Abstract:
A method and apparatus for connecting a primary uplink site and a diverse uplink site includes a satellite and a communication line that couples the primary uplink site and the diverse uplink site. The primary uplink site receives television signals and communicates the signals over the communication line using a video-over-internet protocol. The primary site forms primary uplink signals and selectively communicates the primary uplink signals to the satellite. The diverse uplink site receives the television signals from the primary uplink site through the communication line and forms the diverse uplink signals and selectively communicates the diverse uplink signals to the satellite.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   This application is related to Utility application Ser. No. 11/529,932 entitled “Antenna Hub Configuration”; Ser. No. 11/529,915 entitled “Method and System for Broadcasting in a Satellite Communication System When Switching Between a Primary Site and a Diverse Site”; Ser. No. 11/529,949 entitled “Method and System for Determining Delays Between a Primary Site and Diverse Site in a Satellite Communication System”; Ser. No. 11/529,840 entitled “Method and System for Operating a Satellite Communication System With Regional Redundant Sites and a Central Site”; Ser. No. 11/529,918 entitled “Method and System for Determining Attenuation and Controlling Uplink Power in a Satellite Communication System”; and Ser. No. 11/540,037 entitled “Method and System for Receiving a Beacon Signal in a Satellite Communication System”, filed simultaneously herewith. The disclosures of the above applications are incorporated by reference herein. 
   TECHNICAL FIELD 
   The present disclosure relates generally to satellite communication systems, and more particularly to a method and apparatus for connecting primary and diverse sites in a satellite communication system. 
   BACKGROUND 
   The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
   Satellite broadcasting of television signals has increased in popularity. Satellite television providers continually offer more and unique services to their subscribers to enhance the viewing experience. Providing reliability in a satellite broadcasting system is therefore an important goal of satellite broadcast providers. 
   The use of a back-up site in a satellite broadcasting system is desirable. In such a system, reliable communication between the sites is desirable. 
   SUMMARY 
   In one aspect of the disclosure, a system includes a satellite, a communication line, a primary uplink site and a diverse uplink site. The primary uplink site receives television signals and communicates the television signals over the communication line using a video-over-internet protocol. The primary site forms primary uplink signals and selectively communicates the primary uplink signals to the satellite. A diverse site receives the television signals from a primary uplink site through the communication line and forms diverse uplink signals and selectively communicates the diverse uplink signals to the satellite. 
   In a further aspect of the disclosure, a method includes receiving a television signal at a primary site, broadcasting the television signal through a satellite from the primary site, communicating the television signal through a communication line over a video-over-internet protocol, receiving the television signal from the communication line and broadcasting the television signal through the satellite from the diverse site. 
   One advantage of the disclosure is that the reliability of the system is improved using a video-over-internet protocol. The video-over-internet protocol is controlled through the primary site. 
   Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 

   
     DRAWINGS 
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
       FIG. 1  is an overall system view of a satellite communication system in the continental United States. 
       FIG. 2  is a system view at the regional level of a satellite system. 
       FIGS. 3A ,  3 B and  3 C are block diagrammatic views of the systems illustrated in  FIGS. 1 and 2 . 
       FIG. 4  is a flowchart illustrating a method of operating the system illustrated in  FIG. 3 . 
       FIGS. 5A and 5B  are schematic views of a primary or diverse site illustrated in  FIGS. 3A-C . 
       FIG. 6  is a cutaway view of an antenna according to the present disclosure. 
       FIG. 7  is a flowchart illustrating switching logic for a primary and diverse site. 
       FIGS. 8A and 8B  are flowcharts for determining a primary site equipment status and a diverse site equipment status, respectively. 
       FIGS. 9A and 9B  are flowcharts of an emergency primary to diverse or diverse to primary emergency switchover, respectively. 
       FIGS. 10A and 10B  are flowcharts of a diverse site initialization and a primary site initialization, respectively. 
       FIGS. 11A and 11B  are flowcharts illustrating a radiate/terminate function for a diverse switch and a primary switch, respectively. 
       FIGS. 12A and 12B  are flowcharts of a primary site second trigger point and a diverse site trigger point, respectively. 
       FIG. 13  is a flowchart of a primary clear sky normalized diverse site method of  FIG. 12A . 
       FIGS. 14A and 14B  are flowcharts of a primary to diverse site switch or diverse to primary site switch, respectively. 
       FIG. 15  is a flowchart of a primary site clear sky time duration function. 
       FIG. 16  is a flowchart of a switch to normal path function. 
       FIG. 17  illustrates a summary of a switchover between a primary site and a secondary site. 
       FIG. 18  is a high level view of an integrated receiver decoder having an error conceal module. 
       FIGS. 19A and 19B  are timing charts illustrating the primary site signal, secondary site signal and a gap. 
       FIG. 19B  is a timing chart showing the primary site signal and secondary site signal after error correction. 
       FIG. 20  is a flowchart illustrating a method for controlling uplink power. 
       FIG. 21  is a plot of uplink power versus fade. 
       FIG. 22  is a flowchart of a method of receiving a beacon signal according to the present disclosure. 
   

   DETAILED DESCRIPTION 
   The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
   The present disclosure is described with respect to a satellite television system. However, the present disclosure may have various uses including satellite transmission and data transmission and reception for home or business uses. 
   Referring now to  FIG. 1 , a communication system  10  includes a satellite  12 . The communication system  10  includes a central facility  14  and a plurality of regional facilities  16 A,  16 B,  16 C,  16 D,  16 E and  16 F. Although only one satellite is shown, more than one is possible. The regional facilities  16 A- 16 F may be located at various locations throughout a landmass  18  such as the continental United States, including more or less than those illustrated. The regional facilities  16 A- 16 F uplink various uplink signals  17  to satellite  12 . The satellites downlink downlink signals  19  to various users  20  that may be located in different areas of the landmass  18 . The users  20  may be mobile or fixed users. The uplink signals  17  may be digital signals such as digital television signals or digital data signals. The digital television signals may be high definition television signals. Uplinking may be performed at various frequencies including Ka band. The present disclosure, however, is not limited to Ka band. However, Ka band is a suitable frequency example used throughout this disclosure. The central facility  14  may also receive downlink signals  19  corresponding to the uplink signals  17  from the various regional facilities and from itself for monitoring purposes. The central facility  14  may monitor the quality of all the signals broadcast from the system  10 . 
