Display article   Subject:  Ethernet 10Base-T (Twisted Pair)
   04/30/97   19:07:21


ETHERNET 10BASE-T (TWISTED-PAIR)

Sending messages at 10 million bits per second (Mbps) over
ordinary twisted-pair telephone wire was practically unimaginable
five years ago.  Even more difficult to envision was that such
speeds could be achieved reliably.  Today, with the finalization
of the 10Base-T standard, not only are we running 10 Mbps, but we
are doing so at levels of reliability that far exceed what can be
achieved with coax LANs.


What is 10Base-T?

10Base-T is an IEEE standard for operating Ethernet LANs on
twisted-pair cabling.  The full name of the standard is IEEE
802.3 10Base-T and it defines the requirements for sending
information at 10 million bits per second (Mbps) on ordinary
twisted-pair wiring (telephone wire).

10Base-T enhances the existing 802.3 standard definition with a
modular star topology, a structured cabling methodology, fault
isolation and recovery features, central administration and easy
installation.

Among the defined requirements for 10Base-T are:

-- Connector types -- RJ-45

-- Pin Connections -- 1 and 2 for transmit, 3 and 6 for receive

-- Voltage Levels -- 2.2 volts to 2.8 volts peak

-- Noise Immunity -- To filter outside interference from telephone
systems or other electronic equipment

-- Link Integrity -- To provide constant monitoring of the
twisted-pair cabling, ensuring that the cable is functional (no
shorts or breaks)


What are the benefits of 10Base-T?

To the network manager, the biggest potential advantage of
10Base-T comes from the star wiring scheme.  It provides both
reliability and centralized management.  It's configured like the
hub and spokes of a wheel; the wires go from a central wiring hub
to each node.  If one wire is broken or shorted, the node goes
out of commission, but the network remains operational.

Network Management Capabilities

Network integrity checks are part of the 10Base-T standard and
greatly ease the difficulty in trouble-shooting cable and other
network hardware related problems.

Optional out-of-band network management functions provide for
diagnostics, traffic management and fine tuning of the LAN.

Flexible Expansion

Individual network workstations are easily added or removed from
the LAN with "plug and play" simplicity.  Add another workgroup
by cascading an additional Hub or connecting the Hub to a coaxial
backbone.

Buildings which are wired according to the 10Base-T specification
will already have the modular expansion plugs in the wall and
facilitate quick and easy network connection.

Twisted-Pair Cabling

Twisted-pair cabling is less expensive and easier to work with
than thin Ethernet coaxial cable.  In addition, the twisted-pair
cabling can serve more than one purpose by carrying network data,
voice and other signals within the same cable assembly.


Which network operating systems provide support and what about
compatibility with existing LANs?

As an IEEE standard, 10Base-T is compatible with Novell NetWare,
LANtastic, MS LAN Manager, and other popular network operating
systems.

The standard also ensures complete compatibility and
interoperability of equipment from competing network hardware
vendors.

Note: Many vendors and retailers marketed pre-10Base-T products.
Due to changes in the drafts of the 10Base-T standard (eleven
drafts were issued) before finalization, compatibility of this
equipment cannot be guaranteed.  Radio Shack, as a firm proponent
of industry standards, did not market pre-10Base-T products.


10Base-T: Myth versus Fact

There are many misconceptions surrounding 10Base-T.  Following
are three of the most commonly heard.

Myth 1:  10Base-T is less expensive than coaxial Ethernet.

While twisted-pair cabling is less expensive than coaxial cable,
the overall cost of the 10Base-T installation is greater than
that of a thin Ethernet installation.  Remember, each node on a
10Base-T network must be connected to a Hub or Concentrator.  The
per node cost of the hub may average from $60 to $150 per node in
additional cost.

Furthermore, while 10Base-T product prices continue to fall, the
general industry still demands a small premium for the 10Base-T
hardware components.

