Abstract:
A fully redundant linearly expandable router is comprised of first, second, third and fourth router components. Each router component includes first and second routing engines. First, second and third discrete links couple the first routing engine to the first routing engines, respectively. Fourth and fifth discrete links couple the first routing engine to the first routing engines, respectively. A sixth discrete link couples the routing engine to the routing engine. Seventh, eighth and ninth discrete links couple the second routing engine to the second routing engines, respectively. Tenth and eleventh discrete links couple the second routing engine to the second routing engines, respectively. A twelfth discrete link couples the routing engine to the router engine.

Description:
CROSS REFERENCE 
     This application claims the benefit, under 35 U.S.C. §365 of International Application PCT/US03/18821, filed Jun. 13, 2003, which was published in accordance with PCT Article 21(2) on Dec. 31, 2003 in English and which claims the benefit of United States provisional patent application No. 60/390,845, filed Jun. 21, 2002. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to broadcast routers and, more particularly, to a fully redundant linearly expandable broadcast router having plural routing engines arranged in a fully connected topology. 
     BACKGROUND OF THE INVENTION 
     A broadcast router allows each one of a plurality of outputs therefrom to be assigned the signal from any one of a plurality of inputs thereto. For example, an N×M broadcast router has N inputs and M outputs coupled together by a routing engine which allows any one of the N inputs to be applied to each one of the M outputs. Oftentimes, it is desirable to construct larger broadcast routers, for example a 4N×4M broadcast router. One solution to building larger broadcast routers was to use the smaller broadcast router as a building block of the proposed larger broadcast router. This technique, however, resulted in the exponential growth of the proposed larger broadcast routers. For example; to construct a 4N×4M broadcast router required 16 N×M broadcast routers. As a result, large broadcast routers constructed in this manner were often both expensive and unwieldy. Linearly expandable broadcast routers overcame the problems of geometric expansion. However, conventionally configured linearly expandable broadcast routers suffer from other types of deficiencies. For example, oftentimes, they are susceptible to catastrophic failures which cause plural broadcast router components to fail in response to a single break. 
     SUMMARY OF THE INVENTION 
     A fully redundant linearly expandable router is configured to include three or more router components, each of which includes first and second routing engines. The first routing engines of the three or more router components are arranged in a first fully connected topology whereby an input side of each one of the three or more first routing engines includes a discrete link to an input side of each one of the remaining ones of the three or more first routing engines. Similarly, the second routing engines of the three or more router components are arranged in a second fully connected topology whereby an input side of each one of the three or more second routing engines includes a discrete link to an input side of each one of the remaining ones of the three or more second routing engines. By interconnecting the input sides of the three or more routing engines in this manner, all of the first routing engines will have the same XN inputs, where X is the number of router components forming part of the linearly expandable router and N is the number of inputs to each individual routing engine, and a backup routing engine in the event of a failure thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a fully redundant linearly expandable broadcast router constructed in accordance with the teachings of the present invention; 
         FIG. 2  is an expanded block diagram of a first broadcast router component of the fully redundant linearly expandable broadcast router of  FIG. 1 ; 
         FIG. 3  is an expanded block diagram of a second broadcast router component of the fully redundant linearly expandable broadcast router of  FIG. 1 ; 
         FIG. 4  is an expanded block diagram of a third broadcast router component of the fully redundant linearly expandable broadcast router of  FIG. 1 ; 
         FIG. 5  is an expanded block diagram of a fourth broadcast router component of the fully redundant linearly expandable broadcast router of  FIG. 1 ; 
         FIG. 6  is an expanded block diagram of a first expansion port of the first broadcast router component of  FIG. 2 ; 
         FIG. 7  is an expanded block diagram of an alternate embodiment of the first broadcast router component of the fully redundant linearly expandable broadcast router of  FIG. 1 ; 
         FIG. 8  is an expanded block diagram of an alternate embodiment of the second broadcast router component of the fully redundant linearly expandable broadcast router of  FIG. 1 ; 
         FIG. 9  is an expanded block diagram of an alternate embodiment of the third broadcast router component of the fully redundant linearly expandable broadcast router of  FIG. 1 ; and 
         FIG. 10  is an expanded block diagram of an alternate embodiment of the fourth broadcast router component of the fully redundant linearly expandable broadcast router of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIG. 1 , a fully redundant linearly expandable broadcast router  100  constructed in accordance with the teachings of the present invention will now be described in greater detail. As may now be seen, the fully redundant linearly expandable broadcast router  100  is comprised of plural broadcast router components coupled to one another to form the larger fully redundant linearly expandable broadcast router  100 . Each broadcast router component is a discrete router device which includes first and second router matrices, the second router matrix being redundant of the first router matrix. Thus, each broadcast router has first and second routing engines, one for each of the first and second router matrices, each receiving, at an input side thereof, the same input digital audio streams and placing, at an output side thereof, the same output digital audio streams. As disclosed herein, each of the broadcast router components used to construct the fully redundant linearly expandable broadcast router are N×M sized broadcast routers. However, it is fully contemplated that the fully redundant linearly expandable broadcast router  100  could instead be constructed of broadcast router components of different sizes relative to one another. 
     As further disclosed herein, the fully redundant linearly expandable broadcast router  100  is formed by coupling together first, second, third and fourth broadcast router components  102 ,  104 ,  106  and  108 . Of course, the present disclosure of the fully redundant linearly expandable broadcast router  100  as being formed of four broadcast router components is purely by way of example. Accordingly, it should be clearly understood that a fully redundant linearly expandable broadcast router constructed in accordance with the teachings of the present invention may be formed using various other numbers of broadcast router components as long as the total number of broadcast router components which collectively form the linearly expandable broadcast router is equal to or greater than three. The first, second, third and fourth broadcast router components  102 ,  104 ,  106  and  108  which, when fully connected in the manner disclosed herein, collectively form the fully redundant linearly expandable broadcast router  100 , may either be housed together in a common chassis as illustrated in FIG.  1  or, if desired, housed in separate chassis. While, as previously set forth, the broadcast router components  102 ,  104 ,  106  and  108  may have different sizes relative to one another or, in the alternative, may all have the same N×M size, one size that has proven suitable for the uses contemplated herein is 256×256. Furthermore, a suitable configuration for the fully redundant linear expandable broadcast router  100  would be to couple five broadcast router components, each sized at 256×256, thereby resulting in a 1,280×1,280 broadcast router. 
     The first broadcast router component  102  is comprised of a first router matrix  102   a  and a second (or redundant) router matrix  102   b  used to replace the first router matrix  102   a  in the event of a failure thereof. Similarly, each one of the second, third and fourth broadcast router components  104 ,  106 , and  108  of the fully redundant linearly expandable broadcast router  100  are comprised of a first router matrix  104   a ,  106   a  and  108   a , respectively, and a second (or redundant) router matrix  104   b ,  106   b  and  108   b , respectively, used to replace the first router matrix  104   a ,  106   a  and  108   a , respectively, in the event of a failure thereof. Of course, the designation of the second router matrices  102   b ,  104   b ,  106   b  and  108   b  as backups for the first router matrices  102   a ,  104   a ,  106   a  and  108   a , respectively, is purely arbitrary and it is fully contemplated that any either of a router matrix pair residing within a broadcast router component may act as a backup for the other of the router matrix pair residing within that broadcast router component. 
     As may be further seen in  FIG. 1 , the first router matrix  102   a  of the first broadcast router component  102 , the first router matrix  104   a  of the second broadcast router component  104 , the first router matrix  106   a  of the third broadcast router component  106  and the first router matrix  108   a  of the fourth broadcast router component  108  are coupled together in a first arrangement of router matrices which conforms to a fully connected topology. Similarly, the second router matrix  102   b  of the first broadcast router component  102 , the second router matrix  104   b  of the second broadcast router component  104 , the second router matrix  106   b  of the third broadcast router component  106  and the second router matrix  108   b  of the fourth broadcast router component  108  are coupled together in a second arrangement which, like the first arrangement, conforms to a fully connected topology. In a fully connected topology, each router matrix of an arrangement of router matrices is coupled, by a discrete link, to each and every other router matrix forming part of the arrangement of router matrices. 
     Thus, for the first arrangement of router matrices, first, second and third bi-directional links  110 ,  112  and  114  couples the first router matrix  102   a  of the first broadcast router component  102  to the first router matrix  104   a  of the second broadcast router component  104 , the first router matrix  106   a  of the third broadcast router component  106  and the first router matrix  108   a  of the fourth broadcast router component  108 , respectively. Additionally, fourth and fifth bi-directional links  116  and  118  couple the first router matrix  104   a  of the second broadcast router component  104  to the first router matrix  106   a  of the third broadcast router component  106  and the first router matrix  108   a  of the fourth broadcast router component  108 , respectively. Finally, a sixth bi-directional link  120  couples the first router matrix  106   a  of the third broadcast router component  106  to the first router matrix  108   a  of the fourth broadcast router component  108 . Variously, the bi-directional links  110  through  120  may be formed of copper wire, optical fiber or another transmission medium deemed suitable for the exchange of digital signals. 