   The central facility  14  may also be coupled to the regional facilities through a network such as a computer network having associated communication lines  24 A- 24 F. Each communication line  24 A-F is associated with a respective regional site  16 . Communication lines  24 A- 24 F are terrestrial-based lines. As will be further described below, all of the functions performed at the regional facilities may be controlled centrally at the central facility  14  as long as the associated communication line  24 A-F is not interrupted. When a communication line  24 A-F is interrupted, each regional site  16 A-F may operate autonomously so that uplink signals may continually be provided to the satellite  12 . As will be described below, the central facility  14  may include graphic user interfaces that are identical to those of the regional site  16  so that control and monitoring can take place at the various regional facilities. Each of the regional and central facilities includes a transmitting and receiving antenna which is not shown for simplicity in  FIG. 1 . 
   Referring now to  FIG. 2 , the regional facilities  16 A- 16 F are illustrated collectively as reference numeral  16 . The regional site  16  may actually comprise two facilities that include a primary site  40  and a diverse site  42 . As will be described below, the central site  14  may also include a primary site and diverse site as is set forth herein. The primary site  40  and diverse site  42  of both the central and regional sites are preferably separated by at least 25 miles, or, more preferably, at least 40 miles. In one constructed embodiment, 50 miles was used. The primary site  40  includes a first antenna  44  for transmitting and receiving signals to and from satellite  12 . Diverse site  42  also includes an antenna  46  for transmitting and receiving signals from satellite  12 . 
   Primary site  40  and diverse site  42  may also receive signals from GPS satellites  50 . GPS satellites  50  generate signals corresponding to the location and a precision timed signal that may be provided to the primary site  40  through an antenna  52  and to the diverse site  42  through an antenna  54 . It should be noted that redundant GPS antennas ( 52 A,B) for each site may be provided as illustrated in  FIG. 5 . In some configurations, antennas  44  and  46  may also be used to receive GPS signals. 
   A precision time source  56  may also be coupled to the primary site  40  and to the diverse site  42  for providing a precision time source. The precision time source  56  may include various sources such as coupling to a central atomic clock. 
   The primary site  40  and the diverse site  42  may be coupled through a communication line  60 . Communication line  60  may be a dedicated communication line. The primary site  40  and the diverse site  42  may communicate over the communication line using a video over interne protocol (IP). 
   Various signal sources  64  such as an optical fiber line or copper line may provide incoming signals  66  from the primary site  40  to the diverse site  42 . Incoming signal  66 , as mentioned above, may be television signals. The incoming signals  66  such as the television signal may be routed from the primary site  40  through the communication line  60  to the diverse site  42  in the event of a switchover whether the switchover is manual or a weather-related automatic switchover. A manual switchover, for example, may be used during a maintenance condition. 
   Users  20  receive downlink signals  70  corresponding to the television signals. Users  20  may include home-based systems or business-based systems, both mobile and fixed. As illustrated, a user  20  has a receiving antenna  72  coupled to an integrated receiver decoder  74  that processes the signals and generates audio and video signals corresponding to the received downlink signal  70  for display on the television or monitor  76 . It should also be noted that satellite radio systems may also be used in place of an IRD and TV for use of the satellite signals. 
   Referring now to  FIGS. 3A ,  3 B and  3 C, block diagrammatic views of the control system of the communication system of the present disclosure are illustrated. In  FIG. 3 , the central site  14  includes the primary site  14 A and the diverse site  14 B. A monitoring module  90  is illustrated located at the primary central site  14 A. Those skilled in the art will recognize that the monitoring module  90  may be located in various locations including separately from the primary site. 
   Monitor module  90  may include a system server  91  and displays  92 ,  94  and  96  that display graphical user interfaces for status and control of various functions that will be further described below. The server system  91  is a controller that may control the overall system function. The server may generate control signals that act as a switch. The switches or switch functions may be performed in software alone or in conjunction with various relays or other suitable hardware that corresponds to the particular equipment controlled. The switch of various system components is performed in response to various monitored conditions. The displays  92 ,  94  and  96  may be formed on multiple monitor screens or on different monitor screens. The status and control monitoring may be able to monitor and control the elements in the RF chain and various other conditions associated with satellite transmission and reception. 
   The server  91 , the displays  92 ,  94  and  96  may be coupled to a router  100 . The router  100  may receive information from the various primary and diverse sites for display on the graphical user interfaces so that an operator may easily control various functions at the diverse sites. The router  100  may, therefore, act as a switch or a number of switches for routing various input and output signals. 
   The primary site and the diverse site for each of the central site and the remote sites may be configured identically or nearly identically. Each of the sites includes a router  150  that has various elements coupled thereto. It should be noted that various elements may be coupled twice to provide redundancy in the system. For example, a server  152  is coupled to router  150 . A second server  154  is also coupled to router  150  to provide redundancy to the first server  152 . The servers  152 ,  154  may act as a controller to switch on and off various components of the system in response to monitored condition signals. Block upconverters  156  and block downconverters  158 , as well as block upconverters  160  and block downconverters  162 , are coupled to the router  150 . A global positioning switch  164  and a global positioning system receiver  166  are also coupled to the router. A second global positioning receiver  168  is coupled to router  150 . An antenna control unit  170  and a second antenna control unit  172  are also coupled to the router  150 . The router  150  may also receive information from various elements in the receive and transmit chain. The router  150  may route these receive signals to the various servers  152  and  154  for processing and control purposes. The router  150 , for example, may receive information through a first serial port  180  and a second serial port  182 . The serial ports may be coupled to high-power amplifiers  184 ,  186 , tracking receive interface  188 ,  190 , variable power combined amplifiers  192 ,  194  and spectrum analyzer  196 ,  198 . 
   The router  150  may also be discretely wired to various input sources through a discrete input  200 . A second and third redundant serial port  202  and  204  may be respectively coupled to line drivers  206 ,  208 , dehydrator  210 ,  212 , device control  214 ,  216  and low noise amplifier  218 ,  220 . A graphical user interface  240  may be used to monitor the various conditions of the various devices in the RF chain. The function of these devices will be further described below. In addition, a test loop translator  242  may also be coupled to one of the serial ports  202 ,  204 . The test loop translator  242  may provide an input and output carried out by the waveguide and coaxial switches. 
