TWI771113B - Kvm system and operation method of routing device - Google Patents

Abstract

A Keyboard-Video-Mouse (KVM) system and an operation method of routing device are provided. The KVM system includes a controller and a routing device. The routing device includes a plurality of channel circuits and a multiplexer. The first ends of the channel circuits are coupled to the selection ports of the routing device. The selection terminals of the multiplexer are coupled to the second ends of the channel circuits. The common terminal of the multiplexer is coupled to the common port of the routing device. The multiplexer selects a channel circuit from the channel circuits to couple the second end of the selected channel circuit to the common port of the routing device. The selected channel circuit selectively provides a first degree of attenuation. A non-selected channel circuit of the channel circuits selectively provides a second degree of attenuation higher than the first degree of attenuation.

Description

The operation method of the multi-computer switch and the routing device

The present invention relates to a routing device, and more particularly, to a multi-computer switch and an operating method of the routing device.

A keyboard/video/mouse (KVM) switch, also known as a multi-computer switch, refers to a device that can share the same set of peripheral devices on multiple hosts. Wherein, the peripheral device may include one or more of a keyboard, a screen, a mouse, a speaker and the like. Generally speaking, KVM switches have multiplexers (such as dual four-channel analog multiplexers, such as 74HC4052) to switch the connections between multiple hosts and peripheral devices. However, for various reasons, crosstalk problems may occur between different select ends of the multiplexer. For example, the signal (such as audio, video, text data, etc.) transmitted by the current selection end of the multiplexer will be leaked into the transmission channels of other selection ends (not the current selection end) of the multiplexer, and become the return path noise. information (return path noise).

In view of this, the present invention provides an operation method of a KVM switch and a routing device to effectively attenuate return path noise.

In an embodiment of the present invention, the KVM switch includes a controller and a routing device. The controller is used for sending out a plurality of control signals and a selection signal. The routing device is coupled to the controller. The routing device includes multiple selection ports, multiple channel circuits, common ports and multiplexers. The first end of each channel circuit is respectively coupled to one of the selection ports. Based on the control signals, a selected one of the channel circuits selectively provides a first degree of attenuation. An unselected channel circuit of the channel circuits selectively provides a second degree of attenuation higher than the first degree of attenuation. The multiplexer has multiple select terminals and a common terminal. Each selection end of the multiplexer is respectively coupled to the second end of one of the channel circuits. The common terminal is coupled to the common port. The multiplexer selects the selected channel circuit from the channel circuits based on the selection signal to couple the second end of the selected channel circuit to the common port.

In an embodiment of the present invention, the operation method of the routing device includes: selecting, by a multiplexer, a selected channel circuit from a plurality of channel circuits of the routing device, so as to couple the selected channel circuit to the routing device. a common port, wherein the first end of each channel circuit is respectively coupled to one of the multiple selection ports of the routing device, and each multiple selection end of the multiplexer is respectively coupled to one of the channel circuits the second end of the ; a first degree of attenuation is selectively provided by the selected channel circuit; and a second degree of attenuation higher than the first degree of attenuation is selectively provided by an unselected channel circuit of one of the channel circuits.

Based on the above, the channel circuit of the routing device according to the embodiments of the present invention can selectively provide different attenuation degrees to the signal passing through the channel according to whether it is selected or not. For example, unselected channel circuits can selectively provide a higher attenuation level (second attenuation level) to effectively reduce noise/crosstalk. The selected channel circuit may selectively provide a lower degree of attenuation (first degree of attenuation).

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, the following embodiments are given and described in detail with the accompanying drawings as follows.

The term "coupled (or connected)" as used throughout this specification (including the scope of the application) may refer to any direct or indirect means of connection. For example, if it is described in the text that a first device is coupled (or connected) to a second device, it should be interpreted that the first device can be directly connected to the second device, or the first device can be connected to the second device through another device or some other device. indirectly connected to the second device by a connecting means. Terms such as "first" and "second" mentioned in the full text of the description of this application (including the scope of the patent application) are used to name the names of elements, or to distinguish different embodiments or ranges, rather than to limit the upper limit or the number of elements. The lower limit is not intended to limit the order of elements. Also, where possible, elements/components/steps using the same reference numerals in the drawings and embodiments represent the same or similar parts. Elements/components/steps that use the same reference numerals or use the same terminology in different embodiments may refer to relative descriptions of each other.

