Abstract:
An end-of-branch (EOB) module system for an audio signal distribution system having a wired trunk and a plurality of wired branches extending communicatively from such trunk, the EOB module system including: a plurality of EOB modules including one EOB module electronically coupled at each distal end of each branch and trunk of the audio signal distribution system, where each EOB module of the plurality of EOB modules has a unique address together forming a plurality of unique addresses; a test system able to send a test carrier signal encoded with any one unique address of the plurality of unique addresses at a time onto the trunk; and a switch within each EOB module, responsive to its unique address to place an end-of-line (EOL) load on its respective branch or trunk, and where power for operation of each EOB module is provided by rectification of the test signal.

Description:
TECHNICAL FIELD 
       [0001]    The present invention generally relates to a testing apparatus for individual audio speakers that are each one of a plurality of audio speakers driven by the same amplifier. The present invention also relates to systems comprising a plurality of speakers driven by a common amplifier and having built-in-test capability. 
       BACKGROUND 
       [0002]    An end-of-line (EOL) monitor and test system was developed to verify the operation of a sound system in facilities such as airports, convention centers, industrial and stadiums. The system operates by sending an inaudible tone over the normal sound system, typically in the range of 19 KHz to 20 KHz, and then measuring the voltage and current of the power amps driving the speakers. A fault is declared for any change in the impedance of the load which causes a voltage or current deviation, compared to a preset level, greater than a pre-determined fault threshold. 
         [0003]    The EOL monitor and test system will identify a fault on a single line, but does not tell where on the line the fault occurred. The EOL monitor and test system also will not tell if a line is cut to a speaker on a branch, or, if there are a lot of speakers on the circuit, it will not tell if there is a fault on a single speaker because the change will be too small to measure. To overcome this, all the speakers can be wired in serial fashion on one wire and putting some kind of detecting device on the end of that line, such as an EOL device. This is a very expensive way to wire speakers, and most existing installations run a line down a single hall or corridor and branch off to the sides to areas with one or more speakers in them. If one of these branches is broken, it could not be detected using the EOL device. 
         [0004]    Accordingly, the end-of-branch (EOB) system of the present invention was developed to overcome these problems. Accordingly, it is desirable to be able to detect faults in individual speakers on audio signal lines that are branched from a trunk audio signal line. In addition, it is desirable to achieve such fault detection with a minimum of expense. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
         [0005]    The ability to individually address each speaker leads to another use of the EOB with the addition of a new switch (T) that is connected to another set of terminals so an individual speaker (V) can be disconnected by command. This would allow routing audio to any or all speakers on the amplifiers output from the main system. This would allow paging to a single room without disturbing the whole building, and in turn, turning off a conference room that does not warrant to be interrupted. This could be used with or without the end of line testing that is the primary use of the EOB module. 
       BRIEF SUMMARY 
       [0006]    An apparatus is provided for an end-of-branch (EOB) module system for an audio signal distribution system having a wired trunk and a plurality of wired branches extending from such trunk, the EOB module system including: a plurality of EOB modules including one EOB module electronically coupled at each distal end of each branch and trunk of the audio signal distribution system, where each EOB module of the plurality of EOB modules has a unique address together forming a plurality of unique addresses; a test system able to send a test carrier signal encoded with any one unique address of the plurality of unique addresses at a time onto the trunk and branches; and a switch within each EOB module, responsive to its unique address to place an end-of-line (EOL) load on its respective branch or trunk. The EOB module system, where the EOB module includes a CPU able to drive the switch responsive to receiving the unique address. The EOB module system, where the EOB module includes a programmable CPU. The EOB module system, where power for operation of each EOB module is provided by rectification of the test carrier signal. The EOB module system, where the EOB module includes a demodulator capable of detecting the unique addresses and data. The EOB module system, where the test system is further able to automatically: detect voltage variations in the amplifier responsive to the placement of the EOL load; detect current variations in the amplifier responsive to the placement of the EOL load; determine if one of the voltage variation and the current variation is outside one of a predetermined voltage range and a predetermined current range, respectively; and indicate one of a fault condition and a non-fault condition associated with the one unique address responsive to the determination. The EOB module system, where the EOL includes a resistance, a capacitance, and an inductance coupled in series. The EOB module system, further including a second switch within at least one said EOB module coupled to at least one speaker, respectively, external to said at least one EOB module and operable to disconnect said at least one speaker from said audio test signal. The EOB module system, where the module includes a first switch that is open when no power is applied. The EOB module system, where the audio signal distribution system further includes sub-branches, further including EOB modules electronically coupled to each end of each sub-branch. The EOB module system, where EOB modules removes the EOL load from the branch or trunk after a predetermined time or from a control command from the test system. 
