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Document:	DEChub 90 Ethernet Backplane Owner's Manual
Order Number:	EK-DEHUB-OM
Revision:	001
Pages:	61
Original Filename:

OCR Text

DEChub 90 Ethernet Backplane
Owners Manual
Order Number EK-DEHUB-OM-001

Digital Equipment Corporation

February, 1991
The information in this document is subject to change without notice and should not
be construed as a commitment by Digital Equipment Corporation. Digital Equipment
Corporation assumes no responsibility for any errors that may appear in this document.
The software described in this document is furnished under a license and may be used or
copied only in accordance with the terms of such license.
No responsibility is assumed for the use or reliability of software on equipment that is not
supplied by Digital Equipment Corporation or its affiliated companies.
Restricted Rights: Use, duplication, or disclosure by the U. S. Government is subject to
restrictions as set forth in subparagraph ( c ) ( 1 ) ( ii ) of the Rights in Technical Data and
Computer Software clause at DFARS 252.227–7013.
Copyright © Digital Equipment Corporation 1991
All Rights Reserved.
Printed in U.S.A.
The following are trademarks of Digital Equipment Corporation: DEC, DECbridge,
DECconnect, DEChub, DECnet, DECserver, Digital, LAT, ThinWire, and the DIGITAL
logo.
This document was prepared and published by Educational Services Development and
Publishing, Digital Equipment Corporation.

Contents
About This Manual
1

DEChub 90 Introduction

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–1
1–3

Configuration

Site Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basic Configuration Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DEChub 90 Configuration Rules . . . . . . . . . . . . . . . . . . . . . . . . .
Building Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DEChub 90 Backplane with Terminal Servers . . . . . . . . . . . . . . .
Work Group with Ethernet Repeaters . . . . . . . . . . . . . . . . . . . . .
Configuration Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Termination Configuration Errors . . . . . . . . . . . . . . . . . . . . . . . .
Work Group Bridge Configuration Errors . . . . . . . . . . . . . . . . . .
Repeater Configuration Errors . . . . . . . . . . . . . . . . . . . . . . . . . . .

vii

2–1
2–2
2–2
2–2
2–4
2–5
2–7
2–8
2–13
2–13
2–16
2–18

Work Group Communication Center Installation and
Troubleshooting

Rack Mount Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–2
Solid Wall Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–5
Installation Using DEHUX Wall Mount Plate . . . . . . . . . . . . . . . . . 3–8
Wall Mount Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–8
Office Partition Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–13
iii

iv Contents

Patch Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Installing the Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Installing Work Group Units in the Backplane . . . . . . . . . . . . . . . .
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Specifications and Parts List

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DEChub 90 Backplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DEHUX Wall Mount and Cover . . . . . . . . . . . . . . . . . . . . . . . . . .

3–13
3–14
3–16
3–19

A–1
A–1
A–2
A–2
A–3
A–3
A–3

Related Documentation

Figures
1–1
1–2
2–1
2–2
2–3

DEChub 90 Backplane with Units Installed . . . . . . . . . . . . .
The DEChub 90 Backplane . . . . . . . . . . . . . . . . . . . . . . . . . .
EIA/TIA-568 Standard Distribution Subsystem Architecture .
Typical Configuration with Eight DECservers in Backplane .
Work Group Configuration with DECservers and Work
Group Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–4 Work Group Configuration Supporting Workstations and PCs
2–5 Work Group Configuration Supporting Workstations, PCs,
Terminal Servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–6 Work Group Configuration with Two Backplanes . . . . . . . . . .
2–7 Backplane Improperly Terminated . . . . . . . . . . . . . . . . . . . . .
2–8 Work Group with Backplane Installed in Middle of ThinWire
Segment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–9 Work Group Bridge Installed in Wrong Slot . . . . . . . . . . . . . .
2–10 Two Work Group Bridges Installed in a Single Backplane . . .
2–11 Two Work Group Bridges Installed in Work Group . . . . . . . .
2–12 More Than Two Repeaters . . . . . . . . . . . . . . . . . . . . . . . . . . .
3–1 Installing Rack Mount Brackets to Backplane . . . . . . . . . . . .

1–2
1–5
2–6
2–7
2–9
2–10
2–11
2–12
2–14
2–15
2–16
2–17
2–18
2–19
3–3

Contents v

3–2
3–3
3–4
3–5
3–6
3–7
3–8

Installing the Backplane Power Supply . . . . . . . . . . . . . . . . .
Mounting DEChub 90 Backplane on a Solid Wall . . . . . . . . .
Wall Mount Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Installing the Backplane on the Wall Mount Plate . . . . . . . .
Installing the Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Removing the Back Cover of a Work Group Unit . . . . . . . . . .
Installing a Work Group Unit in the DEChub 90 Backplane .

