Abstract:
An audio/video distribution system that is cost-effective, highly flexible, and capable of being used over an extended area and without the need for a centralized switching and distribution mechanism. The audio/video distribution system includes a distribution cable, at least one audio/video transmitter, at least one receiver, and a control director. The transmitter is configured to receive signals from at least one audio/video source while the receiver is connected to the distribution cable and configured to receive signals from the distribution cable. The control director is connected to the distribution cable and configured to control the transmitter and receiver.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. patent application Ser. No. 09/683,516, filed Jan. 11, 2002, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/319,011 filed Nov. 25, 2001. 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    a. Field of the Invention  
           [0003]    The present invention relates generally to audio and video distribution systems, and more particularly, to an audio/video distribution system that is configured to connect audio and video sources to video users without the need for a centralized switching and distribution apparatus.  
           [0004]    b. Description of the Prior Art  
           [0005]    It is often necessary to connect, switch, and properly route audio and video signals from sources, such as video cameras with audio capabilities and video tape recorders, for example, to end users over an extended area. The need for such switching capabilities exists in a wide variety of applications including television and video production, surveillance systems, home entertainment systems, and a myriad of other applications where audio and video signals must be connected and properly routed.  
           [0006]    In the past, this connection has been performed with centralized switching arrangements. Such switching arrangements typically utilize a switching matrix that has audio/video inputs, audio/video output, and a manual or automated arrangement for connecting the inputs to the outputs.  
           [0007]    Existing systems focus primarily on providing centralized video switching arrangements. For example, U.S. Pat. No. RE34,611, issued to Fenwick et al, discloses a system wherein video programs are transmitted to independently controlled video monitors via a centralized switching matrix. U.S. Pat. No. 6,160,455, issued to Hayashi et al., describes the switching of video programs using a computer local area network for the program setup and selection, and utilizes a centralized video distributor and routing switcher to distribute the audio/video signals. U.S. Pat. No. 5,889,775, issued to Sawicz et al., describes an entertainment server connected to video distribution boxes through the use of one or more crosspoint (centralized) switches. U.S. Pat. No. 6,104,414, issued to Odryna et al., describes an improved digital centralized switching matrix. U.S. Pat. No. 6,160,455, issued to Hayashi et al., describes the switching of video programs using a computer local area network for the program setup and selection, and utilizes a centralized video distributor and routing switcher to distribute the audio/video signals. U.S. Pat. No. 5,889,775, issued to Sawicz et al., describes an entertainment server connected to video distribution boxes through the use of one or more cross point (centralized) switches. U.S. Pat. No. 6,104,414, issued to Odryna et al., describes an improved digital centralized video distribution hub that utilizes a switching matrix. U.S. Pat. No. 5,455,619, issued to Truckenmiller et al., describes a video distribution system designed to distribute specific video programs to rooms (a hotel/motel type of lodging arrangement) using electronic tags, a computerized switching arrangement, and a centralized video distribution point.  
           [0008]    Although a variety of attempts have been made to improve centralized audio/video switching arrangements, a number of shortcomings and distinct disadvantages still exist in such systems. Initially, it is seen that existing audio/video distribution systems require that the audio/video signal from each source be routed over a single cable path back to the centralized switching arrangement. As such, a single cable path must then be utilized to send the audio/video signals from the switching arrangement to the user of the audio/video signal. This results, unfortunately, in a complex and often times, cumbersome, plurality of cables required to convey these audio/video signals. If the audio/video sources and users are in close proximity to each other, this plurality of cables can potentially become quite difficult to manage. On the other hand, however, the plurality of cables are very difficult to manage and very costly to install and maintain in instances where the audio/video sources and users are not in close proximity to each other, as in the case of a building video surveillance system, for example.  
           [0009]    Additionally, once the audio/video sources are in place, moving them to a new location requires installing new cables and identifying new electrical power sources for them. This results in an inflexible and expensive system that is inefficient, cumbersome, and difficult to install, maintain, and upgrade.  
