User resource sharing through the USB interface

User resource sharing through the USB interface
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US 20040268012A1
(19) United States
(12) Patent Application Publication (10) Pub. No.: US 2004/0268012 A1
Ferguson
(54)
(43) Pub. Date:
USER RESOURCE SHARING THROUGH
(52)
Dec. 30, 2004
US. Cl. ............................................................ .. 710/313
THE USB INTERFACE
(76) Inventor: Patrick Lee Ferguson, Cypress, TX
(US)
(57)
ABSTRACT
Correspondence Address:
HEWLETT-PACKARD DEVELOPMENT
A method of sharing user resources in a computer system
COMPANY
Intellectual Property Administration
R0‘ BOX 272 400
through a universal serial bus (USB) interface. The method
may involve, not necessarily in this order, associating at
Fort Collins CO 80527_2400 (Us)
least one USB device With a ?rst user and at least another
’
(21)
Appl. No.:
USB device With a second user; assigning the ?rst user to a
10/461,895
?rst USB port; assigning the second user to a second USB
_
port; permitting the ?rst user to temporarily assume control
(22) Flled:
Jun‘ 13’ 2003
of the computer system through the ?rst USB port for
Publication Classi?cation
(51)
operation of the at least one USB device; and blocking the
Int. Cl.7 ................................................... .. G06F 13/20
second user from access to the computer system While the
?rst user has temporary control of the computer system.
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Patent Application Publication Dec. 30, 2004 Sheet 1 0f 5
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Patent Application Publication Dec. 30, 2004 Sheet 3 0f 5
US 2004/0268012 A1
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Patent Application Publication Dec. 30, 2004 Sheet 4 0f 5
‘601
US 2004/0268012 A1
use 2.0
Controller
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I
Split Start
USB 2.0 Signaling
607
Transaction
Split
Complete
Transactio
Extension
Transmitte
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629
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=
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617
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Return
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619
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Function
Extension
Receiver
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625
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USB 1.1
Device
USB1.1
USB 1.1
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Device
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627
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Fig. 6
Patent Application Publication Dec. 30, 2004 Sheet 5 0f 5
US 2004/0268012 A1
701
USB 2.0
Host
Controller
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711
709
USB 1.1
Downstream
Dec. 30, 2004
US 2004/0268012 A1
USER RESOURCE SHARING THROUGH THE USB
INTERFACE
requirements. The USB standard requires strict adherence to
these transaction latency and electrical requirements, Which
limits the USB extension distance, rather than alloW the
several hundred meters of a typical KVM mode.
CROSS-REFERENCE TO RELATED
APPLICATIONS
[0008]
In addition, the USB requirements prevent the use
[0001] The present application is related to the following
of a KVM sWitch because a sWitch may degrade the USB
US. applications Which are incorporated herein in their
signaling and further reduce the overall extension distance.
entireties: US. application Ser. No.
, ?led
,
entitled “USB Interface Extension Through Split Transac
tion Protocol” by Ferguson (Attorney Docket No. P01
4020); US. application Ser. No.
, ?led
,
entitled “Extension of USB Functionality Through
ShadoWing of a Remote USB Host Controller” by Ferguson
(Attorney Docket No. P01-3865); and US. application Ser.
No.
, ?led , entitled “Method of KVM Extension
Using USB to Legacy Adapters” by Ferguson (Attorney
Docket No. P01-3866).
BACKGROUND OF INVENTION
[0002]
1. Field of the Invention
[0003] The present disclosure relates generally to increas
ing the functionality of a computer USB port and, more
speci?cally, to implementing the sWitching of USB devices
KVM interfaces also enable multiple users to simulta
neously access a single computer system Which aggravates
the problems of a KVM sWitch When USB signaling is
introduced. Old methods of sWitching PS/2 keyboard and
mouse interfaces include physically passing a keyboard and
mouse from user to user. In another solution, a PS/2 sWitch
has the ability to block devices to a user When another user’s
device is in operation to avoid user contention. One obvious
disadvantage of the these old methods is that all but one user
is blocked While another user controls the computer.