   The configuration of the primary site  40 B may be identical to that of the primary site  14 A. The diverse sites may also be configured in a similar manner and have the same inputs  152  through  172 . In this case, router  150  is divided up into two routers  250  and  252 . A subreflector tracker SRT input  254  and  256  may be provided at each router so that the subreflector tracking may be performed. An antenna-programmable controller (APC)  260  and  262  may be coupled to each serial port which is coupled to each router  250 ,  252 . In addition, an antenna environmental system (AES) controller  264 ,  266  may also be coupled to the serial port for input to the router  250 ,  252 . The remaining elements of the diverse site are identical to those above in the primary site. The diverse site  14 B may be exactly identical to that of diverse site  42 B and the other diverse sites in the system. 
   Referring now to  FIG. 4 , a method of operating the overall communication system is set forth. In step  300 , signals such as television signals are received. Of course, various types of signals, including radio or data signals, may be used. As mentioned above, the television signals may be received from various collection points and transmitted to the regional facilities. The television signals may be received in many ways including over-the-air terrestrial-based or through optical fibers. That is, in step  302  the television signals may be communicated to the regional uplink facility. In step  304 , the television signals may be uplinked to the satellite. In step  306 , the television signals may be broadcast to various users from the satellites using various types of transmission methods including spot beams. In step  308 , the control status of the regional site  16  may be monitored or controlled at the regional site  16 . In step  310 , the signals broadcast to the various users may also be downlinked at the central facility. The central facility may monitor the quality of the signals. In step  312 , the regional site  16  itself may be monitored through the graphical user interface as described above. The same graphical user interfaces provided at the regional facilities, may be provided at the central facility so that various systems may be monitored. It should be noted that the monitoring of the regional site  16  and the controls therein, may be performed over a terrestrial communication line as described above. The communication line may be a dedicated communication line or an internet-type network communication line. 
   In step  314 , the regional site  16  may be controlled using the terrestrial communication line described above. The changing of various settings for various RF controls may be set forth and monitored. 
   In step  316 , the control signals are terrestrially communicated to the regional site  16 . In step  318 , if the terrestrial communication has been interrupted, regional control may be the only source of control for the regional facilities in step  320 . In step  318 , if terrestrial communication has not been interrupted, local regional control or central control may be performed in step  322 . After steps  322  and  320 , the system returns back to step  300 . 
   Referring now to  FIGS. 5A and 5B , a schematic of a primary site  40  or diverse site  42  is illustrated. It should be also noted that the central site  14  may also be configured in a similar manner. 
   Each primary site  40  and diverse site  42  includes an indoor portion  400  and an outdoor portion  402 . The outdoor portion includes a limited motion antenna assembly  404 . 
   The indoor portion  400  may receive various channels of television signals. In the present embodiment, four groups of channels A-E, F-J, K-O and P-T are ultimately input to the switch  416 . Channel inputs A through E may use 950-1,200 Megahertz. Each channel includes a first modulator  410  and a second modulator  412 . The modulators  410  and  412  are redundant modulators which are controlled by the modulator switch  414 . That is, the modulator switch  414  is coupled to redundant modulators  410  and  412  and chooses between one or the other switch. The modulator switch  414  may be controlled by the control configuration described above in  FIG. 3 . The modulators  410 ,  412  receive the digital baseband signals and converts them to a second frequency band such as the L-band. Also, the modulators  410 ,  412  are used to place the signals into the desired modulation scheme. As is shown, several groupings of channels may be provided. The outputs of each of the modulator switches  414  are provided to an L-band switch  416 . The L-band switch  416  receives the various inputs from the modulator switches  414 . 
   Secondary or additional inputs such as engineering inputs ENG 1  and ENG 2  may be used to modulate various signals or provide a set of secondary or back-up modulators or modulator switches if both modulators in one of the redundant channels above fail. Also, if one of the modulator switches  414  fails, both engineering chains ENG 1  and ENG 2  are available. The outputs of the additional inputs may be routed to various outputs as a back-up. 
   The L-band switch  416  may also provide a throughput for baseband monitoring. This is illustrated as output  12 B within the L-band switch. Various engineering inputs may also be switched to various outputs through the controller as described above in  FIG. 3 . For example, should the first channel  1  input chain fail, engineering chain  1  may be switched to provide an output through the L-band switch. A plurality of jack fields  418  may also be provided. Jack fields  418  allow the ability to jack in or connect various inputs including another input or the rerouting of various inputs. It should also be noted that each pair of modulators for each channel may have a center frequency that is spaced apart by a pre-determined amount. In the present example, the modulators are spaced apart by a center frequency of 40 megahertz. The output of the L-band switches are grouped together at a summer  412 . Another jack field  424  may be provided so that the signal may be manually monitored. A coupler  430  receives the summed signals from the summing block  420  and provides them to redundant line drivers  432 ,  434 . A switch  436  selects one of the outputs of the line drivers  432 ,  434  to be provided to an output  438  of an indoor portion. The output of each of the switches may be routed to a monitor switch  440 . The switch  440 , as will be described later, provides signals to a spectrum analyzer  442 . That is, in the process of broadcasting, various signals may be routed to the spectrum analyzer. 
   A communication line or plurality of communication lines  444  may be used to couple the indoor portion  400  and the outdoor portion  402 . The L-band signals are transmitted through the communication lines  444 . 
   The outdoor portion  402  may be included within a housing  450  of the antenna  404 . The outdoor portion  402  includes a splitter  460  that splits the signals received from the indoor portion  400  through the communication line  444  and provides them to a first block upconverter  462  and a second block upconverter  464 . Block upconverters  462 ,  464  have an output provided to a switch  466  which routes the output to a test and monitor panel  470  or to an output  472 . Sample points  474  may be used to sample the output of the switches. Thus, it should be noted that one output of one of the block upconverters  462 ,  464  is provided to the variable attenuator. The attenuated signals from the variable attenuator are used for matching signal levels output from the block upconverter. A splitter  476  splits the signals and provides them to high power amplifiers  480 ,  482 . Each high power amplifier may include a monitoring point and adjustment point  484 ,  486  as will be described below. The outputs of the high power amplifiers  480 ,  482  are provided to a variable phase combined amplifier  490 . The variable phase combined amplifier  490  includes a first output  492  that is provided to a test and monitor panel  470 . It is desirable for the output  492  of the variable phase combined amplifier  490  to be zero or nearly zero at the first output. The variable phase combined amplifier  492  combines the outputs of the high power amplifier  480 ,  482  to generate a high-power output. Should one of the high-power amplifiers  480 ,  482  fail, the output of the variable phase combined amplifier reduces to the output of the working high-power amplifier. This happens relatively quickly and thus the on-the-air signal does not become interrupted. 