           [0010]    The general concept of a distributed audio/video switching system has been implemented in cable television systems in the form of distributed switching. Cable television uses a form of distributed switching, whereby different audio/video sources are frequency multiplexed onto the cable. This is accomplished by mixing the baseband audio/video signal with a carrier frequency in a non-linear manner. This causes the baseband audio/video signal to be frequency shifted to a higher-frequency band (or channel) and is accomplished by utilizing a transmitter. By using different carrier frequencies, multiple audio/video signals can be placed on the cable and “stacked” in frequency. To select an audio/video source, a receiver is then tuned to the proper carrier frequency. A number of existing systems utilize this principle to do audio/video switching. For example, U.S. Pat. No. 5,592,482, issued to Abraham, uses frequency multiplexing to distribute multiple video sources to multiple video users. Similarly, U.S. Pat. No. 5,767,894, issued to Fuller et al., discloses a system using a RF (frequency multiplexed) video distribution system to send video information from the video servers to the room TV sets. In this patent, the video distributions system may optionally include a plurality of coaxial cables or optical fibers (using a centralized switching arrangement). U.S. Pat. No. 5,818,512, issued to Fuller also uses a frequency multiplexed switching arrangement.  
           [0011]    Although frequency multiplexing solves some of the cable management and cost issues of the centralized switching arrangements, it also has a number of shortcomings and disadvantages that have not been addressed. Naturally, the high cost of existing frequency multiplexing systems is of substantial concern. A very stable carrier frequency source and multiplex transmitter is required for each video source. The carrier frequency must be very stable because if it changes, the audio/video signal transmitted can interfere with an audio/video signal on an adjacent channel. In a surveillance application, where video sources may be in outside locations, the transmitter will be subject to inclement weather conditions and the stability of the carrier frequency can be influenced by external conditions such as temperature and humidity. Also, the transmitter itself is costly and complex, and can result in a variety of maintenance problems. Furthermore, such systems are one-way systems and it is not possible to control a specific video source. The audio/video sources all transmit on their specific channels, and it is up to the audio/video user to decide which source to use. This increases the cost and complexity of the receiving equipment, which must decode the particular channel of interest.  
           [0012]    Another existing way to accomplish audio/video distribution is to store the audio/video information on computer disk, and send this information over a computer bus or local area network to another computer, which then decodes the digital audio/video to analog audio/video and sends it to a display to be seen. This type of distribution is described in U.S. Pat. No. 6,133,908 issued to Sciobra et al. This system is not a real-time system, where live audio/video from sources is displayed as live audio/video to users. Also, having processors to encode audio/video to digital and then decode the audio/video so that it may be displayed is extremely costly and trouble-prone. Furthermore, transmitting digital audio/video over long distances requires special networking technology that is difficult to manage and costly to install and maintain.  
           [0013]    A number of other cable distribution systems have been developed by utilizing Ethernet and SCSI (Small Computer System Interface) technology. The information that flows over the cable is digital. This is disclosed in U.S. Pat. No. 5,550,584 issued to Yamada. Although such systems use digital signals to control the respective transmitters and receivers on the cable, the actual information (the audio/video information) is stored in analog form and must be converted to digital to send over these cables. Unfortunately, these systems are fully digital systems relying on complex protocols to coordinate the devices connected to the cable as well as complex transmitters and receivers used to send and receive the audio/video information. An illustration of a fully digital distribution system is shown in FIG. 10. FIG. 10 illustrates two video sources (VS 1  and VS 2 ) sending video into a single monitoring station. An analog video signal VS 1   320  is sent from a Video Source  42  into a device  350  that converts the analog signal into a sampled digital representation  333 . This is usually called an A/D device or a frame grabber (since it digitizes an entire video frame at a time) and produces a pixilated frame  334  (because the video frame is now broken up into picture elements (or pixels), with a resolution (pixels/inch) specified by the A/D device  350 . The greater the video resolution, the larger number of pixels would exist in the pixilated frame. For example, if the desired resolution were 480 pixels wide by 320 pixels high (a typical low-medium resolution image, such as used on digital cell phones that capture video), the pixilated frame would consist of 153,600 pixels. If 3 bytes of data are used for each pixel (1 byte for red, 1 