[0009] Many other problems and disadvantages of the
prior art Will become apparent to one skilled in the art after
comparing such prior art With the present invention as
described herein.
BRIEF DESCRIPTION OF THE FIGURES
betWeen users Without the need for a separate sWitching
device.
[0010] Abetter understanding of the present invention can
be obtained When the folloWing detailed description in
[0004] 2. Description of the Related Art
conjunction With the folloWing ?gures.
[0005] Preventing multiple users from simultaneously
[0011] FIG. 1 is a block diagram of a basic computer
interface extension solution in accordance With embodi
ments of the present invention.
accessing computer resources is a problem in USB computer
system architectures. This problem becomes increasingly
advanced When users access peripherals in computer inter
face extension solutions. For example, a standard computer
interface, or a keyboard, video display and a mouse, must be
located close to the computer to Which it is attached. A
keyboard/video/mouse (KVM) extender enables a computer
interface to be located at a greater distance from the com
puter than is typically possible With a standard interface. For
example, a company can place all its employees’ computers
in a rack-mounted system in a locked room and yet still
provide a standard KVM interface at each employee’s desk.
To the employee, it appears as though the computer is still
located at the employee’s desk. This centraliZation of com
[0012] FIG. 2 is a block diagram of another basic com
puter interface extension solution Wherein a manageability
sWitch is introduced into the solution in accordance With
embodiments of the present invention.
[0013] FIG. 3 is a block diagram of a computer interface
extension solution Wherein a manageability sWitch and
multi-system sWitches are introduced into the solution in
accordance With embodiments of the present invention.
[0014] FIG. 4 is a simpli?ed block diagram of exemplary
transmitter circuitry components that are used in an exten
sion transmitter in accordance With embodiments of the
puters enables companies to maintain tighter security over
their computers and also simpli?es the computers’ mainte
nance by locating them in a single place.
present invention.
[0006] In addition, a KVM sWitch can enable multiple
computers to be accessed by means of a single set of
keyboard, video display and mouse. This is convenient in the
receiver circuitry components that are used in an extension
receiver in accordance With embodiments of the present
invention.
situation in Which a user accesses multiple computers such
[0016] FIG. 6 is a How diagram of the extension topology
and operational How of a basic computer interface extension
solution incorporating USB split transactions in accordance
With embodiments of the present invention.
as an application server, a Web or email server and a game
box. With a KVM sWitch, the user can access multiple
computers With a single interface, thus reducing the cost of
both components and maintenance.
[0007] Although, the KVM extension mode of operation
typically supports some standard user I/O protocols, or
“legacy” protocols, such as PS/2, analog video, and serial
communications, a universal serial bus (USB) connection
presents several problems. Most interface extensions such as
KVM use simple, loW frequency data rates and protocols,
[0015] FIG. 5 is a simpli?ed block diagram of exemplary
[0017]
FIG. 7 is a diagram of data How of the method of
the claimed subject matter as it applies to a USB multi-user
sWitch in accordance With embodiments of the present
invention.
[0018]
The components in the ?gures are not necessarily
to scale, emphasis instead being placed upon illustrating the
Whether using either analog or digital signal types. HoWever,
USB has a very complex signaling protocol, data packet
principles of the invention. In the ?gures, like reference
structure and electrical speci?cation, as Well as short latency
ferent vieWs.
numerals designate corresponding parts throughout the dif
Dec. 30, 2004
US 2004/0268012 A1
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENT
systems, methods, features and advantages be included
Within this description, be Within the scope of the invention,
and be protected by the accompanying claims.
[0019]
Certain but not other aspects of the invention are
computer system through a universal serial bus (USB)
interface. The method may involve, not necessarily in this
[0023] FIG. 1 is a block diagram of a basic computer
interface extension solution 100 according to principles of
the present invention. Although the solution 100 is illus
order, associating at least one USB device With a ?rst user
and at least another USB device With a second user; assign
trated as having a host computer system 101 With an
extension transmitter 103 (herein referred to as “transmit
ing the ?rst user to a ?rst USB port; assigning the second
user to a second USB port; permitting the ?rst user to
ter”), for ease of understanding certain but not other prin
ciples of the present invention, the solution 100 is illustrative
temporarily assume control of the computer system through
of only one of many embodiments that may be realiZed in
realized through a method of sharing user resources in a
the ?rst USB port for operation of the at least one USB
device; and blocking the second user from access to the
computer system While the ?rst user has temporary control
of the computer system.
