PATENT DOCUMENT

Publication Number: US-10236106-B2
Application Number: US-201715677214-A
Country: US
Kind Code: B2

Title: Cover for an electronic device

Abstract:
A magnetic attachment mechanism and method is described. The magnetic attachment mechanism can be used to releasably attach at least two objects together in a preferred configuration without fasteners and without external intervention. The magnetic attachment mechanism can be used to releasably attach an accessory device to an electronic device. The accessory device can be used to augment the functionality of usefulness of the electronic device.

Claims:
What is claimed is: 
     
       1. An accessory device capable of magnetically attaching with a separate portable electronic device, the portable electronic device having a housing capable of carrying a first magnetic element and a first electronic component that is capable of providing a first electronic function, the accessory device comprising:
 a body that carries a second magnetic element and a second electronic component that is capable of providing a second electronic function, wherein a cooperating electronic system comprises the first and second magnetic elements attracted to each other such that the body and the housing are attached to each other in a pre-determined orientation and a pre-determined alignment, wherein the pre-determined orientation and the pre-determined alignment allows forming of a communication channel over which the first and second electronic components are capable of communicating with each other in order to provide a third electronic function that the first and the second electronic components are incapable of providing individually. 
 
     
     
       2. The accessory device as recited in  claim 1 , wherein the communication channel is wireless. 
     
     
       3. The accessory device as recited in  claim 1 , wherein the accessory device further comprises a single piece flap pivotally attached to the body. 
     
     
       4. The accessory device as recited in  claim 2 , the single piece flap further comprising an input device. 
     
     
       5. The accessory device as recited in  claim 1 , wherein the portable electronic device is a handheld personal communication device. 
     
     
       6. A method operable by a portable electronic device having a housing that carries a first electronic component capable of providing a first electronic function, a display coupled to a processor, a sensor, a battery, a protective layer having a size and a shape of a front side of the portable electronic device and overlaying the display, the method comprising:
 detecting, by the sensor, when a body portion of an accessory device is magnetically attached to the portable electronic device by a magnetic element carried by the body portion, the body portion further carrying a second electronic component capable of providing a second electronic function; 
 forming, based upon the detecting, a communication channel between the first and second electronic components, wherein the communication channel enables the first and second electronic components to cooperate with each other; and 
 providing, in accordance with the cooperation of the first and second components, a third electronic function (i) that is different than the first and second electronic functions, and (ii) that the first and second electronic components, individually, are incapable of providing. 
 
     
     
       7. The method as recited in  claim 6 , wherein the communication channel is wireless. 
     
     
       8. The method as recited in  claim 6 , wherein the sensor is a magnetic sensor. 
     
     
       9. The method as recited in  claim 8 , wherein the magnetic sensor is a Hall Effect Sensor. 
     
     
       10. The method as recited in  claim 6 , wherein the battery is capable of receiving power by way of the communication channel. 
     
     
       11. The method as recited in  claim 6 , wherein the accessory unit includes an input device. 
     
     
       12. A cooperative electronic system, comprising:
 a portable electronic device; and 
 an accessory device magnetically and separably attached to the portable electronic device, the accessory device comprising:
 a body that defines an internal cavity in which is carried: 
 a magnetic element capable of magnetically attaching the body to a a housing of the portable electronic device in a pre-determined orientation and alignment, wherein the magnetic attachment is such that the portable electronic device and the accessory device form the cooperative electronic system that (i) is portable and (ii) is capable of performing operations and providing functions that cannot be provided by the accessory device and the portable electronic device individually. 
 
 
     
     
       13. The cooperative electronic system as recited in  claim 12 , wherein the portable electronic device includes a charge storage device. 
     
     
       14. The cooperative electronic system as recited in  claim 13 , wherein the accessory device further includes a single piece flap attached to the body. 
     
     
       15. The cooperative electronic system as recited in  claim 13 , the body further comprising:
 an external power connector suitable for receiving external power from an external power supply and passing at least some of the external power to the charge storage device. 
 
     
     
       16. The cooperative electronic system as recited in  claim 15 , wherein the cooperative electronic system is capable of receiving power from the external power supply. 
     
     
       17. The cooperative electronic system as recited in  claim 12 , wherein the portable electronic device is a portable communication device. 
     