     Similarly, for the second arrangement of router matrices, first, second and third bi-directional links  122 ,  124  and  126  couples the second router matrix  102   b  of the first broadcast router component  102  to the second router matrix  104   b  of the second broadcast router component  104 , the second router matrix  106   b  of the third broadcast router component  106  and the second router matrix  108   b  of the fourth broadcast router component  108 , respectively. Additionally, fourth and fifth bi-directional links  128  and  130  couple the second router matrix  104   b  of the second broadcast router component  104  to the second router matrix  106   b  of the third broadcast router component  106  and the second router matrix  108   b  of the fourth broadcast router component  108 , respectively. Finally, a sixth bi-directional link  132  couples the second router matrix  106   b  of the third broadcast router component  106  to the second router matrix  108   b  of the fourth broadcast router component  108 . Again, the bi-directional links  122  through  132  may be formed of copper wire, optical fiber or another transmission medium deemed suitable for the exchange of digital signals. 
     Of course, rather than the single bi-directional links between pairs of router matrices illustrated in  FIG. 1 , in an alternate embodiment of the invention, it is contemplated that the pairs of router matrices may instead be coupled together by first and second uni-directional links. Such an alternate configuration is illustrated in each one of  FIGS. 2-5 . 
     Turning now to  FIGS. 2-5 , the fully redundant linearly expandable broadcast router  100  will now be described in greater detail. The first broadcast router component  102  of the fully redundant linearly expandable broadcast router  100  is illustrated in  FIG. 2 . As may now be seen, the first broadcast router component is comprised of an input side  134 , an output side  136  and the first and second router matrices  102   a  and  102   b , both of which are coupled between the input and output sides  134  and  136 . The input side  134  includes N selectors  138 - 1  through  138 -N arranged such that the output of each one of the selectors provides one of n inputs to the first and second router matrices  102   a  and  102   b . As disclosed herein, each one of the selectors  138 - 1  through  138 -N is a 2:1 selector circuit having, as a first input  140 - 1  through  140 -N, respectively, an input digital audio data stream conforming to the Audio Engineering Society-11 (“AES-11”) standard and, as a second input  142 - 1  through  142 -N, respectively, an input digital audio data stream conforming to the multichannel digital audio interface (“MADI”) standard set forth in the AES-10 standard. In this regard, it should be noted that a MADI input digital audio data stream may contain up to 32 AES digital audio data streams and that each one of the second inputs  142 - 1  through  142 -N contains a single AES digital audio data stream which had previously been extracted from a MADI input digital audio data stream by extraction circuitry (not shown). Thus, the output of each one of the selector circuits  138 - 1  through  138 -N provides one of N input digital audio data streams to each of the first and second router matrices  102   a  and  102   b  of the first broadcast router component  102 . Each one of the selector circuits  138 - 1  through  138 -N further includes a control input (not shown) for selecting between the AES-11 and MADI input digital audio data streams. Of course, it should be readily appreciated that other types of input data streams other than the input digital audio data streams disclosed herein are equally suitable for use with the first broadcast router component  102 , as well as with the second, third and fourth broadcast router components  104 ,  106  and  108 . For example, it is contemplated that the broadcast router components  102 ,  104 ,  106  and  108  may instead be used with other low bandwidth digital signals such as compressed video and data signals. It is further contemplated that, with minor modifications, for example, faster hardware, the broadcast router components  102 ,  104 ,  106  and  108  may be used with non-compressed digital video signals. 
     The selected input digital audio data stream output each one of the selector circuits  138 - 1  through  138 -N is fed into a routing engine  144 , a first expansion port  146 , a second expansion port  148  and a third expansion port  150  of the first router matrix  102   a . Additionally, the selected input digital audio data stream output each one of the selector circuits  138 - 1  through  138 -N is fed into a routing engine  152 , a first expansion port  154 , a second expansion port  156  and a third expansion port  158  of the second router matrix  102   b . Residing within the routing engine  144  of the first router matrix  102   a  is switching means for assigning any one of the input digital audio data signals received as inputs to the routing engine  144  to any one of the output lines of the routing engine  144 . Variously, it is contemplated that the routing engine  144  may be embodied in software, for example, as a series of instructions; hardware, for example, as a series of logic circuits; or a combination thereof. In a broad sense, each one of the first, second and third expansion ports  146 ,  148  and  150  of the first router matrix  102   a  is comprised of a memory subsystem in which: (1) input digital audio data streams received from the selector circuits  138 - 1  through  138 - n  of a first broadcast router component; and (2) input digital audio data streams received from an expansion port of a first router matrix of a second broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling: (1) the transfer of the input digital audio data streams received from the selector circuits  138 - 1  through  138 -N to an expansion port of the first router matrix of another broadcast router component; and (2) the transfer of the input digital audio data streams received from the expansion port of the first router matrix of the other broadcast router component to inputs of the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 . Similarly, residing within the routing engine  152  of the second router matrix  102   b  is switching means for assigning any one of the input digital audio data signals received as inputs to the routing engine  152  to any one of the output lines of the routing engine  152 . Again, it is contemplated that the routing engine  152  may be variously embodied in software, hardware or a combination thereof. In a broad sense, each one of the first, second and third expansion ports  154   156  and  158  of the second router matrix  102   b  is comprised of a memory subsystem in which: (1) input digital audio data streams received from the selector circuits  138 - 1  through  138 -N of the first broadcast router component  102 ; and (2) input digital audio data streams received from an expansion port of a second router matrix of the second broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling: (1) the transfer of the input digital audio data streams received from the selector circuits  138 - 1  through  138 -N to an expansion port of the second router matrix of the second broadcast router component; and (2) the transfer of the input digital audio data streams received from the expansion port of the second router matrix of the second broadcast router component to inputs of the routing engine  152  of the first router matrix  102   b  of the first broadcast router component  102 . 
     Turning momentarily to  FIG. 6 , the expansion port  146  of the first router matrix  102   a  of the first broadcast router component  102  will now be described in greater detail. In this regard, it should be noted that, while only the first expansion port  130  is described and illustrated herein, second and third expansion ports  148  and  150  of the first router matrix  102   a  of the first broadcast router component  102 , first, second and third expansion ports  152 ,  154  and  156  of the second router matrix  102   b  of the first broadcast router component  102 , first, second and third expansion ports  180 ,  182  and  184  of the first router matrix  104   a  of the second broadcast router component  104 , first, second and third expansion ports  188 ,  190  and  192  of the second router matrix  104   b  of the second broadcast router component  104 , first, second and third expansion ports  214 ,  216  and  218  of the first router matrix  106   a  of the third broadcast router component  106 , first, second and third expansion ports  222 ,  224  and  226  of the second router matrix  106   b  of the third broadcast router component  106 , first, second and third expansion ports  248 ,  250  and  252  of the first router matrix  108   a  of the fourth broadcast router component  106  and first, second and third expansion ports  256 ,  258  and  260  of the second router matrix  108   b  of the fourth broadcast router component  108  are similarly configured. Accordingly, the description that follows is equally applicable to those expansion ports as well. 
     As may be seen in  FIG. 6 , the first expansion port  146  of the first router matrix  102   a  of the first broadcast router component  102  includes a first memory space  270  and a second memory space  272 . Variously, the first and second memory spaces  270  and  272  may be comprised of first and second discrete memory devices or, as shown in  FIG. 6 , may be comprised of first and second discrete address spaces within a common memory device. The expansion port  146  further includes control circuitry  274 , for example, a controller, for controlling the transfer of input digital audio data streams, received by the expansion port  146 , to their final destinations. More specifically, the input digital audio data stream output the selector circuit coupled to the expansion port  146 , for example, the selector circuit  138 - 1 , is temporarily stored, or buffered, in the first memory space  270 . The controller  274  then transfers the digital audio data stored in the first memory space  270  to the second memory space  272  of the expansion port  180  of the first router matrix  104   a  of the second broadcast router component  104 . Similarly, the digital audio data stored in the first memory space  270  of the expansion port  180  of the first router matrix  104   a  of the second broadcast router component  104  is transferred to the second memory space  272 . From the second memory space  272 , the controller  274  provides the digital audio data received from the second broadcast router component  104  as inputs to the routing engine  144  for the first router matrix  102   a  of the first broadcast router component  102 . Of course, the configuration and operation of the expansion port  146  is but one device and process suitable for the transfer of digital audio data and it is fully contemplated that other devices and processes involving buffering and/or first-in-first-out (“FIFO”) schemes are equally suitable for the purposes disclosed herein. 
     The second broadcast router component  104  of the fully redundant linearly expandable broadcast router  100  is illustrated in  FIG. 3 . As may now be seen, the second broadcast router component  104  is comprised of an input side  168 , an output side  170  and the first and second router matrices  104   a  and  104   b , both of which are coupled between the input and output sides  202  and  204 . The input side  202  includes N selectors  176 - 1  through  176 -N arranged such that the output of each one of the selectors provides one of N inputs to the first and second router matrices  104   a  and  104   b . As disclosed herein, each one of the selectors  176 - 1  through  176 -N is a 2:1 selector circuit having, as a first input  172 - 1  through  172 -N, respectively, an input digital audio data stream conforming to the AES-11 standard and, as a second input  174 - 1  through  174 -N, respectively, an input digital audio data stream conforming to the MADI standard. Again, it should be noted that a MADI input digital audio data stream may contain up to 32 AES digital audio data streams and that each one of the second inputs  174 - 1  through  174 -N contains a single AES digital audio data stream which had previously been extracted from a MADI input digital audio data stream by extraction circuitry (not shown). Thus, the output of each one of the selector circuits  176 - 1  through  176 -N provides one of N input digital audio data streams to each of the first and second router matrices  104   a  and  104   b  of the second broadcast router component  104 . Each one of the selector circuits  176 - 1  through  176 -N further includes a control input (not shown) for selecting between the AES-11 and MADI input digital audio data streams. 
