Abstract:
A digital central control unit is connected in a master/slave relationship to a plurality of audio, video, and data components, at least one of which may be an analog component. A decoder digital-to-analog unit is positioned at the input of all analog components so that signals transmitted to them from the central control unit are not decoded and converted to analog signals until after the transmission has been completed. An encoder analog-to-digital unit for converting analog signals to digital signals is positioned at the output of each analog component so that their respective analog signals are in encoded digital format when being transmitted to the central control unit. The network is thus all-digital and is therefore not subject to the limitations of networks having analog transmission lines.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates, generally, to an apparatus for interconnecting audio, video, and data components. More particularly, it relates to an apparatus that eliminates the noise and errors that occur during analog data transmission between such components.  
           [0003]    2. Description of the Prior Art  
           [0004]    A conventional audio component such as a speaker is connected to a source of audio signals by wires that carry analog signals. The speaker must therefore be positioned in relatively close proximity to the source of the audio signals if signal attenuation is to be minimized. However, even if the speaker is positioned in close proximity to the source of audio signals, the analog signal transmission will be imperfect. Moreover, extraneous noise will be induced because it is not possible to perfectly shield the wires that extend from the signal source to the speaker. Furthermore, there are many audio, video, or data components where more than one wire is required to make the interconnection. Where there are a relatively large number of audio and video components to be interconnected, such as in a home entertainment center having a television set (which may be of the analog or digital type and which may include a video monitor and the like), a VCR, a CD player, a DVD player, a casette tape player, a radio tuner, a television tuner, a graphics equalizer, and the like, the number of wires is quite high and the connections are rather complicated and messy.  
           [0005]    Another drawback of the present system for interconnecting components is that the number of components that may be interconnected is limited. Once the “audio in,” “audio out,” “video in,” and “video out” ports of a component such as a VCR have been occupied, no further connections can be made.  
           [0006]    What is needed, then, is a means for reducing or eliminating signal transmission errors of the type that occur in analog environments, for reducing or eliminating the amount of noise that exists in a conventional set up of multiple components that includes analog components, a means for reducing the number of wires in such a set up so that intallation complexity is reduced, a means that would enable various audio, video, or data components to be widely spaced apart from their respective signal sources and from each other, a means for providing positive communication between the various components of such a system, and a means for increasing the number of components that may be interconnected.  
           [0007]    However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in this art how these desireable ends could be attained.  
         SUMMARY OF THE INVENTION  
         [0008]    The longstanding but heretofore unfulfilled need for an apparatus that overcomes the limitations of the prior art is now met by a new, useful, and nonobvious invention. The present invention includes an apparatus interconnecting a network of components in a master/slave relationship so that each component is controlled by the master. The apparatus is called a Digital Audio-Video Network System (DAVieS) and includes a central control unit for controlling a plurality of components. The central control unit has digital internal circuitry.  
           [0009]    At least one component of the plurality of components has analog internal circuitry. A single physical transmission path for interconnecting the central control unit to each component of the plurality of components is provided. The transmission paths is in the form of a predetermined signal transmission media, and at least one decoder D/A (digital-to-analog) unit, hereinafter referred to as a DDA means, is provided for decoding and converting digital signals from the central control unit to decoded analog signals at the input of said at least one component having analog internal circuitry. Said at least one DDA means is positioned at the input of said at least one component and there may be as many DDA means as there are components having internal analog circuitry.  
           [0010]    At least one A/D (analog-to-digital) encoder unit, hereinafter referred to as an ADE means, is provided for encoding and converting analog signals from said at least one component having analog internal circuitry to encoded digital signals, and said at least one ADE means is positioned at the output of said at least one component having analog internal circuitry. There may be as many ADE means as there are components having analog internal circuitry.  
           [0011]    The components of any DAVieS may include input devices, output devices, and input/output devices. An ADE means will be positioned between the DAVieS and all input devices, such as an FM radio with an independently controlled tuner, for example. A DDA means will be positioned between the DAVieS and all output devices, such as a speaker, for example. Both ADE and DDA means will be positioned between the DAVieS and all input/output devices, such as a TV tuner, for example.  