   The test and monitor panel  470  is used to monitor the output of the variable phase combined amplifier  490 . A laptop computer or the like may be carried to the antenna and coupled to the test and monitor panel. An Ethernet connection may also be provided to test and monitor panel. An adjustment may be made on one or both of the high-power amplifiers so that the phase is adjusted so that both the outputs of the high-power amplifiers  480 ,  482  are in phase. 
   The output of the variable phase-combined amplifier  490  may be provided to a block downconverter  500 . The block downconverter  500  provides output back to the indoor portion  400  and eventually back to the spectrum analyzer  442  for monitoring. The first four circuits for various groups of channels are identical up to this portion. 
   The first two groups of outputs from the first two variable phase-combined amplifiers  490  are combined at a diplexer  502 . The diplexer  502  provides the signal to the left-hand circularly polarized transmit interface  510  of the antenna  404 . A sample may also be taken to detect the power output at power detector  504 . A switch  506  may control the output to the transmit interface  510  from the diplexer  502 . The second two groups of circuitry from the splitter  460  through the variable phase combined amplifiers  490  are identical. In addition, the diplexer  512  provides a right-hand circularly polarized output through a switch  514  to the second transmit interface  510 . 
   A power motor calibration unit  520  may also be provided. The power detectors  504  may be provided to indoor power meters  628  described below. 
   A tracking interface  524  coupled to the antenna receives left-hand and right-hand circularly polarized signals that are provided to a switch  526 . The switch  526  has an output that is passed through a transmit rejection filter  528  to reject the transmitted signal from the receive signal. An amplifier  530  amplifies the signal and a monopulse plate  532  receives the signal. A pair of block downconverters  534 ,  536  downconvert the divided signal to a lower frequency such as L-band. It should be noted that the signals received at the tracking interface are from a beacon. The outputs of the block downconverter  534 ,  536  are provided to a pair of beacon receivers  538 ,  540  through communication lines  444 . The beacon receivers  538  and  540  are disposed within the indoor portion. The beacon receivers  538 ,  540  may each be coupled to an antenna control unit  542 . It should be noted that the beacon receivers  538 ,  540  are serially connected to a controller or server of the system. Should one of the block downconverters or one of the beacon receivers fail, one serial input to the controller may be provided. The beacon receivers  538 ,  540  are also coupled to the antenna control unit  542 . The antenna control unit  542  provides an alternate to the serial interface should the serial interface fail. The antenna control unit  542  may, for example, be coupled through an Ethernet-type connection. As will be mentioned below, the amount of power to be used in uplinking signals may be determined using the beacon receivers. As will be further described below, deicing control  544  may be provided in the indoor portion while the antenna deicing system  546  is provided at the antenna. Deicing may be provided using hot air techniques. 
   An antenna interface  550  is provided that receives left-hand and right-hand circularly polarized signals. The left-hand and right-hand circularly polarized signals are provided to switches  552  and  554 , respectively. It should be noted that for redundancy three amplifiers  556 ,  558  and  560  are provided. Output switches  562  and  564  are also provided. Sampling points  566  and  568  may be provided prior to the switches  552  and  554 . Also, the output of switches  562  and  564  may be coupled to a bulkhead monitor connection  570 . The output of switches  562  is provided to a first splitter  574  and a second splitter  576 . The split signal is provided to a first block downconverter  580 , a second block downconverter  582 , and the output of the second splitter  576  is provided to a third block downconverter  584  and a fourth block downconverter  586 . The output of the block downconverters  580 - 586  is provided to a coupler which in turn may couple the signals to the switch and ultimately to the spectrum analyzer  542 . 
   The antenna control unit  542  may be coupled to the drive cabinet  590  which in turn is coupled to an isolation transformer  592 . 
   Various other equipment may also be included in the indoor portion such as dehydrators  600 ,  602  that are provided to a manifold and monitor  604 . A pressure gauge output  606  is provided to the dry air interfaces. An isolated ground bar  610  may be provided within the outdoor portion. The indoor portion may also include a block upconverter in variable power combined amplifier control  612 . 
   A monitor and control rack  616  may be used to house the various equipment. The rack may be shared for multiple systems. The rack  616  may include serial, discrete and Ethernet interfaces for use in multiple systems. 
   A pair of GPS receivers  618 ,  620  with redundant antennas  52 A,  52 B may also be provided. The GPS receivers  618 ,  620  provide outputs to switches  622 . The GPS receivers  618 ,  620  may be used to provide a precise time monitor so that precise timing may be provided for the primary site and a reference for switching which will be later described below for the diversity site as provided. 
   Power meters  628  may also be provided to monitor the pre-transmit power of the system from power detectors  504 . Spare Ethernet connections  620  and spare cable  622  may also be provided. 
   The antenna may also include various centers such as a feed temperature status sensor  630 , carbon monoxide sensor  632 , a hub temperature status  634  and a hub door switch  636 . Each of these parameters may be provided to the servers for display on a graphic user interface. 
   Various test points along the circuiting are used to provide the system operators with an assessment of the signals. If one component is not working, a back-up component may be used. Also, the signals may be monitored at various locations so that the precise location of the failing or failed component may be determined. 
   Referring now to  FIG. 6 , an enlarged view of the limited motion antenna  404  is illustrated. Antenna  404  includes housing  450  that houses much of the circuitry in the outdoor portion of  FIG. 5 . The antenna may be mounted on a concrete stand  650  that includes a stairway  652  so that the housing  450  may be reached. Transmit interface  510 , tracking interface  524  and receive interface  550  are shown. 
