Abstract:
Circuits, methods, and apparatus that limit the number of types of connectors needed by an electronic device. One example may provide a connector receptacle capable of adapting to multiple types of connector inserts. In this way, connector inserts conveying one of a number of interfaces can be accepted by the same connector receptacle. This may reduce the number and types of connector receptacles needed on an electronic device.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application Nos. 61/478,805, filed Apr. 25, 2011, which is incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The number of types of electronic devices that are commercially available has increased tremendously the past few years, and the rate of introduction of these devices shows no signs of abating. Devices, such as tablet, laptop, netbook, desktop, and all-in-one computers, cell, smart, and media phones, storage devices, portable media players, navigation systems, monitors, and others, have become ubiquitous. 
         [0003]    Often, these devices communicate with other devices. As just one example, a desktop computer may need to communicate with a monitor or display device. Such communications may take place over a cable. The cable may have connector inserts on each end, where the connector inserts mate with connector receptacles on the desktop and the monitor. 
         [0004]    Currently, electronic devices may include many connector receptacles. For example, a laptop computer may have connectors for Universal Serial Bus (USB), a High-Definition Multimedia Interface (HDMI), Digital Visual Interface (DVI), power, Ethernet, DisplayPort, Thunderbolt, and other types of interfaces. 
         [0005]    Such diversity is not without its downside. The inclusion of so many connectors consumes space inside the electronic device, as well as the surface area of its outer case. This means that smaller devices may only be able to include a limited number of connectors. Customer confusion may also result as users try to sort through a bewildering array of acronyms. Design complexity may also be increased. For example, to avoid damage, each new connector may be constructed such that a connector insert from a cable that supports one interface cannot be improperly inserted into a connector receptacle for another interface. 
         [0006]    Also, as these standards and interfaces evolve, devices with newer connectors may not be compatible with a user&#39;s legacy components. For example, a new computer may have an HDMI connector, while a monitor may have a DVI connector. An adapter to convert signals from HDMI to DVI may be used, but such necessity invokes further customer dissatisfaction. 
         [0007]    Thus, what is needed are circuits, methods, and apparatus that limit the number of types of connector receptacles needed by an electronic device. 
       SUMMARY 
       [0008]    Accordingly, embodiments of the present invention may provide circuits, methods, and apparatus that may limit the number of types of connectors needed by an electronic device. An embodiment of the present invention may provide a connector receptacle capable of adapting to multiple types of connector inserts. In this way, connector inserts conveying one of a number of interfaces may be accepted by the same connector receptacle. This may reduce the number and types of connector receptacles needed on an electronic device. 
         [0009]    In an exemplary embodiment of the present invention, a connector receptacle may have a number of relatively small pads or contacts arranged in an array or other pattern. These pads or contacts may be on a top, bottom, or both a top and bottom surface of the receptacle. Still other pads or contacts may be placed on sides of the receptacle. Each pad or contact may be configured to be connected to a power, ground, or signal line. When a connector insert is engaged with the connector receptacle, the connector receptacle may determine, for each connector receptacle pad, whether the pad has formed an electrical connection with a relatively larger connector insert contact. 
         [0010]    In an exemplary embodiment of the present invention, a connector receptacle includes a number of pads or contacts arranged in an array. Each horizontal line of pads may receive one of a first set of signals, where each signal in the first set of signals has a different frequency. Similarly, each vertical line of pads may receive one of a second set of signals, where each signal in the second set of signals has a different frequency. In this way, each pad has a unique set of two frequencies. Each pad can then be analyzed to determine which frequencies appear at that pad. From this, it may be determined which receptacle pads are connected together through an insert pad. In other embodiments of the present invention, other patters of receptacle contacts or pads may be used, and these signals may be applied in various ways. 
         [0011]    In another exemplary embodiment of the present invention, a connector receptacle includes a number of pads or contacts arranged in an array. A signal may be applied to a first pad. Pads that are nearby may be checked for the presence of the signal. Receptacle pads where the signal is present may be identified as being connected together through an insert pad. 