           [0012]    The DDA meanss and the ADE means are under the control of the central control unit so that no signal travels from a component to the central control unit unless the central control unit commands a component to send a signal and so that no signal travels between components in the absence of a command from the central control unit. The central control unit is adapted to transmit digital commands to the components in accordance with a predetermined communication protocol.  
           [0013]    Accordingly, all transmission and command signals in the network are digital. Thus, noise arising from analog signal transmission is eliminated, external induced noise is eliminated or substantially attenuated, the components may be remotely positioned from the central control unit and from each other without introducing noise, the wiring of the audio and video system is simplified, and the number of components that may be connected to the network is limitless for all practical purposes.  
           [0014]    It is a primary object of this invention to overcome many of the limitations associated with analog transmission of signals in audio and video systems.  
           [0015]    A more specific object is to provide an apparatus for interconnecting audio and video components that reduces signal transmission errors.  
           [0016]    Another specific object is to provide an apparatus for reducing external induced noise in such a system.  
           [0017]    Another object is to provide an interconnection system that would reduce the number of wires employed to set up a video and audio component system.  
           [0018]    Still another object is to facilitate remote placement of components with respect to their respective sources of signals and with respect to each other.  
           [0019]    It is also an object to provide a means for components to communicate with each other.  
           [0020]    These and other important objects, features, and advantages of the invention will become apparent as this description proceeds.  
           [0021]    The invention accordingly comprises the features of construction, combination of elements and arrangement of parts that will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which:  
         [0023]    [0023]FIG. 1 is a high level diagram of the novel system;  
         [0024]    [0024]FIG. 2 is a diagram depicting how devices primarily used as input devices and those primarily used as output devices are connected to the controller of the novel digital stereo network;  
         [0025]    [0025]FIG. 3 diagrammatically depicts the five layer communication protocol of the novel digital stereo network;  
         [0026]    [0026]FIG. 4 depicts a data frame of said network;  
         [0027]    [0027]FIG. 5 depicts the data frames when in use;  
         [0028]    [0028]FIG. 6 diagrammatically depicts how the controller of the novel network and the various components in the audio and video system communicate with one another;  
         [0029]    [0029]FIG. 7A is a flowchart of the steps performed by the novel apparatus;  
         [0030]    [0030]FIG. 7B is a continuation of the flowchart of FIG. 7A; and  
         [0031]    [0031]FIG. 7C is a flowchart depicting the steps performed by the control frames of the novel apparatus.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]    Referring now to FIG. 1, it will there be seen that an exemplary embodiment of the invention is denoted as a whole by the reference numeral  10 .  
         [0033]    The novel Digital Audio-Video Network System (DAVieS)  10  includes a remote control unit  11 , a central control unit (CCU)  12 , and a plurality of components having analog internal circuitry (such as a stereo speaker) or digital internal circuitry (such as a CD player).  
         [0034]    As can be appreciated from FIG. 1, the architecture of the novel system is that of a master/slave network where CCU  12  is the master and an audio, video, and data system having at least one analog component is the slave. In this example, the audio, video, and data system includes a cassette player  14 , plural auxiliary units collectively denoted  16 , a tuner  18 , speakers  20 , a compact disk (CD) player  22 , a digital signal processor (DSP)  24 , a laser disc (LD) player  26 , a digital versatile disc (DVD)  27 , plural video inputs collectively denoted  28 , a video cassette recorder (VCR)  30 , a television set  32 , and a data device such as a printer  33 .  