Myth 2:  10Base-T can utilize the existing telephone wiring.

The telephone wiring plants of many older buildings contain thick
multi-conductor cables, used for a key system -- one using phones
with multiple-line buttons.  A few modern buildings were wired
with silver satin.  None of these wiring systems -- quad,
multi-conductor, or silver satin -- suit modern LAN data
services.  The wires are not sufficiently resistant to electrical
interference.

Bottom line -- unless the building is very new or currently under
construction, the wiring is probably not 10Base-T compliant.

Myth 3:  10Base-T is faster than thin Ethernet.

As subsets of the IEEE 802.3 standard, twisted-pair, thin and
thick Ethernet all operate at 10Mbps.


What components are required for 10Base-T networks?

There are three basic components unique to a 10Base-T LAN:

1. Ethernet Adapter

      RJ-45 port

      Or a 10Base-T Transceiver that converts an RJ-45 connection
      to an AUI connection.

2. Ethernet Hub (or Concentrator)

      The center of the star topology

3. Unshielded Twisted-Pair Cabling

      24AWG Two Twisted-Pair Required (4 wires total)


Ethernet Specifications

                      Thin             Thick            UTP

IEE                   802.3            802.3           802.3
Standard            10Base-2         10Base-5        10Base-T

Speed               10 Mbps          10 Mbps         10 Mbps

Cable              RG-58 Coax          Thick          2-Pair
                      BNC            Ethernet         24-AWG
                                                        UTP

Topology              Bus              Bus             Star

Max. Length         607 ft          1,640 ft          328 ft
Per Segment

No. Devices           30               100              N/A
Per Segment

No. Devices         1,024             1,024            1,024
Per Network


Radio Shack 10Base-T Products

Here are the Radio Shack 10Base-T products.  They are explained
in detail below.

    260-5507   Tandy Ethernet Plus-16 TP
    260-5543   Tandy 12-Port Twisted-Pair Hub
    900-1878   EtherNext Network Command Center (NCC)
    900-1879   EtherNext 10Base-T Host Module
    900-1880   EtherNext Smart 10Base-T Host Module
    900-1881   EtherManager Network Management Software
    260-5545   10-Ft Twisted Pair Cable Assembly
    260-5546   25-Ft Twisted Pair Cable Assembly


260-5507 Tandy Ethernet Plus-16 TP

The Tandy Ethernet Plus-16 TP is a high performance 8/16-bit
half-card adapter for twisted-pair networks.

Features

-- Provides an Ethernet UTP cable connector and a standard AUI connector

-- Automatically determines which network connection is being used

-- One jumper selects the most popular configurations

-- Software setup program for simple installation and configuration

-- Multiple LED indicators for network trouble-shooting

-- Automatic signal polarity detection and correction on UTP
      port

Options

-- 900-1760 Novell Remote Boot PROM

Specifications

-- Hardware Compatibility: Tandy XT, AT and compatibles

-- Driver Support:  Novell NetWare, MS LAN Manager, NETBIOS,
3+Share, 3+Open, PC/NFS, UNIX and XENIX

-- RAM Buffer Size:  16 Kbytes

260-5543 Tandy 12-Port Twisted-Pair Hub

10Base-T is based on the flexible star topology.  At the center
of each star is the Hub or a series of Hubs through which all
network connections are made.  The Hubs can be cascaded or
daisy-chained to build LANs that accommodate thousands of
workstations.

The Hub provides instant connection to any 10Base-T compliant
18-24 gauge UTP cabling system (telephone wire).

The Hub provides eleven (11) modular RJ-45 jacks and one (1) AUI
port.  The AUI port allows connection for existing coax-based
Ethernet networks.

With the Tandy Hub, there is no need to invest in an expensive
chassis or complex mounting hardware.  Each Hub unit is self
contained with separate power supply, thus providing fault
tolerant redundancy.  The Hub's efficient mechanical design
allows quick wall mounting -- no equipment racks are required.