     The selected input digital audio data stream output each one of the selector circuits  176 - 1  through  176 -N is fed into a routing engine  178 , a first expansion port  180 , a second expansion port  182  and a third expansion port  184  of the first router matrix  104   a.  Additionally, the selected input digital audio data stream output each one of the selector circuits  176 - 1  through  176 -N is fed into a routing engine  186 , a first expansion port  188 , a second expansion port  190  and a third expansion port  192  of the second router matrix  102   b . Residing within the routing engine  178  of the first router matrix  104   a  is switching means for assigning any one of the input digital audio data signals received as inputs to the routing engine  178  to any one of the output lines of the routing engine  178 . Variously, it is contemplated that the routing engine  178  may be embodied in software, hardware or a combination thereof. In a broad sense, each one of the first, second and third expansion ports  180 ,  182  and  184  of the first router matrix  104   a  is comprised of a memory subsystem in which: (1) input digital audio data streams received from the selector circuits  176 - 1  through  176 -N of a first broadcast router component; and (2) input digital audio data streams received from an expansion port of a first router matrix of a second broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling: (1) the transfer of the input digital audio data streams received from the selector circuits  176 - 1  through  176 -N to an expansion port of the first router matrix of another broadcast router component; and (2) the transfer of the input digital audio data streams received from the expansion port of the first router matrix of the other broadcast router component to inputs of the routing engine  178  of the first router matrix  104   a  of the second broadcast router component  104 . 
     Similarly, residing within the routing engine  186  of the second router matrix  104   b  is switching means for assigning any one of the input digital audio data signals received as inputs to the routing engine  186  to any one of the output lines of the routing engine  186 . Again, it is contemplated that the routing engine  186  may be variously embodied in software, hardware or a combination thereof. In a broad sense, each one of the first, second and third expansion ports  188 ,  190  and  192  of the second router matrix  104   b  is comprised of a memory subsystem in which: (1) input digital audio data streams received from the selector circuits  176 - 1  through  176 -N of the second broadcast router component  104 ; and (2) input digital audio data streams received from an expansion port of a second router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling: (1) the transfer of the input digital audio data streams received from the selector circuits  176 - 1  through  176 -N to an expansion port of the second router matrix of the other broadcast router component; and (2) the transfer of the input digital audio data streams received from the expansion port of the second router matrix of the other broadcast router component to inputs of the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 . 
     The third broadcast router component  106  of the fully redundant linearly expandable broadcast router  100  is illustrated in  FIG. 4 . As may now be seen, the third broadcast router component  106  is comprised of an input side  202 , an output side  204  and the first and second router matrices  106   a  and  106   b , both of which are coupled between the input and output sides  202  and  204 . The input side  202  includes N selectors  210 - 1  through  210 -N arranged such that the output of each one of the selectors provides one of N inputs to the first and second router matrices  106   a  and  106   b . As disclosed herein, each one of the selectors  210 - 1  through  210 -N is a 2:1 selector circuit having, as a first input  206 - 1  through  206 -N, respectively, an input digital audio data stream conforming to the AES-11 standard and, as a second input  208 - 1  through  208 -N, respectively, an input digital audio data stream conforming to the MADI standard. In this regard, it is again noted that a MADI input digital audio data stream may contain up to 32 AES digital audio data streams and that each one of the second inputs  208 - 1  through  208 -N contains a single AES digital audio data stream which had previously been extracted from a MADI input digital audio data stream by extraction circuitry (not shown). Thus, the output of each one of the selector circuits  210 - 1  through  210 -N provides one of N input digital audio data streams to each of the first and second router matrices  106   a  and  106   b  of the third broadcast router component  106 . Each one of the selector circuits  210 - 1  through  210 -N further includes a control input (not shown) for selecting between the AES-11 and MADI input digital audio data streams. 
     The selected input digital audio data stream output each one of the selector circuits  210 - 1  through  210 - n  is fed into a routing engine  212 , a first expansion port  214 , a second expansion port  216  and a third expansion port  218  of the first router matrix  106   a . Additionally, the selected input digital audio data stream output each one of the selector circuits  210 - 1  through  210 -N is fed into a routing engine  220 , a first expansion port  222 , a second expansion port  224  and a third expansion port  226  of the second router matrix  106   b . Residing within the routing engine  212  of the first router matrix  106   a  is switching means for assigning any one of the input digital audio data signals received as inputs to the routing engine  212  to any one of the output lines of the routing engine  212 . Variously, it is contemplated that the routing engine  144  may be embodied in software, hardware, or a combination thereof. In a broad sense, each one of the first, second and third expansion ports  214 ,  216  and  218  of the first router matrix  106   a  is comprised of a memory subsystem in which: (1) input digital audio data streams received from the selector circuits  210 - 1  through  210 -N of the third broadcast router component  106 ; and (2) input digital audio data streams received from an expansion port of a first router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling: (1) the transfer of the input digital audio data streams received from the selector circuits  210 - 1  through  210 -N to an expansion port of the first router matrix of the other broadcast router component; and (2) the transfer of the input digital audio data streams received from the expansion port of the first router matrix of the other broadcast router component to inputs of the routing engine  212  of the first router matrix  106   a  of the third broadcast router component  106 . Similarly, residing within the routing engine  220  of the second router matrix  106   b  is switching means for assigning any one of the input digital audio data signals received as inputs to the routing engine  220  to any one of the output lines of the routing engine  220 . Again, it is contemplated that the routing engine  220  may be variously embodied in software, hardware or a combination thereof. In a broad sense, each one of the first, second and third expansion ports  222 ,  224  and  226  of the second router matrix  106   b  is comprised of a memory subsystem in which: (1) input digital audio data streams received from the selector circuits  210 - 1  through  210 -N of the first broadcast router component  106 ; and (2) input digital audio data streams received from an expansion port of a second router matrix of the other broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling: (1) the transfer of the input digital audio data streams received from the selector circuits  210 - 1  through  210 -N to an expansion port of the second router matrix of the other broadcast router component; and (2) the transfer of the input digital audio data streams received from the expansion port of the second router matrix of the other broadcast router component to inputs of the routing engine  220  of the second router matrix  106   b  of the third broadcast router component  106 . 
     The fourth broadcast router component  108  of the fully redundant linearly expandable broadcast router  100  is illustrated in  FIG. 5 . As may now be seen, the fourth broadcast router component  108  is comprised of an input side  236 , an output side  238  and the first and second router matrices  108   a  and  108   b , both of which are coupled between the input and output sides  236  and  238 . The input side  236  includes n selectors  244 - 1  through  244 -N arranged such that the output of each one of the selectors provides one of n inputs to the first and second router matrices  108   a  and  108   b . As disclosed herein, each one of the selectors  244 - 1  through  244 -N is a 2:1 selector circuit having, as a first input  240 - 1  through  240 -N, respectively, an input digital audio data stream conforming to the AES-11 standard and, as a second input  242 - 1  through  242 -N, respectively, an input digital audio data stream conforming to the MADI standard. Thus, the output of each one of the selector circuits  244 - 1  through  244 -N provides one of N input digital audio data streams to each of the first and second router matrices  108   a  and  108   b  for the fourth broadcast router component  108 . Each one of the selector circuits  244 - 1  through  244 -N further includes a control input (not shown) for selecting between the AES-11 and MADI input digital audio data streams. 
     The selected input digital audio data stream output each one of the selector circuits  244 - 1  through  244 -N is fed into a routing engine  246 , a first expansion port  248 , a second expansion port  250  and a third expansion port  252  of the first router matrix  108   a . Additionally, the selected input digital audio data stream output each one of the selector circuits  244 - 1  through  244 -N is fed into a routing engine  254 , a first expansion port  256 , a second expansion port  258  and a third expansion port  260  of the second router matrix  108   b . Residing within the routing engine  246  of the first router matrix  108   a  is switching means for assigning any one of the input digital audio data signals received as inputs to the routing engine  246  to any one of the output lines of the routing engine  246 . Variously, it is contemplated that the routing engine  246  may be embodied in software, hardware, or a combination thereof. In a broad sense, each one of the first, second and third expansion ports  248 ,  250  and  252  of the fourth router matrix  108   a  is comprised of a memory subsystem in which: (1) input digital audio data streams received from the selector circuits  244 - 1  through  244 -N of a first broadcast router component; and (2) input digital audio data streams received from an expansion port of a first router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling: (1) the transfer of the input digital audio data streams received from the selector circuits  244 - 1  through  244 -N to an expansion port of the first router matrix of the other broadcast router component; and (2) the transfer of the input digital audio data streams received from the expansion port of the first router matrix of the other broadcast router component to inputs of the routing engine  246  of the first router matrix  108   a  of the fourth broadcast router component  108 . Similarly, residing within the routing engine  254  of the second router matrix  108   b  is switching means for assigning any one of the input digital audio data signals received as inputs to the routing engine  254  to any one of the output lines of the routing engine  254 . Again, it is contemplated that the routing engine  254  may be variously embodied in software, hardware or a combination thereof. In a broad sense, each one of the first, second and third expansion ports  256 ,  258  and  260  of the second router matrix  108   b  is comprised of a memory subsystem in which: (1) input digital audio data streams received from the selector circuits  244 - 1  through  244 - n  of the fourth broadcast router component  108 ; and (2) input digital audio data streams received from an expansion port of a second router matrix of the other broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling: (1) the transfer of the input digital audio data streams received from the selector circuits  244 - 1  through  244 -N to an expansion port of the second router matrix of the other broadcast router component; and (2) the transfer of the input digital audio data streams received from the expansion port of the second router matrix of the other broadcast router component to inputs of the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router component  108 . 