3–4
3–7
3–9
3–11
3–15
3–17
3–18

Tables
2–1
2–2
3–1

Basic Configuration Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–2
DEChub 90 Configuration Rules . . . . . . . . . . . . . . . . . . . . . . 2–3
DEChub 90 Backplane Troubleshooting . . . . . . . . . . . . . . . . . 3–20

About This Manual
This guide gives an overview of the DEChub 90 Ethernet Backplane
and describes how to configure, install, and troubleshoot the DEChub 90
Ethernet Backplane. This guide also gives the specifications and related
documentation for the DEChub 90.

Organization
This guides has three chapters and two appendices.
Chapter

Meaning

Provides an overview of the DEChub 90 backplane and
the optional DEHUX wall mount plate.

Describes the configuration requirements including site
considerations, configuration rules and building wiring.
Typical configurations and configuration errors are also
included.

Describes how install and troubleshoot the DEChub 90
backplane and the optional DEHUX wall mount plate
and cover.

Appendix A

Describes the physical dimensions; environmental and
electrical specifications; parts lists.

Appendix B

Provides related documentation and how to order that
information.

vii

1
DEChub 90 Introduction
The DEChub 90 Backplane and optional DEHUX wall mount plate and
cover is a convenient way to wall or rack mount Digital’s Work Group
family of products. All of Digital’s Work Group products share the same
packaging and interconnect scheme. Each unit can be installed as a
standalone unit connected to other units by ThinWire coax or installed in
the DEChub 90 backplane. The DEChub 90 backplane with work group
units installed becomes a work group hub that is an integral part of a
structured wiring environment.

Features
DEChub 90 Backplane

DEHUX Wall Mount and Cover

•

Eight slot backplane for Digital’s
Work Group Family of Products
–

Provides ThinWire Ethernet
connection and termination

–

Allows Hot-Swap of units

–

Serial management bus

•

Single power supply for units
installed in bakplane

•

Power supply auto-selects
120/240 Vac, 50/60 Hz

•

Rack mountable with provided
rack mount brackets

•

Wall mountable on a solid wall

Wall mount plate for DEChub 90
backplane
–

Provides 10½ inches of
mounting space for patch panel
options

–

Can be installed on:
Solid or hollow walls
Office partitions with provided
hangers

•

Cover for DEHUX wall mount plate
–

Provides protection for the
backplane and patch panel

–

Provides security for the
backplane and patch panel

Figure 1–1 shows the DEChub 90 backplane with eight Work Group units
installed.

1–1

1–2 DEChub 90 Introduction

LJ-00279-TI0

Figure 1–1

DEChub 90 Backplane with Units Installed

DEChub 90 Introduction 1–3

Description
The DEChub 90 backplane and Digital’s Work Group family of products
provide a network hub for a work group of up to 64 people.
Digital’s Work Group Products
Bridges

DECbridge 90 Work Group Bridge (DEWGB)

Repeaters

DECrepeater 90C ThinWire Multiport Repeater (DECMR)
DECrepeater 90T Twisted-Pair Multiport Repeater (DETMR)

Servers

DECserver 90L Terminal Server (DSRVD)

Backplanes

DEChub 90 Ethernet Backplane (DEHUB)

The DEChub 90 backplane, Figure 1–2, provides mounting, power, and
ThinWire Ethernet connections for up to eight Work Group family units
plus the power supply. Work Group units may be installed in any mixture
and order in the backplane with one exception. The DECbridge 90 or
other Work Group unit requiring a +12 V supply must be installed in slots
seven or eight, the slots adjacent to the power supply.
The backplane supplies all power and signals to each unit through a
DIN style connector. Work Group products can be installed or swapped
with with the power on (hot-swap), and snap in with an audible ‘‘click’’ to
indicate proper installation. This allows for upgrades, modifications, or
replacement of units without interruption to other users on the network.
A BNC connector on the backplane provides connection to and termination
of a ThinWire Ethernet segment connected to the building network.
Alternately a DECbridge 90 Work Group Bridge (DEWGB) can provide
connection to an Ethernet backbone through its AUI or BNC connector.
The DEChub 90 backplane can be installed in a standard 19" equipment
rack or on a solid wall. The optional DEHUX wall mount plate and cover
allows the DEChub 90 backplane to be mounted on solid or hollow walls
and office partitions. In addition the DEHUX provides 10½ inches of
mounting space for patch panels and a cover.
Figure 1–2 shows the DEChub 90 backplane and calls out its features.

1–4 DEChub 90 Introduction

Release Lever - Used to release the backplane latching mechanism
when removing and installing Work Group units.

Backplane Connector - Provides power, network connection, and
management signals to Work Group units. Slots one through six
supply +5 V to the unit. Slot seven and eight (adjacent to the power
supply) supply +5 V and +12 V to the unit.
It is recommended that the DECbridge 90 Work Group Bridge be
installed in slot eight.

Mounting Slot - Secures the lower mounting tab of a Work Group
unit and the power supply. The slots are numbered from left to right
one through eight and the power supply slot (double slot).

Power Supply Connector - Provides +5 V and +12 V power from
the power supply to the backplane.

