MXPA97009186A - Computer interconnection system - Google Patents

Abstract

A computerized switching system to couple it to a workstation with a computer located remotely. A signal conditioning unit receives the keyboard and mouse signals generated by a workstation and generates a data packet that is transmitted to a central point of contact switch. The packet is routed or sent through a point of contact switch to another signal conditioning unit located in a computer located remotely. The second signal conditioning unit applies the keyboard and mouse commands to the keyboard and mouse connectors of the computer as if the keyboard and mouse were directly coupled to the remote computer. The video signals produced by the remote computer are transmitted through the point of contact switch to the workstation. The horizontal and vertical synchronization signals are encoded in the video signals to reduce the number of cables that extend between the workstation and the remote computer. The signal conditioning units connected to the work stations include an on-screen programming circuit that produces menus for the user in the display or video display of the workstation

Description

COMPUTER INTERCONNECTION SYSTEM FIELD OF THE INVENTION The present invention relates to systems for interconnecting computers located remotely.

BACKGROUND OF THE INVENTION In a typical local computer network, there are several client computers that are coupled through a communications link to several network server resources. These resources include file servers, print servers, modem servers and CD-ROM servers for example, usually each server is a standalone computer with its own keyboard, mouse and video monitor. Each client computer can use the functions provided by the server computers through the communication link. Most computer networks have one or more system administrators, that is, human operators of server computers. System administrators monitor the operation of software that runs or runs on server computers, loads new software packages, deletes obsolete files, and performs other tasks necessary to maintain network operation. While most of the tasks of the administrator (modifying software, deleting files, etc.) can be performed on the network from a client computer, there are some situations where network administrators must be physically located on the server computers for direct access to them and for their operation. For example, it is not possible to restart a computer from the server on the network. If the computers of the 02092. 0001 server are not together, the time required for a simple task such as restarting them, can be substantial. Although it is possible to run dedicated or exclusive communication links on each server computer in order to allow a system administrator to operate or operate the network from a central location, a large number of cables is required for everything, except for have a simplified network.

SUMMARY OF THE INVENTION The present invention provides a computerized switching system that allows centralized network administrators to operate multiple server computers over long distances without requiring a complicated wiring scheme. In general, the switching system allows the transmission of data between a workstation and a server computer located remotely. A signal conditioning unit receives the keyboard and mouse signals from a workstation and generates a serial data packet that is transmitted to a central point of contact switch. The point of contact switch forwards or sends the keyboard / mouse packet to another signal conditioning unit that is coupled to the server computer located remotely. The signal conditioning unit coupled to the server computer decodes the keyboard / mouse package and applies the signals to a keyboard and mouse connector on the remote computer in the same way as if the mouse and keyboard were directly coupled to the computer. remote computer. The video signals produced by the computer 02092. Remote 0001 is transmitted through the point of contact switch to the workstation. In order to minimize the number of cables that extend between the remote computer and the workstation, the horizontal and vertical synchronization signals as well as the mode signal are encoded with the analog video signals. The present embodiment of the invention allows any of thirty-two work stations to be connected to any of thirty-two remotely located server computers.

BRIEF DESCRIPTION OF THE DRAWINGS The above aspects and many of the accompanying advantages of this invention will be more readily appreciated as it is better understood with reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: Figure 1 is a diagram representing a computerized switching system, in accordance with the present invention, to several work stations and to several computers remotely located; Figure 2 is a block diagram of a signal conditioning unit (capsule) that is coupled to a work station; Figure 2A is a time diagram of a capsule to capsule package in series that is transmitted by the signal conditioning unit shown in Figure 2; Figure 2B is a time diagram of the data packet that is routed within the central point of contact switch; Figure 3 is a block diagram of a signal conditioning unit (capsule) that is coupled to 02092. 0001 a system of remote computers; Figure 4 is a block diagram of a point of contact switch in accordance with the present invention, which routes data between a workstation and a remote server computer; Figure 5 is a block diagram of an input / output card that is used to send and receive signals at the point of contact switch; Figure 6 is a block diagram of a switching card that routes the signals through the point of contact switch; Figure 7 is a schematic diagram showing the interconnection of four switch cards to create a 32x32 switch used in the point of contact switch of the present invention; Figures 8 and 9 are schematic diagrams showing the manner in which the digital and analog 16x16 switch is constructed; Figures 10A-10C are schematic circuit diagrams for encoding horizontal sync, vertical sync and video mode signals in an analog video signal in accordance with another aspect of the present invention; Figures 11A and 11B are schematic circuit diagrams for extracting the horizontal and vertical synchronization signals and the encoded mode signal from an analog video signal; Figure 12A is a circuit diagram of an on-screen programming circuit that produces video displays or displays on the workstation monitor in accordance with another aspect of the present invention; Y 02092. 