     Referring next to  FIGS. 2-5 , as a discrete input digital audio data stream is output each of the selector circuits  138 - 1  through  138 -N, the input digital audio data streams fed to each one of the input side of the routing engine  144 , the first expansion port  146 , the second expansion port  148  and the third expansion port  150  of the first router matrix  102   a  of the first broadcast router component  102  are audio data input streams  1  through N. Similarly, the input digital audio data streams fed to each one of the input side of the routing engine  178 , the first expansion port  180 , the second expansion port  182  and the third expansion port  184  of the first router matrix  104   a  of the second broadcast router component  104  are input digital audio data streams N+1 through  2 N; the input digital audio data streams fed to each one of the input side of the routing engine  212 , the first expansion port  214 , the second expansion port  216  and the third expansion port  218  of the first router matrix of the third broadcast router component  106  are input digital audio data streams  2 N+1 through  3 N; and the input digital audio data streams fed to each one of the input side of the routing engine  246 , the first expansion port  248 , the second expansion port  250  and the third expansion port  252  of the first router matrix  108   a  of the fourth broadcast router component  108  are input digital audio data streams  3 N+1 through  4 N. 
     To function as a 4N×4M broadcast router, the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 , the routing engine  178  of the second router matrix  104   a  of the second broadcast router component  104 , the routing engine  212  of the third router matrix  106   a  of the third broadcast router component  106  and the routing engine  246  of the fourth router matrix  108   a    8  of the fourth broadcast router component  108  must have all of the input digital audio data streams  1  through  4 N provided as inputs to the input side thereof. For the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 , the input digital audio data streams  1  through N are provided to the input side of the routing engine  144  directly. The input digital audio data streams  1  through N input the first, second and third expansion ports  146 ,  148  and  150 , on the other hand, are transferred to the first expansion port  180  of the first router matrix  104   a  of the second broadcast router component  104  over the link  110 , the second expansion port  216  of the first router matrix  106   b  of the third broadcast router component  106  over the link  112  and the third expansion port  252  of the first router matrix  108   a  of the fourth broadcast router component  108  over the link  114 , respectively. From the first expansion port  180  of the first router matrix  104   a  of the second broadcast router component  104 , the second expansion port  216  of the first router matrix  106   a  of the third broadcast router component  106  and the third expansion port  252  of the first router matrix  108   a  of the fourth broadcast router component  108 , the input digital audio data streams  1  through N are input the routing engine  178  of the first router matrix  104   a  of the second broadcast router component  104 , the routing engine  212  of the first router matrix  106   a  of the third broadcast router component  106  and the routing engine  246  of the first router matrix  108   a  of the fourth broadcast router components  108 , respectively. 
     Similarly, for the first router matrix  104   a  of the second broadcast router component  104 , the input digital audio data streams N+1 through  2 N are provided to the input side of the routing engine  178  directly. The input digital audio data streams N+1 through  2 N input the first, second and third expansion ports  180 ,  182  and  184 , on the other hand, are transferred to the first expansion port  130  of the first router matrix  102   a  of the broadcast router component  102  over the link  110 , the first expansion port  214  of the first router matrix  106   a  of the third broadcast router component  106  over the link  116  and the second expansion port  250  of the first router matrix  108   a  of the fourth broadcast router component  108  over the link  118 , respectively. From the first expansion port  180  of the first router matrix  102   a  of the first broadcast router component  102 , the first expansion port  214  of the first router matrix  106   a  of the third broadcast router component  106  and the second expansion port  250  of the first router matrix  108   a  of the fourth broadcast router component  108 , the input digital audio data streams N+1 through  2 N are input the routing engine  144  of the first routing matrix  102   a  of the first broadcast router component  102 , the routing engine  212  of the first routing matrix  106   a  of the third broadcast router component  106  and the routing engine  246  of the first routing matrix  108   a  of the fourth router component  108 ; respectively. 
     For the first router matrix  106   a  of the third broadcast router component  106 , the input digital audio data streams  2 N+1 through  3 N are input the routing engine  212  directly. The input digital audio data streams  2 N+1 through  3 N input the first, second and third expansion ports  214 ,  216  and  218 , on the other hand, are transferred to the second expansion port  182  of the first router matrix  104   a  of the second broadcast router component  104  over the link  116 , the second expansion port  148  of the first router matrix  102   a  of the first broadcast router component  102  over the link  112  and the first expansion port  248  of the first router matrix  108   a  of the fourth broadcast router component  108  over the link  120 , respectively. From the second expansion port  182  of the first router matrix  104   a  of the second broadcast router component  104 , the second expansion port  148  of the first router matrix  102   a  of the first broadcast router component  102  and the first expansion port  248  of the first router matrix  108   a  of the fourth broadcast router component  108 , the input digital audio data streams  2 N+1 through  3 N are input the routing engine  144  of the first router matrix  102   a  of the first broadcast router  102 , the routing engine  178  of the first router matrix  104   a  of the second broadcast router  104  and the routing engine  246  of the first router matrix  108   a  of the fourth broadcast router component  108 . 
     Finally, for the first router matrix  108   a  of the fourth broadcast router component  108 , the input digital audio data streams  3 N+1 through  4 N are input the routing engine  246  directly. The input digital audio data streams  3 N+1 through  4 N input the first, second and third expansion ports  248 ,  250  and  252 , on the other hand, are transferred to the third expansion port  218  of the first router matrix  106   a  of the third broadcast router component  106  over the link  120 , the third expansion port  184  of the first router matrix  104   a  of the second broadcast router component  104  over the link  118  and the third expansion port  150  of the first router matrix  102   a  of the broadcast router component  102  over the link  114 , respectively. From the third expansion port  150  of the first router matrix  102   a  of the first broadcast router component  102 , the third expansion port  184  of the first router matrix  104   a  of the second broadcast router component  104  and the third expansion port  218  of the first router matrix  106   a  of the third broadcast router component  106 , the input digital audio data streams  3 N+1 through  4 N are input the routing engine  144  of the first routing matrix  102   a  of the first broadcast router component  102 , the routing engine  178  of the first routing matrix  104   a  of the second broadcast router component  104  and the routing engine  212  of the first routing matrix  106   a  of the third broadcast router component  106 . In this manner, the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 , the routing engine  178  of the first router matrix  104   a  of the second broadcast router component  104 , the routing engine  212  of the first router matrix  106   a  of the third broadcast router component  106  and the routing engine  246  of the first router matrix  108   a  of the fourth broadcast router component  108  all receive, as inputs thereto, the input digital audio data streams  1  through  4 N. 
     Within the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 , switch logic or other switching means enables any one of the input digital audio data streams  1  through  4 N to be applied to any of the 1 through M outputs thereof. Similarly, switch logic or other switching means within the routing engine  178  of the first router matrix  104   a  of the second broadcast router component  104 , the routing engine  212  of the first router matrix  106   a  of the third broadcast router component and the routing engine  246  of the first router matrix  108   a  of the fourth router component  108  enables any one of the input digital audio data streams  1  through  4 N to be applied to any of the M+1 through 2M, 2M+1 through 3M and 3M+1 through 4M outputs thereof, respectively. The switching logic or other switching means within each of the routing engines  144 ,  178 ,  212 , and  246  is controlled by one or more control inputs which originate at a controller (not shown) or other control circuitry for the linearly expandable broadcast router  100 . 
     As previously set forth, the second router matrices  102   b ,  104   b ,  106   b  and  108   b  are redundant router matrices available for use in the event that the respective one or ones of the first router matrices  102   a ,  104   a ,  106   a  and  108   a  fail. To function as redundant matrices, the second router matrices  102   b ,  104   b ,  106   b  and  108   b  must receive/transmit the same input/output digital audio data streams as the corresponding one of the first router matrices  102   a ,  104   a ,  106   a  and  108   a . Accordingly, the selector circuits  138 - 1  through  138 -N also feed input digital audio data streams  1  through N to each one of the routing engine  152 , the first expansion port  154 , the second expansion port  156  and the third expansion port  158  of the second router matrix  102   b  of the first broadcast router component  102 . Similarly, the selector circuits  176 - 1  through  176 -N also feed input digital audio data streams N+1 through  2 N to each one of the routing engine  186 , the first expansion port  188 , the second expansion port  190  and the third expansion port  192  of the second router matrix  104   b  of the second broadcast router component  104 ; the selector circuits  210 - 1  through  210 -N also feed input digital audio data streams  2 N+1 through  3 N to each one of the routing engine  220 , the first expansion port  222 , the second expansion port  224  and the third expansion port  226  of the second router matrix  106   b  of the third broadcast router component  106 ; and the selector circuits  244 - 1  through  244 -N also feed input digital audio data streams  3 N+1 through  4 N to each one of the routing engine  254 , the first expansion port  256 , the second expansion port  258  and the third expansion port  260  of the second router matrix  108   b  of the fourth broadcast router component  108 . 