         [0007]    An EOB module system for an audio signal distribution system having a wired trunk and a plurality of wired branches extending from such trunk, the EOB module system including: a plurality of EOB modules including one EOB module at each end of each branch and trunk of the audio signal distribution system, where each EOB module of the plurality of EOB modules has a unique address together forming a plurality of unique addresses; a test system able to send a test carrier signal encoded with any one unique address of the plurality of unique addresses at a time onto the trunk; a switch within each EOB module, responsive to its unique address to place an end-of-line (EOL) load on its respective branch or trunk; and where the EOB module includes a CPU able to drive the switch responsive to receiving the unique address. The EOB module system, where: the EOB module includes a programmable CPU; power for operation of each EOB module is provided by rectification of the test signal; and the EOB module includes a comparator able to compare a rectified encoded test carrier signal with a reference voltage to produce the unique address. The EOB module system, where the test system is further able to automatically: detect voltage variations in the amplifier responsive to the placement of the EOL load; detect current variations in the amplifier responsive to the placement of the EOL load; determine if one of the voltage variation and the current variation is outside one of a predetermined voltage range and a predetermined current range, respectively; and indicate one of a fault condition and a non-fault condition associated with the one unique address responsive to the determination. The EOB module system, where the EOL includes a resistance, a capacitance, and an inductance coupled in series. The EOB module system, where the module includes a switch that is open when no power is applied. The EOB module system, where the audio signal distribution system further includes sub-branches, further including EOB modules electronically coupled to each distal end of each sub-branch. 
         [0008]    An EOB module system for an audio signal distribution system having a wired trunk and a plurality of wired branches extending from such trunk, the EOB module system including: a plurality of EOB modules including one EOB module at each end of each branch and trunk of the audio signal distribution system, where each EOB module of the plurality of EOB modules has a unique address together forming a plurality of unique addresses; a test system able to send a test carrier signal encoded with any one unique address of the plurality of unique addresses at a time onto the trunk; a switch within each EOB module, responsive to its unique address to place an end-of-line (EOL) load on its respective branch or trunk; where the EOB module includes a CPU able to drive the switch responsive to receiving the unique address; and where: the EOB module includes a programmable CPU; power for operation of each EOB module is provided by rectification of the test signal; and the EOB module includes a comparator able to compare a rectified encoded test carrier signal with a reference voltage to produce the unique address; the EOL includes a resistance, a capacitance, and an inductance coupled in in series; and where the switch includes a switch that is open when no power is applied. The EOB module system, where the test system is further able to automatically: detect voltage variations in the amplifier responsive to the placement of the EOL load; detect current variations in the amplifier responsive to the placement of the EOL load; determine if one of the voltage variation and the current variation is outside one of a predetermined voltage range and a predetermined current range, respectively; and indicate one of a fault condition and a non-fault condition associated with the one unique address responsive to the determination. The EOB module system, where the audio signal distribution system further includes sub-branches, further including EOB modules electronically coupled to each distal end of each sub-branch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
           [0010]      FIG. 1  is a diagram illustrating an exemplary trunk and branch audio signal distribution system with exemplary end-of-branch modules, according to a preferred embodiment of the present invention; 
           [0011]      FIG. 2  is a diagram illustrating an exemplary end-of-branch module, according to a preferred embodiment of the present invention; 
           [0012]      FIG. 3  is a photograph illustrating an exemplary end-of-branch module, according to a preferred embodiment of the present invention; 
           [0013]      FIG. 4  is a diagram illustrating the circuitry within an exemplary end-of-line device, according to a preferred embodiment of the present invention; 
           [0014]      FIG. 5  is a diagram illustrating a second embodiment of an exemplary end-of-branch module, according to a preferred embodiment of the present invention; and 
           [0015]      FIG. 6  is a diagram illustrating an exemplary trunk and branch audio signal distribution system with exemplary end-of-branch modules, according to a second preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
         [0017]      FIG. 1  is a diagram illustrating an exemplary trunk  106  and branch  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184  audio signal distribution system with exemplary end-of-branch module system  100 , according to a preferred embodiment of the present invention. Test system  102  produces the test signal, monitors the voltage and current through amplifier  104 , and addresses EOB (end-of-branch) devices  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190 , and  194  individually. The EOB devices  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190 , and  194  are active versions of the EOL (end-of-line) device  222  (See  FIG. 2 ). The EOB devices  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190 , and  194  can be used to verify the integrity of lines  106 ,  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184  that have multiple taps and branches  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184  on one amplifier  104 . The system  100  is merely exemplary, and any number of branches  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184 , with any number of speakers  110 ,  112 ,  118 ,  120 ,  122 ,  128 ,  130 ,  132 ,  138 ,  140 ,  146 ,  152 ,  158 ,  160 ,  166 ,  168 ,  170 ,  176 ,  178 ,  180 ,  186 ,  188 , and  192  may be used, limited only by the power in amplifier  104  and the addressing limitations of the CPU  214 . Test system  102  supplies the encoded test signal to the amplifier  104  at the proximal end of trunk  106  and the EOB modules are coupled to the distal end of trunk  106  and the distal ends of branches  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184 . 