byte for green, 1 byte for blue—the basic primary colors), the size of the pixilated frame in bytes would be 1,228,800 bytes. This frame is stored in a frame buffer  352 . A general-purpose digital computer composed of a CPU  351 , memory  353 , and a network interface  354  controls the acceptance and storing of the pixilated frame. It also controls the movement of the pixilated frame into the network interface, and well as provide network coordination and control of the pixilated image transmission to the monitor. If compression is used, this digital computer also performs the compression. Without compression, the data rates become very large. The standard real-time video frame rate is 1 frame every {fraction (1/15)} of a second (NTSC standard). This means that a data rate of approximately 25 megabytes/second (including 35% data communications protocol overhead) must be sustained through the digital computer. Breaking that into bits/second (the standard measure for network data traffic, the data traffic rate across the network of approximately 200 megabits per second would be realized. This can be reduced by digital video compression, but a cost of significantly increased computer size (and power consumption) and significant delays in performing the compression. The digital transmission packets  342  from the VS 1  network interface  354  are shown. Transmitter VS 2  is similar to Transmitter VS 1 , with its VS 2  frame  326  being sent into the A/D  350  from the video source  42 .  336 ,  337 , and  344  are the digitized video, the pixilated frame, and the digital data packet from video source VS 2   326 . These digital data packets  342  and  344  are received by a general-purpose digital computer located in the monitoring station. This general-purpose computer is composed of similar elements  354 ,  352 ,  353 , and  351  to the transmitters. The difference here is a D/A or video device  370  that converts pixilated video frames  334  into sampled frames, reconstitutes the sampled video into continuous video, and sends the video frames to a plurality of video users  48 .  330  is the continuous video for VS 1 , and  332  is the continuous video for VS 2 . Continuous video is required to display correctly on a video monitor. A comparison of a digital distribution system to the present invention is summarized in Appendix A.  
           [0014]    Another cable-oriented distributed switched component audio/video system is disclosed in U.S. Pat. No. 4,581,645 issued to Beyers, Jr. This system is mainly an interconnection system for an audio and video component entertainment system. As such, the cable and its electronic components are designed for short distances where distributed computer control is not a factor. This system is not intended for audio/video sources and users over an extended geographic area, such as a large room, multiple rooms, or building where the control, audio, video, and power must be kept to a single continuous cable.  
           [0015]    Accordingly, there is an established need in the art for a distributed audio/video system that is cost effective, highly flexible, and capable of being used over an extended area  
         SUMMARY OF INVENTION  
         [0016]    The present invention is directed to a low cost, highly flexible audio/video distribution system configured to connect audio and video sources to audio and video users without the need for a centralized switching and distribution mechanism.  
           [0017]    The term “audio/video” as used herein means audio or video or a combination of audio and video. Accordingly, any reference to audio/video should be understood to refer to audio only, video only, or a combination of audio and video.  
           [0018]    An object of the present invention is to provide an audio/video distribution system that offers a substantially low-cost solution to connecting audio/video sources and users. This is accomplished using multiplexed analog video and audio and a simple control system.  
           [0019]    A further object of the present invention is to provide an audio/video distribution system wherein the audio/video transmitters that.place the audio/video sources onto the cable are relatively simple and inexpensive to manufacture and maintain.  
           [0020]    Another object of the present invention is to provide an audio/video distribution system wherein the audio/video receivers extracting audio/video signals from the cable are also simple and inexpensive to manufacture and maintain.  
           [0021]    An additional object of the present invention is to provide an audio/video distribution system utilizing control circuitry with low speed digital components in a cost-effective manner.  
           [0022]    Yet another object of the present invention is to provide an audio/video distribution system that eliminates the need to have individual cables connecting users and sources back to a centralized switch.  
           [0023]    A further object of the present invention is to provide an audio/video distribution system wherein the cable is a single cable assembly that is routed along a path common to the video sources and users.  
           [0024]    Another object of the present invention is to provide an audio/video distribution system including simple and inexpensive diagnostic tools for maintenance and monitoring of the cable and the attached transmitters and receivers.  