0001 Figure 12B is a circuit diagram of a circuit that reverses the polarity of the horizontal and vertical synchronization signals that is used within the on-screen programming circuit of Figure 12A.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY The present invention is a computerized switching system that allows several computers of work stations to be coupled to several server computers located remotely. In the currently preferred embodiment of the invention, up to thirty-two work stations can be connected to any of thirty-two remote computer systems. However, those skilled in the art will recognize that the number of possible interconnections can be easily modified for the environment in which the invention will be used. Referring now to Figure 1, the computerized switching system or point of contact switch in accordance with the present invention, allows several server computers 52, 54, 56 to be coupled with several work stations 62, 64, 66. Each The workstation includes a video monitor 63, a keyboard 65 and a cursor control device such as, for example, a mouse 67. In accordance with the present invention, the signals coming from the keyboard 65 and the mouse 67 are received by a signal conditioning circuit or capsule 70. The capsule transmits the keyboard and mouse signals on a communication link 72 to a central point of contact switch 60. After being routed through the contact point switch 60, the keyboard and mouse signals are retransmitted on another communication link 74 to a capsule 76 which is 02092. 0001 coupled to the server computer located remotely. The capsule 76 supplies the keyboard and mouse signals through the appropriate connectors to the keyboard and mouse input ports of the remote computer, just as if the keyboard 65 and the mouse 67 were directly coupled to the input ports of the remote computer. keyboard and mouse. The audio and video signals produced by the remote computers 52, 54 or 56 of the server are received by the associated capsule 76 and transmitted in the reverse direction along the communication link 74 to the central contact point switch 60. The The central point-of-contact switch routes the audio and video signals to one of the communication links 72 for transmission to a capsule 70. The capsule 70 then supplies the audio and video signals to the video monitor 63 and a 69 horn associated with the work station. From the user's point of view, it seems as if the workstation is directly coupled to the server's remote computer. Figure 2 is a block diagram of a capsule 70. As described above, the capsule functions to receive signals from the mouse and keyboard and to transmit them through the point of contact switch to a computer system of the server located at remotely. In addition, the capsule receives video and audio signals from the server's remote computer via the central point-of-contact switch and supplies them to the video monitor and speaker of the workstation. The capsule 70 generally comprises a central processing unit (CPU) 80 having its own 02092. 0001 random access and read-only memories. The keyboard / mouse interface 82 is coupled to the CPU 80 to receive and condition the electronic signals from a keyboard 65 and the mouse 67. As the user moves the mouse or writes to the keyboard, the keyboard / mouse interface 82 generates a interrupt signal that is fed to the CPU 80. The CPU 80 then reads from the keyboard / mouse interface 82 the signals digitally stored in a buffer or digitally damped and converts the signals into a data packet that will be transmitted to the computer remote As shown in Figure 2A, capsule-to-capsule data pack 90 begins with a unique character 92 that marks the beginning of the data packet, followed by a byte 94 that indicates the length of the packet. The next byte 96 identifies the type of data (mouse, keyboard, monitor, etc.) that the pack represents. The next series of bytes 98 represents the keyboard / mouse data that will be transmitted to the server's computer. Finally, the sum check byte 100 allows error correction to be carried out during the transmission of the error. It should be noted that capsule-to-capsule packages are not limited to transporting keyboard and mouse data. The packages allow the capsule in the workstation to "talk or converse" with the capsule in remote computers. Each capsule sends another acknowledgment that the package was received correctly and, in the case of an error, requests that the package be retransmitted. After the CPU 80 has assembled the capsule to capsule package, the packet is transmitted to a UART QUART 84, which transmits and receives data in series over four 02092. 0001 drivers 84a-84d. The capsule to capsule package is put in series and transmitted by the driver 84a to a line differential controller / receiver 88 which transmits and receives data on several twisted pair cables 72a-72e which are coupled to the central point of contact switch 60 (shown in Figure 1). In the presently preferred embodiment of the invention, the line differential controllers / receivers are those of model No. DS8921, manufactured by National Semiconductor. The controllers transmit a positive version of the data by one cable of the twisted pair cables and the reverse of the data by the other twisted pair cable. This allows data to be transmitted along cables up to 500 feet (152 m) in length without the use of additional amplifiers. Since the user is operating on the server's remote computer, the remote computer can transmit commands that accept mouse and keyboard operation. These include the sensitivity of the mouse, the rate of repetition of the keyboard, the activation of one or more LEDs on the keyboard (such as, for example, blocking or securing numbers, blocking or securing uppercase letters, etc.) . The keyboard / mouse commands contained in a capsule-to-capsule packet transmitted from the remote computer are received on the twisted pair cable 72b by the line differential controller / receiver 88. The UART 84 converts received key / mouse commands in series in a parallel format and supplies the data to the CPU 80. The CPU 80 then generates the appropriate signals that are fed to the keyboard / mouse interface 82 and applied to the keyboard 62b and the mouse 62c. Video signals transmitted from the server's remote computer are received in three games 02092. 