[0020]
In certain but not other embodiments, the blocking
of the second user from access to the computer system is
limited to devices assigned to the ?rst user. In some
instances, the at least one USB device of the method is
selected from the group consisting of a keyboard, a mouse,
a joystick, and a USB human interface class device. The
blocking of the method typically requires identi?cation of
the at least one device and may includes a number of
different identi?cation techniques. For example, the identi
?cation of the at least one device could include identifying
a device class for the at least one device, it could include
identifying the device through an application program that is
resident on the computer system, it could include monitoring
a USB device driver for the at least one USB device, or it
could include snooping of USB transactions that occur
betWeen the at least one USB device and the computer
system.
[0021] Still other aspects of the present invention are
realiZed through a USB communication system for sharing
user resources. The USB communication system may
include a host computer system having a USB host control
ler, a ?rst USB hub circuitry, and transmitter circuitry. The
USB host controller may be con?gured to operate using a
split transaction for the USB communications. In the illus
trated embodiment, the USB communication system also
includes receiver circuitry that has a second USB hub
circuitry for receiving a non-USB format of USB commu
nication signals as the signals appear betWeen split start and
split complete transaction operations at the host computer
system. The illustrated transmitter circuitry is con?gured to
forWard the non-USB formatted USB communication sig
accordance With principles of the present invention. The
transmitter 103 is connected to an extension receiver 105
(herein referred to as “receiver” Which is connected to a
user 107. The user 107 is representative of standard user
interface products such as a keyboard, mouse, monitor,
serial port, audio devices, USB ports, etc. The solution 100
is commonly implemented as a KVM extension, hoWever, as
Will be understood When vieWing the description of the
invention, the solution 100 includes more than typical KVM
extension capabilities. For example, as described in greater
detail herein, the same type of sWitching currently employed
for PS/2 sWitching is implemented With USB interface
devices. The ?exibility and expandability of USB is used to
assign individual ports to different users Which alloWs
enhanced sWitching control through the USB operational
model. The USB sWitch is embedded in the USB topology
and removes the need for a separate sWitching device.
Further, although data travels bi-directionally betWeen the
host computer system 101 and the user 107, in accordance
With USB speci?cation terminology, the transmitter 103 and
the receiver 105 are labeled as though data transfer occurs
only in one direction, i.e., from the host computer system
101 to the user 107.
[0024] The transmitter 103 and receiver 105 are connected
With a single cable such as a cable compatible With all
versions of category 5, 6, 7, or better cables. The connection
could also be made With ?ber optic or other type of high
speed data transmission cabling. The distance betWeen the
transmitter 103 and receiver 105 ranges approximately 300
meters. In this manner are the user interface devices of the
user 107 alloWed to communicate effectively With the host
computer system 101 across long distances, “long” as com
pared to user/host communication distances in a system
Without the transmitter 103/receiver 105 pair. Although
illustrated external to the host 101, the transmitter 103 may
be positioned internal to the host computer system 101 and
nals across an extension betWeen the transmitter circuitry
and the receiver circuitry. A user transaction lockout ?lter
use an internal connector With the motherboard of the
may be placed betWeen the ?rst USB hub circuitry and the
second USB hub circuitry that performs snooping of the
USB communication signals that appear betWeen the split
start and the split complete transaction operations at the host
[0025] FIG. 2 is a block diagram of another basic com
puter interface extension solution 200 Wherein a manage
computer system. At least one USB user interface device is
communicatively coupled to the receiver circuitry and
system 101.
ability sWitch 205 is introduced into the solution, Which
includes multiple host computer systems 201 and 203. The
solution 200 also includes multiple transmitters 207 and
209, and multiple receivers 211 and 213 that support the
communication extension for multiple users 215 and 217,
respectively. The manageability sWitch 205 encompasses
receives USB communication signals from the second USB
hub circuitry. These USB communication signals may cor
respond to the non-USB formatted communication signals
that appear betWeen the split start and split complete trans
action operations at the host computer system. One or more
users may share the host computer system through the
technology used to map a speci?c user to a speci?c system,
to converge a large number of systems to a small number of
users for system administration or head trader access, and to
receiver circuitry and the transmitter circuitry.
share a single system betWeen tWo or more users.