           [0025]    In accordance with a first aspect of the invention, an audio/video distribution system is provided including a distribution cable, at least one audio/video transmitter, at least one receiver, and a control signal generator. The transmitter is configured to receive analog signals from at least one audio/video source and place these signals on the cable, while the receiver is connected to the distribution cable and configured to receive the analog signals from the distribution cable. The control signal generator is connected to the distribution cable and configured to control the transmitter and receiver.  
           [0026]    These and other objects, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the preferred embodiments, which follow. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0027]    The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, where like designations denote like elements, and in which:  
         [0028]    [0028]FIG. 1 is an illustrative schematic view showing a preferred embodiment of the overall layout of the present invention;  
         [0029]    [0029]FIG. 2A is an illustrative schematic view showing a preferred embodiment of a battery powered power module of the present inventions;  
         [0030]    [0030]FIG. 2B is an illustrative schematic view showing a preferred embodiment of an AC utility power module of the present invention;  
         [0031]    [0031]FIG. 3A is an illustrative schematic view showing a preferred embodiment of the transmitter of the present invention without video synchronization;  
         [0032]    [0032]FIG. 3B is an illustrative schematic view showing a preferred embodiment of the transmitter of the present invention with video synchronization;  
         [0033]    [0033]FIG. 4A is an illustrative schematic view showing a preferred embodiment of the receiver of the present invention without video synchronization;  
         [0034]    [0034]FIG. 4B is an illustrative schematic view showing a preferred embodiment of the receiver of the present invention with video synchronization;  
         [0035]    [0035]FIG. 5 is an illustrative schematic view showing a preferred embodiment of the control signal generator of the present invention;  
         [0036]    [0036]FIG. 6 is an illustrative schematic view showing a preferred embodiment of the cable status monitor of the present invention;  
         [0037]    [0037]FIG. 7 is an illustrative schematic view showing a preferred embodiment of the cable extender of the present invention; and  
         [0038]    [0038]FIG. 8 is an illustrative schematic view showing a preferred embodiment of the synchronization generator of the present invention.  
         [0039]    [0039]FIG. 9 illustrated a simplified operation of the present invention.  
         [0040]    [0040]FIG. 10 illustrates prior art-a digital distribution system. Like reference numerals refer to like parts throughout the several views of the drawings. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0041]    Shown throughout the figures, the present invention is generally directed towards a low cost, highly flexible audio/video distribution system configured to connect audio and video sources to audio and video users without the need for a centralized switching and distribution mechanism.  
         [0042]    Referring primarily to FIG. 1, the overall system layout for the audio/video distribution system is shown. In the preferred embodiment of the present invention, a cable  30  is utilized as shown. The cable  30  is a passive media that may be composed in any of a wide variety of configurations. Preferably, the cable  30  will be a combination of a plurality of electrical cables or optical fiber that provides a transmission media for the audio/video, control, power, and video synchronization signals that comprise the system. The cable  30  may be terminated, if desired, at each end using the appropriate terminators  36  to match the characteristic impedance (electrical or optical) of the cable  30 . As such, it is seen that the terminators  36  can be used to stabilize the signals on the cable  30 .  
         [0043]    Transmitter  40  and receiver  46  has a unique binary address. Signals from the control signal generator  44  (and programmed by the programming sequencer  54 ) are sent to each transmitter  40  or receiver  46  through the cable  30  to control certain properties of them. One specific property of the transmitter  40  is the ability to connect or disconnect its audio/video source to the cable. Each transmitter  40  has one of two states with respect to the cable  30 : connected or disconnected. When a transmitter  40  is in the disconnected state, it represents an electrically activated non-interfering mode to the cable  30 , and not physical disconnection, as in the case of a relay or an accidental unplugging of the transmitter  40  from the cable  30 , for example. When the transmitter  40  is in the connected state, it has the ability to send audio/video signals to the cable  30  so that they may be sent to other devices connected to the cable  30 . In this case, the connection consists of an electrically activated connection and not a physical connection. A variety of other states may also be controlled in the transmitter  40  and will be described later in this section. In the most preferred embodiment, however, only one transmitter  40  may be connected to the cable  30  at any given time.  