         [0012]    In an exemplary embodiment of the present invention, once it is determined which receptacle pads are shorted by insert pads, the identity of the connector insert may be determined. For example, each insert may have a unique pad arrangement which identifies the connector insert as being a connection for a specific interface, such as a USB, HDMI, DVI, power, Ethernet, DisplayPort, Thunderbolt, or other type of interface. In a specific embodiment of the present invention, each of a number of connector inserts may have a similar pad pattern, with one or more pads omitted, where the omissions indicate the type of connector insert. 
         [0013]    In another exemplary embodiment of the present invention, the type of connector insert is determined before the connections among the receptacle pads are determined. In a specific embodiment of the present invention, the type of connector insert may be indentified by determining that a unique pattern of a subset of the receptacle pads are connected together through an insert pad. Once this occurs, the remaining connections can be determined. 
         [0014]    In another embodiment of the present invention, once the identity of a connector insert is determined, the validity of that determination may be checked. This reduces the possibility that an improperly made connector insert may cause damage to a connector receptacle. This validity may be achieved by using handshaking signals or by other techniques. 
         [0015]    In various embodiments of the present invention, the connector insert may be registered with the connector receptacle when inserted, while in other embodiments of the present invention, the connector insert is not registered, and may instead move relative to the connector receptacle even after insertion. By updating the connector receptacle pad connection information, a proper connection between insert and receptacle may be maintained even as the insert moves relative to the receptacle. 
         [0016]    In various embodiments of the present invention, the connector insert may be non-binding, that is, it may be shaped so that it may be removed using a non-axial force. In still other embodiments, the connector insert may be thin. In this way electronic device thickness is not limited. Also, in various embodiments of the present invention, a self-wiping feature may be included. 
         [0017]    Various embodiments of the present invention may incorporate one or more of these and the other features described herein. A better understanding of the nature and advantages of the present invention may be gained by reference to the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  illustrates a computer system that may be improved by the incorporation of embodiments of the present invention; 
           [0019]      FIG. 2  illustrates a method of forming a connection between a connector receptacle and connector insert according to an embodiment of the present invention; 
           [0020]      FIG. 3  illustrates another method of forming a connection between a connector receptacle and a connector insert according to an embodiment of the present invention; 
           [0021]      FIG. 4  illustrates an array of receptacle pads according to embodiment of the present invention; 
           [0022]      FIG. 5  illustrates a connector insert according to an embodiment of the present invention; 
           [0023]      FIG. 6  illustrates the connections formed between connector receptacle pads when a connector insert is inserted into a connector receptacle according to an embodiment of the present invention; 
           [0024]      FIG. 7  illustrates a method of determining locations of connector insert pads according to an embodiment of the present invention; 
           [0025]      FIG. 8  illustrates another method of determining locations of connector insert pads according to an embodiment of the present invention; 
           [0026]      FIG. 9  illustrates a contact or pad pattern for a connector insert according to an embodiment of the present invention; 
           [0027]      FIG. 10  illustrates another pattern of pads or contacts on a connector insert according to an embodiment of the present invention; 
           [0028]      FIG. 11  illustrates circuitry associated with a connector receptacle pad according to an embodiment of the present invention; and 
           [0029]      FIG. 12  illustrates a portion of a connector receptacle pad according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0030]      FIG. 1  illustrates a computer system  100  that may be improved by the incorporation of embodiments of the present invention. This computer system  100  may include desktop computer  110 , monitor  120 , keyboard  130 , and mouse  140 . In this example, desktop computer  110  may drive monitor  120  with signals provided over cable  167 . Cable  167  may include connector insert  160 , which may be inserted into connector receptacle  165 . A second connector insert  150  may also be inserted into desktop computer  110 , for example at connector receptacle  170 . Connector insert  150  may be partially surrounded by connector insert housing  155 , and attached to cable  157 . Cable  157  may in turn be connected to another connector insert, which may in turn be connected to another device, such as a storage device, media player, or other electronic device (not shown). 
         [0031]    While in this example a computer system  100  including desktop computer  110  is improved by the incorporation of one or more embodiments of the present invention, other electronic devices, such as tablet, laptop, netbook, and all-in-one computers, cell, smart, and media phones, storage devices, portable media players, navigation systems, monitors, and others may be improved the incorporation of one or more embodiments of the present invention. 