ThinWire Ethernet BNC Connector - Connects the backplane to a
ThinWire Ethernet segment. The DEChub 90 backplane provides 50
ohm termination of a ThinWire Ethernet. The DEChub 90 backplane
must be connected directly to the end of a ThinWire Ethernet
segment, no T-connector or terminator.

Backplane Serial Port MMJ Connector - Connects the backplane’s
serial management bus to the serial managment bus of another
DEChub 90 backplane in the same work group.

Power Supply - Provides +5 V and +12 V power to the backplane.

Power Supply AC Connector - Provides AC power to the power
supply.

DEChub 90 Introduction 1–5

4
5
6

7
8

LJ-00315-TI0

Figure 1–2

The DEChub 90 Backplane

2
Configuration

Site Considerations
When planning to use the Work Group Communications Center the
following considerations need to be made.
•

•

Location of the Work Group Communication Center (DEChub 90
backplane and DEHUX wall mount and cover).
–

Equipment closet (rack or wall mount)

–

Equipment rack

–

Work Area (wall or partition mount)

Network requirements
–

Standalone unit

–

Part of a ThinWire Ethernet

–

Connect to a ThickWire backbone

Building and office cabling and interconnect requirements. Digital’s
DECconnect family of products can provide these needs. Refer to
Appendix B for a list of available documentation.

2–1

2–2 Configuration

Configuration Rules
The configuration rule for the DEChub 90 backplane and Digital’s Work
Group family of products fall in to two categories. Those that apply to
network wiring in general and those that apply to the DEChub 90.

Basic Configuration Rules
There are a number of rules that relate to segment length, number of
repeaters and number and location of bridges. These rules are given in
Table 2–1.
Table 2–1 Basic Configuration Rules
Subject

Rule

ThinWire Segment

Maximum length of 185 meters
Maximum of 30 stations or nodes

ThickWire Segment

Maximum length of 500 meters
Maximum of 200 stations or nodes

Repeaters

There can be no more than two (2) repeaters
between any stations on a network segment

Bridges

Maximum of seven (7) bridges between any two (2)
stations on a local area network (LAN)

DEChub 90 Configuration Rules
The DEChub 90 backplane has a number of configuration rules and
guidelines that must be followed when installing and using the unit.
These rules are given in Table 2–2. In addition, normal ThinWire rules
apply as they relate to cable lengths, segmentation by repeaters and
bridges, and so on.

Configuration 2–3

Table 2–2 DEChub 90 Configuration Rules
Subject

Rule

Standalone installation
(not connected to an
Ethernet segment)

A 50 ohm terminator must be connected to the BNC
connector on the right hand side of the backplane
unit.
A typical standalone installation of the backplane
uses the DECbridge 90 Work Group Bridge for its
connection to an Ethernet backbone.

DECbridge 90 backplane
connected to a ThinWire
Ethernet segment

The ThinWire cable must be plugged directly
into the Backplane BNC connector, that is, no
T-connector and terminator.
The backplane must be at one end of the ThinWire
segment.
For cable length planning the backplane is the
equivalent of 65 meters of ThinWire cable. When
the backplane is installed at one end of a ThinWire
Ethernet segment the segment is limited to a
maximum of 120 meters.
The backplane with or without Work Group family
units installed is the equivalent of 15 nodes on a
ThinWire segment.
Maximum of two backplanes in a ThinWire segment.

Two backplanes in a
ThinWire Ethernet
segment

Each backplane must be at an end of the Ethernet
segment.
The ThinWire cable must be plugged directly
into each backplane’s BNC connector, that is, no
T-connector and terminator.
The serial management bus (MMJ connector) for
each backplane is to be connected.
For cable planning the two backplanes combined are
the equivalent of 130 meters of ThinWire cable. The
ThinWire segment between the two backplanes is
limited to 55 meters.
The two backplanes with or without work group
units are the equivalent of 30 nodes on a ThinWire
segment.

Work Group unit
installation

Work Group units may be installed in the Backplane
in any mixture with the exception of the DECbridge
90 Work Group Bridge.

2–4 Configuration

Table 2–2 (Cont.) DEChub 90 Configuration Rules
Subject

Rule

Installing a DECbridge
90 Work Group Bridge in
the backplane

Only one DECbridge 90 Work Group Bridge per
backplane.
Only one DECbridge 90 Work Group Bridge in a
work group.
It is recommended that it be installed in Slot eight
of the backplane, next to the power supply. The
DECbridge 90 can also be installed in slot seven.
The DECbridge 90 configuration rules must be
followed. The backplane and attached network
segments become a ‘‘workgroup’’ network with no
other bridges and a maximum of 200 Ethernet
addresses allowed.

Building Wiring
When installing the DEChub 90 Backplane and Digital’s Work Group
family of products the wiring of the network must be considered and
planned. Well-planned network connectivity provides tangible benefits
such as:
•

Improved management of connections

•

Lower cost of moves, additions, and changes

•

Increased life span of the cable plant and active components

A structured approach to cabling is an important component of a wellplanned network. The wiring system consists of passive components that
are divided into three main elements.
•

Backbone—the connection between the communication closet and
the equipment room within a building and the connection between
buildings.