0001 or sets of twisted pair cables 72f, 72g, and 72h by a set of line differential receivers 90. The output signals produced by the line differential receivers 90 are supplied to a video amplifier 92. The output of the amplifier of video is coupled to a sync extraction circuit 94 that eliminates an embedded horizontal and vertical synchronization signal, as well as a mode signal of the green, blue and red video signals, respectively. The sync extraction circuit 94 supplies the red, blue and green analog video signals as well as the horizontal and vertical synchronization signals in separate conductors to a screen programming circuit 99 which is further described in detail below. The on-screen programming circuit 99 feeds the video signals to a connector 96 which is coupled to the video monitor of the workstation by a conventional video cable 97. As will be further described in detail below, the horizontal synchronization signals and vertical are embedded in the green and blue video signals in order to minimize cables that extend between the workstation and the remote server computer as well as to reduce the complexity of the point of contact switch. The CPU 80 also reads a set of four monitor detection drivers 95 to determine what type of monitor is connected to it. The monitor detection data is generated and transmitted in a capsule to capsule package as shown in Figure 2A. The remote computer receives the data from the monitor and supplies it to the remote computer in order to adjust its video signals in accordance with this. 02092. 0001 In addition to transmitting and receiving the keyboard and mouse signals from the remote computer, the capsule 70 can communicate with the central point of contact switch. The data that will be transmitted to the central point of contact switch is sent on a twisted pair cable 72c, while the data transmitted from the central point of contact switch is received on a pressed pair cable 72d. The commands sent between the capsule 70 and the central point of contact switch allow a user to connect the workstation to another remote computer, allow the central point of contact switch to interrogate about the condition or status of the capsule, update the wired microprogram (firmware) of the capsule, etc., using the packet structure shown in Figure 2B as will be described later. When the user wishes to send a command to the central point of contact switch, a special key sequence is used. In the present embodiment of the invention, all the commands are preceded by the "printscreen" keys and end with the "enter" key. The CPU 80 parses the sequence of keys pressed on the keyboard and analyzes this sequence of keys to determine the destination of the command. If the command is directed to the same capsule, the data packet is not produced. If the command is directed to the remote computer, a package of capsule to capsule is generated and transmitted. If the command is directed to the central point of contact switch, the CPU assembles a command packet that is transmitted to the central point of contact switch on the twisted pair cable 72c. In Figure 3 is shown the block diagram of a capsule 76 that is coupled to the remote computers 02092. 0001 of the server. The capsule 76 includes a central processing unit (CPU) 120 which is coupled to a keyboard / mouse interface 134. The keyboard / mouse interface 134 supplies the signals to the keyboard and mouse connectors of the server computer and receives the signals from the same connectors. The keyboard and mouse signals from the keyboard and mouse connectors of the computer are read by the CPU 120 and assembled in a capsule-to-capsule package in the same manner as the capsule-to-capsule package described above and shown in the Figure 2a. The capsule to capsule package produced by the CPU 120 is supplied to a UART QUAD 136 that transmits the package in series via a conductor 136b to a line differential controller 140. The line differential controller controls a twisted pair cable 74a that it is coupled to the central point of contact switch. A capsule to capsule package that is transmitted from a workstation is received on a twisted pair cable 74b and supplied to the line differential receiver 140. The output signal of the line differential receiver is supplied to the UART QUAD 136 which converts the Package a serial format in a parallel format. The CPU reads the packet and then transmits the received keyboard and mouse signals to the keyboard and mouse interface 134, where the signals are supplied to the keyboard and mouse connectors of the remote computer in the same way as if the keyboard and mouse were directly connected to the server's remote computer. The particular format of the signals applied to the keyboard and mouse connectors may vary with the type of remote computer. The CPU inside the capsule 76 is therefore programmed to translate or convert the signals 02092. 