         [0044]    When a transmitter  40  is connected to the cable  30 , the analog audio/video signals from the transmitter  40  are sent to all components connected to the cable  30 . Preferably, any receiver  46  that is connected to the cable  30  will have the ability to receive this audio/video signal. The control information, as sent by the control signal generator  44 , can control states within the receiver  40 , as will be described later. The transmitter  40  and receiver  46  may also contain circuitry that will take signals from the control signal generator and control auxiliary devices connected to the transmitter  40  and receiver  46 .  
         [0045]    The control signal generator  44  sends signals to each transmitter  40  to connect it to the cable  30  for some period of time so that a receiver  46  may receive its audio/video signals. Signals are then sent to the control signal generator  44  to disconnect it from the cable  30  so that another transmitter  40  may connect to the cable  30 . The effect of this is to display the audio/video information from each audio/video source  42  in some programmed fashion to an activated audio/video receiver  46 . An illustrative example of this would be a video surveillance with 3 video cameras (with audio) and their associated transmitters  40  located at strategic points around a building. A monitoring facility is located somewhere inside the building. This monitoring facility contains a video monitor (with audio) and a video tape recorder. These two devices (the video monitor and video tape recorder) are connected to receivers  46 . These transmitters  40  and receivers  46  are connected to a common audio/video cable  30 . A control signal generator  44  is also located in the monitoring facility. The control signal generator  44  may either be programmed (or manually operated) to switch the video cameras so that they may cause their analog audio/video information to be sent to the video monitor and video tape recorder.  
         [0046]    All the components connected to the cable  30 , including the audio/video sources  42 , may obtain their electrical power from the cable  30 . This is supplied to the cable  30  through a power module  34  that is connected to an external power source  32 . Thus, in the above example, the video cameras do not have to be connected to a separate power source, but may obtain their power directly from the cable  30 .  
         [0047]    If the length of the cable  30  is longer than some critical length (as determined by the actual technology of the cable  30 ), a cable extender  50  may be used to boost the cable  30  signals and allow the cable  30  length to be extended. A programming sequencer  54  may be included. Programming sequencer  54  may be a programmable computing device or a manual device. The preferred function of the programmed sequencer  54  is to provide the control signal generator  44  with the commands needed to control the transmitters  40  and receivers  46 . The cable status monitor  146  listens to the various signals on the cable  30  and allows them to be monitored to insure proper working of the system.  
         [0048]    The system of the present invention may contain a video synchronization component if desired. Normally, each video frame of the video source is sent at a time interval that is determined by a clocking source contained with each audio/video source  42 . Thus, the start of a video frame from one source may not coincide in time with the start of the frame from another video source. In this case, when audio/video sources  42  are switched from one to another, the video picture on the audio/video user device  48  will require some time to synchronize to the new video source  42 . Audio/video user  48  may include a video monitor or station, video tape recorder, or any other suitable recording, viewing, monitoring, or storage apparatus. This time may be lengthy (1-2 seconds), but is generally not a problem for most applications, but it does limit the speed at which the audio/video sources  42  and their respective transmitters  40  may be switched. To allow the audio/video transmitters  40  to be switched at a higher rate, video synchronization may be used. This would use another signal (a synchronization signal) on the cable  30  to cause each audio/video source  42  to cause their video frames to be locked in phase with each other. When the audio/video sources  42  are switched, since the frames are synchronized, the audio/video user device  48  will not have to specifically resynchronize to the new audio/video source  42 . Because of this synchronization, the audio/video sources  42  may be switched, if desired, after a one or two video frame delay.  