   Referring now to  FIG. 7 , a high level flowchart executed by the controllers or servers within the system illustrates the flow of switching between the primary site and the diverse sites. Several of the steps illustrated by a double rectangle method are described in detail in other figures. In step  700 , the diverse switching method is started. In step  702 , a manual or automatic switch position is determined. In step  704 , the diverse switch is not in an automatic setting. Step  702  is again executed. In step  704 , the diverse switch is in automatic. Step  706  determines if the diverse site is not on the air. If the diverse site is not on the air, the equipment status of the diverse site is checked. This will be described below in a further flowchart. If the status returned in step  708  is good in step  710 , the system continues to step  712  which determines if a trigger point from the diverse site is reached. Trigger point  1  initiates initialization of the diverse site which will be described below. In step  714 , if the method determines that continuation to the diverse site is warranted, step  716  is performed. In step  716 , if the primary site trigger point  2  has been reached, step  718  is performed. In step  718 , if the trigger point  2  has been reached, step  720  is performed which initiates the primary to diverse switch site. This will be further described below. After step  714  and  718 , if the answer to either of the questions is no, step  702  is again executed. Also, after step  720  and the primary site has been switched to the diverse site, step  702  is again executed. 
   Referring back to step  706 , if the diverse site is on the air, step  724  is performed in which the primary site clear sky time duration is determined. After the sky has been cleared for a certain amount of time, the system may again switch to the primary site. After step  724 , step  726  determines whether or not to continue to the primary site based upon the clear sky time duration. If a continuation to the primary site is performed, a switch to the normal path is performed in step  728 . After step  728 ,  702  is executed. 
   If a continuation to the primary site is not warranted in step  726 , step  730  is performed in which a diverse site equipment status is performed. This will be described below. In step  732 , if the status if good, step  734  is performed in which the primary site is initialized if trigger point  1  is reached. In step  736 , if continuation to the primary site is warranted, step  738  determines whether the diverse site trigger point  2  has been reached. This will be described further below. In step  740 , if a continuation to the primary site is determined by checking the diverse site trigger point, step  42  initiates a switch from the diverse site to the primary site. After step  742 , step  702  is again performed. 
   Referring back to step  710  and step  732 , if the status of the primary site in step  710  or the status of the diverse site is not good in step  732 , steps  744  and  746  are respectively performed. Steps  744  and  746  will be further described below. 
   After steps  744  and  746 , step  702  is again performed. 
   It should be noted that the various trigger points and the steps to the process may be displayed on a graphical user interface shown in  FIG. 3 . 
   Referring now to  FIGS. 8A and 8B , the process for checking the equipment status of the primary site in step  708  of  FIG. 7  and checking the equipment status of the diverse site in step  730  of  FIG. 7  are nearly identical. Therefore, each of the identical steps is labeled in  FIG. 8B  with a prime. The steps are identical except for the reference to either the primary site or the diverse site depending on the original step. Therefore,  FIG. 8A  will be discussed and the changes to  FIG. 8B  will be highlighted. 
   In step  800 , the primary site equipment status is displayed as red or other indicator on the Graphical User Interface. If there is no communication fault at the primary site, step  804  is performed in which one or both of the traveling wave tubes are determined if they are ready. If the traveling wave tubes are ready, step  806  is performed in which it is determined if the primary site uplink power control is active. If the uplink power control is active, the system returns back to step  710  of  FIG. 7  in step  808 . If a communication fault is present at the primary site or one or both of the traveling wave tubes is not ready in step  806  or the primary site does not have the uplink power control ready, step  810  generates a message of the primary site failure and sets the diverse switch to manual in step  812 . Step  818  sets the primary site display to red or other indicator and returns a NO status in step  816  so that step  744  of  FIG. 7  is performed. 
   Referring now to  FIG. 8B , each of the same process steps of  FIG. 8A  is performed except with reference to the diverse site. If the diverse site is ready in step  808  prime, the status is good and the system continues to step  734  of  FIG. 7 . If the diverse site is not ready, the system returns to step  732  in which the status would not be good and thus step  746  is performed thereafter. In step  814  prime, the diverse site graphical user interface is displayed to red. 
   Referring now to  FIGS. 9A and 9B , steps  744  and  746  of  FIG. 7  are illustrated in further detail. In step  840 , the diverse radiate/terminate switch position is determined. In step  842 , if the switch is not in radiate position, step  844  is performed in which a command to change the diverse radiate/terminate switch position to radiate is performed. If the switch is not in the radiate position in step  846 , step  848  generates a message that the primary to diverse switch failure is performed. In step  850 , the primary site graphical user interface may be changed to a different color such as red to indicate a failure. The system returns in step  852 . Referring back to steps  842  and  846 , if the switch is placed in radiate, step  854  un-mutes the diverse block upconverter or removes the traveling wave tube inhibit signal. In step  856 , a primary site timer delay (P2D) is performed. If the delay is achieved in step  858 , the system continues to step  860 . If the delay is not achieved, step  856  is continually performed until the delay has been achieved. In step  860 , the primary block upconverter is muted or the traveling wave tube is set to inhibit. In step  862 , the diverse site graphical user interface is changed to an indicator such as green to indicate the diverse site is operating. 
   Referring now to  FIG. 9B , similar steps to those shown in  9 A are illustrated except that the diverse to primary switchover is performed. The process in  FIG. 9B  returns in step  842  prime to step  746  of  FIG. 7 . 
   Referring now to  FIGS. 10A and 10B , step  712  and  734  of  FIG. 7  are performed. Again, these figures are complimentary. In step  712  of  FIG. 7 , the steps necessary to prepare the diverse site during a first fade event is determined. In step  880 , the primary site fade level is determined. The primary site fade level may be determined using received beacons as will be further described below. In step  880 , the primary site variable phase combined amplifier status is determined. If the variable phase combined amplifiers are not combining the traveling wave tubes (HPAs  480 ,  482  of  FIG. 5 ) in step  844 , step  886  is performed in which it is determined whether the fade of the primary site minus three decibels, the answer is no, the system returns to step  890 . In step  884 , if the variable phase combined amplifiers are combining the traveling wave tubes outputs, step  888  is performed. If the fade is not greater than a threshold such as TP 1 , step  890  is again performed and the system is returned. In steps  886  and  888 , if the system is greater than test point  1  minus 3 decibels or is greater than test point  1  in step  888 , step  892  the primary switch from radiate determining is performed as will be further described below in  FIG. 11 . 
   After step  892 , the system returns to step  894  with a YES status to step  714 . 
   Referring now to  FIG. 10B , the identical steps are performed except with respect to primary site initialization. Steps  886  prime and  881  prime use a fade threshold TD 1  of the diverse site for its variable. The variable TD 1  and TP 1  may be equivalent. 