         [0035]    The total number of components that can be interconnected in accordance with the teachings of this invention is 65,536 (2 to the sixteenth power). The components can be classified into 256 (2 to the eighth power) categories where each category consists of 256 components. However, only eleven categories are currently in use. The following eleven categories identify all existing audio, video, and data equipment:  
                                   Category No.   Category Description                   1   Audio Play/Record       2   Audio Play Only       3   Audio Record Only       4   Video Only Play/Record       5   Video Only Play       6   Video Only Record       7   Audio/Video Play/Record       8   Audio/Video Play       9   Audio/Video Record       10    Data Devices       11    CCU                  
 
         [0036]    As mentioned earlier, the individual components may have internal circuitry that is analog or digital in design. The following table indicates how existing audio, video, and data components may be classified:  
                                                       Audio   Audio   Video   Video           Component   Play   Rec   Play   Rec   Category                   Cassette   X   X           1       CD   X               2       VCR   X   X   X   X   7       Tuner   X               2       LCD   X       X       8       TV  (analog or digital)     X   X   X   X   7       Record player   X               2       DSP Unit   X   X           1       Equalizer   X   X           1       Speaker/Amplifier       X           3       Monitor           X   X   4       DSS/Cable box   X       X       8       Printer                   ?       CCU                   ?                  
 
         [0037]    Most components may be classified as both Playing or Input and Recording or Output devices. However, speakers and analog amplifiers can only be classified as Output devices whereas radio tuners and CD players are pure Input devices. Other components such as TV sets are predominately used as Output devices but some sets are wired to have both Input and Output capabilities. FIG. 2 depicts this classification scheme. In this particular example, the input devices are cassette player  14 , tuner  18 , CD  22 , DSP  24 , VCR  30 , equalizer  38 , DSS/Cable box  40 , CCU  42 , LCD  44 , and monitor  46 . The output devices are speaker  20 , TV  32 , analog amplifier  34 , and monitor  48 .  
         [0038]    In the novel apparatus, all analog signals generated by analog components are converted to digital signals and encoded prior to transmission to CCU  12 , and the encoded digital signals generated by CCU  12  are transmitted to the analog components in digital form and decoded and converted to analog signals at the input of the component.  
         [0039]    Components having internal digital circuits, and having a digital output, such as CD, LCD, and DVD players, already generate digital signals so their signals may not need to be converted prior to transmission to CCU  12  and the digital signals from the CCU to such components need not be converted.  
         [0040]    The component digital output signals are grouped into packets of data and transmitted through a digital network.  
         [0041]    The bandwidth of the United States NTSC, standard analog TV signal, is 6 MHz per channel; by the Nyquist Theorem, this translates into 12 M samples per second. With 24 bit samples, a minimum speed of 288 Mbits per second is required, without applying any digital compression, to transmit analog TV signals through a digital media. For analog stereo signals, the bandwidth is between 20Hz-20KHz which translates to 40 K samples per second. With 24 bit samples, and without applying digital compression, the digital transmission speed should be 960 Kbits per second.  
         [0042]    By applying the Digital Television compression standard, this translates into 5 to 8 Mbits per second digital data transmission speed. The Digital Television Compression Standard is based on the ISO/IEC IS 13818 International Standard, MPEG-2 Video Standard, the Digital Audio Compression (AC-3) Standard, and the ISO/IEC MPEG-2 Systems Standard. To compress audio signals alone with AC-3 standard, the data transmission speed will most likely be less than 300 kbits per second.  
         [0043]    To process at least one video signal and multiple audio signals, a data transmission speed range of 10-150 Mbits per second is needed; conventional fiber media transmits data at speeds far in excess of that rate. The novel digital stereo network  10  employs a single fiber optic cable as the preferred data transmission means, but it will still work if media such as coax cable, twisted pairs, wireless, or the like are used. By employing conventional digital signal compression, the novel apparatus processes multiple video and audio signals simultaneously.  
         [0044]    The communication protocol for DAVieS  10  is similar to the protocol used by computer network communications. However, it is simpler because the components of DAVieS  10  can only answer requests generated by CCU  12 ; none of the components can generate requests as can the components in a conventional computer network. Thus, the communication between CCU  12  and the components is termed “synchronous” because conventional networks are asynchronous, i.e., they involve random access communication between components.  
         [0045]    Moreover, conventional computer networks are typically linked with other computer networks, thereby adding another level of complexity to the protocol. The novel DAVieS of this invention is not in cross network communication with other DAVieSs and for this additional reason the novel protocol is less complex than known computer network protocols.  