         [0049]    [0049]FIG. 9 provides another illustration of the operation of the present invention. FIG. 9 shows two video sources and transmitters labeled VS 1  and VS 2 . A control signal generator  44  and programming sequencer  54  send control signals  87  over the cable to alternately allow video frames  320  from transmitter VS 1  and video frames  326  from transmitter VS 2  to be sent over the cable. The control signal generator  44  and programming sequencer  54  also send control signals  87  over the cable to alternately allow video frames  320  sent from transmitter VS 1  to be received by receiver VS 1 , and video frames  326  from transmitter VS 2  to be received by receiver VS 2 . This works as follows:  
         [0050]    The video source  42  sends a set of video frames into a cable connect switch  82 . The cable connect switch  82  is controlled by signals  85  sent from the control receiver/decoder  302 , which, in turn, is controlled by cable control signals  87 . The receiver is controlled by a similar control receiver/decoder  304  to turn on and off the cable receiver switch  306 . The programming sequencer  54  sends a command to transmitter VS 1  and receiver VS 1  to turn on their cable connect switches  82  and  306 . This allows a single video frame  322  from the video stream  320  sent by the video source  42  over the cable to be received by receiver VS 1  so that the video frame  322  is sent to a video user  48 . The programming sequencer  54  then sends a command to transmitter VS 2  and receiver VS 2  to turn on their cable connect switches  82  and  306  after the end of the current video frame. This allows a single video frame  328  from the video stream  326  sent by the video source  42  over the cable to be received by receiver VS 2  so that the video frame  328  is sent to a video user. This has the effect of multiplexing alternating video frames  324  over the cable.  
         [0051]    [0051]FIGS. 2A and 2B are illustrative schematic views showing power modules  34  that place electrical power on the cable  30 . Electrical power is supplied from either a battery  64 , AC utility power  70 , or from any of a wide variety of other sources. This power is then converted via battery converter/regulator  63  or AC power supply  68  to a voltage that is significantly higher then the voltage requirements of the audio/video sources  42 . It is then coupled to the cable  30  as cable power  62  using a power cable coupler  60  in such a manner that electrical current cannot flow back through either the AC power supply  68  or the battery converter/regulator  63 . This is so that multiple power modules  34  may be used on the cable  30  to insure adequate power for all the audio/video user devices  48  over the entire length of the cable  30 . The purpose of supplying power at a higher then needed voltage is to compensate for a drop in the voltage of the cable power  62  due to long length of the cable  30   
         [0052]    [0052]FIGS. 3A and 3B show a preferred illustrative embodiment of the transmitter  40 . FIG. 3A shows the transmitter  40  without video synchronization, and FIG. 3B shows the transmitter  40  with synchronization. Cable power  62  is sent to a power converter  72 , which reduces the voltage so that it is compatible with the power requirements (A/V power  74 ) of the audio/video source  42  and the A/V transmitter  40 . Control signals  87  from the cable  30  are sent to the control receiver/decoder  88 . The transmitter  40  contains a unique address, which is decoded by the control receiver/decoder  88  along with other commands destined for this address. This control receiver/decoder  88  decodes commands from the cable, and controls both cable connect/disconnect signals  85  and amplifier control signals  83 . The connect/disconnect signals  85  control the cable connect switch  82 . The connect switch  82  connects the audio/video in from source  89  to the cable  30  when it is in the ON state, or disconnects itself from the cable  30  when it is in the OFF state. The control receiver/decoder  88  responds to cable control signals  87  to set the cable connect/disconnect signal  85  either to ON or OFF. In addition, other audio/video signal characteristics (such as signal gain, audio or video equalization characteristics, etc.) may be controlled by the amplifier control signal  83 . The amplifier control signal  83  controls the desired characteristics of the A/V amplifier and signal conditioner  84 . This is a variable gain amplifier with controllable equalization parameters. It may also have other characteristics for special functions. In other, simpler implementations, if the signal from the A/V source  89  is of sufficient strength, it is not necessary for the A/V amplifier and signal conditioner  84  to be present. Audio/video information comes in to the transmitter  40  through the A/V in from source  89  and is received by the A/V receiver  86 . This A/V receiver  86  simply provides correct termination of A/V in from source  89  signals. In addition, the Control Receiver/Decoder  88  has the capability of providing control signals  200  for devices that are contained within the AV Source  42 . The Control Receiver/Decoder  88  optionally has the capability of receiving device control signals from the Control signal generator  140 , converting these signals  200  to match the requirements of the AV Source  42 , and sending these to the AV Source  42 .  