•

Horizontal—the connection between, and including, the outlet and the
termination in the communication closet.

•

Work Area—an area containing a station and the connection between
the station and outlet.

The DEChub 90 Backplane provides the centralized distribution point in
the horizontal element of a structured wiring environment. The DEChub

Configuration 2–5

90 backplane can be installed in the telecommunications closet or the
open office environment replacing the telecommunications closet.
The concept of structured wiring is based on the assumption that cable
plants are designed to to provide service for 15 to 20 years. Devices
attached to the cable plant are often expected to be replaced by new
technology and remain connected for a much briefer period of time. This
means the cable must be reusable, identifiable, and simple to add or
change.
The Electronics Industry Association (EIA) and Telecommunications
Industry Association (TIA) have been working toward a standard for
telecommunications wiring for commercial buildings. After it is approved
this standard will be published as EIA/TIA-568. The stated goal of this
standard is to provide a uniform wiring system to support multi-product,
multi-vendor environments.
EIA/TIA-568 defines telecommunications wiring for a building or multiple
buildings in a campus environment. The standard specifies wiring system
parameters, including topology, distances, media and connector pin
assignments. EIA/TIA recognizes three types of wiring: horizontal,
backbone, and work area. This overall structure is shown in Figure 2–1.

Typical Configurations
This sections provides examples of typical Work Group configurations
using the DEChub 90 Backplane. These examples show:
•

A DEChub 90 Backplane with eight terminal servers

•

A Work Group using a Work Group Bridge and seven Ethernet
repeaters

•

A Work Group using a Work Group Bridge and a combination of
Ethernet repeaters and terminal servers

•

A Work Group using two backplanes a Work Group Bridge and a
combination of Ethernet repeaters and terminal servers

2–6 Configuration

Use LKG-3164-89A here

Figure 2–1

EIA/TIA-568 Standard Distribution Subsystem Architecture

Configuration 2–7

DEChub 90 Backplane with Terminal Servers
The DEChub 90 Backplane provides a clean well organized approach to
supporting a group of terminal servers in an Ethernet environment. A
single backplane supports up to a maximum of 64 terminals depending on
the number of terminal servers installed. Figure 2–2 shows the DEChub
90 being used to connect eight DECserver 90L’s to a ThickWire backbone
using an Ethernet repeater and H4005 Transceiver.

Th i ckw i r e

8 D E C s e rv e r 9 0 L U n i ts

H4005

Th i n W i r e
Po w e r
Su p p l y
D EM PR
or
D ESPR

P a t c h Pa n e l

T o 6 4 T e rm i n a l s
LJ-00566-TI0.DG

Figure 2–2

Typical Configuration with Eight DECservers in Backplane

2–8 Configuration

Work Group with Ethernet Repeaters
The DEChub 90 Backplane can support a variety of work group
configurations that include workstations, personal computers (PCs), and
terminals. The following configuration examples show how the DEChub
90 backplane and Digital’s family of Work Group products can be used to
support a wide variety of work group configurations.
Figure 2–3 shows a configuration that supports a work group with a lot of
terminals and a few workstations.
Figure 2–4 shows a configuration that supports a workgroup of
workstations and PCs using multiple Ethernet repeaters. These repeaters
can support ThinWire Ethernet, Twisted-Pair Ethernet or a combination
of both.
Figure 2–5 shows a configuration that supports a combination of
workstations, PCs, and terminals.
Figure 2–6 shows a configuration with two DEChub 90 backplanes used
to support a large work group.

Configuration 2–9

7 D E C s e rv e r 9 0 L U n i ts
W GB
Th i n W i r e
Se g m e n t to
W o r ksta ti o n s
Po w e r
Su p p l y

Th i n W i r e
to D EM PR
P a t c h Pa n e l

T o 5 6 T e rm i n a l s
LJ-00563-TI0.DG

Figure 2–3 Work Group Configuration with DECservers and Work
Group Bridge

2–10 Configuration

7 R e p e a t e rs
W GB
Th i n W i r e
Se g m e n t to
W o r ksta ti o n s
Po w e r
Su p p l y

Th i n W i r e
to D EM PR
P a t c h Pa n e l

T o 5 6 Wo rk s t a t i o n s
LJ-00564-TI0.DG

Figure 2–4
PCs

Work Group Configuration Supporting Workstations and

Configuration 2–11

D E C s e rv e r 9 0 L

R e p e a te r s
W GB
Th i n W i r e
Se g m e n t to
W o r ksta ti o n s
Po w e r
Su p p l y

Th i n W i r e
to D EM PR
P a t c h Pa n e l

T o 1 6 T e rm i n a l s
T o 4 0 Wo rk s t a t i o n s

LJ-00565-TI0.DG

Figure 2–5 Work Group Configuration Supporting Workstations, PCs,
Terminal Servers

2–12 4Configuration

3
D E C s e rv e r 9 0 L R e p e a t e r s

D EC Br i d g e 9 0
H4005

Pow er
Supply

P a t c h P a ne l

T o 3 2 T e rm i n a l s
T o 1 8 W o rk s t a t i o n s

MMJ
Cable

8 R e p e a t e rs

Pow er
Supply

Patch Panel

T h i n Wi re t o 3 2
Wo rk s t a t i o n s
Twisted Pair to
2 4 Wo rk s t a t i o n s
LJ-00567-TI0.DG

Figure 2–6

Work Group Configuration with Two Backplanes

Configuration 2–13

Configuration Errors
This section provides examples of various configuration errors that may
occur when installing a work group using the DEChub 90 Backplane.

