Passive video multiplexing method and apparatus priority to prior provisional application

• US 7,424,551 B2
• Filed: 09/14/2001
• Issued: 09/09/2008
• Est. Priority Date: 03/29/2001
• Status: Expired due to Fees

• Current Assignee: Avocent Corporation (Vertiv Holdings Co.)
• Original Assignee: Avocent Corporation (Vertiv Holdings Co.)
• Inventors: Thomas, Christopher L., Kirshtein, Philip M., Odyrna, Vic
• Primary Examiner(s): Follansbee; John
• Assistant Examiner(s): Tran; Nghi V
• Application Number:
  US09/951,774
• Publication Number:
  US 20020143996A1
• Time in Patent Office: 2,552 Days
• Field of Search: 709/249, 709/248, 709/250, 709/223, 709/224
• US Class Current: 709/250
• CPC Class Codes: H04L 49/206 Real Time traffic
• CPC Class Codes: H04L 49/35 Switches specially adapted for specific applications
• CPC Class Codes: H04L 67/125 involving control of end-device applications over a network

Abstract

A passive video multiplexing method and apparatus for encoding video synchronization signals within a KVM extension system. A Rack Interface Pod (RIP) is provided for receiving video signals from a network server and providing them to a remote user via a local area network (LAN). The analog signals received by the RIP are transmitted to a Rack Connection Manager (RCM) having video processing logic, a supervisory processor, a KVM switch system, and Ethernet interface circuitry. A plurality of ARI systems are connected to the RCM, and a plurality of network servers, intended to be controlled by the remote user, are connected to each ARI by a respective wiring strip or Pod Expansion Module (PEM). The RCM performs selective switching by sourcing current through a pair of diodes associated with an active channel of the PEM while reverse biasing diodes associated with an inactive channel to select a network server among the plurality of network servers. Switching of video is accomplished without processing the video signals.

Claims

1. A method of encoding video synchronization signals H_sync, V_sync within a keyboard, video, mouse (KVM) extension system, the method comprising:

encoding R, G, B video signals differentially around respective common mode voltage signals, the common mode signals representing encoded functions of combinations of the video synchronization signals; and

differentially driving R, G, B video signals so as to allow removal of their respective common mode signals, such that

(i) a net alternating current produced by each of the differential video signals is substantially zero; and

(ii) a net alternating current produced by encoded synchronization signals is substantially zero.

2. The method of claim 1, wherein said common mode voltage signals representing video synchronization signals are removed via an analog differential amplifier.

3. A method of encoding video synchronization signals within a keyboard, video, mouse (KVM) server management system, the method comprising:

providing a plurality of interface ports for receiving KVM signals from a plurality of servers, each interface port including a differential video channel;

providing a pair of switching diodes for each differential video channel;

multiplexing different video channels down to common differential channels;

encoding R, G, B video signals around their respective common mode signals for each differential channel;

differentially driving R, G, B video signals and their respective common mode signals, said common mode signals representing functions of video synchronization signals H_sync and V_sync, respectively;

switching individual differential video channels by varying common mode voltages of respective individual differential channels, and forward biasing or reverse biasing the switching diodes for enabling or disabling a respective differential channel; and

providing both common mode and differential mode terminations at a receiving end of the R, G, B video signals so as to remove common mode signals from said video signals and extract original video synchronization signals.

4. A method of interfacing KVM signals provided by an Analog Long Interconnect port to network server, said method comprising:

differentially driving R, G, B video channel signals with video synchronization encoded on respective common mode signals, the common mode signals representing encoded functions of combinations of the video synchronization signals;

providing corrective frequency compensation for the transmission losses encountered by R, G, B channel signals in extended cabling;

multiplexing between a plurality of cabling extensions; and

forwarding the R, G, B channel signals to a remote user through a network interface.

5. A keyboard, video, mouse (KVM) server management system, comprising:

a plurality of network interfaces, each interface having network ports for communicating KVM signals to a remote user workstation, each said user workstation communicatively coupled to the network for communicating KVM signals to a plurality of network servers via corresponding network ports; and

a switch for communicating KVM signals between the remote user workstations and a select network server from among said plurality of network servers.