[0022] Other systems, methods, features and advantages
[0026] FIG. 3 is a block diagram of a computer interface
extension solution 300 Wherein a manageability sWitch 309
and multi-system sWitches 331 and 333 are introduced into
the solution 300. The multi-system sWitches 331 and 333
of the invention Will be or Will become apparent to one With
skill in the art upon examination of the folloWing ?gures and
detailed description. It is intended that all such additional
Dec. 30, 2004
US 2004/0268012 A1
enable users 335 and 337 to access multiple transmitter/
receiver pairs; i.e. a transmitter/receiver pair 311 and 321
and a transmitter/receiver pair 313 and 323 in the case of
user 335 and a transmitter/receiver pair 315 and 325 and a
transmitter/receiver pair 317 and 327 in the case of user 337.
An administrative user 339 is also illustrated that provides
the capability to monitor the users 337 and 335 and make
adjustments to the solution 300 con?guration if necessary.
The administrative user 339 accesses the manageability
cation link represented by R145 connector 505. Due at least
in part to the transmitter core 406, the USB hub 404
operation is as de?ned in USB 2.0 speci?cation chapter 11
Which describes the USB 2.0 to 1.1 translation requirements
for split transactions.
[0031] The split transaction protocol de?ned in the USB
2.0 speci?cation de?nes the converting of transactions
betWeen 2.0 signaling and 1.1 signaling through a hub. The
sWitch 309 via a transmitter/receiver pair 319 and 329.
transmitter 402 implements the USB hub 404 Which attaches
using 2.0 signaling to the host controller 405. All devices
[0027] In general, users are assigned to each USB port
such that each user’s collection of ports may be used to
devices, thus requiring the split transaction protocol as
assume control of the user interface of a host computer
de?ned in the USB 2.0 speci?cation and described further
system 341 and temporarily block other users for a speci?ed
period of time. In the illustrated embodiment, blocking is
herein. The split transaction protocol de?nes separate start
and complete transactions betWeen the host controller 405
limited to devices assigned to the user. This includes but is
not limited to keyboard, mouse, joystick, and USB HID
be completed doWnstream from the transmitter hub 404.
(human interface device) class devices. The operation
requires the identi?cation of a device and device class
through host applications, through USB device drivers,
through snooping of USB transactions, or any combination
of hardWare and softWare tools to identify the device and/or
the device class.
[0028] Once devices are identi?ed and assigned to users,
transactions to and from the devices can be monitored by a
device on the bus, such as a hub 703 (see FIG. 7). The hub
703 then identi?es Which device is in communication to the
doWnstream from the transmitter hub 404 attach as 1.1
and the 2.0 hub to alloW the sloWer USB 1.1 transaction to
[0032] This split transaction format provides an opportu
nity to hide the extension electrical layer and latency. The
transaction requests and responses are transported across the
extension media to and from the receiver in a non-USB
format Where the transaction is re-initiated as USB 1.1
transactions. The transmitter circuitry 402 manages the
upstream 2.0 communication and the receiver circuitry 502
manages the doWnstream 1.1 communication. The extension
device control of the host computer system 341 by tempo
rarily disabling the doWnstream ports assigned to other users
latency is absorbed in the latency betWeen the start and
compete split transactions Which tolerate the additional
latency and the true bus transaction latency still meets the
USB speci?cation since it is contained entirely betWeen the
receiver and the local doWnstream devices (e.g., betWeen the
receiver 105 and the user 107).
to prevent responses. All device addresses doWnstream of
temporarily disabled ports must be knoWn and transactions
addressed to these devices must respond With a NAK
handshake to avoid the disconnect of the device for lack of
[0033] FIG. 6 is a How diagram of the extension topology
and operational How of a basic computer interface extension
solution incorporating USB split transactions according to
certain but not other aspects of the present invention. In the
host
via
non-NAK
(“negative
acknowledgement”)
responses, i.e., real data, and assigns the user that oWns that
response. In the meantime, all temporarily disabled ports
should forWard a token of some sort, generate bogus trans
actions, or other meaningless activity to avoid being put into
suspend mode. Although described in relation to the illus
trated hub 703, the user sWitch hub may be implemented at
any point in the USB topology, including the root hub.