Termination Configuration Errors
The DEChub 90 backplane must be properly terminated in order for the
ThinWire segment to function properly. The DEChub 90 is the equivalent
of 65 meters of ThinWire cable terminated at one end with 50 ohms.
Figure 2–7 shows a backplane installed with its terminator or properly
terminated ThinWire segment missing.
Because the DEChub 90 terminates one end of a ThinWire Ethernet
segment it cannot be installed in the middle of a segment. Figure 2–8
is an example of the DEChub 90 installed in the middle of a ThinWire
Ethernet segment.

2–14 Configuration

M i ssi n g
Te r m i n a to r

CONF-4

Figure 2–7

Backplane Improperly Terminated

Configuration 2–15

Te r m i n a to r

W o r ksta ti o n

T- C o n n e cto r
to
Ba ckp l a n e

W o r ksta ti o n

Figure 2–8
Segment

Te r m i n a to r

Work Group with Backplane Installed in Middle
L J -of
0 0 5ThinWire
69-TI0.DG

2–16 Configuration

Work Group Bridge Configuration Errors
The DECbridge 90 must be installed in either slot 8 or slot 7 of the
DEChub 90 backplane. If it is not installed in one of these slots it will not
function because of missing supply voltages. The recommended slot for
the DECbridge 90 is slot 8. Figure 2–9 shows the DECbridge 90 installed
in the wrong slot.

WGB

WG B N o t i n Sl o t 8 .
CONF-1

Figure 2–9

Work Group Bridge Installed in Wrong Slot

Configuration 2–17

When configuring a work group only one DECbridge 90 Work Group
Bridge can be used. The reasons for this restriction are as follow:
1. The DEChub 90 backplane +12V power supply can only support one
Ethernet backbone transceiver circuit.
2. When two bridges are a part of a work group; a network failure can
make one of the bridges look like it is a part of the other bridge’s
work group. This can cause the address table of the other bridge to be
overloaded.
Figure 2–10 shows a single backplane with more than one Work Group
Bridge installed. Figure 2–11 shows a work group with more than two
bridges installed.

W GB

M o re t ha n On e W GB.
CONF-2

Figure 2–10

Two Work Group Bridges Installed in a Single Backplane

2–18 Configuration
W GB

W GB

CONF-3

Figure 2–11

Two Work Group Bridges Installed in Work Group

Repeater Configuration Errors
When installing repeaters in an Ethernet environment there must be no
more than two repeaters between any node on a segment. Figure 2–12
shows a violation of the two repeater rule.

Configuration 2–19

H4000

R e p e a t e rs

D EM PR

R e p e a t e rs

LJ-00568-TI0.DG

Figure 2–12

More Than Two Repeaters

3
Work Group Communication Center
Installation and Troubleshooting
The DEChub 90 backplane can be installed in a 19" equipment rack or on
a wall or office partition using the DEHUX wall mount plate. The wall
mount plate holds the backplane, standard 19" rack mount patch panels
and an optional cover. This section covers the following:
•

•

Installing the DEChub 90 backplane
–

In a 19" equipment rack

–

On a solid wall

Installing the DEChub 90 backplane using the DEHUX wall mount
plate
–

On a wall

–

On an office partition

•

Installing distribution panels in the DEHUX wall mount plate

•

Installing the DEHUX cover

•

Troubleshooting the DEChub 90 backplane

3–1

3–2 Work Group Communication Center Installation and Troubleshooting

Rack Mount Installation
The DEChub 90 backplane comes with rack mount brackets and mounting
hardware to allow the unit to be installed in a standard RETMA 19"
equipment rack.
1. Locate the rack mount brackets and four (4) #6 screws that came with
your backplane.
2. Attach the rack mount brackets, using the #6 screws, to the backplane
as shown in Figure 3–1.
3. Install the backplane in the equipment rack using the four 10-32
screws and U-nuts (if necessary) supplied with the backplane.
4. Install the backplane power supply as shown in Figure 3–2.
a. Catch the mounting tabs on the bottom of the power supply in the
mounting slots of the backplane.
b. Raise the two release levers for the power supply slot.
c.