For various reasons, crosstalk problems may occur between different select ends of the multiplexer. For example, the signal transmitted by the current selection terminal of the multiplexer will be leaked into the transmission channel of other selection terminals (not the current selection terminal) of the multiplexer, and become return path noise. In order to reduce the noise in the return path, in some embodiments, a voltage divider resistor is set in the transmission channel connected to each selection end of the multiplexer. That is, attenuation levels are provided in these transmission paths to reduce return path noise. However, the resistance value of the voltage divider depends on the degree of influence of the return path noise on different hosts, so it is difficult to design. Furthermore, the voltage divider resistor configured in the transmission channel will reduce the amplitude of the current transmission signal, so it is necessary to configure an additional power amplifier in the signal path connected to the common end of the multiplexer, thereby increasing the computer switch (and the cost of a KVM switch). In addition, the additional power amplifier will amplify the background noise and reduce the signal-to-noise ratio.

FIG. 1 is a schematic block diagram of a circuit of a KVM switch 100 according to an embodiment of the present invention. The KVM switch 100 includes a routing device 101 and a controller 102 . The controller 102 can send a plurality of control signals (eg, the control signals S1 - Sn) and selection signals (eg, the selection signal SM) to the routing device 101 . In some embodiments, the KVM switch 100 can allow the user to input commands through an operation interface (not shown), and the controller 102 can correspondingly send out the control signals S1 -Sn and the selection signal SM according to the commands input by the user. The number of the control signals S1-Sn and the selection signal SM may be determined according to design requirements, which is not limited in this embodiment.

According to different design requirements, the implementation of the controller 102 may be in the form of hardware, firmware, software (ie, programs), or a combination of the foregoing three. In hardware, the controller 102 may be implemented as a logic circuit on an integrated circuit. The related functions of the controller 102 may be implemented in hardware using a hardware description language (eg, Verilog HDL or VHDL) or other suitable programming language. For example, the related functions of controller 102 may be implemented in one or more microcontrollers, microprocessors, application specific integrated circuits (ASICs), digital signal processors (DSPs), field programmable logic gate arrays ( FPGA) and/or various logic blocks, modules and circuits in other processing units. In the form of software and/or firmware, the relevant functions of the controller 102 can be implemented as programming code, such as using a general programming language (eg, C, C++ or assembly language) or other suitable programming languages. The programming code may be recorded/stored in "non-transitory computer readable media" including, for example, read-only memory, tape, disk, card, semiconductor memory, programmable logic circuits and/or storage devices . A computer, a central processing unit, a microcontroller or a microprocessor can read and execute the programming code from the non-transitory computer-readable medium to achieve related functions.

In the embodiment shown in FIG. 1, the routing device 101 can be coupled to the controller 102 to receive the control signals S1-Sn and the selection signal SM. The routing device 101 includes a plurality of selection ports (eg, selection ports P1 - Pn), a plurality of channel circuits (eg, channel circuits 110_1 - 110_n), a multiplexer 120 and a common port COM. The number n of the selection ports P1 ˜Pn and the channel circuits 110_1 ˜ 110_n can be determined according to design requirements, which is not limited in this embodiment. According to practical applications, the selection ports P1-Pn can be coupled to multiple hosts, such as servers, workstations, personal computers, notebook computers or other hosts. According to design requirements, in some embodiments, the layout positions of the channel circuits 110_1 ˜ 110_n of the routing device 101 may be relatively close to the selection ports P1 ˜Pn.

In this embodiment, each of the channel circuits 110_1 ˜ 110_n has a first terminal and a second terminal. The first end of each of the channel circuits 110_1 ˜ 110_n is coupled to a corresponding one of the selection ports P1 ˜Pn of the routing device 101 . For example, the first end of the channel circuit 110_1 is coupled to the selection port P1, and the first end of the channel circuit 110_n is coupled to the selection port Pn. The multiplexer 120 has a plurality of selection terminals (eg, selection terminals C1 to Cn) and one common terminal (eg, the common terminal CM). Each of the selection terminals C1 ˜ Cn is respectively coupled to the second terminal of a corresponding one of the channel circuits 110_1 ˜ 110_n. For example, the selection terminal C1 of the multiplexer 120 is coupled to the second terminal of the channel circuit 110_1, and the selection terminal Cn of the multiplexer 120 is coupled to the second terminal of the channel circuit 110_n. The common terminal CM of the multiplexer 120 is coupled to the common port COM of the routing device 101 . According to practical applications, the common port COM can be coupled to peripheral devices, such as a keyboard, a screen, a mouse, a speaker or other devices.