     
       18. The cooperative electronic system as recited in  claim 12 , wherein power is wirelessly transmitted between the accessory device and the portable electronic device. 
     
     
       19. The cooperative electronic system as recited in  claim 12 , wherein the portable electronic device is a tablet device. 
     
     
       20. The cooperative electronic system as recited in  claim 12 , wherein the accessory device includes a single piece flap attached to the body and that includes an input device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/408,204, filed Jan. 17, 2017, entitled “Cover for an Electronic Device,” which is a continuation of U.S. patent application Ser. No. 15/081,310, filed Mar. 25, 2016, now U.S. Pat. No. 9,568,954, entitled “Cover for an Electronic Device,” which is a continuation of U.S. patent application Ser. No. 14/590,904, filed Jan. 6, 2015, now U.S. Pat. No. 9,329,630, entitled “Cover,” which is a continuation of U.S. patent application Ser. No. 14/340,449, filed Jul. 24, 2014, now U.S. Pat. No. 8,975,991, entitled “Cover,” which is a continuation of U.S. patent application Ser. No. 13/621,173, filed Sep. 15, 2012, now U.S. Pat. No. 8,884,730, entitled “Multi-Peek Mode Tablet Device,” which is a continuation of U.S. patent application Ser. No. 12/971,536, filed Dec. 17, 2010, now U.S. Pat. No. 8,344,836, entitled “Consumer Electronic Product,” which is a continuation-in-part of U.S. Design patent application Ser. No. 29/375,197, filed Sep. 17, 2010, now U.S. Design Pat. No. D658,186, entitled “Cover,” and which claims the benefit of U.S. Provisional Application No. 61/384,179, filed Sep. 17, 2010, entitled “Apparatus and Method for Magnetic Attachment,” of the contents of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     FIELD 
     The described embodiments generally relate to portable electronic devices. More particularly, the present embodiments describe various releasable attachment techniques well suited for portable electronic devices. 
     BACKGROUND 
     Recent advances in portable computing includes the introduction of hand held electronic devices and computing platforms along the lines of the iPad™ tablet manufactured by Apple Inc. of Cupertino, Calif. These handheld computing devices can be configured such that a substantial portion of the electronic device takes the form of a display used for presenting visual content leaving little available space for an attachment mechanism that can be used for attaching an accessory device. 
     Conventional attachment techniques generally rely upon mechanical fasteners that typically require at least an externally accessible attaching feature on the electronic device to mate with a corresponding attaching feature on the accessory device. The presence of the external attaching feature can detract from the overall look and feel of the handheld computing device as well as add unwanted weight and complexity as well as degrade the appearance of the hand held computing device. 
     Therefore a mechanism for releasably attaching together at least two objects is desired. 
     SUMMARY 
     This paper describes various embodiments that relate to a system, method, and apparatus for releasably attaching an accessory to an electronic device. 
     A magnetic attachment system includes at least a first coded magnetic structure. The first coded magnetic structure, in turn, includes at least a first plurality of magnetic elements and a restraining feature mechanically connected to the first plurality of magnetic elements. The first plurality of magnetic elements are arranged to form a first magnetic code. In the described embodiment, the restraining feature applies a restraining force to the first plurality of magnetic elements at a first position that corresponds to an inactive state of the magnetic attachment system. The magnetic attachment system changes from the inactive state to an active state only when the coded magnetic structure magnetically interacts with a second coded magnetic structure having magnetic elements arranged to form a second magnetic code that fully correlates with the first magnetic code. 
     A method of magnetically attaching a first object having a first housing and a second object having a second housing can be carried out by providing the first object having a first magnetic attachment system enclosed in the housing. The first magnetic attachment system includes at least a first coded magnetic structure where a first magnetic field generated by the first coded magnetic structure has a value of magnetic flux density less than a threshold value at an exterior surface of the first housing, Next first coded magnetic structure is introduced to a second magnetic field generated by a second coded magnetic structure enclosed in the second housing. The first magnetic attachment system is activated only when the second magnetic field is generated by a second coded magnetic structure that fully correlates with the first coded magnetic structure. When the first magnetic attachment system is activated, the value of the magnetic flux density at the exterior surface of the first housing increases to a value that is greater than the threshold value that causes the first and second objects to magnetically attach to each other. 
     In one aspect of the described embodiment, the first and second objects magnetically attach to each other at a pre-defined position and orientation. 