     The routing engine  152  of the second router matrix  102   b  of the first broadcast router component  102 , the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 , the routing engine  220  of the second router matrix  106   b  of the third broadcast router component  106  and the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router component  108  must have all of the input digital audio data streams  1  through  4 N provided as inputs thereto. For the routing engine  152  of the second router matrix  102   b  of the first broadcast router component  102 , the selector circuits  138 - 1  through  138 -N provide input digital audio data streams  1  through N as inputs thereto. The input digital audio data streams  1  through N input the first, second and third expansion ports  154 ,  156  and  158 , on the other hand, are transferred to the first expansion port  188  of the second router matrix  104   b  of the second broadcast router component  104  over the link  122 , the second expansion port  224  of the second router matrix  106   b  of the third broadcast router component  106  over the link  124  and the third expansion port  260  of the second router matrix  108   b  of the fourth broadcast router component  108  over the link  126 , respectively. From the first expansion port  188  of the second router matrix  104   b  of the second broadcast router component  104 , the second expansion port  224  of the second router matrix  106   b  of the third broadcast router component  106  and the third expansion port  260  of the second router matrix  108   b  of the fourth broadcast router component  108 , the input digital audio data streams  1  through N are input the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 , the routing engine  220  of the second router matrix  106   b  of the third broadcast router component  106  and the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router components  108 , respectively. 
     Similarly, for the second router matrix  104   b  of the second broadcast router component  104 , the input digital audio data streams N+1 through  2 N are directly input the routing engine  186 . The input digital audio data streams N+1 through  2 N input the first, second and third expansion ports  188 ,  190  and  192 , on the other hand, are transferred to the first expansion port  154  of the second router matrix  102   b  of the broadcast router component  102  over the link  122 , the first expansion port  222  of the second router matrix  106   b  of the third broadcast router component  106  over the link  128  and the second expansion port  258  of the second router matrix  108   b  of the fourth broadcast router component  108  over the link  130 , respectively. From the first expansion port  154  of the second router matrix  102   b  of the first broadcast router component  102 , the first expansion port  222  of the second router matrix  106   b  of the third broadcast router component  106  and the second expansion port  258  of the second router matrix  108   b  of the fourth broadcast router component  108 , the input digital audio data streams N+1 through  2 N are input the routing engine  152  of the second routing matrix  102   b  of the first broadcast router component  102 , the routing engine  220  of the second routing matrix  106   b  of the third broadcast router component  106  and the routing engine  254  of the second routing matrix  108   a  of the fourth router component  108 , respectively. 
     For the second router matrix  106   b  of the third broadcast router component  106 , the input digital audio data streams  2 N+1 through  3 N are input the routing engine  220  directly. The input digital audio data streams  2 N+1 through  3 N input the first, second and third expansion ports  222 ,  224  and  226 , on the other hand, are transferred to the second expansion port  190  of the second router matrix  104   b  of the second broadcast router component  104  over the link  128 , the second expansion port  156  of the second router matrix  102   b  of the first broadcast router component  102  over the link  126  and the first expansion port  256  of the second router matrix  108   b  of the fourth broadcast router component  108  over the link  132 , respectively. From the second expansion port  190  of the second router matrix  104   b  of the second broadcast router component  104 , the second expansion port  156  of the second router matrix  102   b  of the first broadcast router component  102  and the first expansion port  256  of the second router matrix  108   b  of the fourth broadcast router component  108 , the input digital audio data streams  2 N+1 through  3 N are input the routing engine  152  of the second router matrix  102   b  of the first broadcast router  102 , the routing engine  186  of the second router matrix  104   b  of the second broadcast router  104  and the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router component  108 . 
     Finally, for the second router matrix  108   b  of the fourth broadcast router component  108 , the input digital audio data streams  3 N+1 through  4 N are input the routing engine  254  directly. The input digital audio data streams  3 N+1 through  4 N input the first, second and third expansion ports  256 ,  258  and  260 , on the other hand, are transferred to the third expansion port  226  of the second router matrix  106   b  of the third broadcast router component  106  over the link  132 , the third expansion port  192  of the second router matrix  104   b  of the second broadcast router component  104  over the link  130  and the second expansion port  156  of the second router matrix  102   b  of the broadcast router component  102  over the link  126 , respectively. From the second expansion port  156  of the second router matrix  102   b  of the first broadcast router component  102 , the third expansion port  192  of the second router matrix  104   b  of the second broadcast router component  104  and the third expansion port  226  of the second router matrix  106   b  of the third broadcast router component  106 , the input digital audio data streams  3 N+1 through  4 N are input the routing engine  152  of the second routing matrix  102   b  of the first broadcast router component  102 , the routing engine  186  of the second routing matrix  104   b  of the second broadcast router component  104  and the routing engine  220  of the second routing matrix  106   b  of the third broadcast router component  106 . In this manner, the routing engine  152  of the second router matrix  102   b  of the first broadcast router component  102 , the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 , the routing engine  220  of the second router matrix  106   b  of the third broadcast router component  106  and the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router component  108  all receive, as inputs thereto, the input digital audio data streams  1  through  4 N. 
     Within the routing engine  152  of the second router matrix  102   b  of the first broadcast router component  102 , switch logic or other switching means enables any one of the input digital audio data streams  1  through  4 N to be applied to any of the 1 through M outputs thereof. Similarly, switch logic or other switching means within the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 , the routing engine  220  of the second router matrix  106   b  of the third broadcast router component and the routing engine  254  of the second router matrix  108   b  of the fourth router component  108  enables any one of the input digital audio data streams  1  through  4 N to be applied to any of the M+1 through 2M, 2M+1 through 3M and 3M+1 through 4M outputs thereof, respectively. The switching logic or other switching means within each of the routing engines  152 ,  186 ,  220 , and  254  is controlled by one or more control inputs which originate at a controller (not shown) or other control circuitry for the fully redundant linearly expandable broadcast router  100 . 
     Each one of the 1 through M digital audio data streams output the routing engines  144  and  152  of the first and second routing matrices  102   a  and  102   b , respectively, of the first broadcast router component  102  are propagated to a corresponding one of first selector circuits  160 - 1  through  160 -M. The first selector circuits  160 - 1  through  160 -M collectively determine whether the 1 through m digital audio data streams output the routing engine  144  of the first routing matrix  102   a  or the 1 through M digital audio data streams output the routing engine  152  of the second routing matrix  102   b  shall be the output of the first broadcast router component  102 . Each one of the first selector circuits  160 - 1  through  160 -M share a common control input (not shown) for selecting whether the digital audio data streams output the routing engine  144  or the digital audio data streams output the routing engine  152  shall be passed by the first selector circuits  160 - 1  through  160 -M. 
     Similarly, each one of the M+1 through 2M digital audio data streams output the routing engines  178  and  186  of the first and second routing matrices  104   a  and  104   b , respectively, of the second broadcast router component  104  are propagated to corresponding ones of first selector circuits  228 - 1  through  228 -M. The first selector circuits  228 - 1  through  228 -M collectively determine whether the 1 through M digital audio data streams output the routing engine  178  of the first routing matrix  104   a  or the 1 through M digital audio data streams output the routing engine  186  of the second routing matrix  104   b  shall be the output of the second broadcast router component  104 . Each one of the first selector circuits  228 - 1  through  228 -M share a common control input (not shown) for selecting whether the digital audio data streams output the routing engine  178  or the digital audio data streams output the routing engine  186  shall be passed by the first selector circuits  228 - 1  through  228 -M. 
     Similarly again, each one of the 2M+1 through 3M digital audio data streams output the routing engines  212  and  220  of the first and second routing matrices  106   a  and  106   b , respectively, of the third broadcast router component  106  are propagated to corresponding ones of first selector circuits  228 - 1  through  228 -M. The first selector circuits  228 - 1  through  228 -M collectively determine whether the 2M+1 through 3M digital audio data streams output the routing engine  212  of the first routing matrix  106   a  or the 2M+1 through 3M digital audio data streams output the routing engine  220  of the second routing matrix  106   b  shall be the output of the third broadcast router component  106 . Each one of the first selector circuits  228 - 1  through  228 -M share a common control input (not shown) for selecting whether the digital audio data streams output the routing engine  212  or the digital audio data streams output the routing engine  220  shall be passed by the first selector circuits  228 - 1  through  228 -M. 
     Finally, each one of the 3M+1 through 4M digital audio data streams output the routing engines  246  and  254  of the first and second routing matrices  108   a  and  108   b , respectively, of the fourth broadcast router component  108  are propagated to corresponding ones of first selector circuits  262 - 1  through  262 -M. The first selector circuits  262 - 1  through  262 -M collectively determine whether the 3M+1 through Mm digital audio data streams output the routing engine  246  of the first routing matrix  108   a  or the 3M+1 through 4M digital audio data streams output the routing engine  256  of the second routing matrix  108   b  shall be the output of the fourth broadcast router component  104 . Each one of the first selector circuits  262 - 1  through  262 -M share a common control input (not shown) for selecting whether the digital audio data streams output the routing engine  246  or the digital audio data streams output the routing engine  254  shall be passed by the first selector circuits  262 - 1  through  262 -M. 
     Thus, in the foregoing manner, each one of the first, second, third and fourth broadcast router components  102 ,  104 ,  106  and  108  has a router matrix pair, specifically, the router matrix pairs  102   a  and  102   b ,  104   a  and  104   b ,  106   a  and  106   b , and  108   a  and  108   b , configured such that a first one of the router matrix pair may readily function as a back-up to a second one of the router matrix pair in the event of a failure thereof. To switch between the first and second ones of the router matrix pair, for example, to switch from the first router matrix  102   a  to the second router matrix  102   b , the common control input to the corresponding first selector circuits  160 - 1  through  160 -M, which had been previously set such that the output of the first router matrix  102   a  is passed by the selector circuits  160 - 1  through  160 -M, is switched between states such that the first selector circuits  160 - 1  through  160 -M shall now pass the output of the second router matrix  102   b.    
