High-end KVM switching system

Details High-end KVM switching system High-end KVM switching system

1999-12-02

2002-05-14

Wu, Xiao (Department: 2675)

Computer graphics processing and selective visual display system

Display peripheral interface input device

Including keyboard

C345S001100

Reexamination Certificate

active

06388658

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a switching system for interconnecting a plurality of computer user terminals or workstations each having user interface devices, including a keyboard, a video display unit, and a cursor control device or mouse (KVM), with a plurality of computers in a computer network, allowing a user to access any one or more of said computers from the user interface devices of a single terminal or workstation. It is denoted “high end” because of the potentially large number of computers which may be interconnected with the system.
BACKGROUND AND SUMMARY OF THE INVENTION
A keyboard-video-mouse (KVM) switching system for selectively interconnecting a single workstation with a plurality of remotely located computers, a “low-end” system, is described for example in U.S. Pat. No. 5,499,377 (Designed Enclosures, Inc.) and such systems are available from Cybex Inc., and other suppliers. “High end” KVM systems, in which multiple workstations may be selectively interconnected with any one of multiple computers via a computerized switching hub are available from, inter alia, Cybex Inc., Apex PC Solutions Inc., Rose Electronics Inc., Lightwave Communications Inc., C-C-C Group Limited. These systems greatly facilitate system administration in a local area network from a single workstation, which may be located in a different room or building from interconnected computers such as servers in a large client server network. Interconnecting cabling needs are also reduced. A typical high end KVM switching system is described in U.S. Pat. No. 5,721,842 (Apex). Signal conditioning interface units receive keyboard and mouse signals from a workstation and generate serial digital data packets which are transmitted to a switching hub comprising a central crosspoint switch. The crosspoint switch routes the keyboard/mouse packet to another signal conditioning interface unit coupled to the selected remote computer. Analogue video output signals from the remote computer are transmitted via central analogue crosspoint switching arrangement to the workstation, so that it appears to the workstation user that there is a direct connection between the workstation keyboard, video monitor and mouse to any one of 32 remotely-located computers. The switching hub comprises a master Central Processing Unit (CPU), a plurality of identical transmit/receive cards, a plurality of switch cards each comprising a 16×16 digital crosspoint switch and a separate 16×16 analogue crosspoint switch, a digital backplane and a separate analogue backplane. Such a system has to be powered down for removal or upgrading of cards, and a failure on one switch card or in the master CPU will cause the whole system to fail. In contrast, the present invention provides a high end KVM system with distributed control, i.e. without a master CPU, and in which all cards and components are “hot-swappable,” a significant advantage which allows for simple maintenance and updating of the system to interconnect more workstations and computers, without any system down time.
U.S. Pat. No. 5,884,096 (Apex) describes a similar high end KVM switching system.
The present invention provides a switching system for interconnecting a plurality of computer user terminals (
1
-
16
), having user interface devices including a keyboard (
1
b
), a video display unit (
1
a
) and a cursor control device (
1
c
), with a plurality of computers (
201
-
328
) in a computer network, allowing a user to access any one or more of said computers from the user interface devices or a single terminal, comprising a switching hub (
40
) for routing keyboard and cursor control signals transmitted from any one (1) of the terminals (
1
-
16
) to a selected computer (
201
), and for routing video signals received from the said computer to said one of the terminals, said signals being in both digital and analogue form, a user interface module (
17
-
32
) for receiving said transmitted keyboard and cursor control signals, coupled between said plurality of computer user terminals (
1
-
16
) and said switching hub (
40
), a computer interface module (
51
-
178
) for receiving said received video signals, coupled between said plurality of computers (
201
-
328
) and said switching hub (
40
), characterized in that the physical architecture of the switching hub (
40
) is a modular system comprising a plurality of switch modules (
41
), each module comprising an analogue transmitter (
43
) circuit and/or an analogue receiver (
42
) circuit, each including an analogue crosspoint switching arrangement, a programmable digital circuit (
44
) for handling digital data signals and including a digital crosspoint switching arrangement, and a backplane (
45
) interface between the said analogue (
42
,
43
) and digital (
44
) circuits.
In another aspect, the invention provides a switching hub (
40
) comprising a plurality of removable and hot swappable switch modules (
41
) each with its own crosspoint switching arrangement (
402
,
501
,
502
) and central processing unit (
400
), each module comprising an analogue transmitter (
43
) circuit and/or an analogue receiver (
42
) circuit, a programmable digital circuit (
44
) for handling digital data signals and a backplane (
45
) interface between the said analogue (
42
,
43
) and digital (
44
) circuits.
In a further aspect, the invention provides a switching hub (
40
) comprising a crosspoint switching arrangement (
402
,
501
,
502
), including an analogue crosspoint switch (
501
,
502
) with a switch topology based on a switched transconductance architecture.
In a still further aspect, the invention provides a switching hub (
40
) which is a modular system comprising a plurality of switch modules (
41
), each module comprising a separate analogue transmitter (
43
) circuit or an analogue receiver (
42
) circuit, each including an analogue crosspoint switching arrangement, a separate programmable digital circuit (
44
) for handling digital data signals and including a digital crosspoint switching arrangement, and a backplane (
45
) interface between the said analogue (
42
,
43
) and digital (
44
) circuits, said analogue circuit embodying stripline structures for video bus channel paths.
The invention also provides methods of switching KVM signals in a KVM system, using the system described, and in the manner as herein set forth.
Modular System
In its preferred embodiment, the invention creates a truly modular system, which is very easily scaleable to the desired system, in terms of connecting more users and computers as needs change, by simply adding more modules to the system. This is achieved by providing switch modules, or packs of cards, for transmit and receive modes, providing access to a pre-determined number of user- or computer interfaces of the system. In the described embodiment, a system is provided where each switch module can handle sixteen video channels, and with nine modules loaded, the system will allow sixteen users to control
128
computers in a non-blocking way.
Economic System Architecture
In its preferred embodiment, the invention reduces costs of design and manufacture by splitting each switch module into an analogue card and a digital card, wherein the digital card is a common card which may be used interchangeably for both transmit and receive modes, i.e. bundled either with an analogue receiver or transmitter card.
Hot Swap
In its preferred embodiment, the invention provides a fully “hot-swappable” modular KVM system. Every single removable module in the system may therefore be hot swappable, i.e. may be plugged or unplugged in a powered on condition. This includes; power-supplies, fan modules, all cards, control panel.
CAN-bus as Internal Communication
In its preferred embodiment, the invention provides communication between all cards based on a Controller Area Network (CAN) bus, for example; all switching information, system information, update information for the main CPU, update information for the programmable logic devices, control information.
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