         [0018]    In the example system shown in  FIG. 1 , the EOL device  222  would overload the amplifier  104  at the test tone frequency if added to every speaker  110 ,  112 ,  118 ,  120 ,  122 ,  128 ,  130 ,  132 ,  138 ,  140 ,  146 ,  152 ,  158 ,  160 ,  166 ,  168 ,  170 ,  176 ,  178 ,  180 ,  186 ,  188 , and  192  on the lines  106 ,  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184  powered by amplifier  104 , and a fault would not be detected if only one of the many branches  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184  is cut. The EOB devices  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190 , and  194  will use the same EOL  222  load circuit but it will not be connected until each specific EOB device  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190 , and  194  is addressed by the test system  102 , one at a time. Each EOB device  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190 , and  194  may then be identified with a single load  222  (See  FIG. 2 ) on the amplifier  104 . 
         [0019]      FIG. 2  is a diagram illustrating an exemplary end-of-branch module  162 , according to a preferred embodiment of the present invention. The module includes a CPU  214  that receives and sends a serial data stream on serial port  244  via RS232 port  218  and driver  219  for purposes of programming the CPU  214 . CPU  214  is powered at power input  238  over line  217  from Vcc  210 . Power at Vcc  210  is generated from the high frequency test signal  252  through exemplary 20 KHz tuned circuit  204 , bridge rectifier  206 , and shunt regulator  208 . 
         [0020]    The test system  104  will generate an inaudible test tone  252  and modulate the test tone with a unique code  250  for each EOB device  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190 , and  194 . As the code  250  is detected at contact  242  of the CPU  214 , a switch  220  will switch in the EOL  222  circuit and the test system  104  will detect the amplifier  104  current. A fault will be reported for any EOB module  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190  or  194  that does not load the circuit as expected by the test system  102 . Each EOB module  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190 , and  194  will be assigned a unique code  250  so a reported fault can be identified with the physical location of that fault. 
         [0021]    While the EOB modules  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190  or  194  are shown at the end first branches  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184 , and off trunk  106 , additional sub-branches off branches  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184  are possible. Accordingly, each speaker  110 ,  112 ,  118 ,  120 ,  122 ,  128 ,  130 ,  132 ,  138 ,  140 ,  146 ,  152 ,  158 ,  160 ,  166 ,  168 ,  170 ,  176 ,  178 ,  180 ,  186 ,  188 , and  192  could have its own EOB module, with the leads from the branches  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184  to speakers  110 ,  112 ,  118 ,  120 ,  122 ,  128 ,  130 ,  132 ,  138 ,  140 ,  146 ,  152 ,  158 ,  160 ,  166 ,  168 ,  170 ,  176 ,  178 ,  180 ,  186 ,  188 , and  192  being sub-branches. 
         [0022]    The power for each EOB module  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190  or  194  will not be derived from the normal program audio, but only the high frequency test tone  252 . Speakers  110 ,  112 ,  118 ,  120 ,  122 ,  128 ,  130 ,  132 ,  138 ,  140 ,  146 ,  152 ,  158 ,  160 ,  166 ,  168 ,  170 ,  176 ,  178 ,  180 ,  186 ,  188 , and  192  in some areas may not be used for long periods of time with normal program audio, but can still be tested at any time using the test tone as a reliable supply of power. 