         [0046]    Since a conventional computer local area network (LAN) uses a seven layer communication model, the novel DAVieS can use the same protocol with many unused features, or the novel DAVieS may use a five layer communication model where the five layers are physical, data, transport, presentation and application layers.  
         [0047]    [0047]FIG. 3 depicts the relationships between the five layers of the communication protocol for the novel DAVieS.  
         [0048]    The primary function of physical layer  50  is to control the Input and Output (I/O) devices that put data onto and retrieve data from the physical wires, cables, or other media, including wireless.  
         [0049]    The function of data layer  52  is to create data frames. Data layer  52  receives a series of bits of data, i.e., a bit stream  50 A, from physical layer  50  and reconstructs the bits into data frames  60  and sends said data frames to transport layer  54  for further analysis. Similarly, data layer  52  receives outbound data from transport layer  54  and calculates an error correction code. It then packs the data into a data frame and delivers it to physical layer  50  for transmission.  
         [0050]    Data layer  52  also regulates DAVieS traffic by queueing data before transmitting it since only one data frame can be sent at any one time. A data frame  60  is depicted in FIG. 4.  
         [0051]    As indicated in FIG. 4, each frame  60  begins with a Preamble  62  that is used to synchronize clocks between the sender and the receiver components. The size of the Preamble field varies depending upon the speed of the communication network.  
         [0052]    A Starting Delimiter field  64  marks the beginning of the frame boundary. It contains analog encoding of signals other than 0s and 1s so that they cannot occur accidentally in application data.  
         [0053]    Frame Control (FC) field  66  consists of two bytes and is used to distinguish between different types of frames. For example, frames include control frames, normal audio data frame, normal video data frames, video and audio (e.g., MPEG-2 and AC-3) compressed video, and audio data frames with header information (e.g., a typical header might request that data be sent to multiple addresses). There are many other types of frames as well. A two byte Frame Control field can distinguish up to 65,536 unique data frames.  
         [0054]    A one byte Destination Type (or Destination Flag) field  68  is used to identify up to fifteen recipient addresses which are to be followed by a data frame. Destination Type field  68  also identifies up to sixteen types of broadcasting methods. Examples of broadcasting methods include broadcasting to all components (e.g., broadcasting of timing or synchronization signals), broadcasting to all speakers, broadcasting to all TV sets, and so on. The following table explains how the Destination Type field is used:  
                                   Field Bit Value   Field Description                   0000 0001   One destination address       0000 0010   Two destination addresses       0000 1111   Fifteen destination addresses       0001 0001   Broadcast to one set of addresses -           addresses having the same first 14           bits as the Destination address       0010 0011   Broadcast to three sets of           addresses - addresses having the           same first 12 bits as one of the           Destination addresses       1111 0000   Broadcast to all addresses -           No Destination address in this case                  
 
         [0055]    With the exception of the broadcast-to-all signal, the Destination Address field  70  consists of 1-15 addresses; each address requires two bytes of storage. Broadcasting and multiple addresses are used when there is a plurality of components in the apparatus that use the data frame for the same or different purposes, such as recording and/or display, e.g. The two byte address scheme enables the apparatus to be scaleable up to 65,536 components.  
         [0056]    The Source Address field  72  is in the same format as the Destination Address  70  except it identifies the data sender instead of the data receiver. The receiving component uses the sender address to send reply data to the sender.  
         [0057]    Data Field  74  follows Source Address field  72 . The data length is theoretically unlimited, but for practical reasons a maximum length of 64K is recommended.  
         [0058]    Check Sum field  76  is used to detect data transmission errors. It uses Cyclic Redundancy Code (CRC), a check sum algorhithm also used in conventional computer network communication protocol.  
         [0059]    End Delimiter field  78  marks the end of the frame boundary. Like Starting Delimiter  64 , it includes analog encoding of signals other than 0s and 1s so that they do not occur accidentally in the application data.  
         [0060]    The length of the data may be calculated based upon the Starting and End Delimiters  64 ,  78 . It is possible to have data of unlimited length, but for practical purposes the length of the application data field should be less than 65,636 bytes.  
         [0061]    Thus, data layer  52  recreates the bit stream from physical layer  50  into a frame  60  with the FIG. 4 format. Data layer  52  then delivers the frames to transport layer  54  for further processing.  