   Referring now to  FIGS. 11A and 11B , steps  892  and  892  prime of  FIGS. 10A and 10B  are illustrated in further detail. Yellow may be used as a display for a “hot standby” where the radiate/terminate switch (controlling its block upconverter for example) is in the radiate position with the signal still muted at the diverse site. Red may be used as a failure. In step  900 , the diverse radiate switch position is read. In step  902 , if the switch is not in radiate position, a command is generated to change the switch to the radiate position in step  904 . After step  904 , step  906  is performed. Steps  902  and  906  determine if the switch is in radiate position. In steps  902  and  906  if the switch is in radiate position, step  908  is performed in which the diverse site graphical user interface is displayed differently such as in “yellow.” In step  910  the system returns a YES status back to step  712  in step  894 . 
   Referring back to step  906 , if the switch is not in radiate position in step  906 , step  912  generates a message of diverse site failure and step  914  sets the diverse switch to manual. Step  916  generates a graphical user interface color such as red to indicate a problem with the diverse site. In step  918 , the system returns a NO to step  894 . 
   Referring now to  FIG. 11B , the identical process is used for determining whether the primary switch is in radiate or terminate. Therefore, these commands will not be further described below. 
   It should be noted that the above first fade function is where a “hot” standby mode is entered. If in the loop the system returns back to a clear sky, the system will return back to the primary function. If conditions worsen, a second threshold level converts the system into transmitting to the other site. That is, if the primary site is transmitting, a diverse site is used. If the diverse site is transmitting, the primary site is used. 
   Referring now to  FIG. 12A , step  716  of  FIG. 7  is illustrated in further detail. In step  950 , the primary site fade level is determined. As mentioned above, the fade level may be determined based upon the received beacon signals. In step  952 , the primary sites variable phase combined amplifiers status is determined. If the variable phase combined amplifiers are combining the traveling wave tubes (HPA) outputs in step  954 , step  956  is performed. In step  956 , if the primary fade level is not greater than a second threshold (TP 2 ), step  958  is performed. If the primary fade level is less than the first threshold (TP 1 ), step  950  is again executed. After step  958 , if the primary fade level is less than test point  1  (TP 1 ), step  960  is performed. Step  950  will be further described below. After step  960 , the system returns a NO back to step  716  in step  962 . 
   Referring back to step  956 , if the primary fade level is greater than the second threshold TP 2 , step  964  is performed. Referring back to step  954 , if the variable phase combined amplifiers are not combining the traveling wave tube outputs, step  966  is performed. If the primary fade is greater than a second threshold minus three decibels or some other value, step  964  is performed. In step  966 , the diverse site variable phase combined amplifier status is determined. In step  968 , if the variable phase combined amplifiers are combining the traveling wave tube outputs, step  970  is performed in which a diverse fade it is determined whether the diverse fade is less than the diverse test second (TD 2 ) threshold. If the diverse fade is not less than the diverse second threshold (TD 2 ), step  962  returns a NO status. Referring back to step  970 , if a diverse fade is less than the second diverse threshold, step  972  is performed. 
   Referring back to step  968 , if the variable phase combined amplifier is not combining the traveling wave tube (high power amplifier outputs), step  974  is performed in which it is determined whether the diverse fade is less than the second diverse threshold minus three decibels. If the diverse fade is not less than the diverse threshold minus three decibels, step  962  is again performed. In step  974 , if the diverse fade is less than the second diverse threshold minus three decibels, step  972  is performed. Step  972  performs a diverse site equipment status that was described above in steps  708  and  730  and in  FIGS. 8A and 8B . 
   If the status is good in step  976 , a return of YES is performed in step  978 . If the status is not good in step  976 , step  962  returns a NO status in  716 . 
   Referring back to step  966 , if the primary fade is not greater than the second primary threshold minus three decibels, step  980  is performed. In step  980 , if the primary fade is not less than the first primary threshold minus three decibels, step  950  is performed. This performs no switchover. In step  980 , if the primary fade is less than the first primary threshold minus three decibels, step  982  is performed in which a primary clear sky normalized diverse site function is performed. This step will be further described below. After step  982 , step  962  returns a NO condition. 
   Referring now to  FIG. 12B , the identical process with respect to the diverse site trigger point  2  (TP 2 ) is performed. Thus, the entire process is exactly the same except that the thresholds have been changed from the primary thresholds to the diverse thresholds in steps  958 ′,  966 ′ and  960 ′. The thresholds have been changed in steps  970 ′ and  974 ′ from the diverse thresholds to the primary thresholds in steps  970 ′ and  974 ′. Also, steps  960  and  982  do not have a corollary in  FIG. 12B . 
   Referring now to  FIG. 13A , steps  960  and  982  are identical steps from  FIG. 12  that normalize the radiate/terminate switch at the diverse site after a set amount of time of a primary site clear sky condition. It is desirable to broadcast using the primary site when conditions are suitable. In step  1000 , if a clear sky counter has not been started, step  1002  starts a clear sky counter. The system then returns to step  1004 . 
   Referring back to step  1000 , if the clear sky counter has been started, step  1006  reads the clear sky counter. In step  1008 , if the counter is not equal to 30 minutes, the system returns to step  1004 . If the counter is equal to 30 minutes in step  1008 , step  1010  commands the diverse site radiate/terminate switch to terminate. In step  1012 , if the terminate switch is not in terminate, the diverse switch is set to manual. In step  1014 , a message of switch failure is generated in step  1016  and diverse site graphical user interface may be displayed in a red color to indicate a failure. In step  1020 , a counter is stopped. 
   Referring back to step  1012 , if the switch is in a terminate condition, the diverse site graphical user interface (GUI) is displayed in a light blue or other color indicator in step  1022 . In step  1020 , the counter is stopped to indicate the system has now been changed over to the primary site. 
   Referring now to  FIGS. 14A and 14B , steps  720  and  742  of  FIG. 7  are illustrated in further details. In step  1040 , the block upconverter may be used to initiate or discontinue transmission. Also, the traveling wave tube inhibit function may also be used to inhibit or enable transmission. In step  1040 , the diverse block upconverter is un-muted. In step  1042 , the diverse timer (P2D) delay is read. If the delay has not been achieved in step  1044 , step  1042  is again performed. If the delay has been achieved in step  1044 , step  1046  mutes the primary block upconverter or sets the traveling wave tube to inhibit. In step  1048 , the diverse site graphical user interface may be changed to a different color such as green to indicate it is transmitting. In step  1050 , the primary site graphical user interface is set to a yellow or different color to indicate a stand-by mode. In step  1052 , the system returns to step  720 . 