         [0023]    The operation is based on the reception of code  250  in the form of a standard serial data stream  250  (like that used for RS232) to convey the unique code  250  to address a particular EOB device  162 , for example. The code  250  will tell the CPU  214  to turn on the switch  220  by sending an ON signal from switch driver port  248  along line  226  which will put the EOL load circuit  222  across the speaker line  216 . This load  222  will automatically be removed after a short time to keep from dragging down its own supply voltage Vcc  210  and the supply voltages of the other EOB devices  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  172 ,  182 ,  190 , and  194  on the speaker circuit. The short time will be long enough for test system  102  to detect the EOL  222  load and determine if there is a fault at that branch  156  of the speaker line  106 . The test system  102  will then move on to test the next EOB device  172  on the line  164 . Multiple tests may be used to insure there is truly a fault. One design option is for a second code to be sent that turns off all loads  222 . This code could also precede the testing to insure the loads  222  are all off before the test begins. Another fail-safe option in the CPU  214  program will detect its brownout voltage of Vcc  210  to the CPU  214  and turn off the switch  220  before the CPU  214  shuts down just to make sure the switch  220  is always left off. Power is provided to CPU  214  over line  217  from Vcc  210 . 
         [0024]    The actual operation starts when a test tone signal  252  is applied to all EOBs  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190  or  194  on that amplifier&#39;s  104  speaker line  106  and branches  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , and  184 . What follows uses EOB  164  as an example: operation of all EOBs  114 ,  124 ,  134 ,  142 ,  148 ,  154 ,  162 ,  172 ,  182 ,  190  and  194  is the same. 
         [0025]    The test tone signal  252  is rectified by bridge rectifier  206  and charges the main supply capacitor  254 . This may take several seconds but once charged, main supply capacitor  254  will supply power for the rest of the test. The signal at  228  is rectified by rectifier  230 , stored on capacitor  258 , and measured by the CPU  214 . A second signal on the sample and hold capacitor  260  is driven with pulse width modulation (PWM) from the PWM contact  246  of CPU  214  to be a reference  234  for the input  232  of the comparator  236 . The short time constant at input  232  of comparator  236  is fast enough to change at the rate of the data rate at  250 , but slower than the test tone carrier, so the net output from the comparator  236  is the data  250  that is modulating the input signal  252 . Since both inputs  232  and  234  are the same voltage, except for the modulation, the only difference between the two appears in output  250  of comparator  236 . It only takes a small change to create an output  250  from the comparator  236 , which is also independent of actual level on line  228 , but dependent on the changes,  258  vs.  260 , in that level. This allows the signal  250  to be detected over a ten to one range of input test signal  252  level as long as the reference level  260  can be established first and power is sufficient to operate the switch  220  when needed. 
         [0026]    When the switch  220  applies the load EOL device  222 , the incoming test signal  252  voltage drops due to the impedance of the load of the EOL device  222 . Since the EOL device  222  drops the voltage available at Vcc  210 , a separate capacitor  256  is used to power the EOB  162  while the switch  220  is on, thus insuring that EOB device  164  can always be removed as an EOL device  222  load. 
         [0027]    The biggest problem is supplying enough power to run all the electronics in the EOB device  164 . A shunt voltage regulator  208  is used so that no power is wasted by the shunt voltage regulator  208  until it is up to operating value for Vcc  210 . As the input voltage  252  increases, the shunt voltage regulator  208  clamps the voltage Vcc  210  to keep voltage Vcc  210  from going any higher by shunting off the excess power. This power Vcc  210  is supplied from a resonant circuit  204  (at the test tone frequency) by shunting the resonant current of the circuit thru the EOB device  162 . The actual AC voltage on the resonant circuit  204  tap  228  at normal test signal levels  252  are in excess of 150 VAC, and as high as 500 VAC, but the voltage and current are 90 degrees out of phase at  228 . So, there is zero power consumed, except for the loss of the EOB device&#39;s  162  power needs. The three volt drop at Vcc  210  in series with the resonant circuit  204  is insignificant. At the voltages on  228  the current is very small so the current of the EOB device  162  must be very small. By very careful selection of all the parts and by operating the CPU  214  at low clock frequency and voltage, the total current needed is less than one milliampere. The switch  220  needs twenty milliamperes, but for only seven-hundred milliseconds, so it is operated from the charge on a capacitor  256 . All the diodes are extremely low leakage to allow rectification with only nanoamperes of current. The comparator  236  draws  0 . 12  milliamperes and the CPU  214  is the balance of the load. 