In this embodiment, the multiplexer 120 can select a channel circuit from the channel circuits 110_1 ˜ 110_n based on the selection signal SM sent by the controller 102 to couple the second end of the selected channel circuit to the common port COM . The channel circuits 110_1 ˜ 110_n can selectively provide different degrees of attenuation to the signals passing through the channel circuits 110_1 ˜ 110_n based on the control signals S1 ˜Sn sent by the controller 102 , respectively. For example, the multiplexer 120 may select the channel circuit 110_1 based on the control signal S1, and the selected channel circuit 110_1 may selectively provide a lower attenuation level (first attenuation level) based on the control signal S1. In addition, other channel circuits (unselected channel circuits, such as the channel circuit 110_n) can also selectively provide a second attenuation degree higher than the first attenuation degree based on the control signal (eg Sn). In this way, when the signal passed through the selected channel circuit 110_1 is cross-talked to other channel circuits 110_n, the channel circuit 110_n can provide a higher attenuation level (the second attenuation level), so that the return path generated by the cross-talk is noisy. The signal can be attenuated to a greater extent to solve the problem of crosstalk. For the implementation details of the channel circuits 110_1 to 110_n, reference may be made to various embodiments described later.

FIG. 2 is a schematic flowchart of an operation method of a routing device according to an embodiment of the present invention. Please refer to FIG. 1 and FIG. 2 . In step S210, the multiplexer 120 in the routing device 101 can select a channel circuit from the channel circuits 110_1-110_n in the routing device 101 according to the selection signal SM, and couple the second end of the selected channel circuit to the routing device 101 common port COM. In step S220, the selected channel circuits of the channel circuits 110-110_n may selectively provide the first attenuation degree, and one (or more) unselected channel circuits of the channel circuits 110-110_n may selectively provide A second degree of attenuation higher than the first degree of attenuation.

FIG. 3 is a schematic block diagram of a channel circuit 300 according to an embodiment of the present invention. The channel circuit 300 shown in FIG. 3 can be used as an implementation example of any one of the channel circuits 110_1 ˜ 110_n in FIG. 1 . The channel circuit 300 shown in FIG. 3 may refer to the relevant description of any one of the channel circuits 110_1 to 110_n shown in FIG. 1 , and the selection port P2 shown in FIG. 3 may refer to the relevant description of any one of the selection ports P1 to Pn shown in FIG. 1 . The multiplexer 120 shown in FIG. 3 may refer to the related description of the multiplexer 120 shown in FIG. 1 , and (or) the selection terminal C2 shown in FIG. 3 may refer to the relevant description of any one of the selection terminals C1 to Cn shown in FIG. 1 . illustrate. For any one of the channel circuits 110_1 to 110_n shown in FIG. 1 , reference may be made to the related description of the channel circuit 300 shown in FIG. 3 .

In the embodiment shown in FIG. 3 , the channel circuit 300 may be coupled to a corresponding selection port (eg selection port P2 ) of the routing device 101 and a corresponding selection terminal (eg selection terminal) of the selection terminals C1 - Cn of the multiplexer 120 C2) between. In the embodiment shown in FIG. 3 , the channel circuit 300 may include a resistor R1 and a controllable current path circuit 310 . The first terminal of the resistor R1 is coupled to the selection port P2 , and the second terminal of the resistor R1 is coupled to the selection terminal C2 of the multiplexer 120 . According to the actual design, in the embodiment shown in FIG. 3 , the controllable current path circuit 310 may be coupled to the first end of the resistor R1 . The controllable current path circuit 310 may be controlled by a corresponding one of the control signals S1 ˜ Sn (eg, the control signal S2 ). According to the control signal S2 sent by the controller 102 , the controllable current path circuit 310 can change the signal attenuation degree of the channel circuit 300 . For example, when the controller 102 and the multiplexer 120 select the channel circuit 300, the controllable current path circuit 310 may not draw current (at this time, the channel circuit 300 has the first attenuation level). When the controller 102 and the multiplexer 120 do not select the channel circuit 300, the controllable current path circuit 310 can draw current from the first end of the resistor R1, for example, the voltage dividing resistor of the controllable current path circuit 310 (described in detail later) can be The voltage of the first end of the resistor R1 is pulled down (at this time, the channel circuit 300 has a higher second attenuation degree). Based on the voltage dividing operation between the controllable current path circuit 310 and the resistor R1, the return path noise from the corresponding selection terminal C2 to the selection port P2 can be attenuated as much as possible.