     A method of selectively activating a display device can be carried out by determining if a first portion of the display device is viewable, activating only the first viewable portion of the display device, and presenting visual content only at the first viewable portion of the display device. 
     In another embodiment of the method, if a second portion of the display is determined to be viewable, the second portion being different than the first portion, the second viewable portion of the display is activated, and visual content is presented at the second viewable portion. 
     A display device includes at least a first sensor arranged to generate a first signal indicating that a first portion of the display device is viewable and a processor, the processor arranged to interpret the first signal. Based upon the interpretation of the first signal, the processor activates only the viewable first portion of the display device, and causes visual content to be presented only at the viewable first portion. 
     In another embodiment, the display device includes a second sensor arranged to generate a second signal indicating that a second portion of the display is viewable, the second portion being different than the first portion. The processor interprets the second signal and based upon the interpretation of the second signal activates the viewable second portion of the display device, and presents visual content at the viewable second portion. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  is a simplified block diagram of an article and an electronic device that can be releasably attached to each other in a desired and repeatable manner. 
         FIG. 2A  is a simplified perspective view of an article that can be releasably attached to an electronic device via a side magnetic attachment system, in accordance with one described embodiment. 
         FIG. 2B  shows the article and the electronic device of  FIG. 2A  attached in accordance with the side magnetic attachment system. 
         FIG. 3A  is a simplified perspective view of an article that is releasably attachable to an electronic device via a top magnetic attachment system in accordance with one described embodiment. 
         FIG. 3B  shows the article and the electronic device of  FIG. 3A  magnetically attached to each other to form a cooperating system using the top magnetic attachment system. 
         FIG. 4A  is a simplified perspective view of an article that is releasably attachable to an electronic device via the top and side magnetic attachment systems. 
         FIG. 4B  shows a cooperating system of the attached article and the electronic device shown in  FIG. 4A  in a closed configuration. 
         FIG. 4C  shows the cooperating system of  FIG. 4B  in an open configuration. 
         FIG. 5  shows a top perspective view of an electronic device in accordance with the described embodiments. 
         FIG. 6  shows another embodiment of a magnetic attachment feature. 
         FIG. 7A  shows an electronic device in proximity to another object in the form of an accessory device having a magnetic attachment feature. 
         FIG. 7B  shows a graphical representation of magnetic interaction between the electronic device and the accessory device of  FIG. 7A  in accordance with the described embodiments. 
         FIG. 7C  shows a graphical representation of a cooperating system formed by the magnetic attachment of the accessory device and the electronic device as shown in  FIGS. 7A and 7B . 
         FIG. 8A  shows an embodiment of an attachment feature in an electronic device. 
         FIG. 8B  shows an embodiment of an attachment feature in an accessory device corresponding to the attachment feature shown in  FIG. 8A . 
         FIG. 9A  shows a representative device attachment feature in an inactive state. 
         FIG. 9B  shows the representative device attachment feature of  FIG. 9A  activated by another magnetic attachment feature. 
         FIG. 9C  shows the magnetic attachment feature in the inactive state in the presence of magnetically active object. 
         FIG. 10  shows an implementation of a device attachment feature that utilizes a leaf spring arrangement as a retaining mechanism. 
         FIG. 11A  shows an embodiment of a keyed magnetic attachment system in an inactive state and a matching magnetic attachment system. 
         FIG. 11B  shows the keyed magnetic attachment feature of  FIG. 11A  activated by the matching magnetic attachment system. 
         FIG. 12  shows a shifting position for the keyed magnetic attachment feature shown in  FIG. 11A . 
         FIG. 13  shows a graph summarizing a magnetic attachment force versus relative position of the keyed magnetic attachment feature. 
         FIGS. 14 and 15  show various embodiments of magnetic elements used in the keyed magnetic attachment feature. 
         FIG. 16A  shows a first perspective view of the electronic device in the form of a tablet device and the accessory device in the form of a protective cover. 
         FIG. 16B  shows a second perspective view of the electronic device in the form of a tablet device and the accessory device in the form of a protective cover. 
         FIG. 17A  shows a closed configuration of the cooperating system formed by the tablet device and protective cover shown in  FIGS. 16A and 16B . 
         FIG. 17B  shows an open configuration of the cooperating system shown in  FIG. 17A . 
         FIG. 18  shows a top view of an embodiment of a segmented cover assembly. 