         [0028]    The EOB device  162  has an RS232 driver  219  that is powered from the RXD line  218  coming in and needs no power from the internal system Vcc  210 . RS232 driver  219  is only needed for programming and debugging the CPU  214 , which is done with the RS232 driver  219  connected to an external computer that supplies the power. While the present invention has been illustrated using RS232 serial data communication technology, those of skill in the art, enlightened by the present disclosure, will appreciate that Universal Serial Bus (USB) technology, or other serial data communications technology, may be used in place of RS232 technology, and is within the scope of the present invention. 
         [0029]    There exists a possibility that the switch  220  could stick on and leave the EOL  222  load on the speaker line  216 . In this case, the 20 kHz signal could cause a resistor in the EOL  222  to burn up. For this reason, a special class of fusible, flame proof resistor is used for the 10 ohm resistor in the EOL  220  circuit. If this fuse action does happen, the EOB  164  would no longer work and would cause a fault report, so it could be identified and replaced. 
         [0030]    The opposite problem of the EOL  222  sticking on at low input voltage could drop the Vcc  210  to a level too low for the CPU  214  to operate, but in this case the switch  220  also runs out of power so it opens up and fixes the problem. 
         [0031]      FIG.3  is a photograph illustrating an exemplary end-of-branch module  164 , according to a preferred embodiment of the present invention. The end-of-branch module  164  can be made quite small, the illustrated EOB module  162  having a two-inches by two-inches form factor. Leads  302  connect to the end of the trunk  106 , or branch  108 ,  116 ,  126 ,  136 ,  144 ,  150 ,  156 ,  164 ,  174 , or  184 , or sub-branch (lines to speakers), etc. 
         [0032]      FIG. 4  is a diagram illustrating the circuitry within an exemplary end-of-line device  222 , according to a preferred embodiment of the present invention. Input resistor  402  is preferably a flame resistant resistor  402 . Inductive load  406  is coupled to resistor  402  through capacitor  404 . The resonant frequency of the EOL  222  circuit is not the test signal carrier frequency, and so the EOL  222  circuit creates a load at the test signal frequency when switched in as a load. 
         [0033]      FIG. 5  is a diagram illustrating a second embodiment of an exemplary end-of-branch module, according to a preferred embodiment of the present invention. The ability to individually address each speaker  508  leads to another use of the EOB  502  with the addition of a switch  506  that is connected to another set of terminals so an individual speaker  508  can be disconnected by command. Switch driver line  512  connects CPU  214  switch driver output  510  to switch  506  enabling control of the supply of the audio signal on audio signal line  504  to speaker  508 . The use of a plurality of such EOBs  502  allows routing audio to any or all speakers  110 ,  112 ,  118 ,  120 ,  122 ,  128 ,  130 ,  132 ,  138 ,  140 ,  146 ,  152 ,  158 ,  160 ,  166 ,  168 ,  170 ,  176 ,  178 ,  180 ,  186 ,  188 , and  192  on the amplifiers  104  output from the main system. This would allow paging to a single room without disturbing the whole building, and in turn, turning off a conference room that does not want to be interrupted. 
         [0034]      FIG. 6  is a diagram illustrating an exemplary trunk  606  and branch  608 ,  610 ,  612 ,  614  audio signal distribution system  600  with exemplary addressable audio modules  616 ,  630 ,  624 ,  628 ,  632 ,  636 ,  640 , and  644 , according to a second preferred embodiment of the present invention. Addressable audio modules  616 ,  630 ,  624 ,  628 ,  632 ,  636 ,  640 , and  644  may be addressed by the test system  602  to turn speakers  618 ,  622 ,  626 ,  630 ,  634 ,  638 ,  642 , and  646 , respectively, ON or OFF. The addressable audio modules  616 ,  630 ,  624 ,  628 ,  632 ,  636 ,  640 , and  644  are preferably EOB modules  502  with switch  506  and associated circuitry. Switch  506  enables remote configuration of the ON/OFF status of each speaker  618 ,  622 ,  626 ,  630 ,  634 ,  638 ,  642 , and  646 , respectively, in addition to providing the branch integrity testing capability of the EOB module  162 . 
         [0035]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.