         [0032]    Connector receptacles, such as connector receptacles  165  and  170 , may receive and provide signals in compliance with various standards or interfaces, such as USB, HDMI, DVI, DisplayPort, thunderbolt, or other interface. To support a large number of standards or interfaces, a correspondingly large number of connector receptacles currently need to be included in desktop computer  110 . These connectors may add expense, complexity, and size to desktop computer  110 . This large number of conductors also degrades the aesthetics of desktop computer  110  or other electronic device, and adds to customer confusion and dissatisfaction. 
         [0033]    Accordingly, embodiments of the present invention provide connector receptacles that are capable of accepting a variety of connector inserts that support a variety of interfaces and standards. In a specific embodiment of the present invention, a connector receptacle includes a number of relatively small contacts or pads. These contacts may be arranged on a bottom of a connector receptacle, a top of a connector receptacle, or both a bottom and top of a connector receptacle. In other embodiments of the present invention, contacts or pads may also be included along sides of a connector receptacle. In still other embodiments of the present invention, receivers and transmitters for fiber-optic signals may be included in the connector receptacle. When a connector insert is inserted into the connector receptacle, various ones of the receptacle pads may be shorted by pads or contacts on the connector insert. By identifying which receptacle pads are connected to each other, the locations of connector insert pads may be determined. When each type of connector insert has a unique pattern, the identity of a type of connector insert may be learned using the insert pad locations. Once the type of connector insert is identified, contacts or pads in a connector receptacle may be configured to provide or receive power or other signals. An example of the operation of such a connector receptacle is outlined in the following figure. 
         [0034]      FIG. 2  illustrates a method of forming a connection between a connector receptacle and connector insert according to an embodiment of the present invention. This figure, as with the other included figures, is shown for illustrative purposes and does not limit either the possible embodiments of the present invention or the claims. 
         [0035]    In act  210 , a connector insert is inserted into a connector receptacle. In various embodiments of the present invention, the connector insert may be registered in the connector receptacle, that is, the connector insert may be formed to fit into the connector receptacle without substantial movement. In other embodiments of the present invention, the connector insert may not be registered in a connector receptacle, that is, the connector insert may be formed such that it is free to move inside the connector receptacle after insertion. 
         [0036]    In act  220 , the insertion is detected by the receptacle. In various embodiments of the present invention, this detection may be determined in a number of ways. For example, the connector receptacle may include a door or cover. This door or cover may be pushed out of the way when a connector insert is inserted, thereby triggering detection of the insertion. In other embodiments of the present invention, a mechanical contact may be deflected when a connector insert is inserted. In still other embodiments of the present invention, the presence of a connector insert may be detected when two or more receptacle pads are connected to each other through a pad on the insert. 
         [0037]    In act  230 , the receptacle identifies which receptacle pads are connected together through connector insert pads. This may be done in several ways, including the illustrative methods as outlined below. 
         [0038]    In act  240 , the connections among receptacle pads made by insert pads are used to identify a connector insert type. This identification may be made in several ways, including illustrative methods as outlined below. The identification may determine that the connector insert supports a USB, HDMI, DVI, power, Ethernet, DisplayPort, Thunderbolt, or other type of interface. Additionally, as other interfaces are developed in the future, firmware updates may be provided to allow connector receptacle support. 
         [0039]    Once an insert type is identified, the insert may be verified in act  250 . Various embodiments of the present invention may perform this function in various ways. For example, a hand shaking or other authentication, identification, or validation method may be used. 
         [0040]    Once an insert is verified, circuitry associated with receptacle pads may be configured in act  260 . An example of this circuitry is also shown below. 
         [0041]    In other embodiments of the present invention, these acts may be performed in various orders or sequences. For example, the connector insert type may be identified before receptacle pad connections are identified. In these embodiments, the identification is used to locate the connector insert pads. An example is shown in the following figure. 
         [0042]      FIG. 3  illustrates another method of forming a connection between a connector receptacle and a connector insert according to an embodiment of the present invention. In act  310 , a connector insert may be inserted into a connector receptacle. As before, in act  320 , the insertion of the connector insert is detected by the receptacle. In act  330 , the connector insert type is identified. In act  340 , the location of the connector insert pads are determined. In act  350 , the connector insert type may be verified. Receptacle pad circuits may be configured in act  360 . 