         [0062]    Transport layer  54  (FIG. 3) identifies the source and destination addresses of inbound and outbound data. Thus, the transport layer may also be thought of as the access controller means of a component; it grants access to a component based upon the destination address and frame type of the inbound data. Transport layer  54  strips the inbound address information from a data frame and adds the destination and source addresses to an outbound data frame.  
         [0063]    Transport layer  54  also receives each data frame from data layer  52  as aforesaid and identifies the destination of the data frame and compares the destination address with the predetermined component address. If said addresses match, the control frame is extracted to identify control characteristics of the frame. For example, a cassette player may not have an internal clock; accordingly, time information is not used by such component.  
         [0064]    Transport layer  54  then passes each data frame  60  to presentation layer  56  for further processing. The transport layer also receives outbound data from presentation layer  56 , adds the frame control bytes, the destination address, and the source address to the data frame. The data is then presented to data layer  52  for sending.  
         [0065]    Presentation layer  56  performs coding and decoding of transmission data. It receives inbound data from transport layer  54 . Based upon the format provided by frame control bytes, presentation layer  56  performs data decompression as required. It also compresses outbound data, if required, from application layer  58  for transmission by the transport layer. Some of the compression methods are specified by MPEG-1, MPEG-2, AC-3, ATSC standard A52, etc.  
         [0066]    Application layer 58 converts data from digital signals to analog signals and vice versa. Reference numeral  58 A indicates an analog signal that is sampled and digitized into a digital signal  58 B. For inbound data, the signal conversion process first extracts data from data frames  60  to produce a continuous data stream. DDA devices are then used to convert the bits of data into analog signals for use by a component&#39;s analog circuit. For outbound data, ADE devices first convert the analog signals from an analog component to digital signals. The data is then grouped into frames for transmission by presentation layer  56 .  
         [0067]    For components having digital internal circuitry, application layer  58  provides a continuous bit stream of data to the internal circuitry or to presentation layer  56 .  
         [0068]    Novel system  10  employs two communication methods: In accordance with the first method, CCU  12  broadcasts information or data to all or a preselected number of the components that collectively form DAVieS  10 . In accordance with the second method, CCU  12  sends out control frames to one or more components to request transmission of data from the component or to request that said component or components receive data from the CCU. The data may be a control signal such as time of day, for example. Significantly, all components of the DAVieS  10  react to CCU  12  commands, i.e., said components do not communicate asynchronously with CCU  12 .  
         [0069]    DAVieS  10  begins functioning only after CCU  12  has been turned on. Before power is delivered to CCU  12 , the master and the components or slaves will not interact with the CCU or each other. As indicated in FIG. 5, using left and right audio information as an example, after it has been activated, CCU  12  sends a timing signal to synchronize all components on DAVieS  10 ; in this example timing signals  61 ,  63 ,  71 ,  73  are sent to all units. The CCU then sends a control signal to each component such as set-time, turn-on, turn-off, send data, receive data, and other specialized commands. In this example, left audio information from the CCU to the left speaker is sent as at  69  and right audio information from the CCU to the right speaker is sent as at  79 . Control signals from the CCU that request data are sent to the respective inputs of the components; in this example, a Request Tuner for Left Audio Information to be sent to the CCU is denoted  65  and the same Request for Right Audio Information is denoted  75 . Control signals from the CCU that send data are sent to the outputs of said components. In the example of FIG. 5, reference numeral  69  indicates Left Audio Information from the CCU to the left speaker and reference numeral  79  represents Right Audio Information from the CCU to the right speaker. The CCU may also request from an input component that data be sent to a processing component such as a digital signal processor. However, all new messages must originate with the CCU.  
         [0070]    CCU  12  controls data flow on DAVieS  10  by regulating the speed of data transmission and the size of data transmission, i.e., it serves as a traffic controller. CCU  12  also provides the time of day and date information to all on-line components. The CCU could also be used as a digital signal processor since almost all audio and video signals must go through the CCU to reach a component such as a speaker or a TV set, so it is advantageous for the CCU to process the digital signals as well.  