Rock the power supply into place. Verify the alignment of the
power supply connector and backplane connector as the power
supply is rocked into place.

d. Lower the two release levers to lock the power supply in place.
5. Attach the power cord to the power supply and to a working AC
outlet. Verify that the green LED on the power supply lights.
You are ready to make the necessary network connections and install
Work Group units in the backplane. Refer to Chapter 2 for configuration
rules and guidelines for the backplane. When installing Work Group units
in the backplane refer to their related documentation for installation and
verification procedures and additional configuration requirements.

Work Group Communication Center Installation and Troubleshooting 3–3

LJ-00194-TI0

Figure 3–1

Installing Rack Mount Brackets to Backplane

3–4 Work Group Communication Center Installation and Troubleshooting

LJ-00200-TI0

Figure 3–2

Installing the Backplane Power Supply

Work Group Communication Center Installation and Troubleshooting 3–5

Solid Wall Installation
The DEChub 90 backplane can be mounted directly to a solid wall (wood
that is a minimum of 3/8" thick) using the two slotted mounting holes on
the back of the unit.
NOTE
The total weight of the DEChub 90 backplane and eight modules
is approximately 23 pounds. This plus the weight and stress
provided by cables must be considered when choosing a location
for the DEChub 90 backplane.
1. Mark the location for the two #10 mounting screws.
a. The screws should be 16 inches on center.
b. To place the LED indicators of the Work Group units at eye level
it is recommended that the mounting screws be approximately 58
inches from the floor.
2. Using a 7/64 inch bit drill pilot holes at the locations marked on the
wall.
3. Screw the wood screws into the pilot hole until each screw head is 1/8
inch from the surface of the wall.
4. Set the slotted holes on the back of the backplane over the heads of
the screws and slide down until the screws contact the top of the slots,
Figure 3–3.
5. Install the backplane power supply as shown in Figure 3–2.
a. Catch the mounting tabs on the bottom of the power supply in the
mounting slots of the backplane.
b. With one hand raise the two release levers for the power supply
slot.
c.

With your other hand rock the power supply into place. Verify the
alignment of the power supply connector and backplane connector
as the power supply is rocked into place.

d. Lower the two release levers to lock the power supply in place.
6. Attach the power cord to the power supply and to a working AC
outlet. Verify that the green LED on the power supply lights.

3–6 Work Group Communication Center Installation and Troubleshooting

You are ready to make the necessary network connections and install
Work Group units in the backplane. Refer to Chapter 2 for configuration
rules and guidelines for the backplane. When installing Work Group units
in the backplane refer to their related documentation for installation and
verification procedures and additional configuration requirements.

Work Group Communication Center Installation and Troubleshooting 3–7

LJ-00571-TI0.DG

Figure 3–3

Mounting DEChub 90 Backplane on a Solid Wall

3–8 Work Group Communication Center Installation and Troubleshooting

Installation Using DEHUX Wall Mount Plate
The DEChub 90 backplane can be mounted on a wall or office partition
using the the DEHUX wall mount plate and cover. In addition the
DEHUX wall mount plate accommodates a variety of industry standard
patch panel sizes for up to 64 connections.
The wall mount plate comes with the hardware required to mount the
unit on a solid wall, hollow wall, or office partition.
NOTE
The total weight of the DEChub 90 backplane, DEHUX wall mount
and cover, and eight modules is approximately 45 pounds. This
plus the weight of options and cables must be considered when
choosing a location for the wall mount plate and backplane.

Wall Mount Installation
1. Locate the wall mount plate (Figure 3–4), and and have someone hold
it in place against the wall. To place the LED indicators of the Work
Group units at eye level it is recommended that the top of the wall
plate be approximately 63 inches from the floor.
NOTE
Note that there are eight slotted mounting holes in the wall
mounting plate, use the four nearest the corners for stability.
The others are to be used if the unit cannot be securely
fastened to the mounting surface using the four corner holes.
2. Mark the four slotted mounting hole locations on the wall and set the
wall mounting plate aside.

Work Group Communication Center Installation and Troubleshooting 3–9

LJ-00572-TI0.DG

Figure 3–4

Wall Mount Plate

3–10 Work Group Communication Center Installation and Troubleshooting

3. Select the appropriate fastener for the mounting surface.
The supplied wood screws can be used when the mounting surface is
wood that is a minimum of 3/8" thick.
The supplied hollow wall fasteners can be used when the mounting
surface is a hollow wall that is a maximum of 5/8" thick.
4. Using the selected fastener prepare to hang the wall mounting plate.
Wood Screws:
a. Using a 7/64 inch bit drill pilot holes at the locations marked on
the wall.
b. Screw the wood screws into the pilot hole until the screw head is
1/4 inch from the surface of the wall.
Hollow Wall Fasteners:
a. Using a 7/16 inch bit drill pilot holes at the locations marked on
the wall.
b. Insert the hollow wall fasteners in the pilot holes and set in place
by tightening the screws.
c.

Unscrew each mounting screw until the screw head is 1/4 inch
from the wall.