The Tandy Hub automatically amplifies and retimes signals,
allowing network stations to be up to 328 feet from the Hub.
Each network connection requires two (2) twisted-pair (4 wires)
-- one pair for transmit and one pair for receive.

The Hub features "built-in" network management, detects jabbering
network stations and automatically isolates the defective station
-- without affecting the other stations on the network.  When the
problem is corrected, the Hub immediately reactivates the
connection.  In addition, the Hub is continuously checking for
cable faults -- which provides quick identification and repair of
cable breaks.

The Hub design does not provide out of band management
capabilities.

Hub Unit Specifications

-- Dimensions With Mounting Frame:  16 1/2" high x 3" wide x 7" deep

-- Clearance Specifications:  5" vertical clearance between Hubs
when wall mounted

-- LED Indicators:  1 Traffic, 1 Collision, and 12 Jabber

-- Power Requirements:  100 to 250 Vac 47 to 63 Hz. 0.5 A

900-1878 EtherNext Network Command Center (NCC)

This six-slot chassis is used to house and connect up to six
10Base-T modules.  Each module can be "hot swapped" without
bringing down the power.  Five separate Ethernet backplanes in
each NCC allow multiple Ethernet systems to run simultaneously.
The chassis contains an international power supply that
automatically adapts to variations in line voltage and frequency.

Wall mounting requires the WKIT01 mounting kit, available for
$125.00.

900-1879 EtherNext 10Base-T Host Module

This module is a complete 802.3 repeater that provides (12) RJ-45
jacks for connections to workstations, file servers and other
Concentrators.  LEDs indicate link, partition and collision
status.

900-1880 EtherNext Smart 10Base-T Host Module

A dual function module, it is a complete 802.3 repeater and
provides (12) RJ-45 jacks for connections to workstations, file
servers and other Concentrators.  The module also functions as a
Network Management Module by monitoring and controlling all other
Host Modules within the same Concentrator.  A serial port is
available for out-of-band network management.

900-1881 EtherManager Network Management Software

EtherManager, in conjunction with the Smart 10Base-T Host Module,
provides management of every component of a LAN system.  The
status and topology of each Concentrator can be viewed; back-up
links configured to rechannel in case of primary link failure;
vital network statistics gathered; and alarm thresholds preset to
locally or remotely, through a unique paging system, notify the
network administrator.

UTP Cable

Cables are 24-AWG with RJ-45 connectors installed on each end.

Cables contain 4-twisted pairs, two twisted pair required for
network data, leaving two twisted pair free for voice or other
data requirements.

-- 26-5545   10-Ft Twisted Pair Cable Assembly

-- 26-5546   25-Ft Twisted Pair Cable Assembly

Glossary of Terms Used

AUI -- Attachment Unit Interface.  A 15-pin D-Style connector.
The IEEE 802.3 standard requires an AUI connector on both thin
and 10Base-T Ethernet adapters.  When used with an external
transceiver, an AUI connector allows connection to network
segments of different media types.

BNC -- A connector for thin Ethernet coaxial cable.

Hub -- A device used to provide connectivity between data
terminal equipment in a network.

IEEE -- Institute of Electrical and Electronic Engineers.  A
professional society that issues its own standards and is a
member of ANSI and ISO.

IPX -- Integrated Protocol Interchange.  The set of conventions
used in Novell NetWare which defines parameters for communication
between networked devices.

Node -- A computer, workstation or other device in a network.

Telco Connector -- A 25-pair polarized connector used to
consolidate multiple voice or data lines.

Twisted-Pair Wire -- Two insulated copper wires twisted together.
The twists are varied in length to reduce the potential for
signal interference between pairs.  In cables greater than
twenty-five pairs, the cables are grouped and bound together in a
common cable sheath.

Workgroup -- A networking unit, usually consisting of less than
twelve nodes.