         [0071]    Operating CCU  12  as a digital signal procesor also reduces overall DAVieS  10  traffic, thereby freeing up more bandwidth for data transmission.  
         [0072]    [0072]FIG. 6 diagrams the communication between CCU  12  and one of the components of DAVieS  10 . Preferably, the time is broadcast twice as indicated by the CCU and the component reacts by setting the time twice; the second time is for redundancy, i.e., just in case the first signal to set time was missed for any reason. In the example of FIG. 6, CCU  12  next sends a request for left audio information from the component, which in this example is tuner  18 . The tuner reacts by sending digitized left audio information to CCU  12 . The CCU receives and signal processes the left audio information. It then sends a signal to set the volume of the left speaker, and the left speaker reacts by setting the volume. CCU  12  then sends digitized left audio information to the left speaker. The left speaker receives the left audio information, a DDA device positioned at the input of the speaker converts it to analog, and an amplifier amplifies the analog signal to a specific volume, and drives the speaker. The CCU then broadcasts the time again and a similar set of control signals such as those depicted in FIG. 6 is repeated.  
         [0073]    Each component should have the same communication protocol. FIG. 7 discloses, in flowchart form, how the data are processed.  
         [0074]    More particularly, program  80  begins at Start block  82  and flows to function block  84  where the buffer memory is erased by a Clean Buffer Memory instruction so that old commands in the CCU buffer memory are deleted. The program then flows to function block  86  where a Set Variables instruction performs the function its name expresses. At function block  88 , an Initialize Station ID signal performs that function, and units are initialized at function block  90 . A command instructing all components to receive data from CCU  12  is sent to the components when the program flows to Receive Data function block  92 .  
         [0075]    When data arrives at a component, a decision is made at decision block  94  as to whether or not the data has arrived at the correct address. If it has not, the data is discarded and the program flows along No path  95 , returning to the input of Receive Data function block  92 , and waits for the data to arrive. If the address is correct, the program flows to decision block  96 ; at this time, the program decides whether or not the signal is a control signal as distinguished from a request for data signal. If it is not a control signal, the program flows along No path  97  to decision block  98  where it is determined whether or not the signal from the CCU is a request for data from the component at that particular address. If it is not, the program flows along No path  99  to decision block  100  where a determination is made as to whether or not the data is in receivable form because if it is not a control signal or a request for data signal, then the data may be corrupted. If it is determined that the data is not in receivable form, the program discards the data and flows along No path  101  and returns to the input of Receive Data function block  92 . If the data is determined to be in receivable form, said data is extracted from its data frame at Extract Data From Frame function block  102 , moved to a buffer at Move Data to In Buffer function block  104 , and an identification flag is associated with such data at Set In Buffer Flag function block  106 . The program then flows along path  107  to the input of Receive Data function block  92  and the above-recited steps are repeated for new incoming data. The program also flows to DSP and Filter Processing function block  108  where the expressed functions are performed. If the data, which is in digital form because CCU  12  generates only digital signals, is to be sent to a component having an internal digital circuit (such as a CD player, for example), then the program flows to said digital circuit of said component as indicated by block  110 . If the data is bound for a component having an internal analog circuit, such as a speaker, the program flows to In Buffer to D/A function block  112  where the data awaits sending to digital-to-analog converter  114 . The data exits D/A converter  114  in analog form and is applied to the analog circuit of the component as at  116 .  
         [0076]    If decision block  98  determines that the signal from CCU  12  is a request for data, the program flows along Yes path  105  to Available Data decision block  134 . If the component is unable to send data, the program flows along No path  95  to the input of Receive Data function block  92 . If it is determined that the component is capable of sending data, the program flows along Yes path  137  to Ready to Send? decision block  126  (FIG. 7B). If the available data is not ready to send, the program returns along No path  129  to the input of Ready to Send? decision block  126  and waits for the data. The loop is continued until the data is ready to send, whereupon it follows Yes path  127  and is handled as set forth in the following paragraph.  