     Each one of the 1 through M, M+1 through 2M, 2M+1 through 3M and 3M+1 through 4M digital audio data streams passed by the first selector circuits  160 - 1  through  160 -M,  194 - 1  through  194 -M,  228 - 1  through  228 -M and  262 - 1  through  262 -M, respectively, are then propagated to a corresponding second selector circuit  162 - 1  through  162 -M,  196 - 1  through  196 -M,  230 - 1  through  230 -M and  264 - 1  through  264 -M. As disclosed herein, each one of the second selector circuits  162 - 1  through  162 -M,  196 - 1  through  196 -M,  230 - 1  through  230 -M and  264 - 1  through  264 -M is a 1:2 selector circuit having an input coupled to a corresponding output of the first selector circuit  160 - 1  through  160 -M,  194 - 1  through  194 -M,  228 - 1  through  228 -M and  262 - 1  through  262 -M, a first output  164 - 1  through  164 -M,  198 - 1  through  198 -M,  232 - 1  through  232 -M and  266 - 1  through  266 -M configured to transmit an output digital audio data stream conforming to the AES-11 standard and a second output  166 - 1  through  166 - m,    200 - 1  through  200 -M,  234 - 1  through  234 -M and  268 - 1  through  268 -M configured to transmit an output digital audio data stream conforming to the MADI standard. Each one of the second selector circuits  162 - 1  through  162 -M,  196 - 1  through  196 -M,  230 - 1  through  230 -M and  264 - 1  through  264 -M further includes a control input (not shown) for selecting between the AES-11 and MADI output digital audio data streams. 
     In an alternate embodiment of the invention not shown in the drawings, the selector circuits  138 - 1  through  138 -N,  176 - 1  through  175 -N,  210 - 1  through  210 -N,  244 - 1  through  244 -N,  162 - 1  through  162 -M,  196 - 1  through  196 -M,  230 - 1  through  230 -M and  264 - 1  through  264 -M may be omitted if the broadcast router components  102 ,  104 ,  106  and  108  are instead configured to handle input digital audio data streams conforming to a single standard, for example, the AES-11 standard, the MADI standard or another standard not specifically recited herein. In accordance with this configuration, however, each of the N input digital audio data streams for the first broadcast router component  102  would be fed directly to the routing engine  144 , first expansion port  146 , second expansion port  148  and third expansion port  150  of the first router matrix  102   a  and the routing engine  152 , first expansion port  154 , second expansion port  156  and third expansion port  158  of the second router matrix  102   b . Similarly, each of the N input digital audio data streams for the second broadcast router component  104  would be fed directly to the routing engine  178 , first expansion port  180 , second expansion port  182  and third expansion port  184  of the first router matrix  104   a  and the routing engine  186 , first expansion port  188 , second expansion port  190  and third expansion port  192  of the second router matrix  104 . Similarly again, each of the N input digital audio data streams for the third broadcast router component  106  would be fed directly to the routing engine  212 , the first expansion port  214 , the second expansion port  216  and the third expansion port  218  of the first router matrix  106   a  and the routing engine  220 , the first expansion port  222 , the second expansion port  224  and the third expansion port  226  of the second router matrix  106   b . Finally, each of the N input digital audio data streams for the fourth broadcast router component  108  would be fed directly to the routing engine  246 , the first expansion port  248 , the second expansion port  250  and the third expansion port  252  of the first router matrix  108   a  and the routing engine  254 , the first expansion port  256 , the second expansion port  258  and the third expansion port  260  of the second router matrix  108   b . In further accordance with this alternate embodiment of the invention, each of the M output digital audio data streams output the first selector circuits  160 - 1  through  160 -M,  194 - 1  through  194 -M,  228 - 1  through  228 -M and  262 - 1  through  262 -M of the first, second, third and fourth broadcast router components  102 ,  104 ,  106  and  108 , respectively, would be outputs of the fully redundant linearly expandable broadcast router  100  itself. 
     Referring next to  FIGS. 7-10 , an alternate configuration of the broadcast router components of the fully redundant linearly expandable broadcast router  100  will now be described in greater detail. More specifically, for each of the first, second, third and fourth broadcast router components  102 ,  104 ,  106  and  108 , the first, second and third expansion ports have been removed in favor of a transmitting expansion port, a first receiving expansion port, a second receiving expansion port and a third receiving expansion port. By the term “transmitting” expansion port, it is intended to refer to an expansion port from which data is transmitted to a selected destination. Similarly, by the term “receiving” expansion port, it is intended to refer to an expansion port which receives data from a destination. 
     The alternate configuration of the first broadcast router component  102  may be seen in  FIG. 7 . As may now be seen, the first router matrix  102   a  is now comprised of the routing engine  144 , a transmitting expansion port  276 , a first receiving expansion port  278 , a second receiving expansion port  280  and a third receiving expansion port  282 . Similarly, the second router matrix  102   b  is comprised of the routing engine  152 , a transmitting expansion port  284 , a first receiving expansion port  286 , a second receiving expansion port  288  and a third receiving expansion port  290 . In a broad sense, the transmitting expansion port  276  of the first router matrix  102   a  is comprised of a memory subsystem in which input digital audio data streams received from the selector circuits  140 - 1  through  140 -N of the first broadcast router component  102  are buffered before transfer to plural destinations and a processor subsystem for controlling the transfer of the input digital audio data streams received from the selector circuits  140 - 1  through  140 -N to a receiving expansion port of the first router matrix  104   a  of the second broadcast router component  104 , a receiving expansion port of the first router matrix  106   a  of the third broadcast router component  106  and a receiving expansion port of the first router matrix  108   a  of the fourth broadcast router component  108 . Conversely, each one of the first, second and third expansion ports  278 ,  280  and  282  of the first router matrix  102   a  are, in a broad sense, comprised of a memory subsystem in which input digital audio data streams received from a transmitting expansion port of the first router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling the transfer of the input digital audio data streams received from the transmitting expansion port of the first router matrix of the other broadcast router component to inputs of the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 . 
     Similarly, in one sense, the transmitting expansion port  276  of the second router matrix  102   b  is comprised of a memory subsystem in which input digital audio data streams received from the selector circuits  140 - 1  through  140 -N of the first broadcast router component  102  are buffered before transfer to plural destinations and a processor subsystem for controlling the transfer of the input digital audio data streams received from the selector circuits  140 - 1  through  140 -N to a receiving expansion port of the second router matrix  104   a  of the second broadcast router component  104 , a receiving expansion port of the second router matrix  106   b  of the third broadcast router component  106  and a receiving expansion port of the second router matrix  108   b  of the fourth broadcast router component  108 . Conversely, each one of the first, second and third expansion ports  278 ,  280  and  282  of the second router matrix  102   b  are, in one aspect, comprised of a memory subsystem in which input digital audio data streams received from a transmitting expansion port of the second router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling the transfer of the input digital audio data streams received from the transmitting expansion port of the second router matrix of the other broadcast router component to inputs of the routing engine  144  of the second router matrix  102   b  of the first broadcast router component  102 . 
     The alternate configuration of the second broadcast router component  104  may be seen in  FIG. 8 . As may now be seen, the first router matrix  104   a  is now comprised of the routing engine  178 , a transmitting expansion port  292 , a first receiving expansion port  294 , a second receiving expansion port  296  and a third receiving expansion port  298 . Similarly, the second router matrix  102   b  is comprised of the routing engine  186 , a transmitting expansion port  300 , a first receiving expansion port  302 , a second receiving expansion port  304  and a third receiving expansion port  306 . In a broad sense, the transmitting expansion port  292  of the first router matrix  104   a  is comprised of a memory subsystem in which input digital audio data streams received from the selector circuits  172 - 1  through  172 -N of the second broadcast router component  104  are buffered before transfer to plural destinations and a processor subsystem for controlling the transfer of the input digital audio data streams received from the selector circuits  172 - 1  through  172 -N to a receiving expansion port of the first router matrix  102   a  of the first broadcast router component  102 , a receiving expansion port of the first router matrix  106   a  of the third broadcast router component  106  and a receiving expansion port of the first router matrix  108   a  of the fourth broadcast router component  108 . Conversely, each one of the first, second and third expansion ports  294 ,  296  and  298  of the first router matrix  104   a  are, in a broad sense, comprised of a memory subsystem in which input digital audio data streams received from a transmitting expansion port of the first router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling the transfer of the input digital audio data streams received from the transmitting expansion ports of the first router matrix of the other broadcast router components to inputs of the routing engine  178  of the first router matrix  104   a  of the second broadcast router component  102 . 
     Similarly, in one sense, the transmitting expansion port  300  of the second router matrix  104   b  of the second broadcast router component  104  is comprised of a memory subsystem in which input digital audio data streams received from the selector circuits  172 - 1  through  172 -N of the second broadcast router component  104  are buffered before transfer to plural destinations and a processor subsystem for controlling the transfer of the input digital audio data streams received from the selector circuits  172 - 1  through  172 -N to a receiving expansion port of the second router matrix  102   b  of the first broadcast router component  102 , the second router matrix  106   b  of the third broadcast router component  106  and the second router matrix  108   b  of the fourth broadcast router component  108 . Conversely, each one of the first, second and third expansion ports  303 ,  304  and  306  of the second router matrix  104   b  are, in one aspect, comprised of a memory subsystem in which input digital audio data streams received from an transmission expansion port of the second router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling the transfer of the input digital audio data streams received from the transmitting expansion port of the second router matrix of the other broadcast router component to inputs of the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 . 