5. Set the slotted holes of the wall mount plate over the heads of the
screws, and slide down until the screws contact the top of the slots.
6. Tighten the mounting screws.
7. Place the backplane over the four hooks on the wall mount plate,
and press down until the backplane locks into place as shown in
Figure 3–5.

Work Group Communication Center Installation and Troubleshooting 3–11

LJ-00316-TI0

Figure 3–5

Installing the Backplane on the Wall Mount Plate

3–12 Work Group Communication Center Installation and Troubleshooting

8. Install the backplane power supply as shown in Figure 3–2.
a. Catch the mounting tabs on the bottom of the power supply in the
mounting slots of the backplane.
b. Raise the two release levers for the power supply slot.
c.

Rock the power supply into place. Verify the alignment of the
power supply connector and backplane connector as the power
supply is rocked into place.

d. Lower the two release levers to lock the power supply in place.
9. Attach the power cord to the power supply and to a working AC
outlet. Verify that the green LED on the power supply lights.
You are ready to make the necessary network connections and install
Work Group units in the backplane. Refer to Chapter 2 for configuration
rules and guidelines for the backplane. When installing Work Group units
in the backplane refer to their related documentation for installation and
verification procedures and additional configuration requirements.

Work Group Communication Center Installation and Troubleshooting 3–13

Office Partition Mounting
1. Locate the office partition brackets and four (4) #6 screws that came
with the wall mount plate.
2. Attach the office partition brackets, using the #6 screws, to the wall
mount plate.
3. Hang the wall mount plate on the office partition.
4. Attach the backplane to the wall mount plate as shown in Figure 3–5.
5. Install the backplane power supply as shown in Figure 3–2.
a. Catch the mounting tabs on the bottom of the power supply in the
mounting slots of the backplane.
b. Raise the two release levers for the power supply slot.
c.

Rock the power supply into place. Verify the alignment of the
power supply connector and backplane connector as the power
supply is rocked into place.

d. Lower the two release levers to lock the power supply in place.
6. Attach the power cord to the power supply and to a working AC
outlet. Verify that the green LED on the power supply lights.
You are ready to make the necessary network connections and install
Work Group units in the backplane. Refer to Chapter 2 for configuration
rules and guidelines for the backplane. When installing Work Group units
in the backplane refer to their related documentation for installation and
verification procedures and additional configuration requirements.

Patch Panel
The patch panel may be Digital Equipment Corporation supplied or
customer supplied. The DEHUX mounts will accept a variety of standard
19 inch panels with a maximum height of 10½ inches. This provides
space for two standard 5¼ inch or 3½ inch high patch panels. Each panel
is secured to the mounting brackets using four screws. The left hand
mounting bracket pivots to allow access to the back of the installed patch
panels without fully removing the patch panel(s). Cables are dressed
down the left side using cable-ties and the loops stamped in the hinged
mounting bracket.

3–14 Work Group Communication Center Installation and Troubleshooting

Installing the Cover
The DEHUX cover is an attractive office environment compatible
enclosure providing protection and security for the backplane and
installed components. After you are finished installing and cabling the
Work Group units you can install the cover as shown in Figure 3–6. For
security the cover has two holes in its lower left and right corners that
align with two holes in the wall mount plate. You can use a lock or some
other device to lock the cover in place.
To install the DEHUX cover:
1. Place the cover over the wall mount plate, backplane, and distribution
panels.
2. Slide the cover down until the top back edge of the cover catches on
the top lip of the wall mount plate.
The cover can be locked to the wall plate using holes located at the
lower left and lower right of the cover.
3. Mark the location label and slide it in to the slots on the top of the
cover.

Work Group Communication Center Installation and Troubleshooting 3–15

LJ-00570-TI0.DG

Figure 3–6

Installing the Cover

3–16 Work Group Communication Center Installation and Troubleshooting

Installing Work Group Units in the Backplane
When installing Work Group units in the backplane refer to their related
documentation for complete installation and verification procedures.
The following steps provide the basic procedure for physically installing
Work Group units in the backplane.
1. If the Work Group unit to be installed in the backplane has a cover on
the back of the unit, remove the cover (Figure 3–7).
To remove the back cover on a Work Group unit:
a. Insert a small screwdriver into the top mounting hole in the cover.
b. Lift up on the latch.
c.

While lifting up on the latch, pull the top of the cover away from
the unit and down.

2. Place the lower mounting tab, located on the back of the unit, in the
appropriate mounting slot on the backplane (Figure 3–8).
3. Rock the unit into place. An audible ‘‘click’’ is heard when the unit is
securely latched in place.

Work Group Communication Center Installation and Troubleshooting 3–17

LJ-00320-TI0

Figure 3–7

Removing the Back Cover of a Work Group Unit

3–18 Work Group Communication Center Installation and Troubleshooting

LJ-00074-TI0

Figure 3–8

Installing a Work Group Unit in the DEChub 90 Backplane

Work Group Communication Center Installation and Troubleshooting 3–19

Troubleshooting
This section provides information on troubleshooting the DEChub 90
Backplane and power supply. Before you begin you should:
1. Verify the installation of the unit.
–

Does the installation of the unit meet the configuration rules given
in Chapter 2.