         [0077]    As indicated in the upper righthand corner of FIG. 7B, after the analog data has been applied to the analog circuit  116 , an analog-to-digital converter (ADE)  118  performs its stated function and delivers the data to A/D to Out Buffer  120  where it awaits transfer to DSP and Filter Processing means  122 ; note that the input of DSP and Filter Processing function block  122  is also connected to digital circuit  110 . The program then flows to Set Out Buffer Flag function block  124  that marks the data as ready to send. It is then determined whether or not the data is ready to be sent at the Ready to Send? decision block  126 . If the answer is in the affirmative, the program flows along Yes path  127  to Add Header and Trailer and Calculate CRC function block  128  which performs those functions. The data frame is sent to an out buffer at Send Out Buffer-Frame function block  130 , and the program then flows to Reset Out Buffer function block  132  which performs that function. The program then flows to the input of Receive Data function block  92 .  
         [0078]    If the decision is made at decision block  96  (FIG. 7A) that the signal from CCU  12  is a control signal, the program flows along Yes path  139  to a process, also disclosed in flowchart form, for processing control frames. That process is disclosed in FIG. 7C and is denoted  140  as a whole.  
         [0079]    It is first determined at decision block  142  whether or not the control signal from the CCU is a set time signal. If the decision is made in the affirmative, the program flows along Yes path  143  and the time is set by means represented by Set Time function block  144 . The program then flows to the input of Receive Data function block  92 . If the signal is determined to be a signal other than a set time signal, the program flows along No path  145  to decision block  146  where it is determined whether or not the signal is a command to deliver power to the component. If it is determined that the signal is a turn-on signal, the program flows along Yes path  147  to Turn On function block  148  where suitable means performs that function. The program then flows to the input of Receive Data function block  92 .  
         [0080]    If the signal is determined to be a signal other than a turn on signal, the program flows along No path  149  to decision block  150  where it is determined whether or not the signal is a command to terminate power to the component. If it is determined that the signal is a Turn-Off signal, the program flows along Yes path  151  to Turn Off function block  152  where suitable means performs that function. The program then flows to the input of Receive Data function block  92 .  
         [0081]    If the signal is determined to be a signal other than a Turn-Off signal, the program flows along No path  153  to decision block  154  where it is determined whether or not the signal is a Synchronize command. If it is determined that the signal is a synchronize signal, the program flows along Yes path  155  to Set Synchronization function block  156  where suitable synchronization means performs that function. The program then flows to the input of Receive Data function block  92 .  
         [0082]    If the signal is determined to be a signal other than a synchronize signal, the program flows along No path  157  to decision block  158  where it is determined whether or not the signal is a request identification signal. If it is determined that the signal is a Request ID signal, the program flows along Yes path  159  to Send ID function block  160  where suitable means is employed to send the ID of the component to the CCU. The program then flows to the input of Receive Data function block  92 .  
         [0083]    If the signal is determined to be a signal other than a Request ID signal, the program flows along No path  161  to decision block  162  where it is determined whether or not the signal is a Ping signal from CCU  12 . If it is determined that the signal is a Ping signal, the program flows along Yes path  163  to Return Ping function block  164  where suitable means returns the Ping to CCU  12 . The program then flows to the input of Receive Data function block  92 .  
         [0084]    If the signal is determined to be a signal other than a Ping signal, the program flows along No path  165  to decision block  166  where it is determined whether or not the signal is a command to set the volume of the component. If it is determined that the signal is a Set Volume signal, the program flows along Yes path  167  to Set Volume function block  168  where suitable means performs that function. The program then flows to the input of Receive Data function block  92 .  
         [0085]    If it is determined that the signal is not a Set Volume signal, the program flows along No path  169  to still another decision block, like decision blocks  142 ,  146 ,  150 ,  154 ,  158 ,  162 , and  166 , and the process as described above continues until all of the commands from the CCU have been identifed and carried out.  
         [0086]    It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained.  
         [0087]    Since certain changes may be made in the foregoing method without departing from the scope of the invention, it is intended that all steps contained in the foregoing method or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.  
         [0088]    It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.  
         [0089]    Now that the invention has been described.