         [0043]    Again, receptacle circuitry may identify which receptacle pads or contacts are connected to each other through connector insert pads in various ways. Examples are shown in the following figures. 
         [0044]      FIG. 4  illustrates an array  400  of receptacle pads  430  according to embodiment of the present invention. Receptacle pads  430  may be joined by vertical lines  410  and horizontal lines  420 . In a specific embodiment of the present invention, low amplitude signals at various frequencies may be applied to vertical lines  410  and horizontal lines  420 . In this way, each connector receptacle pad or contact  430  may receive two signals having different frequencies. For example, if a signal having frequency F 1  is applied to vertical line  410  and a signal having frequency F 10  is applied to horizontal line  420 , pad  430  may receive a signal having components at frequency F 1  and frequency F 10 . 
         [0045]    In various embodiments of the present invention, the frequencies may be allocated in various ways. For example, in some embodiments of the present invention, harmonics are avoided and not used. In other embodiments of the present invention, horizontal lines may have signals having frequencies in a first range, while vertical lines may have signals having frequencies and a second range. In still other embodiments of the present invention, these frequency ranges may overlap at least partially. 
         [0046]    In some embodiments of the present invention, each line may receive a signal having a unique frequency. In still other embodiments of the present invention, lines near each other may have unique frequencies, while lines that are far enough apart such that their pads cannot be shorted by a connector insert pad may share a frequency. 
         [0047]    While round pads or contacts are shown in this and the other included examples, pads or contacts in either or both a connector insert or connector receptacle may have other shapes and they may be arranged in other patterns. For example, the pads or contacts may be square, rectangular, oblong, or have other shapes. 
         [0048]    Various connector inserts may be used according to embodiments of the present invention. In a specific embodiment of the present invention, a connector insert may have rounded edges such that the connector insert may be extracted from a connector receptacle by a non-axial force. In other embodiments of the present invention, the connector insert may have other shapes. The connector insert may have pads on one or both of a top and bottom surface. In other embodiments of the present invention, a connector insert may have one or more pads along its sides. In still other embodiments of the present invention, one or more fiber-optic cables may be included in the connector insert. An example of a connector insert according to an embodiment of the present invention is shown in the following figure. 
         [0049]      FIG. 5  illustrates a connector insert  500  according to an embodiment of the present invention. Connector insert  500  includes a portion to be inserted  510 , and a number of pads or contacts  530  that are connected to conductors (not shown) inside cable  520 . Again, in various embodiments of the present invention, connector insert  500  may fit, that is be registered, in a connector receptacle, while in other embodiments of the present invention, connector insert  500  is not registered when it is inserted into a connector receptacle. 
         [0050]    Again, connector insert  500  may have a rounded shape such that it may be extracted from a connector receptacle using a non-axial force, that is, it may be non-binding. In still other embodiments of the present invention, connector insert  500  may have other shapes. Also, connector insert  500  may include other features, such as a connector housing or other structure that may be manipulated by a user during insertion. In various embodiments of the present invention, the connector insert may be inserted in either of two orientations, such as right-side-up or up-side-down, and be correctly recognized by the connector receptacle. In various embodiments of the present invention, connector insert  500  and corresponding receptacle may include a self-wiping feature. 
         [0051]    In various embodiments of the present invention, connector insert  500  may be attached to a cable. In other embodiments of the present invention, connector insert  500  may be an adapter that provides a conversion from connector insert  500  to a conventional USB, HDMI, DVI, power, Ethernet, DisplayPort, Thunderbolt, or other type of connector. 
         [0052]    When connector insert  500  is inserted into a connector receptacle, contacts or pads on the connector insert may connect various connector receptacle pads together. An example is shown in the following figure. 
         [0053]      FIG. 6  illustrates the connections formed between connector receptacle pads when a connector insert is inserted into a connector receptacle according to an embodiment of the present invention. In this example, a number of connector insert pads or contacts  640  each form electrical contact with a number of connector receptacle pads or contacts  630 . As before, each vertical line  610  may receive a signal having a first specific frequency, and each horizontal line  620  may receive a signal having a second specific frequency. In this way, each connector receptacle pad  630  receives signals at two specific frequencies. When two such receptacle pads are connected together by a connector insert pad, each such receptacle pad will receive more than two such signals. The identity of these signals may then be used to determine which connector receptacle pads are connected to each other through connector insert pads. 