[0029] FIG. 4 is a simpli?ed block diagram of exemplary
transmitter circuitry components 402 that are used in an
extension transmitter (e.g., transmitter 103) according to
certain but not other principles of the present invention. The
transmitter circuitry components 402 employ the techniques
of the claimed subject matter. The transmitter circuitry
components 402 are con?gured to support the transmitter
103 in an extension solution such as the extension solution
illustrated embodiment, a USB 2.0 Host Controller 601
operates at a host computer Where USB 2.0 signaling 603
begins a split start transaction 605 (also knoWn as a ‘start
split’ transaction). An extension transmitter 607 includes a
USB 2.0 hub 609 and an extension function 611. The
extension function 611 coordinates extension signaling 613
such that non-USB signals may be forWarded by a forWard
transaction request 615 to an extension receiver 617. The
extension receiver 617 includes an extension function 619
that operates in conjunction With another USB 2.0 hub 621.
With the assistance of at least the extension function 619, the
USB hub 621 performs USB 1.1 signaling 623 to execute
full/loW speed transactions 625 With at least one USB 1.1
device 627.
100. HoWever, unlike transmitter circuitry of the prior art,
[0034]
the transmitter circuitry 402 includes a USB hub 404 and
USB host controller 405. The USB hub and host controller
404 and 405 are introduced such that the transmitter cir
USB 2.0 host controller 601 by passing from a USB 1.1
device 627 to the USB 2.0 hub 621 Where the extension
function 619 aids in the extension signaling 613 to send
return transaction results 629. A split complete transaction
cuitry components 402 operate With a USB protocol to
In a similar manner, USB signals are sent to the
support USB devices such as a keyboard and mouse oper
631 may then begin for the particular USB signaling that is
ating at the user 107 end of the solution 100. The transmitter
being extended.
components 402 also include a transmitter core 406 and a
communication link to a receiver, e.g., receiver 105, repre
sented by R145 connector 408.
[0030] FIG. 5 is a simpli?ed block diagram of exemplary
receiver circuitry components 502 that are used in an
extension receiver (e.g., receiver 105) that operates accord
ing to and complements the transmitter circuitry components
402. The receiver circuitry components 502 include a USB
hub component 504, a receiver core 506, and a communi
[0035] In other Words, the USB 2.0 host controller 601
communicates With the extension transmitter 607, Which
includes the upstream USB 2.0 hub 609 and the extension
function 611, via USB 2.0 signaling 603. The extension
function 611 communicates via extension signaling 613 With
the corresponding extension function 619 in the extension
receiver 617. As previously stated, the extension receiver
617 includes the doWnstream USB 2.0 hub 621. The exten
sion receiver 617 communicates via USB 1.1 signaling 623
Dec. 30, 2004
US 2004/0268012 A1
to several USB 1.1 devices 627. In accordance With USB
speci?cation terminology, the terms “upstream” and “doWn
stream” With respect to the USB 2.0 hub 609 and the USB
2.0 hub 621 are used in compliance With the speci?cation
terminology although, as Will be understood by those of
ordinary skill in the art and vieWing this disclosure, in actual
practice the communication is bi-directional so that What is
upstream in one eXample could be doWnstream in another,
and vice versa.
[0036]
FIG. 7 is a diagram of the data How of the method
of the claimed subject matter as it applies to a USB multi
user sWitch. A USB 2.0 host controller 701 communicates
With a USB 2.0 hub 703 in order to communicate With USB
1.1 devices 705. The USB 2.0 hub 703 communicates USB
2.0 upstream 707 and USB 1.1 doWnstream 709. A user
transaction lockout ?lter 711, that may include snooping
functions for pulling ID information and monitoring and
controlling bus activity, is introduced to facilitate the non
USB signals that are the subject of the extension as previ
ously described more fully herein.