–

Are the Work Group units working properly. Refer to the related
documentation for each unit.

2. Note the fault condition.
3. Isolate the problem. Use Table 3–1 as a guide to determine the
probable cause and the suggested solution.

3–20 Work Group Communication Center Installation and Troubleshooting

Table 3–1 DEChub 90 Backplane Troubleshooting
If...

Then...

Do this...

The LED on power
supply is ‘‘blinking’’

Short or overload
caused by a Work
Group unit

Remove all units from
backplane.
Verify each unit by installing
units one at a time. Replace
the unit causing the problem.
Problem occurs with every
unit tested in backplane, a
possible bad power supply or
backplane. Replace the power
supply. If the problem still
exists replace the backplane.

The LED on the
power supply is not
‘‘on’’

Power supply not
receiving AC power

Check that the AC power cord
is connected to an AC outlet
and that it is properly seated
in the power supply connector.
Verify that the AC outlet
is working. If the problem
still exists replace the power
supply.

DECbridge 90 Work
Group Bridge does
not work

Unit is not receiving
+12 V

Unit is not installed in
slot seven or eight of the
backplane. Install the unit in
slot seven or eight. Slot eight
is recommended.

Two DECbridge
90’s installed in slot
seven and eight

Remove one of the units.

A
Specifications and Parts List

Specifications
Mechanical
Component Weights
DEChub 90 backplane

2.27 kg (5 lb)

DEChub 90 power supply

1.82 kg (4 lb)

DEHUX wall mount panel

5.45 kg (12 lb)

DEHUX cover

4.55 kg (10 lb)

Work Group Unit

.68 kg (1.5 lb) typical

Wall Mount Option (DEHUX)
Mounting Area:

Required Clearances:

Height

73.66 cm (29 in)

Width

54.61 cm (21½ in)

Top and Bottom

30.48 cm (12 in)

Sides

2.54 cm (1 in)

Front
(outward from wall)

62.23 cm (24½ in)

A–1

A–2 Specifications and Parts List

Rack Mount Option (DEChub 90)
Mounting Area:

Required Clearances:

Height

30.48 cm (12 in)

Width

44.45 cm (17½ in)

Depth
(excluding cables)

16.51 cm (6½ in)

Top and Bottom

30.48 cm (12 in)

Sides (beyond Rack)

2.54 cm (1 in)

Rear (behind rack)

15.24 cm (6 in)

Front
(in front of rack)

30.48 cm (12 in)

Electrical
Input Voltage:

120 Vac nominal, single phase or 240 Vac nominal, single
phase. Power supply will auto select correct voltage range.

Line Frequency:

47 to 63 Hz

Input Current:

3.8 amps at 120 Vac
1.9 amps at 240 Vac

Power:

90 watts maximum

Environmental
Cooling: Convection and fan.
Operating Temperature: +5°C to +50°C
Operating Humidity: 10% to 95%, noncondensing

Specifications and Parts List A–3

Parts Lists
DEChub 90 Backplane
Quantity Description
1

DEChub 90 Backplane, 8 slots

Power Supply

AC power cord

BC-16M-06 ThinWire office cable

Rack mount brackets

8-32 x 1/2" machine screws

10-32 x 1/2" machine screws

10-32 U-nuts

10 x 1" wood screws

DEHUX Wall Mount and Cover
Quantity Description
1

DEHUX wall mount plate

DEHUX cover

Location Label

Partition hangers

8-32 x 5/16" machine screws

10 x 1" wood screws

3/16 x 2" hollow wall fasteners

10-32 x 1/2" machine screws

10-32 U-nuts

B
Related Documentation
Document Title

Order Number

Network Wiring and Applications Guide

EB-K2411-42

OPEN DECconnect System Guide

EC-H0631-42

DECconnect System Requirements Workbook

EK-DECSY-EG

DECconnect System Fiber Optic Installation Guide

EK-DECSY-FI

DECconnect System Fiber Optic Planning and
Configuration Guide

EK-DECSY-FP

OPEN DECconnect Components and Applications
Catalog

EB-K2407-42

Ordering Information
Customers may order documents by phone or mail.
Continental USA and Puerto Rico
Call 800-258-1710 or mail to:
Digital Equipment Corporation
Peripherals and Supplies Group
P.O. Box CS2008
Nashua, NH 03061
New Hampshire, Alaska, and Hawaii
Call 1-603-884-6660.
Outside the USA and Puerto Rico
Mail to:
Digital Equipment Corporation
Attn: Accessories and Supplies Business Manager
c/o Local Subsidiary or Digital-Approved Distributor

B–1

B–2 Related Documentation

Digital Personnel
Digital personnel may order these documents from:
Digital Equipment Corporation
444 Whitney Street
Northboro, MA 01532
Attn: Publishing and Circulation Services (NRO3/W3)
Order Processing Section