         [0054]    As an example, connector receptacle pad  660  and its horizontal and vertical neighbors may be connected together through connector insert pad  640 . This may be determined by reading a signal on connector receptacle pad  660 . Specifically, this signal may include frequency compliments at frequencies F 1 , F 2 , F 3 , F 13 , F 14 , and F 15 . This information may be used to determine that each of the horizontal and vertical neighbors of connector receptacle pad  660  are connected or shorted to connector receptacle pad  660  through connector insert pad  640 . In various embodiments of the present invention, this information may be determined in various ways. For example, the signals on the receptacle pads may be processed by a digital signal processor, fast-Fourier transform circuit, notch filters, or other appropriate circuitry. 
         [0055]    It should also be noted that receptacle circuitry may mistakenly determine that pad  650  is an electrical contact with pad  660  as well. Specifically, this may occur since the signals on pad  650 , F 3  and F 13 , appear on pad  660 . In various embodiments of the present invention, this may be handled in one of a number of ways. In one embodiment of the present invention, this is ignored, and pad  650  is treated as though it is actually connected to pad  660 . In such an embodiment, if the spacing between connector insert pads is sufficient, connector receptacle pad  650  cannot be connected to another connector insert pad, and therefore treating it as though it is connected to connector insert pad  640  cause no harm. In still other embodiments of the present invention, signals on pad  650  are analyzed. Since connector receptacle pad  650  only includes frequency compliments F 3  and F 13 , it can be determined that connector receptacle pad  650  is not electrically connected to receptacle pad  660  through insert pad  640 . 
         [0056]    In various embodiments of the present invention, the signals on pads  630  may be read in various ways. For example, signals on the pads may be read one at a time. In other embodiments of the present invention, some or all of these signals on the various pads  630  may be read in parallel. 
         [0057]    When signals on pads  630  are read one at a time, various methods may be used to accelerate the process of determining connections among pads  630 . For example, the identity of a group of pads connected together may be used to skip one or more readings of connector receptacle pad signals. For example, once it is determined that pad  660  is connected to its horizontal and vertical neighbors, one or more pads may be skipped, whereupon the signals on pad  670  are read next. This reduces the amount of data needed to determine the connector insert configuration and to speed the reading process. 
         [0058]    An example of a method of determining which receptacle pads are connected together through insert pads is shown in the following figure. Again, this information may be used to identify the locations of connector insert pads, and therefore a type of connector insert. 
         [0059]      FIG. 7  illustrates a method of determining locations of connector insert pads according to an embodiment of the present invention. In act  710 , a signal having one of a first set of frequencies is applied to each horizontal line. In act  720 , a signal having one of a second set of frequencies is applied to each vertical line. In act  730 , frequencies present on a first receptacle pad are read. In act  740 , it may be determined which receptacle pads are connected to the first receptacle pad through an insert pad. In act  750 , it is determined whether there are more receptacle pads to read. If so, a next receptacle pad to be read is determined in act  760 . Again, in some embodiments of the present invention, some intelligence can be used to try to skip over some receptacle pads, as described above. In act  770 , frequencies are read at the next receptacle pad. In act  770 , it is determined which receptacle pads are connected to the next receptacle pad through an insert pad. When all receptacle pads have been checked in act  750 , the process is done in act  790 . 
         [0060]    Again, in various embodiments of the present invention, a connector insert may move relative to a receptacle. Accordingly, this process may be restarted or updated on a periodic basis, such that proper connection may be maintained even after a connector insert has moved. 
         [0061]    In other embodiments of the present invention, other techniques of determining connections among receptacle pads may be determined. For example, signals may be applied to a subset of connector receptacle pads. For example, a signal may be applied to connector receptacle pads one at a time. An example is shown in the following figure. 
         [0062]      FIG. 8  illustrates another method of determining locations of connector insert pads according to an embodiment of the present invention. A signal is applied to a first receptacle pad in act  810 . In act  820 , it is determined which receptacle pads are connected to the first receptacle pad by an insert pad. This may be done by determining which receptacle pads also receive the signal. In act  830 , it is determined whether or more receptacle pads remain to be checked. If so, the next receptacle pad to be checked is determined in act  840 . Again, some intelligence may be used to skip over one or more pads before this next reading is taken. In act  850 , a signal may be applied at the next receptacle pad. Again, it may be determined which receptacle pads are connected to the next receptacle pad through an insert pad in act  860 . When there are no more receptacle pads to be checked, the process is done in act  870 . Again, this process may be restarted at various times. 
         [0063]    Connector inserts that support various standards or interfaces may each have a unique contact pattern. In this way, the contact pattern determined above may be used to identify the connector insert and the standard or interface that is supported. In various embodiments of the present invention, the location of each contact on a connector insert is determined, then the connector insert is identified. In other embodiments of the present invention, one or more identifying features are determined and used to identify a connector insert. From this identification, the location of each contact on a connector insert may be determined. Examples are shown in the following figures. 
         [0064]      FIG. 9  illustrates a contact or pad pattern for a connector insert according to an embodiment of the present invention. Connector insert contact pattern  900  may include one or more features  910  and  920 . These features may have various shapes, and may be unique and thereby identify the type of connector insert. These features may also be separated by a specific distance  930 , which may be used to indentify a type of connector insert. In still other embodiments of the present invention, other features may be used to identify the type of connector. 
         [0065]    In another embodiment of the present invention, instead of determining the location of each pad or contact on a connector insert, the locations of only a subset of the pads or contacts on a connector insert are determined. An example is shown in the following figure. 
         [0066]      FIG. 10  illustrates another pattern of pads or contacts on a connector insert according to an embodiment of the present invention. In this example, the locations of pads or contacts in range  1010  are identified. Once the locations of these pads are known, the locations of the remaining pads are contacts may be extrapolated. The identity of the type of connector may be determined by detecting the absence of one or more pads or contacts. In this example, pads or contacts  1020 ,  1030 , and  1040  have been removed from zone  1010 . The absence of pads or contacts  1020 ,  1030 , and  1040  may be used to identify a specific connector type. 
         [0067]    Once the specific connector type is identified, the connector insert may be verified. This may be done using and shaking, authentication, verification, or other methods. Verification is particularly useful in avoiding a situation where a noncompliant connector insert is inserted into a connector receptacle. If a noncompliant connector insert is inserted into connector receptacle and is mistakenly recognized as a valid connector insert, damage to the connector insert may result. 
         [0068]    Once verified (if verification is desired), circuitry associated with the connector receptacle pads may be configured. An example of such circuitry is shown in the following figure. 
         [0069]      FIG. 11  illustrates circuitry associated with a connector receptacle pad according to an embodiment of the present invention. In this example, the pads may be tied to VCC, ground, or to a signal line. Specifically, transistor M 2  may be enabled, thereby pulling the pad up to VCC. Alternately, transistor Ml may be enabled, thereby grounding the pad. In this way, power may be supplied or received from a pad on a connector insert. In other configurations, buffer B 1  may be enabled, thereby allowing an input signal to be output onto the pad. In still other configurations, buffer B 2  may be enabled, thereby allowing ended signals received on the pad to be provided as an output. In still other embodiments of the present invention, buffers B 1  and B 2  may be replaced by a bidirectional tristate or pass gate. 
         [0070]    Again, each pad may receive signals at two frequencies, shown here as signals FIN 1  and FIN 2 . These signals may be AC coupled to the pad such that the pad&#39;s DC level is not disturbed during operation. Signals on the pad may be read on line FOUT. 
         [0071]    Pads on a connector insert may be formed in various ways. For example, they may be printed or metallic pads for durability. Pads in the connector receptacle may be under a spring tension such that contact is maintained between receptacle pads and insert pads. An example of a portion of a connector receptacle pad is shown in the following figure. 
         [0072]      FIG. 12  illustrates a portion of a connector receptacle pad according to an embodiment of the present invention. The connector receptacle pad may include one or more spring portions  1220  located on a substrate  1210 . When a connector insert is inserted, force in direction  1250  compresses spring portion  1220 , thereby ensuring that electrical contact is maintained between the connector receptacle pad and a connector insert pad. 
         [0073]    The above description of embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Thus, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.