   Referring now to  FIG. 14B , steps  1040  prime through  1052  prime are identical except with respect to the primary site rather than the diverse site. Therefore, these steps will not be further described below. 
   Referring now to  FIG. 15 , step  724  of  FIG. 7  is described in further detail. Once the primary site enters into a clear sky condition, this function will time the switch over to the primary path either by a timer or manually entered set time clock. If a rain fade or equipment failure occurs during this routine, the function is not performed. 
   In step  1100 , if the timer is selected, step  1102  sets the timer to a value such as 60 minutes. In step  1104 , if the time has expired, step  1106  returns a YES function, yes to step  724 . In step  1104 , if the time has not expired, the primary site fade level is determined in step  1106 . In step  1106 , the primary site fade level is determined. After step  1106 , step  1108  reads the primary variable phase combined amplifier status. In step  1110 , if the variable phase combined amplifier is combining the traveling wave tube outputs, step  1112  determines whether the primary fade is less than the first primary threshold. If the primary fade is less than the first primary threshold (TP 1 ), step  1114  is performed. Step  1114  performs a primary site equipment status. In step  1114 , if the status is good in step  1116 , the diverse site fade level is determined in step  1118 . In step  1120 , the primary variable phase combined amplifier status is determined. 
   In step  1122 , if the variable phase combined amplifiers are combining with the traveling wave tubes in step  1112 , step  1124  is performed in which the fade level is compared to the diverse site threshold. If the diverse site fade is less than the first diverse site threshold (TD 1 ), the system returns to step  1106 . In step  1122 , if the variable phase combined amplifier is not combining with the traveling wave tube, step  1126  is performed in which it is determined whether the diverse fade is less than the first diverse threshold minus three decibels. If it is in step  1126 , step  1128  is performed in which the diverse site equipment status is determined. A diverse site equipment status is also determined if the diverse fade is less than the first diverse threshold in step  1124 . In step  1126 , if the answer is NO, step  1106  is performed. 
   Referring back to step  1128 , if the diverse site equipment status is performed, step  1130  is performed in which it is determined whether the status is good. If the status is not good, the system returns a YES in steps  1106 . If the status is good, step  1100  is again performed. 
   Referring back to step  1100 , if the timer is not selected, step  1132  is performed. In step  1132 , the clock is set to a default time such as time  0100  and step  1134  is determined. In step  1134 , if the clock does equal the selected time, step  1106  returns a YES. 
   Referring back to step  1110 , if the variable phase combined amplifiers are not combining with the traveling wave tube, step  1136  is performed in which the primary fade is compared to the first primary threshold (TP 1 ) minus three decibels. If the primary fade is less than the first threshold minus three decibels, step  1114  is performed. In step  1136 , if the primary fade is less than the first primary threshold minus three decibels, step  1138  returns a NO in step  724 . 
   Referring now to  FIG. 16 , an initiate switch to normal path function is performed that corresponds to step  728  of  FIG. 7 . This function places the primary site back on the air. After the switch occurs, a primary site is placed into on-the-air and the graphic user interface may be placed to green. 
   The diverse site may be placed into a warm standby mode in which the status may be changed to a light blue and the radiate/terminate switch placed into terminate at the diverse site. In step  1150 , the diverse to primary switching is performed. This corresponds to step  742  and was described in  FIG. 14B  above. In step  1152 , the diverse radiate/terminate switch is commanded to terminate. In step  1154 , if the switch is in terminate, step  1156  sets the diverse site graphical user interface to light blue or provides another indicator. The system returns in step  1158 . In step  1154 , if the switch is not in terminate, step  1160  sets the diverse switch to manual. In step  1162 , a message of switch failure is generated. In step  1164 , the diverse site graphical user interface is changed to display a red or other indication of a site failure. 
   Referring now to  FIG. 17 , a summary of the method of changing between a primary site and a diverse site is set forth. Generally, the following method is used to project into the future a switching time taking into consideration various factors. A future switching time is determined both for the primary site and the diverse site so that a user has a slight gap between receiving the signals from the primary site and signals received from the diverse site. 
   In step  1200 , uplinking is performed using the primary site. In step  1202 , a changeover trigger is determined. The changeover trigger is described above as an increase in rain fade, an emergency condition, a maintenance condition or the like. 
   In step  1204 , a time to communicate with a diverse site is determined. The time to communicate with a diverse site includes many factors including the type of connection, the exclusivity of the connection, the speed at which the information travels, and the distance between the primary site and the diverse site. The distance may be a significant factor since a diverse site may be separated by a primary site by tens of miles such as 50 miles. As mentioned above, the signals may be communicated in a video over internet protocol format. This time may be measured experimentally. It may be determined at various times throughout the day or determined right before a changeover is required. 
   In step  1206 , the time to perform the switchover routine is also determined. This is the time that it takes to process the changeover and may thus be referred to as a switchover processing time. As was mentioned above, the block upconverters may be used to control the switchover. The block upconverter may be controlled by the controller which takes a finite amount of time to command and to switch-on or power-up and switch-off or power-down the device. 
   In step  1208 , an amount of time gap to generate at a receiving device is determined. The gap may be calculated at the primary site. The time gap is determined so that at the receiving device signals uplinked from the primary site are received followed by an empty space or gap, where thereafter the signals uplinked from the diversity site begin. This may be also experimentally determined. The time gap may vary but should be small enough to be compensated in an error control module as described below. 
   In step  1210 , a precise time at the primary and diverse site is determined using various methods that may include receiving a global positioning signal having the time therein. 
   In step  1212 , the future time for switching the primary site to OFF is determined. That is, the time for switching the primary site to OFF is projected slightly into the future. The future time for switching the primary site to OFF may take into consideration the various parameters set forth above in steps  1206 ,  1208  and  1210 . Namely, the time for determining the site to switch up may take into consideration the times determined in steps  1204  through  1208 . Also, in step  1214 , the future time for the diversity site to switch ON or broadcast is also determined. Both of the times are based upon the parameters such as the time to communicate with the diverse site, the time to perform the switchover routine and the time to generate a gap between the devices. In step  1216 , the primary site stops broadcasting based upon the future time set forth above and the diverse site begins broadcasting in step  1218 . 