         [0053]    The signal flow through the transmitter  40  is as follows. The audio/video signals from the source come into the transmitter  40  via the A/V in from source  89  circuit and received by the A/V receiver  86 . These signals can flow, if desired, through the A/V amplifier and signal conditioner  84  to the cable connect switch  82 , where they then flow out over the cable  30 .  
         [0054]    For a transmitter  40  with video synchronization, a slightly different control receiver/decoder with synchronization  92  is used. This is similar to the control receiver/decoder  88 , but has the additional capability of receiving the A/V synchronization signal  90  from the cable  30 . This control receiver/decoder with synchronization  92  feeds the A/V synchronization signal  90  to the A/V receiver with video synchronization  94 , and on to the audio/video source via the A/V synchronization signals  100 . The control receiver/decoder with synchronization  92  also uses the synchronization signals  90  to synchronize the cable connect disconnect signal  85  so that the cable connect switch  82  connects the audio/video information to the cable  30  at the beginning of a video frame. The Control Receiver/Decoder  92  may incorporate timing correction to compensate for cable length. In addition, the Control Receiver/Decoder  92  has the capability of providing control signals  200  for devices that are contained within the AV Source  42 . The Control Receiver/Decoder  92  optionally has the capability of receiving device control signals from the Control signal generator  140 , converting these signals  200  to match the requirements of the AV Source  42 , and sending these to the AV Source  42 .  
         [0055]    [0055]FIGS. 4A and 4B show preferred embodiments of the receiver  46 . FIG. 4A shows the receiver  46  without video synchronization, and FIG. 4B shows the receiver  46  with video synchronization.  
         [0056]    Each receiver  46  has a unique address. With reference to FIG. 4A, cable control signals  87  contain addresses and commands from the cable  30  and are decoded via the A/V control receiver/decoder  112 . The control receiver/decoder  112  responds to the commands addressed to this receiver and changes the state of the receiver connect/disconnect signals  114 . These signals turn the audio or video (or some other combination) ON or OFF from the A/V cable receiver  118 . In addition, the Control Receiver/Decoder  112  has the capability of providing control signals  201  for devices that are contained within the AV User  48 . The Control Receiver/Decoder  112  optionally has the capability of receiving device control signals from the Control signal generator  140 , converting these signals  201  to match the requirements of the AV User  48 , and sending these to the AV User  48 . In an alternate embodiment, it may be desirable not to utilize control signals to activate/deactivate receivers, such that the receivers continuously communicate with signals transmitted over the distribution cable.  
         [0057]    In the preferred embodiment of the present invention, the signal flow is as follows: audio/video signals  81  from the cable  30  enter the A/V cable receiver  118 . The A/V cable receiver  118  continually monitors the audio/video signals  81  from the cable  30  in a fashion that does not interfere or cause loading of the cable  30 . The A/V cable receiver  118  is controlled by the connect/disconnect signals  114  discussed above. The output of the A/V cable receiver  118  is sent to the A/V output driver  120 , which conditions the audio/video output  122  for transmission to the A/V user.  
         [0058]    For a receiver that uses synchronized video signals as depicted in FIG. 4B, the A/V synchronization signal  90  is received from the cable  30  and sent to a control receiver/decoder  126 . This control receiver/decoder  126  not only controls the connect/disconnect signals  114 , but extracts A/V synchronization signals  128  that are sent to the A/V output driver with synchronization  130 . The control receiver/decoder  126  causes the receiver connect disconnect signals  114  to switch the A/V cable receiver  118  at the beginning of the video frame. The A/V output driver with synchronization  130  converts the audio and video received from the A/V cable receiver  118  and the A/V synchronization signals  128  to the proper levels and timings to be sent to the A/V user. A/V signals  132  and synchronization signals  164  are sent from the A/V output driver  130  to the A/V user  48 . The control receiver/decoder  126  may incorporate timing correction to compensate for cable length. In addition, the Control Receiver/Decoder  126  has the capability of providing control signals  201  for devices that are contained within the AV User  48 . The Control Receiver/Decoder  126  optionally has the capability of receiving device control signals from the Control signal generator  140 , converting these signals  201  to match the requirements of the AV User  48 , and sending these to the AV User  48 .  