FIG. 4 is a circuit block diagram illustrating the controllable current path circuit 310 shown in FIG. 3 according to an embodiment of the present invention. In the embodiment shown in FIG. 4 , the controllable current path circuit 310 may include a resistor R2 (voltage dividing resistor) and a switch SW. The first terminal of the switch SW may be coupled to the first terminal of the resistor R1. The first terminal of the resistor R2 is coupled to the second terminal of the switch SW. The second end of the resistor R2 can be coupled to the reference voltage VSS (eg, a ground voltage or other fixed voltages). In this embodiment, the switch SW can be controlled by the control signal S2 of the controller 102 to change the attenuation degree of the channel circuit 300 . For example, when the control signal S2 indicates that the channel circuit 300 is the selected channel circuit, the switch SW is turned off. At this time, the channel circuit 300 attenuates the signal passing through the resistor R1 with the first attenuation degree. Conversely, when the control signal S2 indicates that the channel circuit 300 is an unselected channel circuit, the switch SW is turned on. At this time, the channel circuit 300 attenuates the signal passing through the resistor R1 by a second attenuation degree (higher than the first attenuation degree). Therefore, the signal amplitude of the return path noise from the corresponding selection terminal C2 to the selection port P2 can be reduced as much as possible. In other embodiments, the positions of the resistor R2 and the switch SW can be interchanged, and are not limited to the coupling manner shown in FIG. 4 .

FIG. 5 is a circuit block diagram of a channel circuit 600 according to another embodiment of the present invention. The channel circuit 600 shown in FIG. 5 can be used as an implementation example of any one of the channel circuits 110_1 ˜ 110_n in FIG. 1 . The channel circuit 600 shown in FIG. 5 may refer to the relevant description of any one of the channel circuits 110_1 to 110_n shown in FIG. 1 , and the selection port P2 shown in FIG. 5 may refer to the relevant description of any one of the selection ports P1 to Pn shown in FIG. 1 . The multiplexer 120 shown in FIG. 5 may refer to the relevant description of the multiplexer 120 shown in FIG. 1 , and (or) the selection terminal C2 shown in FIG. 5 may refer to the relevant description of any one of the selection terminals C1 to Cn shown in FIG. 1 . illustrate. For any one of the channel circuits 110_1 to 110_n shown in FIG. 1 , reference may be made to the related description of the channel circuit 600 shown in FIG. 5 .

In this embodiment, the channel circuit 600 may be coupled between a corresponding selection port (eg, selection port P2 ) of the routing device 101 and a corresponding selection terminal (eg, selection terminal C2 ) of the multiplexer 120 . According to design requirements, the channel circuit 600 may include a resistor R1 and a controllable current path circuit 610 . The first terminal of the resistor R1 is coupled to the selection port P2 , and the second terminal of the resistor R1 is coupled to the selection terminal C2 of the multiplexer 120 . The channel circuit 600 , the resistor R1 and the controllable current path circuit 610 shown in FIG. 6 can be deduced by referring to the related description of the channel circuit 300 , the resistor R1 and the controllable current path circuit 310 shown in FIG. 3 . Different from the embodiment shown in FIG. 3 , the controllable current path circuit 610 shown in FIG. 5 may be coupled to the second end of the resistor R1 . According to the control signal S2 sent by the controller 102 , the controllable current path circuit 610 can change the signal attenuation degree of the channel circuit 600 . For example, when the controller 102 and the multiplexer 120 select the channel circuit 600, the controllable current path circuit 610 may not draw current (when the channel circuit 600 has the first attenuation level). When the controller 102 and the multiplexer 120 do not select the channel circuit 600, the controllable current path circuit 610 can draw current from the second end of the resistor R1, for example, the voltage dividing resistor of the controllable current path circuit 610 (described in detail later) can be Pull down the voltage of the second end of the resistor R1 (at this time, the channel circuit 600 has a higher second attenuation degree). Based on the voltage dividing operation between the controllable current path circuit 610 and the resistor R1, the noise from the selection port P2 to the corresponding selection terminal C2 can be attenuated as much as possible.