[0037] In the illustrated embodiment, the USB 2.0 hub 703
function is best implemented in a USB 2.0 hub that only
alloWs USB 1.1 connections doWnstream. This creates a
natural split in the USB topology betWeen 2.0 and 1.1 device
transactions that can easily be intercepted during the con
4. The method of claim 1 Wherein the blocking requires
identi?cation of the at least one device.
5. The method of claim 4 Wherein the identi?cation of the
at least one device includes identifying a device class for the
at least one device.
6. The method of claim 4 Wherein the identi?cation of the
at least one device comprises identifying through an appli
cation program that is resident on the computer system.
7. The method of claim 4 Wherein the identi?cation of the
at least one device includes monitoring a USB device driver
for the at least one USB device.
8. The method of claim 4 Wherein the identi?cation of the
at least one device comprises snooping of USB transactions
that occur betWeen the at least one USB device and the
computer system.
9. The method of claim 8 Wherein signaling type for the
snooping is selected from the group consisting of USB 1.1
protocol, USB 2.0 protocol, and split transaction protocol
Within the USB 2.0 de?nition.
10. A USB communication system for sharing user
resources comprising:
version process. Using the split start and complete token
a host computer system having a USB host controller, a
requests, doWnstream transactions can be ?ltered before
being initiated on the doWnstream ports. This avoids con
?rst USB hub circuitry, and transmitter circuitry, the
USB host controller being con?gured to operate using
tention conditions associated With real-time snooping and
interception of transactions already initiated on the bus.
a split transaction for the USB communications;
[0038] Although a system and method has been described,
receiver circuitry having a second USB hub circuitry that
the invention is not intended to be limited to the speci?c
form set forth herein, but on the contrary, it is intended to
cover such alternatives, modi?cations, and equivalents, as
can be reasonably included Within the spirit and scope of the
signals as the signals appear betWeen split start and
split complete transaction operations at the host com
invention as de?ned by the appended claims.
[0039] While various embodiments of the invention have
been described, it Will be apparent to those of ordinary skill
in the art that many more embodiments and implementations
are possible that are Within the scope of this invention.
receives a non-USB format of USB communication
puter system, the transmitter circuitry being con?gured
to forWard the non-USB formatted USB communica
tion signals across an extension betWeen the transmitter
circuitry and the receiver circuitry;
a user transaction lockout ?lter disposed betWeen the ?rst
system through a universal serial bus (USB) interface com
USB hub circuitry and the second USB hub circuitry
that performs snooping of the USB communication
signals that appear betWeen the split start and the split
complete transaction operations at the host computer
prising:
system;
What is claimed is:
1. A method of sharing user resources in a computer
associating at least one USB device With a ?rst user and
at least another USB device With a second user;
assigning the ?rst user to a ?rst USB port;
assigning the second user to a second USB port;
permitting the ?rst user to temporarily assume control of
the computer system through the ?rst USB port for
at least one USB user interface device communicatively
coupled to the receiver circuitry that receives USB
communication signals from the second USB hub cir
cuitry, the USB communication signals corresponding
to the non-USB formatted communication signals that
appear betWeen the split start and split complete trans
action operations at the host computer system; and
operation of the at least one USB device; and
one or more users sharing the host computer system
blocking the second user from access to the computer
system While the ?rst user has temporary control of the
computer system.
through the receiver circuitry and the transmitter cir
cuitry.
2. The method of claim 1 Wherein the blocking of the
11. The USB communication system for sharing user
second user from access to the computer system is limited to
devices assigned to the ?rst user.
3. The method of claim 1 Wherein the at least one USB
resources of claim 10 Wherein the one or more users that
cuitry are con?gured to block other users of the devices that
device is selected from the group consisting of a keyboard,
are controlled by the one or more users.
a mouse, a joystick, and a USB human interface class
device.
share the host computer system through the receiver cir
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