         [0059]    [0059]FIG. 5 shows a preferred embodiment of the control signal generator of the present invention. Control signal generator sequencing signals  144  enter the Control signal generator Module  140  as shown. This Control signal generator Module  140  converts the sequencing signals  144  into the proper cable control signals  87  for the cable  30 . The Control signal generator Module  140  may change media type as well. If the control signals and audio/video portion of the cable  30  is composed of fiber optic cable, then the Control signal generator Module  140  would provide the proper conversion from electrical to optical. The Control signal generator Module  140  also provides buffering and timing, sending the cable control signals  87  over the cable  30  in the proper time sequence. In addition, the Control signal generator Module  140  has the capability of receiving device control information  202  from an external source, converting to the proper cable control signals  87 , and sending it to the proper Transmitter  40  or Receiver  46 .  
         [0060]    [0060]FIG. 6 shows the cable status monitor  146 . This monitor samples the cable control signals  87 , the cable power  62 , the A/V synchronization signals  90  and the cable A/V signals  81 . It compares these signals against a reference standard, and if these signals are not within tolerance, alarms are generated to indicate malfunction conditions.  
         [0061]    [0061]FIG. 7 shows a preferred embodiment of the cable extender  50  of the present invention. The cable extender  50  contains a set of reversing switches  148 ,  154 , and  158 . Because the repeaters  150 ,  152 ,  156  perform their function in only one direction, provision must be made to reverse the “direction” of the repeaters  150 ,  152 ,  156 . The cable A/V signals  81  are brought into an A/V cable repeater reversing Switch  148  and A/V cable repeater  150 . The A/V cable repeater  150  amplifies and regenerates the audio/video signals on the cable  30 . The purpose of the reversing switches are to provide this “reversal” so the repeaters  150 ,  152 ,  156 ) may be set to the proper “direction” to properly repeat or regenerate the signal. An example of this is if the audio/video source is connected to the left side of FIG. 7, the “direction” of the A/V cable repeater  150  is correct. If the audio/video source is connected to the right side of FIG. 7, the “direction” of the A/V repeater  150  must be reversed.  
         [0062]    A/V cable repeater reversing switch  148  and A/V repeater  150  are for the cable A/V signals  81 . Reversing switch  154  and control signal cable repeater  152  are for the control signals  87 . Synchronization signal cable repeater reversing switch  158  and synchronization signal cable repeater  156  are for the A/V Synchronization Signals  90 . For cable power  62 , a cable power cutoff switch  160  is used to break the continuity of the cable power  62  so that additional cable power may be introduced onto the cable in order to bring the cable power back into tolerance. The repeater power selector switch  162  simply lets additional cable power flow either to the left or right of the cutoff switch to account for the location of the power module  34 . The reversing switches may configure themselves properly by automatically sensing the signal direction on the cable.  
         [0063]    [0063]FIG. 8 shows a preferred embodiment of the synchronization generator  142 . A sync generator module  168  contains a stable timing source and circuitry to place the timing signals  90  on the cable  30 . The synchronization generator  142  may also obtain its timing from external source  145 . A sync converter  143  converts this timing so that is compatible with the cable  30  and places these converted signals  90  on the cable  30 .  
         [0064]    In the preferred embodiment, the cable  30  is comprised of individual twisted pair copper conductors for the cable A/V signals  81 , A/V synchronization signals  90 , and cable control signals  87 . Straight copper conductors are preferably utilized for cable power  62 . However, it will be appreciated by those skilled in the art that the cable A/V signals  81 , A/V synchronization signals  90 , and control signals  87  may be of different technology, including coaxial cable (either individual or multiplexed), or optical fiber (either individual or multiplexed). The control signal  87  protocols and levels may be either proprietary (such as the Dallas/Maxim Semiconductor Microlan technology), or a standard protocol, including IEEE LA/V protocols. The cable power  62  may be direct current, alternating current, or some other combination.  
         [0065]    Since many modifications, variations, and changes in detail can be made to the described preferred embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.  
         [0066]    Thus, the scope of the invention should be determined by the appended claims and their legal equivalents.