FIG. 6 is a circuit block diagram illustrating the controllable current path circuit 610 shown in FIG. 5 according to an embodiment of the present invention. In the embodiment shown in FIG. 6 , the controllable current path circuit 610 may include a resistor R2 and a switch SW. The first terminal of the switch SW can be coupled to the second terminal of the resistor R1. The first terminal of the resistor R2 is coupled to the second terminal of the switch SW. The second end of the resistor R2 can be coupled to the reference voltage VSS (eg, a ground voltage or other fixed voltages). The switch SW can be controlled by the control signal S2 of the controller 102 to change the attenuation degree of the channel circuit 600 . For example, when the control signal S2 indicates that the channel circuit 600 is the selected channel circuit, the switch SW is turned off. At this time, the channel circuit 600 attenuates the signal passing through the resistor R1 with the first attenuation degree. Conversely, when the control signal S2 indicates that the channel circuit 600 is an unselected channel circuit, the switch SW is turned on. At this time, the channel circuit 600 attenuates the signal passing through the resistor R1 by a second attenuation degree (higher than the first attenuation degree). Therefore, the signal amplitude of the noise from the selection port P2 to the corresponding selection terminal C2 can be reduced as much as possible. In other embodiments, the positions of the resistor R2 and the switch SW can be interchanged, and are not limited to the coupling manner shown in FIG. 6 .

FIG. 7 is a circuit block diagram of a channel circuit 900 according to another embodiment of the present invention. The channel circuit 900 shown in FIG. 7 can be used as an implementation example of any one of the channel circuits 110_1 to 110_n in FIG. 1 . The channel circuit 900 shown in FIG. 7 may refer to the relevant description of any one of the channel circuits 110_1 to 110_n shown in FIG. 1 , and the selection port P3 shown in FIG. 7 may refer to the relevant description of any one of the selection ports P1 to Pn shown in FIG. 1 . The multiplexer 120 shown in FIG. 7 may refer to the related description of the multiplexer 120 shown in FIG. 1 , and (or) the selection terminal C3 shown in FIG. 7 may refer to the relevant description of any one of the selection terminals C1 to Cn shown in FIG. 1 . illustrate. For any one of the channel circuits 110_1 to 110_n shown in FIG. 1 , reference may be made to the related description of the channel circuit 900 shown in FIG. 7 .

In this embodiment, the channel circuit 900 may be coupled between a corresponding selection port (eg, selection port P3 ) of the routing device 101 and a corresponding selection terminal (eg, selection terminal C3 ) of the multiplexer 120 . In the embodiment shown in FIG. 7 , the channel circuit 900 may include a resistor R1 , a resistor R2 and a controllable current path circuit 910 . The first end of the resistor R1 is coupled to the selection port P3. The first end of the resistor R2 is coupled to the second end of the resistor R1. The second terminal of the resistor R2 is coupled to the selection terminal C3 of the multiplexer 120 . The controllable current path circuit 910 may be coupled to the second end of the resistor R1 and the first end of the resistor R2. The controllable current path circuit 910 may be controlled by a corresponding one of the control signals S1 ˜ Sn (eg, the control signal S3 ). According to the control signal S3 sent by the controller 102 , the controllable current path circuit 910 can change the signal attenuation degree of the channel circuit 900 .

For example, when the controller 102 and the multiplexer 120 select the channel circuit 900, the controllable current path circuit 910 may not draw current (at this time, the channel circuit 900 has the first attenuation level). When the controller 102 and the multiplexer 120 do not select the channel circuit 900 , the controllable current path circuit 910 can draw current from the second end of the resistor R1 and the first end of the resistor R2 , such as the voltage divider of the controllable current path circuit 910 . A resistor (described in detail later) can pull down the voltage at the second end of the resistor R1 (at this time, the channel circuit 900 has a higher second attenuation level). Based on the voltage dividing operation of the controllable current path circuit 910, the return path noise from the corresponding selection terminal C3 to the selection port P3 can be attenuated, and the noise from the selection port P3 to the corresponding selection terminal C3 can also be attenuated.