0001 in its proper format. The commands sent from the capsule 76 to the central point of contact switch allow the remote computer to interrogate about the condition or state of the capsule, update the wired microprogram (firmware) of the capsule, etc., using the package structure of Figure 2B. As with the user capsule, all commands are preceded by the "printscreen" key and end with the "enter" key. The CPU 120 parses the key sequence of the keyboard and analyzes the typed sequence to determine the destination of the command. If the command is directed to the capsule 76, the data packet does not occur. If the command is directed to the workstation, a package of capsule to capsule is generated and transmitted. If the command is directed to the central point of contact switch, the CPU assembles a command packet that will be transmitted to the central point of contact switch on a twisted pair cable 74d. The signals from the video port of the remote computer are supplied via a video cable 143 to a connector 144. As will be described below, the analog video signals red, green and blue, together with the signals of horizontal synchrony and vertical, they are supplied to a sync combination circuit 146 that encodes the horizontal and vertical synchronization signals in green and blue analog video signals, respectively. The current mode of the monitor (i.e., the correct polarity of the horizontal and vertical sync pulses) is coded by the sync combination circuit 146 in the red analog video signal. The output of the synchronization combination is supplied to an amplifier 148 which conditions the signals and supplies the video signal 02092. 0001 to three line differential controllers 140 which transmit the signals on three separate twisted pair wires 74f, 74g, and 74h to the central point-of-contact switch. The monitor detection data received from a remote workstation is decoded by the CPU 120 and supplied to a set of monitor detection conductors 147. The remote computer receives the monitor detection data on these drivers and adjusts its video signals for the particular monitor that will display or display the video signals. The audio signals produced by the remote computer are supplied to a line differential controller 140 and transmitted over a twisted pair cable 74c to the central point of contact switch. Figure 4 is a block diagram of the central point of contact switch. The central switch 60 includes a master processing unit (CPU) 150, several input cards 152, several switching cards 154 and several output cards 156. Each of the input cards transmits signals and receives signals from up to eight of server computers located remotely while each of the output cards transmits and receives signals from up to eight of the workstations located remotely. The master CPU 150 is coupled to each of the input cards 152, the switch cards 154 and each of the output cards 156 by a digital main distribution bar 158. Together with the master CPU, the input cards , the switch cards and the output cards are connected through a local area network. 02092. 0001 The capsule packages are routed from the input card by means of the switching card to an output card and vice versa, in a digital backplane 160. Analog video and audio signals are transmitted between the input cards, and the switching card 154 and the output cards 156 in a separate analogue rear plane 162. A block diagram of an input card 152 is shown in Figure 5. The output cards 156 are identical to the input cards, with the exception that the direction of the audio / video signals is inverted and, therefore, will not be discussed separately. The input card 152 includes its own CPU 170 which transmits and receives data from the master CPU 150. The signals transmitted from the remote computer of the server are received by a set of line differential controllers / receivers 172a-b. Commands sent from the remote computer to the central point of contact switch are received by an octal UART 173, where the commands are converted from a serial format to one in parallel. The UART feeds the commands to the CPU 170, where they are interpreted and sent to the master CPU 150. To transmit data between the input, output and switching cards of the contact point switch, the data is packaged in the format shown in Figure 2B by the CPU of the card that sends the packet. A packet begins with a unique character 112 that marks the start of the packet. A destination address 114 follows the start character. The address uniquely identifies one of the cards in the point of contact switch. A byte 116 indicates the size of the packet, while a byte 118 indicates the type of data included in the packet. 02092. 0001 package. A series of bytes 120 are the data that will be transmitted from one card to another. After the data, a byte 122 indicates the unique address of the sending card. A sum check byte 124 follows the address of the emitter and a unique character 126 is sent as a terminal or a tail block. The transmission of all data packets between the contact point switch cards is controlled by the master CPU 150. Returning to Figure 5, the commands generated by the CPU 170 that will be transmitted to the capsule that is coupled to a remote server computer are transmitted over the driver 174b to a line differential controller 172. The capsule packets received from the central computer are routed or sent through the input card over the driver 174c to the digital backplane 160. Similarly, the capsule-to-capsule packets transmitted from the remote workstation are received from the digital backplane, routed through the input card over the driver 174d and supplied to the line differential controller 172a. In order to protect or shield the video signals from noise in the digital backplane, the video and audio signals transmitted from the remotely located server computer are routed on a separate analogue backplane 162. The signals The audio signals received from the remote computer are routed through the input card over a conductor 174e and are applied to the analogue backplane 162. The video signals are received by the line differential receivers 172a and routed through the card. input on the 174f-h conductors to the analogue backplane. 02092. 0001 In the present embodiment of the invention, each input card includes up to eight sets of line differential controllers / receivers 172a-172f (the remaining six controllers / receivers are not shown) to receive signals from up to eight server computers located at remotely. The signals from each remotely located computer are routed through the input card to the digital and analogue backplanes in the manner described above. Figure 6 is a block diagram of a switching card 154. The switching card includes its own central processing unit (CPU) 180. The CPU 180 transmits and receives signals from the master CPU 150 in order to control the position of a 16x16 digital point of contact switch 182 and an analog 16x16 point of contact switch 184, using a set of control leads 183. The digital point of contact switch 182 connects the keyboard / mouse signals transmitted between a workstation and a remote server computer, as well as audio signals generated by the server's remote computer to the workstation. The analog point of contact switch 184 transmits the video signals between a remote computer of the server and any of the work stations. Figure 7 shows the manner in which the digital backplane portion of the 32x32 point of contact switch is configured using four switch cards 154a, 154b, 154c and 154d, in order to transmit signals between the 32 work stations and the 32 computers of the server located remotely. The switching card 154a has sixteen input lines 186 which are coupled with sixteen computers of the 02092. 0001 server located remotely and sixteen output lines 188 that are coupled to sixteen work stations. The switching card 154b has sixteen input lines coupled with another sixteen remotely located server computers and sixteen output lines 194 which are coupled with each of the sixteen output lines 188 of the switching card 154a. The switching card 154c has sixteen input lines 198 which are coupled to the sixteen input lines 186 of the switching card 154a. The sixteen input lines 200 of the switching card 154c are coupled with another sixteen work stations located remotely. The switching card 154d has sixteen input lines 204 which are coupled to each of the sixteen input lines 192 of the switch card 154b. The sixteen output lines 206 of the switch card 154d are coupled to the sixteen output lines 200 of the switch card 154c. The analogue backplane is constructed similarly to the digital backplane described above. As can be seen, the arrangement of switch cards 154a, 154b, 154c and 154d, allows data from any of the thirty-two remotely located computers to be coupled with any of the thirty-two workstations located in remote For each signal that will be transmitted between the server computer located remotely to a corresponding work station, a switching arrangement of the type shown in Figure 7 is required. In the present embodiment of the invention, each work station sends and receive capsule-to-capsule packages as well as receive audio and video signals from the computer 02092. 0001 remote. Therefore, for the 32x32 digital switch shown in Figure 6, the digital backplane includes two sets of switches of the type shown in Figure 7 and, the analog backplane includes four other sets of switches for the video signals and of audio In the currently preferred embodiment of the invention, 16x16 digital switches 182 are implemented using a pair of 16x8 digital switches, as shown in Figure 8. Each 16x16 switch comprises switches 210 and 216. Switch 210 has sixteen input lines 212 and eight lines 214. The switch 216 has sixteen input lines 218 which are coupled to each of the input lines 212 and eight output lines 220. In the presently preferred embodiment of the invention, each of the switches 16x8, 210 and 216 have part numbers CD22M24945Q, manufactured by Harris. The analogue backplane in which the video signals are transmitted is configured in the same manner as the switch shown in Figure 7. However, due to the higher bandwidth required, each 16x16 switch 184 is implemented using eight 8x4 analog switches with model number DG884DN, manufactured by Siliconix. As can be seen in Figure 9, a 16x16 analog switch is implemented using the switches 222, 224, 226 and 228, each having eight input lines and four output lines. The input lines of the switches 222, 224, 226 and 228 are connected in parallel. A second set of switches 230, 232, 234 and 236, each has eight input lines and four output lines. The entry lines 02092. 0001 of the switches 230, 232, 234 and 236 are connected in parallel. The outputs of the switch 230 are coupled in parallel with the outputs of the switch 222 and, the outputs of the switch 232 are coupled in parallel with the outputs of the switch 224. The outputs of the switch 234 are coupled in parallel with the outputs of the switch 226 and, the outputs of the switch 236 are coupled in parallel with the outputs of the switch 228. To minimize the number of wires that must extend between the remote computer to the workstation, the present invention encodes the signals of horizontal and vertical synchronization over the analog color video signals transmitted from the remote computer. Figures 10A-10C show the details of the sync combination circuit 146 (Figure 3) that encodes the vertical and horizontal synchronization signals as well as the monitor mode signal. Figure 10A shows a circuit that encodes the horizontal sync signal over the green video signal produced by a remote computer. The circuit includes an Exclusive O gate (XOR) 250 having a first input that receives the horizontal synchrony signal produced by the computer system. A resistor 252 and a capacitor 254 are connected in series between the first input of the XOR gate and the ground. At the junction of resistor 252 and capacitor 254, there are two series of reversing gates 256 and 258 connected. The output of the inverter 258 is supplied to the second input of the XOR gate 250. The gate XOR 250 operates or functions to encode the horizontal signal as a positive forward pulse regardless of what the normal state of the horizontal synchronization signal is. The voltage of capacitor 254 is equal 02092. 0001 to the average valve of the horizontal synchronization signal. The output of the reversing gate 258 has a logic level equal to the non-active state of the horizontal synchronization signal. The output of gate XOR 250 is coupled to the inverting input of an amplifier circuit 260. The non-inverting input of amplifier 260 is connected to receive the green analog video signal. When the horizontal sync signal is in its normal state, the output of the amplifier 260 follows the green analog video signal. However, when the horizontal sync signal is active, the active video is at zero volts and the amplifier 260 produces a negative forward horizontal sync pulse. Figure 10B shows a circuit that encodes the vertical synchronization signal over the blue analog video signal produced by the remote computer. The circuit comprises an Exclusive O gate (XOR) 270, a resistor 272 a capacitor 274 and a pair of inverters 276, 278 that are connected in the same manner as the horizontal synchronization circuit shown in FIG. 10A and described above. The output of the XOR gate is always a positive forward pulse when the vertical synchronization signal is activated. The output of the gate XOR is fed to the inverting input of an amplifier 280. When the vertical signal is in its normal state, the output of the amplifier 280 follows the blue analog video signal. However, when the vertical synchronization signal is activated, a negative forward pulse, V-sync, is created by the amplifier. Figure 10C is an electronic circuit that encodes the video monitor mode. The mode refers to the polarity of horizontal synchronization signals and 02092. 0001 vertical. Changes in the mode affect the size of the display or display of video produced by a video monitor. To encode the mode of the video signal, the circuit shown in Figure 10C is used. The circuit comprises two AND gates 284 and 286. The AND gate 284 has an input coupled to the inverter output 258 (shown in FIG. 10A). The gate AND 286 has an input coupled with the output of the inverter 278 (shown in FIG. 10B). The rest of the entrances of the AND gates 284 and 286, are coupled to the output of the XOR gate 270 (shown in Figure 10B), so that the mode signal is encoded only on the red video signal, when the vertical synchronization signal is activated. The output of the AND gates 284 and 286 are coupled in series with a pair of resistors 290 and 292, respectively. The receivers 290 and 292 are coupled together in a common node 291. Connected between the node 291 and the earth, there is a resistor 293. Each time the vertical synchronization signal is active, the AND gates 284 and 286 produce a voltage in the node 291 that is proportional to the video monitor mode. The proportional voltage is fed to the inverting input of an amplifier 294. The non-inverting input of the amplifier 294 is connected to receive the red analog video signal produced by the remote computer. When the vertical sync signal is in its normal state, the output signal of the comparator 294 follows the red analog video signal. However, when the vertical sync signal is activated, the mode signal is encoded in the red video signal. After the video signals have been transmitted from the server's remote computer and through the analog point of contact switch to the 02092. 0001 remote work station, the sync signals of the green and blue video signals are extracted. To extract the horizontal sync signal from the green video signal, the circuit shown in Figure HA is used. The green video signal is received by the capsule in a differential receiver 90 which produces an output signal that is fed to a non-inverting input of a cutting amplifier 302. The output signal of the amplifier 302 is the green analog video signal which is fed to the video monitor. A resistor 306 is arranged or located between the non-inverting input of a comparator 304 with the output of the differential receiver 90. Connected between a non-inverting output of the comparator 304 and the non-inverting input there is a feedback resistor 308. An inverting input of the comparator 304 is attached to a constant reference voltage which is supplied by the voltage divider defined by resistors 310 and 312. When the output signal of differential receiver 90 has a magnitude below the voltage supplied at the inverter input of the comparator 304, the inversion output of the amplifier 304 creates a positive forward pulse. The positive forward pulse is supplied to an input of a gate 0 Exclusive (XOR) 314. Coupled to another input of gate O Exclusive 314 is the horizontal mode signal (H mode) that will be recovered from the analog video signal red as will be described below. Gate XOR 314 adjusts the polarity of the horizontal sync signal, depending on the value of the H mode signal. The circuit required to extract the vertical sync signal from the blue video signal is the same as the circuit shown in the Figure HA, with the exception of 02092. 0001 that gate 0 Exclusive (XOR) receives the V mode signal in order to adjust the polarity of the vertical synchronization signal. To recover the video mode signal, the present invention uses the circuit shown in Figure 11B. The red analog video signal is received in a capsule by a line differential receiver 90 that produces the red analog video signal. The output of the line differential receiver 90 is coupled to the reversing inputs of a pair of comparators 320 and 324. The comparators 324 are controlled by the output of a shot 326 that is triggered by the rising edge of the vertical synchronization pulse, so that the comparators only change state when the vertical synchronization signal is active. The non-inverting input of the comparator 324 is provided with a reference voltage produced by a voltage divider comprising a resistor 326 and a resistor 328. The reversing input of the comparator 320 is provided with a constant voltage produced by a voltage divider that it comprises a resistor 330 and a resistor 332. A resistor 334 is positioned between the output of the comparator 320 and the reversing input of the comparator 324. Finally, a resistor 336 is placed between the reversing input of the comparator 320 and the insertion input of the comparator 320. comparator 324. The mode extraction circuit produces two signals, the H mode and the V mode signals, which have logic levels that are dependent on the magnitude of the encoded mode signal in the red video signal. If the magnitude of the mode signal is between 0 and -0.15 volts, the H mode signal will be low and the V mode signal will be low. When the mode signal has a magnitude between -0.15 and -0.29 02092. 0001 volts, the H mode signal will be high and the V mode signal will remain low. The V mode signal is high and the H mode signal is low when the magnitude of the mode signal is between -0.29 volts and -0.49 volts. Both signals, the H mode and the V mode signals, are high when the magnitude of the mode signal is less than -0.49 volts. As will be appreciated, the values provided above will differ if different circuit components are used. Once the video mode signal has been decoded from the red video signal, the H mode and V mode values are used to adjust the polarity of the horizontal and vertical synchronization signals, using the XOR gate shown in Figure HA. As can be seen, the circuits shown in Figures 10A-10C and HA, 11B, reduce the number of cables that must be extended between the remote computer of the server and the workstation by coding the synchronization and mode signals in the video signals. color at a time when signals are normally not used. Having described the components of the present invention, its operation or operation is described below. To connect a workstation to a remote computer, a user sends a command that causes the central point-of-contact switch to couple the keyboard / mouse signals to one of the remote computers. As indicated above, the commands that perform the operation of the point of contact switch are inserted between the keys of the "printsecreen" and "enter" keys. The capsule connected to the workstation detects these keys and transmits a packet to the CPU in one of the output cards. The CPU then transmits the packet to the master CPU which validates the request and issues a 02092. 0001 command to the switch cards to adjust the position of the digital and analog switches of 16x16, 182 and 184 (Figure 6). Once the position of the switches has been adjusted, the master CPU tells the computer's capsule 76 that the connection has occurred. The keyboard / mouse signals are then packaged and transmitted as capsule-to-capsule packets through the point of contact switch. The video and audio signals from the remote computer are transmitted from the remote computer to the workstation. As indicated above, the present invention provides the ability to allow a user to send commands from a workstation to the central point of contact switch in response to messages that are displayed or displayed on the video monitor. The on-screen programming circuit 99 shown in Figure 2 produces video signals that display a menu of commands that will be selected by the user. Figure 12A is a circuit diagram of the on-screen programming circuit 99. The circuit includes a set of three-state or tristate buffer or buffer storage facilities 352, 354 and 356 that have their inputs connected to the red, green and blue video signals supplied by the sync extraction circuit 94 (shown in FIG. Figure 2). When buffer memories or tri-state buffers are energized, the red, green and blue video signals are passed to the video monitor. When the three-state or tri-state buffer 352, 354 and 356 are in their high impedance state, the video signals are produced by a screen programming circuit 364 as will be described. 02092. 0001 The on-screen programming circuit 99 produces its own horizontal and vertical synchronization signals, using a synchronization generator 358. The horizontal and vertical synchrony signals produced are supplied to a switch 360 which selects either the synchronization signals produced by the internal synchronization generator 358 or the external horizontal and vertical synchronization signals recovered from the green and blue video signals transmitted from the remote computer. The switch 360 receives a signal on a conductor 361 which is coupled to the CPU 80 (Figure 2), which determines which set of horizontal and vertical synchronization signals will be selected. The horizontal and vertical synchronization signals selected by the switch 360 are fed to the video monitor at the user's workstation. Also connected to the output of the switch 360 is a synchronization polarizer 362 that forces the polarity of the selected horizontal and vertical synchronization signals to be active low. The details of the synchronization polarizer 362 are shown in Figure 12B. The synchronization polarizer includes a pair of Exclusive OR gates (XOR) 400 and 402. The XOR 400 gate has an input directly connected to the synchronization signal that will be polarized. A resistor 404 is connected between the synchronization signal and the other input of gate XOR 400. Connected between the second input of gate XOR 400 and the earth is a capacitor 406. The voltage on capacitor 406 is the average voltage of the capacitors 406. Sync signals. The output of the XOR 400 gate feeds an input of the XOR gate 402. The other input of the XOR gate 402 is coupled with a logic high signal. The output of the XOR 402 gate will be a 02092. 0001 negative forward pulse every time the synchronization signal is activated regardless of the normal state of the synchronization signal. The outputs of the synchronization polarizer 362 are coupled to a horizontal and vertical synchronization input in an on-screen processor 364. The on-screen processor produces red, green and blue video signals that display or display one or more alphanumeric characters that are programmed in your internal video ROM. To dictate which characters will be placed on the video screen, the CPU 80 generates I2C interface signals in series on a pair of conductors 363 and 365. These signals are applied to the on-screen processor 364 which causes the processor to recover from the internal video RAM the characters that will be displayed on the display. video. The on-screen processor 364 provides two signals HBFK and HTONE which it supplies to an overlaid logic control circuit 366. Also supplied to the superimposed control logic circuit, there are four signals of the CPU 80 of the user capsule. These four signals are H Tone Enable, OSD Enable, System Video Enable and Transparent. The superimposed control logic circuit 366 reads the value of these logic signals and activates or deactivates a set of buffer memories or tristate buffer memories 368, 370 and 372 in the buffer memories or tristate buffer memories 352, 354 and 356 These tri-state dampening memories 368, 370 and 372 couple the outputs of the on-screen processor 364 with the conductors which are connected to the color inputs of the monitor. When the three-state or tri-state buffer memories 353, 354 and 356 are in their high impedance state, and the three-phase buffer memories 02092. 0001 368, 370 and 372 are active, then the video screen will only display or display those signals produced by the on-screen processor. Conversely, if the buffer memories 368, 370 and 372 are in their high impedance state, and the three-state or tristate buffer memories 352, 354 and 356 are active, then the monitor displays or displays the video signals produced by the monitor. remote computer system. If the two sets of tri-state buffer 368, 370, 372 and 352, 354 and 356 are active, then the monitor will display the video signals produced by both the on-screen processor and the remote computer system. The following is a Table that defines the logic of the superimposed control logic circuit 366. 02092. 0001 02092. 0001 It is considered that the construction of the superimposed control logic circuit 366 provided by the above Table is within the skill of any engineer in digital electronics. To activate the display or display of programming on the screen, the user begins the escape sequence by pressing the "printscreen" key. The CPU inside the user's capsule recognizes this key and produces a menu on the video screen. The user then selects one or more menu items by typing them on the keyboard or moving the mouse. The CPU then interprets these mouse / keyboard inputs as commands that will be transmitted to the central point of contact switch. Once the user completes a command by activating the "enter" key, the CPU can generate one or more packets that will be transmitted to the central point of contact switch, which allows the user to connect to a different computer, monitor the status from a different computer, etc. 02092. 0001 As can be seen, the present invention allows a user to access any of thirty-two computers remotely located from a central workstation. The system operates separately from a network, so that if the network fails, the user can still have access to each of the server's computers. In addition, the capsules act as translators between different types of keyboard / monitor and different computers. Because all capsule-to-capsule packages have the same format, previously incompatible equipment can be easily coupled. While the preferred embodiment of the invention has been shown and described, it will be appreciated that various changes may be made in the present without departing from the spirit and scope of the invention. For example, although the present invention is described with respect to work stations that are connected to computers remotely located for system administration purposes, it will be appreciated that the invention also has additional uses. For example, it may be desirable to locate expensive computational equipment away from relatively inexpensive or low-cost terminals. Therefore, the present invention could be used in academic assignments where it is desirable to allow students to operate computers located remotely from one or more work stations. It is believed that the present invention has numerous applications, since it is desirable to separate the computer equipment from the display computer and from the data entry devices. Therefore, the scope of the invention will be determined only from the following claims. 02092. 0001

Claims (8)

1. CLAIMS: 1. A system for connecting several work stations of the type that includes a keyboard, a mouse and a video monitor with several remote computer systems, comprising: A plurality of first signal conditioning units coupled to the work stations to receive electronic signals produced by the keyboard and the mouse and to create a serial data packet that includes the electronic signals; A plurality of first communication links coupled to the first signal conditioning units for transporting serial data packets; A central point of contact switch including several inputs and several outputs, the central point of contact switch receives the serial data packets from one input and routes the serial data packet to one or more of the outputs; A plurality of second communication links coupled with the outputs of the central point of contact switch; and A plurality of second signal conditioning units coupled to the remote computer systems, for receiving the serial data packets transmitted on one of the communication links of the plurality of second switch communication links and for supplying the packets of data to a keyboard and mouse input of the remote computer. The system according to claim 1, wherein the plurality of second signal conditioning units receive video signals produced by the remote computer systems and transmit the video signals towards 02092. 0001 the central switch in a communication link of the plurality of second communication links. The system according to claim 2, wherein the video signals include a red, green and blue video signal, as well as a horizontal and vertical synchronization signal and, wherein each of the second signal conditioning units includes a encoder circuit that encodes the horizontal and vertical synchronization signal in two of the red, green or blue video signals before the video signals are transmitted to the central switch. The system according to claim 3, wherein the video signals include a signal so as to indicate a polarity of the horizontal and vertical synchronization signal and, where the encoder circuit encodes the signal in one of the signals of red, green or blue video before the video signals are transmitted to the central switch. The system according to claim 3, wherein the first signal conditioning units include a decoder circuit for eliminating the horizontal and vertical synchronization signals of the red, green or blue video signals. The system according to claim 5, wherein the decoder circuit removes the signal from the red, green or blue video signals. The system according to claim 6, wherein the decoder circuit includes a circuit for adjusting the polarity of the horizontal and vertical synchronization signals based on the decoded mode signal. The system according to claim 7, further comprising a screen programming circuit included in the first signal conditioning unit, the 02092. 0001 on-screen programming circuit produces video signals that are displayed or displayed by the video monitor. 02092. 0001