         FIGS. 19A-19C  show a detailed view of a hinge span in accordance with the described embodiments. 
         FIG. 20A  shows a side view of the segmented cover assembly shown in  FIG. 18  attached to a tablet device. 
         FIGS. 20B and 20C  show cross section views of the segmented cover assembly and tablet device of  FIG. 20A . 
         FIG. 21A  shows a cross sectional side view of one embodiment of the hinge span of  FIGS. 19A-19C  magnetically attached to a housing having a curved surface. 
         FIG. 21B  shows a cross sectional side view of another embodiment of the hinge span magnetically attached to a housing having a flat surface. 
         FIGS. 22A and 22B  show cross sectional and perspective views of a fixture used to assemble the hinge span in accordance with the described embodiments. 
         FIG. 23  shows a side view of a segmented cover configured to support a tablet device in a keyboard state. 
         FIGS. 24A and 24B  show side and perspective views, respectively, of the segmented cover configured to support a tablet device in a display state. 
         FIGS. 25A and 25B  show the segmented cover assembly configured as various embodiments of a hanging apparatus. 
         FIGS. 26A and 26B  show rear and front views, respectively, of a tablet device having a front and rear image capture device held by the handle. 
         FIGS. 27A-27C  show a cooperating system of a segmented cover and tablet device configured to activate only uncovered portions of a display in a peek mode. 
         FIGS. 28A-28D  show various exploded views of portions of a pivoting hinge assembly in accordance with the described embodiments. 
         FIG. 29  shows an exploded view of a top cover assembly in accordance with the described embodiments. 
         FIG. 30  is a cross sectional view of the top cover assembly shown in  FIG. 29  in place upon a tablet device highlighting the relationship between an embedded magnet in the top cover assembly and a magnetically sensitive circuit in the tablet device. 
         FIG. 31A  shows a cross sectional view of a hinge span magnetically engaged with a corresponding device attachment feature in an active state in accordance with the described embodiments. 
         FIG. 31B  shows a cross sectional view of the device attachment feature of  FIG. 31A  in an inactive state. 
         FIGS. 32 and 33  shows perspective views of a device attachment feature incorporating a leaf spring as a retaining mechanism in accordance with the described embodiments. 
         FIG. 34  shows a flowchart detailing a process of magnetic attachment in accordance with the described embodiments. 
         FIG. 35  shows a flowchart detailing a process for activating a coded magnetic attachment feature in accordance with the described embodiments. 
         FIG. 36  shows a flowchart detailing a process for forming initiating a magnetic attachment in accordance with the described embodiments. 
         FIG. 37  shows a flowchart detailing a process for a peek mode operation in accordance with the described embodiments. 
         FIG. 38  shows a flowchart detailing a process for assembly of a hinge span in accordance with the described embodiments. 
         FIG. 39  shows a flowchart detailing a process for determining a configuration of magnetic elements in a magnetic attachment system in accordance with the described embodiments. 
         FIG. 40  is a block diagram of an arrangement of functional modules utilized by a portable media device. 
         FIG. 41  is a block diagram of an electronic device suitable for use with the described embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The following description relates in general to a mechanism that can be used to attach together at least two suitably configured objects. In one embodiment, this can be accomplished without the use of conventional fasteners. Each of the objects can include an attachment feature arranged to provide a magnetic field having appropriate properties. When the attachment features are brought into proximity with each other, the magnetic fields can cooperatively interact based upon their respective properties, result in the objects magnetically attaching to each other in a desired and repeatable manner. For example, due at least in part to the cooperative nature of the interaction of the magnetic fields, the objects can attach to each other in a pre-determined position and relative orientation without external intervention. For example, the cooperative magnetic interaction can result in the objects self-aligning and self-centering in a desired orientation. 
     The objects can remain in the magnetically attached state if and until a releasing force of sufficient magnitude is applied that overcomes the overall net attractive magnetic force. In some cases, however, it can be desirable to detach the objects serially (along the lines of a zipper) in which case, the releasing force only need be of sufficient magnitude to overcome the net magnetic attractive force of one pair of magnetic elements at a time. Connectors such as mechanical fasteners are not required to attach the objects together. Furthermore, to prevent undue interference to the magnetic interaction between the magnetic attachment features, at least a portion of the objects in the vicinity of the magnetic attachment features can be formed of magnetically inactive materials such as plastic or non-ferrous metals such as aluminum or non-magnetic stainless steel. 