FIG. 8 is a circuit block diagram of a channel circuit 1000 according to yet another embodiment of the present invention. The channel circuit 1000 shown in FIG. 8 can be used as an implementation example of any one of the channel circuits 110_1 ˜ 110_n in FIG. 1 . The channel circuit 1000 shown in FIG. 8 may refer to the relevant description of any one of the channel circuits 110_1 to 110_n shown in FIG. 1 , and the selection port P4 shown in FIG. 8 may refer to the relevant description of any one of the selection ports P1 to Pn shown in FIG. 1 . The multiplexer 120 shown in FIG. 8 may refer to the related description of the multiplexer 120 shown in FIG. 1 , and (or) the selection terminal C4 shown in FIG. 8 may refer to the relevant description of any one of the selection terminals C1 to Cn shown in FIG. 1 . illustrate. For any one of the channel circuits 110_1 to 110_n shown in FIG. 1 , reference may be made to the related description of the channel circuit 1000 shown in FIG. 8 .

In the embodiment shown in FIG. 8 , the channel circuit 1000 may be coupled to a corresponding selection port (eg, selection port P4 ) among the selection ports P1 ˜Pn of the routing device 101 and a corresponding one of the selection terminals C1 ˜Cn of the multiplexer 120 . between select terminals (eg select terminal C4). The channel circuit 1000 may include a switch SW1 , a switch SW2 and a voltage divider circuit 1010 . The common terminal of the switch SW1 is coupled to the selection port P4. The common terminal of the switch SW2 is coupled to the selection terminal C4 of the multiplexer 120 . The voltage divider circuit 1010 is coupled between the first selection terminal of the switch SW1 and the first selection terminal of the switch SW2. The second selection terminal of the switch SW2 is coupled to the second selection terminal of the switch SW1. According to design requirements, the switches SW1 and SW2 may be controlled by corresponding control signals in the control signals S1 - Sn (for example, both are controlled by the control signal S4 ). The switches SW1 and SW2 can change the attenuation level of the signal provided by the channel circuit 1000 according to the control signal S4 sent by the controller 102 . For example, when the control signal S4 indicates that the channel circuit 1000 is the selected channel circuit, the switches SW1 and SW2 can bypass the voltage divider circuit 1010 to electrically connect the selection port P4 to the selection terminal C4 of the multiplexer 120 . At this time, the signal attenuation degree of the channel circuit 1000 is the first attenuation degree.

Conversely, when the control signal S4 indicates that the channel circuit 1000 is an unselected channel circuit, the switch SW1 can couple the selection port P4 to the voltage divider circuit 1010 , and the switch SW2 can couple the selection terminal C4 of the multiplexer 120 to the voltage divider circuit 1010 . At this time, the signal attenuation degree of the channel circuit 1000 is the second attenuation degree (greater than the first attenuation degree). The channel circuit 1000 attenuates the signal passing through the channel circuit 1000 with a second, higher degree of attenuation. Therefore, the signal amplitude of the return path noise from the corresponding selection terminal C4 to the selection port P4 can be reduced, and/or the signal amplitude of the noise from the selection port P4 to the corresponding selection terminal C4 can be reduced.

FIG. 9 is a circuit block diagram illustrating the voltage divider circuit 1010 shown in FIG. 8 according to an embodiment of the present invention. In the embodiment shown in FIG. 9 , the voltage dividing circuit 1010 may include a resistor R101 and a resistor R102 . The first terminal of the resistor R101 is coupled to the first selection terminal of the switch SW1. The second terminal of the resistor R101 is coupled to the first selection terminal of the switch SW2. The first end of the resistor R102 may be coupled to the first end of the resistor R101. The second end of the resistor R102 is coupled to the reference voltage VSS (eg, ground voltage or other fixed voltages). When the control signal S4 indicates that the channel circuit 1000 is an unselected channel circuit, the signal will flow through the voltage divider circuit 1010 . At this time, the signal amplitude of the return path noise from the corresponding selection terminal C4 to the selection port P4 can be reduced by voltage division.

FIG. 10 is a circuit block diagram illustrating the voltage divider circuit 1010 shown in FIG. 8 according to another embodiment of the present invention. In this embodiment, the voltage dividing circuit 1010 may include a resistor R101 and a resistor R102. The voltage dividing circuit 1010 , the resistor R101 and the resistor R102 shown in FIG. 10 can be analogized with reference to the voltage dividing circuit 1010 , the resistor R101 and the resistor R102 shown in FIG. 9 . The difference from FIG. 9 is that the first end of the resistor R102 shown in FIG. 10 can be coupled to the second end of the resistor R101 . When the control signal S4 indicates that the channel circuit 1000 is an unselected channel circuit, the signal will flow through the voltage divider circuit 1010 . At this time, the signal amplitude of the noise from the selection port P4 to the corresponding selection terminal C4 can be reduced by voltage division.

FIG. 11 is a circuit block diagram illustrating the voltage divider circuit 1010 shown in FIG. 8 according to another embodiment of the present invention. As shown in FIG. 11 , the voltage dividing circuit 1010 may include a resistor R103 , a resistor R104 and a resistor R105 . The first terminal of the resistor R103 is coupled to the first selection terminal of the switch SW1. The first end of the resistor R104 is coupled to the second end of the resistor R103. The second terminal of the resistor R104 is coupled to the first selection terminal of the switch SW2. The first end of the resistor R105 is coupled to the second end of the resistor R103 and the first end of the resistor R104. The second end of the resistor R105 is coupled to the reference voltage VSS. When the controller 102 and the multiplexer 120 do not select the channel circuit 1000 , the signal will flow through the voltage divider circuit 1010 . Based on the voltage dividing operation of the voltage dividing circuit 1010, the return path noise from the corresponding selection terminal C4 to the selection port P4 can be attenuated, and the noise from the selection port P4 to the corresponding selection terminal C4 can also be attenuated.

To sum up, the channel circuit according to the embodiments of the present invention can selectively provide different attenuation degrees to the signal passing through the channel according to whether it is selected or not. For example, unselected channel circuits can selectively provide a higher second attenuation level to effectively reduce noise/crosstalk. The selected channel circuit may selectively provide a lower first attenuation level.

Although the present invention has been disclosed above by the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, The protection scope of the present invention shall be determined by the scope of the appended patent application.

100: Multi-computer switcher 101: Routing device 102: Controller 110_1, 110_n, 300, 600, 900, 1000: Channel circuit 120: Multiplexer 310, 610, 910: Controllable Current Path Circuits 1010: Voltage divider circuit C1, C2, C3, C4, Cn: select end CM: common terminal COM:Common port P1, P2, P3, P4, Pn: Port selection R1, R2, R101, R102, R103, R104, R105: Resistors S1, S2, S3, S4, Sn: control signal S210, S220: steps SM: select signal SW, SW1, SW2: switch VSS: reference voltage

FIG. 1 is a schematic block diagram of a circuit of a KVM switch according to an embodiment of the present invention. FIG. 2 is a schematic flowchart of an operation method of a routing device according to an embodiment of the present invention. FIG. 3 is a circuit block diagram of a channel circuit according to an embodiment of the present invention. FIG. 4 is a circuit block diagram illustrating the controllable current path circuit shown in FIG. 3 according to an embodiment of the present invention. FIG. 5 is a circuit block diagram of a channel circuit according to another embodiment of the present invention. FIG. 6 is a circuit block diagram illustrating the controllable current path circuit shown in FIG. 5 according to an embodiment of the present invention. FIG. 7 is a circuit block diagram of a channel circuit according to still another embodiment of the present invention. FIG. 8 is a circuit block diagram of a channel circuit according to yet another embodiment of the present invention. FIG. 9 is a circuit block diagram illustrating the voltage divider circuit shown in FIG. 8 according to an embodiment of the present invention. FIG. 10 is a circuit block diagram illustrating the voltage divider circuit shown in FIG. 8 according to another embodiment of the present invention. FIG. 11 is a circuit block diagram illustrating the voltage divider circuit shown in FIG. 8 according to another embodiment of the present invention.

100: Multi-computer switcher

101: Routing device

102: Controller

110_1, 110_n: channel circuit

120: Multiplexer

C1, Cn: selection terminal

CM: common terminal

COM:Common port

P1, Pn: select port

S1, Sn: control signal

SM: select signal

Claims (10)

A multi-computer switcher comprising: a controller for issuing a plurality of control signals and a selection signal; and A routing device coupled to the controller, wherein the routing device includes: Multiple choice ports; a plurality of channel circuits, wherein each of the channel circuits has a first end and a second end, the first end of each of the channel circuits is respectively coupled to one of the selection ports, and based on the the control signals, a selected channel circuit of the channel circuits selectively provides a first degree of attenuation, and an unselected channel circuit of the channel circuits selectively provides a degree of attenuation higher than the first degree of attenuation the second degree of attenuation; a common port; and A multiplexer has a plurality of selection terminals and a common terminal, wherein each of the selection terminals of the multiplexer is respectively coupled to the second terminal of one of the channel circuits, and the common terminal is coupled to to the common port, and the multiplexer selects the selected channel circuit from the channel circuits based on the selection signal to couple the second end of the selected channel circuit to the common port. The KVM switch of claim 1, wherein any one of the channel circuits comprises: a first resistor having a first end coupled to one of the selection ports, wherein a second end of the first resistor is coupled to one of the selection ports of the multiplexer; and A controllable current path circuit coupled to the first end or the second end of the first resistor, wherein the controllable current path circuit is controlled by a corresponding control signal among the control signals. The KVM switch of claim 2, wherein the controllable current path circuit comprises: a switch, a first end of which is coupled to the first end or the second end of the first resistor, wherein the switch is controlled by the corresponding control signal; and A second resistor, the first end of which is coupled to a second end of the switch, wherein a second end of the second resistor is coupled to a reference voltage. The KVM switch of claim 2, wherein the controllable current path circuit comprises: a second resistor, a first end of which is coupled to the first end or the second end of the first resistor; and A switch has a first end coupled to a second end of the second resistor, wherein a second end of the switch is coupled to a reference voltage, and the switch is controlled by the corresponding control signal. The KVM switch of claim 1, wherein any one of the channel circuits comprises: a first resistor having a first end coupled to one of the selection ports; a second resistor having a first end coupled to a second end of the first resistor, wherein a second end of the second resistor is coupled to one of the selection ends of the multiplexer; and a controllable current path circuit coupled to the second end of the first resistor and the first end of the second resistor, wherein the controllable current path circuit is controlled by a corresponding control signal among the control signals . The KVM switch of claim 5, wherein the controllable current path circuit comprises: a switch, a first end of which is coupled to the second end of the first resistor and the first end of the second resistor, wherein the switch is controlled by the corresponding control signal; and A third resistor, the first end of which is coupled to a second end of the switch, wherein a second end of the third resistor is coupled to a reference voltage. The KVM switch of claim 1, wherein any one of the channel circuits comprises: a first switch having a first selection terminal, a second selection terminal and a first common terminal, wherein the first common terminal of the first switch is coupled to one of the selection ports, and the first A switch is controlled by a corresponding control signal among the control signals; a second switch having a third selection terminal, a fourth selection terminal and a second common terminal, wherein the second common terminal of the second switch is coupled to one of the selection terminals of the multiplexer , the fourth selection terminal of the second switch is coupled to the second selection terminal of the first switch, and the second switch is controlled by the corresponding control signal; and A voltage divider circuit is coupled between the first selection terminal of the first switch and the third selection terminal of the second switch. The KVM switch of claim 7, wherein the voltage divider circuit comprises: a first resistor, a first terminal and a second terminal of which are respectively coupled to the first selection terminal of the first switch and the third selection terminal of the second switch; and A second resistor, a first end of which is coupled to the first end or the second end of the first resistor, wherein a second end of the second resistor is coupled to a reference voltage. The KVM switch of claim 7, wherein the voltage divider circuit comprises: a first resistor having a first end coupled to the first selection end of the first switch; a second resistor having a first end coupled to a second end of the first resistor, wherein a second end of the second resistor is coupled to the third selection end of the second switch; and A third resistor has a first end coupled to the second end of the first resistor and the first end of the second resistor, wherein a second end of the third resistor is coupled to a reference voltage. A method of operating a routing device, comprising: A selected channel circuit is selected from a plurality of channel circuits of the routing device by a multiplexer to couple the selected channel circuit to a common port of the routing device, wherein a first channel circuit of each of the channel circuits is one end is respectively coupled to one of the multiple selection ports of the routing device, and each multiple selection ports of the multiplexer is respectively coupled to a second end of one of the channel circuits; selectively providing a first attenuation level by the selected channel circuit; and A second degree of attenuation higher than the first degree of attenuation is selectively provided by an unselected channel circuit of the channel circuits.

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