     The alternate configuration of the third broadcast router component  106  may be seen in  FIG. 9 . As may now be seen, the first router matrix  106   a  is now comprised of the routing engine  212 , a transmitting expansion port  308 , a first receiving expansion port  310 , a second receiving expansion port  312  and a third receiving expansion port  314 . Similarly, the second router matrix  106   b  is comprised of the routing engine  220 , a transmitting expansion port  316 , a first receiving expansion port  318 , a second receiving expansion port  320  and a third receiving expansion port  322 . In a broad sense, the transmitting expansion port  308  of the first router matrix  106   a  is comprised of a memory subsystem in which input digital audio data streams received from the selector circuits  210 - 1  through  210 -N of the third broadcast router component  106  are buffered before transfer to plural destinations and a processor subsystem for controlling the transfer of the input digital audio data streams received from the selector circuits  210 - 1  through  210 -N to a receiving expansion port of the first router matrix  102   a  of the first broadcast router component  102 , a receiving expansion port of the first router matrix  104   a  of the second broadcast router component  104  and a receiving expansion port of the first router matrix  108   a  of the fourth broadcast router component  108 . Conversely, each one of the first, second and third expansion ports  310 ,  312  and  314  of the first router matrix  106   a  are, in a broad sense, comprised of a memory subsystem in which input digital audio data streams received from a transmitting expansion port of the first router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling the transfer of the input digital audio data streams received from the transmitting expansion ports of the first router matrix of the other broadcast router components to inputs of the routing engine  212  of the first router matrix  106   a  of the third broadcast router component  106 . 
     Similarly, in one sense, the transmitting expansion port  316  of the second router matrix  106   b  of the third broadcast router component  106  is comprised of a memory subsystem in which input digital audio data streams received from the selector circuits  210 - 1  through  210 -N of the third broadcast router component  106  are buffered before transfer to plural destinations and a processor subsystem for controlling the transfer of the input digital audio data streams received from the selector circuits  210 - 1  through  210 -N to a receiving expansion port of the second router matrix  102   b  of the first broadcast router component  102 , a receiving expansion port of the second router matrix  104   b  of the second broadcast router component  104  and the second router matrix  108   b  of the fourth broadcast router component  108 . Conversely, each one of the first, second and third expansion ports  318 ,  320  and  322  of the second router matrix  106   b  are, in one aspect, comprised of a memory subsystem in which input digital audio data streams received from a transmission expansion port of the second router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling the transfer of the input digital audio data streams received from the transmitting expansion port of the second router matrix of the other broadcast router component to inputs of the routing engine  220  of the second router matrix  106   b  of the third broadcast router component  106 . 
     The alternate configuration of the fourth broadcast router component  108  may be seen in  FIG. 10 . As may now be seen, the first router matrix  108   a  is now comprised of the routing engine  246 , a transmitting expansion port  324 , a first receiving expansion port  326 , a second receiving expansion port  328  and a third receiving expansion port  330 . Similarly, the second router matrix  108   b  is comprised of the routing engine  254 , a transmitting expansion port  332 , a first receiving expansion port  334 , a second receiving expansion port  336  and a third receiving expansion port  338 . In a broad sense, the transmitting expansion port  324  of the first router matrix  108   a  is comprised of a memory subsystem in which input digital audio data streams received from the selector circuits  244 - 1  through  244 -N of the fourth broadcast router component  108  are buffered before transfer to plural destinations and a processor subsystem for controlling the transfer of the input digital audio data streams received from the selector circuits  244 - 1  through  244 -N to a receiving expansion port of the first router matrix  102   a  of the first broadcast router component  102 , a receiving expansion port of the first router matrix  104   a  of the second broadcast router component  104  and a receiving expansion port of the first router matrix  106   a  of the third broadcast router component  106 . Conversely, each one of the first, second and third expansion ports  326 ,  328  and  330  of the first router matrix  108   a  are, in a broad sense, comprised of a memory subsystem in which input digital audio data streams received from a transmitting expansion port of the first router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling the transfer of the input digital audio data streams received from the transmitting expansion ports of the first router matrix of the other broadcast router components to inputs of the routing engine  246  of the first router matrix  108   a  of the fourth broadcast router component  108 . 
     Similarly, in one sense, the transmitting expansion port  332  of the second router matrix  108   b  of the fourth broadcast router component  108  is comprised of a memory subsystem in which input digital audio data streams received from the selector circuits  244 - 1  through  244 -N of the fourth broadcast router component  108  are buffered before transfer to plural destinations and a processor subsystem for controlling the transfer of the input digital audio data streams received from the selector circuits  244 - 1  through  244 -N to a receiving expansion port of the second router matrix  102   ba  of the first broadcast router component  102 , the second router matrix  104   b  of the second broadcast router component  104  and the second router matrix  106   b  of the third broadcast router component  106 . Conversely, each one of the first, second and third expansion ports  334 ,  336  and  338  of the second router matrix  108   b  are, in one aspect, comprised of a memory subsystem in which input digital audio data streams received from a transmission expansion port of the second router matrix of another broadcast router component may be buffered before transfer to their final destination and a processor subsystem for controlling the transfer of the input digital audio data streams received from the transmitting expansion port of the second router matrix of the other broadcast router component to inputs of the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router component  108 . 
     Referring next to  FIGS. 7-10 , as a discrete input digital audio data stream is output each of the selector circuits  138 - 1  through  138 -N, the input digital audio data streams fed to the routing engine  144  and the expansion transmission port  276  of the first router matrix  102   a  of the first broadcast router component  102  are audio data input streams  1  through N. Similarly, the input digital audio data streams fed to the routing engine  178  and the transmission expansion port  292  of the first router matrix  104   a  of the second broadcast router component  104  are input digital audio data streams N+1 through  2 N; the input digital audio data streams fed to the routing engine  212  and the transmission expansion port  308  of the first router matrix  106   a  of the third broadcast router component  106  are input digital audio data streams  2 N+1 through  3 N; and the input digital audio data streams fed to each one of the routing engine  246  and the transmission expansion port  324  of the first router matrix  108   a  of the fourth broadcast router component  108  are input digital audio data streams  3 N+1 through  4 N. 
     As before, to function as a 4N×4M broadcast router, the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 , the routing engine  178  of the second router matrix  104   a  of the second broadcast router component  104 , the routing engine  212  of the third router matrix  106   a  of the third broadcast router component  106  and the routing engine  246  of the fourth router matrix  108   a  of the fourth broadcast router component  108  must have all of the input digital audio data streams  1  through  4 N provided as inputs to the input side thereof. For the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 , the input digital audio data streams  1  through N are provided to the input side of the routing engine  144  directly. The input digital audio data streams  1  through N input the transmitting expansion port  276 , on the other hand, are transferred to the first receiving expansion port  294  of the first router matrix  104   a  of the second broadcast router component  104  over the link  110 , the second receiving expansion port  312  of the first router matrix  106   b  of the third broadcast router component  106  over the link  112  and the second receiving expansion port  330  of the first router matrix  108   a  of the fourth broadcast router component  108  over the link  114 , respectively. From the first receiving expansion port  294  of the first router matrix  104   a  of the second broadcast router component  104 , the second receiving expansion port  312  of the first router matrix  106   a  of the third broadcast router component  106  and the second receiving expansion port  330  of the first router matrix  108   a  of the fourth broadcast router component  108 , the input digital audio data streams  1  through N are input the routing engine  178  of the first router matrix  104   a  of the second broadcast router component  104 , the routing engine  212  of the first router matrix  106   a  of the third broadcast router component  106  and the routing engine  246  of the first router matrix  108   a  of the fourth broadcast router components  108 , respectively. 
     Similarly, for the first router matrix  104   a  of the second broadcast router component  104 , the input digital audio data streams N+1 through  2   n  are provided to the input side of the routing engine  178  directly. The input digital audio data streams N+1 through  2 N input the transmitting expansion port  292 , on the other hand, are transferred to each of the first receiving expansion port  278  of the first router matrix  102   a  of the broadcast router component  102  over the link  110 , the first receiving expansion port  310  of the first router matrix  106   a  of the third broadcast router component  106  over the link  116  and the second receiving expansion port  328  of the first router matrix  108   a  of the fourth broadcast router component  108  over the link  118 , respectively. From the first receiving expansion port  278  of the first router matrix  102   a  of the first broadcast router component  102 , the first receiving expansion port  310  of the first router matrix  106   a  of the third broadcast router component  106  and the second receiving expansion port  328  of the first router matrix  108   a  of the fourth broadcast router component  108 , the input digital audio data streams N+1 through  2 N are input the routing engine  144  of the first routing matrix  102   a  of the first broadcast router component  102 , the routing engine  212  of the first routing matrix  106   a  of the third broadcast router component  106  and the routing engine  246  of the first routing matrix  108   a  of the fourth router component  108 , respectively. 
     For the first router matrix  106   a  of the third broadcast router component  106 , the input digital audio data streams  2 N+1 through  3 N are input the routing engine  212  directly. The input digital audio data streams  2 N+1 through  3 N input the transmitting expansion ports  308 , on the other hand, is transferred to each of the second receiving expansion port  296  of the first router matrix  104   a  of the second broadcast router component  104  over the link  116 , the second receiving expansion port  280  of the first router matrix  102   a  of the first broadcast router component  102  over the link  112  and the first receiving expansion port  326  of the first router matrix  108   a  of the fourth broadcast router component  108  over the link  120 , respectively. From the second receiving expansion port  296  of the first router matrix  104   a  of the second broadcast router component  104 , the second receiving expansion port  280  of the first router matrix  102   a  of the first broadcast router component  102  and the first receiving expansion port  326  of the first router matrix  108   a  of the fourth broadcast router component  108 , the input digital audio data streams  2 N+1 through  3 N are input the routing engine  144  of the first router matrix  102   a  of the first broadcast router  102 , the routing engine  178  of the first router matrix  104   a  of the second broadcast router  104  and the routing engine  246  of the first router matrix  108   a  of the fourth broadcast router component  108 . 