6. A method of encoding video synchronization signals within a keyboard, video, mouse (KVM) server management system, the method comprising:

providing a plurality of interface ports for receiving KVM signals from a plurality of servers;

providing in each server interface port a pair of switching diodes for each differential video channel;

multiplexing differential video channels down to common differential channels;

encoding R, G, B video signals around their respective common mode signals for each differential channel;

differentially driving R, G, B video signals and their respective common mode signals, said common mode signals representing functions of video synchronization signals Hsync and Vsync, respectively;

switching differential channels by varying the common mode voltages of respective channels; and

receiving both common mode and differential mode terminations at a receiving end.

7. The method of claim 6, wherein the switching step further comprising:

forward biasing or reverse biasing the switching diodes in order to enable or disable respective individual channels.

8. The method of claims 7, further comprising:

providing R, G, B video signals so as to remove common mode signals from said video signals; and

extracting original video synchronization signals.

9. A keyboard, video, mouse (KVM) server management system, comprising:

a network interface unit comprising;

a network port communicatively coupled to a network to communicate digitized KVM signals with a remote user workstation via said network;

a plurality of interface ports communicatively coupled directly to a corresponding plurality of servers via corresponding lines;

a signal conditioner to convert native KVM signals from a server into an intermediate format for transmission over one of the corresponding lines;

at least one switch communicatively coupled to at least one interface port for communicating keyboard and mouse signals between a select server among a plurality of servers coupled to said switch via corresponding lines, each line coupled to said switch comprising a plurality of wires, each said wire including a single diode; and

wherein R, G, B signals are encoded around their respective common mode voltage signals using a sync on green encoding on one of R, G, B color components in order to select a server among said plurality of servers, the common mode signals representing encoded functions of combinations of video synchronization signals.

10. A method of encoding video synchronization signals in a keyboard, video, mouse (KVM) server management system, comprising:

communicatively coupling a network port of a network interface unit to a network for communicating digitized KVM signals with a remote user workstation;

communicatively coupling a plurality of interface ports to a corresponding plurality of servers via corresponding lines;

converting native KVM signals from a server into an intermediate format for transmission over one of the corresponding lines;

communicatively coupling at least one switch to at least one interface port for communicating keyboard and mouse signals between a select server among a plurality of servers coupled to said switch via corresponding lines, each line coupled to said switch comprising a plurality of wires, each said wire including a single diode; and

encoding R, G, B signals are around their respective common mode voltage signals using a sync-on-green technique in order to select a server among said plurality of servers, the common mode signals representing encoded functions of combinations of video synchronization signals.

11. A keyboard, video, mouse (KVM) server extension system, comprising:

a network interface unit comprising;

a network port communicatively coupled to a network to communicate digitized KVM signals with a remote user workstation via said network;

an interface port to communicatively couple to a server via a communication link; and

a signal conditioner to convert native KVM signals from the server into an intermediate format for transmission over the communication link.

12. A video signal switch, comprising:

a plurality of server blade backplane slots to receive server blades outputting a corresponding plurality of differentially encoded video signals around a plurality of common mode voltages;

a backplane in which the plurality of server blades in the backplane slots commonly connect and communicate, the backplane including a pair of diodes for each of said blades to control switching among the plurality of differentially encoded video signals; and

at least one receiver communicating with the backplane to receive the differentially encoded video signals switched by the diodes.

13. A switch as in claim 12, wherein the receiver is physically coupled to the backplane.

14. A method of encoding video synchronization signals H_sync, V_sync within a keyboard, video, mouse (KVM) extension system, the method comprising:

encoding R, G, B video signals differentially around respective common mode voltage signals, the common mode signals representing encoded functions of combinations of both the video synchronization signals H_sync, V_sync; and

differentially driving R, G, B video signals so as to allow removal of their respective common mode signals, such that

(i) a net alternating current produced by each of the differential video signals is substantially zero; and

(ii) a net alternating current produced by encoded synchronization signals is substantially zero.