   In step  1220 , the primary signals, gap and diverse site signals are received in that order at the receiving device. In step  1222 , error concealment is performed at the receive device before the signals are displayed on the television in step  1224 . Any residual time gap in the received signals is removed. 
   Referring now to  FIG. 18 , the IRD  74  and antenna  72  illustrated in  FIG. 1  is set forth in further detail. The IRD  74  may include an error concealment module  1240  among its other known functions such as tuning in tuner  1242 , demodulating in demodulator  1244  and decoding in a forward error correction decoder  1246 . Controller  1248  may contain the error concealment module  1240 . The error concealment module  1240  performs many functions including removing slight gaps or discontinuities in the signal so that they are not readily observable by the viewer in an output signal  1249 . 
   Referring now to  FIG. 19A , an integrated receiver decoder (IRD)  74  is illustrated receiving a primary site signal  1250 , followed by a time gap  1252 , followed by the diverse site signal  1254  in accordance with the method set forth in  FIG. 17 . 
   Referring now to  FIG. 19B , IRD  74  is shown transmitting primary site signal  1255  and diverse site signal  1251 . The IRD  74  may modify the signals to remove any gap between them so that the television  76  has no observable gap therebetween. It should be noted that various techniques for error concealment, such as digitally manipulating the signals and the user of buffers, is known in current generation DirecTV integrated receiver decoders. This error concealment can be used to allow a gap between the signals. By providing a gap, an overlap in the signals is avoided. An overlap in the signals may cause errors in the integrated receiving device  74 . 
   Referring now to  FIG. 20 , a method for changing the uplink power is set forth. It should be noted that the uplink power applies to the primary site, the diverse site or the central site  14 . In step  1270 , a clear sky uplink power is established. This is a baseline and a delta from the baseline will be determined below. In step  1272 , a first beacon signal is received and converted to a first beam power signal. In step  1274 , a second beacon signal is received and converted to a second beacon power signal. The beacon power signals in step  1272  and  1274  are received using the antenna  404  and the associated circuitry set forth above, including the beacon receiver and the block downconverter illustrated in  FIG. 5 . In step  1276 , the first beacon power signal and the second beacon power signal are compared. The comparison compares the first beacon power signal and the second power beacon signal. In step  1278 , the strongest powered beacon signal is selected to form a selected signal. In step  1280 , the amount of fade in terms of power is determined. In step  1282 , a fade threshold is established. In step  1284 , the uplink power is determined as a delta (Δ) of the clear sky power. That is, based upon the threshold and the amount of fade, a new uplink power may be determined. The beacon power signal may be broadcast to multiple pieces of equipment. Each piece of equipment (such as those shown in  FIG. 5 ) may then use the beacon information for various control methods. Amplifiers and block upconverters (BUC) are examples of suitable equipment to receive the beacon power signals. A suitable broadcast method is through the Ethernet connection. Each device such as the amplifier and BUC then determines a fade and an adjustment for fade. The amplifier and block upconverter act as a controller in this respect. 
   Once the new uplink power is determined, the uplink speed is determined in step  1286 . If the uplink speed is greater than a pre-determined speed, the uplink power is limited in step  1288 . The uplink speed limits how quickly the uplink power is ramp. It operates as a second layer of protection so that the high power amplifiers prevent ramping power so quickly that a large phase shift is introduced in the uplink that may cause the receivers on the ground to momentarily loose lock. Typical values of uplink speed are one to three decibels per second. After step  1288  and after step  1286  if the uplink speed is greater than the uplink speed, the uplink forward power limit is compared to the uplink powered determined in step  1284  or  1288  in step  1290 . If the uplink power is over the forward limit, then the power is limited in step  1292  to the maximum power that a block upconverter should be commanded to. If the uplink power is not over the forward limit, and after step  1282  the antenna is broadcast with the calculated uplink power in step  1294 . 
   Referring now to  FIG. 21 , a plot of the uplink power versus fade is illustrated. The lower horizontal line corresponds to the clear sky power. The fade thresholds T is also illustrated. The second horizontal line  1302  illustrates the forward power limit. 
   It should be noted that the beacon signals in step  1272  and  1274  are locked on to the same downlink beacon signal. The uplink power compensation may be based on a unit-less constant, K, the fade, the transmit and receive signal frequency and a fade threshold T. The fade is a calculated value within the server or controller. The K value, the transmit and receive signal frequency values and the threshold values may all be user generated. These values may be experimentally determined based in part on the capabilities of the particular transmitting capabilities. The uplink power control (UPC) is best defined as:
 
UPC= K (FADE-THRESHOLD)( F   Tx   /F   Rx ) 2  
 
   Referring now to  FIG. 22 , a method of operating the system is illustrated. The system may be also understood with reference to  FIG. 5 . 
   In step  1320 , a tracking interface is selected. The tracking interface is illustrated as  524  and is coupled to the antenna. In step  1322 , a beacon signal is received. This may include error checking, amplifying and passing the signal through a monopulse plate  532 . In step  1324 , the beacon signal is divided into a first beacon signal and a second beacon signal at the monopulse plate  532 . The first beacon signal and the second beacon signal are passed to block downconverters  534 ,  536 . In step  1326 , the first beacon signal is block downconverted and in step  1328 , the second beacon signal is block downconverted. The signals are then communicated in step  1330  to the indoor unit and to respective beacon receivers  538  and  540  of  FIG. 5  through a communication line  444 . In step  1332 , the beacon signals are serially connected to a controller to determine uplink power. In step  1334 , the serial connection is checked to determine whether or not the serial connection has failed. If the serial connection has not failed, the uplink power is determined in step  1336  and the new uplink power is used to broadcast the signal in step  1338 . 
   If the serial connection has failed in step  1334 , the antenna control unit may be coupled to each of the beacon receivers  538  and  540 . The antenna control unit  542  has an Ethernet connection to the controller. The beacon signals are communicated through the Ethernet connection through the antenna control unit  542  in step  1340 . The controller then determines the uplink power in step  1336  and broadcasts with that uplink power in step  1338 . 
   Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.