     Finally, for the first router matrix  108   a  of the fourth broadcast router component  108 , the input digital audio data streams  3 N+1 through  4 N are input the routing engine  246  directly. The input digital audio data streams  3 N+1 through  4 N input the transmitting expansion port  324 , on the other hand, is transferred to each one of the third receiving expansion port  314  of the first router matrix  106   a  of the third broadcast router component  106  over the link  120 , the third receiving expansion port  298  of the first router matrix  104   a  of the second broadcast router component  104  over the link  118  and the third receiving expansion port  282  of the first router matrix  102   a  of the broadcast router component  102  over the link  114 , respectively. From the third receiving expansion port  282  of the first router matrix  102   a  of the first broadcast router component  102 , the third receiving expansion port  298  of the first router matrix  104   a  of the second broadcast router component  104  and the third receiving expansion port  314  of the first router matrix  106   a  of the third broadcast router component  106 , the input digital audio data streams  3 N+1 through  4 N are input the routing engine  144  of the first routing matrix  102   a  of the first broadcast router component  102 , the routing engine  178  of the first routing matrix  104   a  of the second broadcast router component  104  and the routing engine  212  of the first routing matrix  106   a  of the third broadcast router component  106 . In this manner, the routing engine  144  of the first router matrix  102   a  of the first broadcast router component  102 , the routing engine  178  of the first router matrix  104   a  of the second broadcast router component  104 , the routing engine  212  of the first router matrix  106   a  of the third broadcast router component  106  and the routing engine  246  of the first router matrix  108   a  of the fourth broadcast router component  108  all receive, as inputs thereto, the input digital audio data streams  1  through  4 N. 
     In this embodiment as well, the second router matrices  102   b ,  104   b ,  106   b  and  108   b  are redundant router matrices available for use in the event that the respective one or ones of the first router matrices  102   a ,  104   a ,  106   a  and  108   a  fail. To function as redundant matrices, the second router matrices  102   b ,  104   b ,  106   b  and  108   b  must receive/transmit the same input/output digital audio data streams as the corresponding one of the first router matrices  102   a ,  104   a ,  106   a  and  108   a . Accordingly, the selector circuits  138 - 1  through  138 -N also feed input digital audio data streams  1  through N to each of the routing engine  152  and the first transmitting expansion port  284  of the second router matrix  102   b  of the first broadcast router component  102 . Similarly, the selector circuits  176 - 1  through  176 -N also feed input digital audio data streams N+1 through  2 N to each of the routing engine  186  and the transmitting expansion port  300  of the second router matrix  104   b  of the second broadcast router component  104 ; the selector circuits  210 - 1  through  210 -N also feed input digital audio data streams  2 N+1 through  3 N to each of the routing engine  220  and the transmitting expansion port  316  of the second router matrix  106   b  of the third broadcast router component  106 ; and the selector circuits  244 - 1  through  244 - n  also feed input digital audio data streams  3 N+1 through  4 N to each of the routing engine  254  and the transmitting expansion port  332  of the second router matrix  108   b  of the fourth broadcast router component  108 . 
     Also as before, the routing engine  152  of the second router matrix  102   b  of the first broadcast router component  102 , the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 , the routing engine  220  of the second router matrix  106   b  of the third broadcast router component  106  and the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router component  108  must have all of the input digital audio data streams  1  through  4 N provided as inputs thereto. For the routing engine  152  of the second router matrix  102   b  of the first broadcast router component  102 , the selector circuits  138 - 1  through  138 -N provide input digital audio data streams  1  through N as inputs thereto. The input digital audio data streams  1  through N input the transmitting expansion port  284 , on the other hand, is transferred to each of the first receiving expansion port  306  of the second router matrix  104   b  of the second broadcast router component  104  over the link  122 , the second receiving expansion port  320  of the second router matrix  106   b  of the third broadcast router component  106  over the link  124  and the first receiving expansion port  334  of the second router matrix  108   b  of the fourth broadcast router component  108  over the link  126 , respectively. From the first receiving expansion port  306  of the second router matrix  104   b  of the second broadcast router component  104 , the second receiving expansion port  320  of the second router matrix  106   b  of the third broadcast router component  106  and the first receiving expansion port  334  of the second router matrix  108   b  of the fourth broadcast router component  108 , the input digital audio data streams  1  through N are input the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 , the routing engine  220  of the second router matrix  106   b  of the third broadcast router component  106  and the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router components  108 , respectively. 
     Similarly, for the second router matrix  104   b  of the second broadcast router component  104 , the input digital audio data streams N+1 through  2 N are directly input the routing engine  186 . The input digital audio data streams N+1 through  2 N input the transmitting expansion port  300 , on the other hand, is transferred to each one of the third receiving expansion port  290  of the second router matrix  102   b  of the first broadcast router component  102  over the link  122 , the third receiving expansion port  322  of the second router matrix  106   b  of the third broadcast router component  106  over the link  128  and the second receiving expansion port  336  of the second router matrix  108   b  of the fourth broadcast router component  108  over the link  130 , respectively. From the third receiving expansion port  290  of the second router matrix  102   b  of the first broadcast router component  102 , the third receiving expansion port  322  of the second router matrix  106   b  of the third broadcast router component  106  and the second receiving expansion port  336  of the second router matrix  108   b  of the fourth broadcast router component  108 , the input digital audio data streams N+1 through  2 N are input the routing engine  152  of the second routing matrix  102   b  of the first broadcast router component  102 , the routing engine  220  of the second routing matrix  106   b  of the third broadcast router component  106  and the routing engine  254  of the second routing matrix  108   a  of the fourth router component  108 , respectively. 
     For the second router matrix  106   b  of the third broadcast router component  106 , the input digital audio data streams  2 N+1 through  3 N are input the routing engine  220  directly. The input digital audio data streams  2 N+1 through  3 N input the transmitting expansion port  316 , on the other hand, is transferred to each one of the second receiving expansion port  304  of the second router matrix  104   b  of the second broadcast router component  104  over the link  128 , the first receiving expansion port  286  of the second router matrix  102   b  of the first broadcast router component  102  over the link  124  and the third receiving expansion port  338  of the second router matrix  108   b  of the fourth broadcast router component  108  over the link  132 , respectively. From the second receiving expansion port  304  of the second router matrix  104   b  of the second broadcast router component  104 , the first receiving expansion port  286  of the second router matrix  102   b  of the first broadcast router component  102  and the third receiving expansion port  338  of the second router matrix  108   b  of the fourth broadcast router component  108 , the input digital audio data streams  2 N+1 through  3 N are input the routing engine  152  of the second router matrix  102   b  of the first broadcast router  102 , the routing engine  186  of the second router matrix  104   b  of the second broadcast router  104  and the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router component  108 . 
     Finally, for the second router matrix  108   b  of the fourth broadcast router component  108 , the input digital audio data streams  3 N+1 through  4 N are input the routing engine  254  directly. The input digital audio data streams  3 N+1 through  4 N input the transmitting expansion port  332 , on the other hand, is transferred to each one of the first receiving expansion port  318  of the second router matrix  106   b  of the third broadcast router component  106  over the link  132 , the first receiving expansion port  302  of the second router matrix  104   b  of the second broadcast router component  104  over the link  130  and the second receiving expansion port  288  of the second router matrix  102   b  of the first broadcast router component  102  over the link  126 , respectively. From the second receiving expansion port  288  of the second router matrix  102   b  of the first broadcast router component  102 , the first receiving expansion port  302  of the second router matrix  104   b  of the second broadcast router component  104  and the first receiving expansion port  318  of the second router matrix  106   b  of the third broadcast router component  106 , the input digital audio data streams  3 N+1 through  4 N are input the routing engine  152  of the second routing matrix  102   b  of the first broadcast router component  102 , the routing engine  186  of the second routing matrix  104   b  of the second broadcast router component  104  and the routing engine  220  of the second routing matrix  106   b  of the third broadcast router component  106 . In this manner, the routing engine  152  of the second router matrix  102   b  of the first broadcast router component  102 , the routing engine  186  of the second router matrix  104   b  of the second broadcast router component  104 , the routing engine  220  of the second router matrix  106   b  of the third broadcast router component  106  and the routing engine  254  of the second router matrix  108   b  of the fourth broadcast router component  108  all receive, as inputs thereto, the input digital audio data streams  1  through  4 N. Further processing of the input digital audio streams  1  through  4 N will then proceed in the manner hereinabove described with respect to  FIGS. 2-5 . 
     Thus, there has been disclosed and illustrated herein a robust linearly expandable broadcast router which, by employing a fully connected topology between the plural broadcast router components forming the linearly expandable broadcast router, enjoys improved fault tolerance over prior linearly expandable broadcast routers using plural bus structures to interconnect the plural broadcast router components. Further, by eliminating redundant links, the linearly expandable broadcast router represents an economical and cost-effective solution to many broadcast router needs. While preferred embodiments of this invention have been shown and described herein, various modifications and other changes can be made by one skilled in the art to which the invention pertains without departing from the spirit or teaching of this invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow.