EtherExpress Hub board
and a network node should not exceed 100 meters.
Network Node to RJ-45 Jack Cable
Network nodes (such as workstations) connect to RJ-45 harmonicas, RJ-45
patchpanels, or RJ-45 wall jacks via 4-pair cables which have RJ-45
plugs on each end. These cables are standard items which can be
purchased from a number of sources. Make sure when purchasing cables
that you specify 10BASE-T compatible cable. The following information
will assist you if you are building your own cables.
Only 4 of the 8 pins on the RJ-45 plugs and jacks are actually used in
10BASE-T. These are pin numbers 1,2,3, and 6. You must ensure that the
cable connects these 4 pins straight through from RJ-45 plug to RJ-45
plug.
Adapter Cable to RJ-45 Jack Wiring
If you are installing a 10BASE-T structured wiring system using
punchdown blocks you must ensure that the path from the EtherExpress Hub
to each RJ-45 Wall Jack Plug is wired correctly. Figure 3 shows the
relationship between each pin of an EtherExpress Hub board's 50 pin
female High-Density "D" connector, the Adapter Cable's 50 pin female
Telco Connector, and the 12 RJ-45 jacks that each EtherExpress Hub board
can be connected to. It also provides the pin-outs of male and female
gender 50 pin connectors (Telco and High-Density "D").
Crossover Cable Construction
If you will be using one of the EtherExpress Hub's 10BASE-T ports for an
"uplink" or "downlink" to another 10BASE-T hub you will need a crossover
cable. Crossover cables may be purchased from a number of sources, or
constructed. The following information will assist you if you are
constructing your own crossover cables.
Pin 1 of the RJ-45 plug on one end of the cable is connected to pin 3 of
the RJ-45 connector on the other end. Pin 2 is connected to pin 6, pin
3 is connected to pin 1, and pin 6 is connected to pin 2. Refer to
figure 4 when constructing crossover cables.
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