     The objects can take many forms and perform many functions. When magnetically attached to each other, the objects can communicate and interact with each other to form a cooperative system. The cooperating system can perform operations and provide functions that cannot be provided by the separate objects individually. In another embodiment, at least one device can be used as an accessory device. The accessory device can be magnetically attached to at least one electronic device. The accessory device can provide services and functions that can be used to enhance the operability of the electronic device(s). For example, the accessory device can take the form of a protective cover that can be magnetically attached to the electronic device. The protective cover can provide protection to certain aspects (such as a display) of the electronic device while enhancing the overall look and feel of the electronic device. The magnetic attachment mechanism used to magnetically attach the accessory and the electronic device can assure that the cover can only attach to the electronic device in a specific orientation. Moreover, the magnetic attachment mechanism can also assure proper alignment and positioning of the protective cover and the electronic device. 
     The protective cover can include at least a hinge portion. The hinge portion can be magnetically attached to the electronic device using a magnetic attachment feature. The hinge portion can be pivotally connected to a flap that can be placed upon a portion of the electronic device to be protected. The protective cover can include electronic circuits or other elements (passive or active) that can cooperate with electronic elements in the electronic device. As part of that cooperation, signals can be passed between the protective cover and the electronic device that can, for example, be used to modify operations of the electronic device, operations of electronic circuits or elements of the protective cover, and so forth. 
     As an example, the electronic device can include a magnetically sensitive circuit such as a Hall Effect sensor and as such can detect the presence of a magnetic field. The Hall Effect sensor can respond to the presence (or absence) of the magnetic field by generating a signal. The signal can be used to alter an operating state of the electronic device. Accordingly, the protective cover can include a magnetic element such as a permanent magnet having a magnetic field that can cause the Hall Effect sensor to generate the signal. The magnetic element can be positioned on the protective cover in a location that triggers the Hall Effect sensor to generate the signal when the cover is placed on or in proximity to a surface of the electronic device. The signal can indicate that the protective cover is in a predetermined position relative to the electronic device that can result in a change in an operating state of the electronic device. For example, with the portion of the protective cover having the magnetic element in proximity to the Hall Effect sensor, the magnetic field from the magnetic element can cause the Hall Effect sensor to generate a signal. The signal can, in turn, be used to alter the operating state to one consistent with the display of the electronic device being fully covered. On the other hand, when the portion of the protective cover having the magnetic element is removed to the point where the Hall Effect sensor no longer responds to the magnetic field of the magnetic element, then the Hall Effect sensor can generate another signal. The other signal can result in the electronic device entering another, different, operating state consistent with at least a portion of the display being uncovered and viewable. 
     These and other embodiments are discussed below with reference to  FIGS. 1-41 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. For the remainder of this discussion, a first and second object each suitably configured to magnetically attach to each other in accordance with the described embodiments will be described. It should be noted, however, that any number and type of suitably configured objects can be magnetically attached to each other in a precise and repeatable manner. In particular, for simplicity and clarity, for the remainder of this discussion, the first object is presumed to take the form of an electronic device and in particular a handheld electronic device. 
       FIG. 1  is a simplified block diagram of article  10  and electronic device  12  that can be releasably attached to each other in a desired and repeatable manner. More specifically, article  10  and electronic device  12  can attach to each other at a pre-determined position and relative orientation without external intervention and without the use of mechanical fasteners. Article  10  and electronic device  12  can remain attached to each other if and until a releasing force is applied that overcomes the engagement between them. In some cases, however, it can be desirable to detach article  10  and electronic device  12  serially (along the lines of a zipper) in which case, a releasing force can be applied that can undo the engagement between article  10  and electronic device  12  about one attachment component at a time. For example, an attachment component can include a suitably matched pair of magnetic elements, one in article  10  and a second in electronic device  12 . 
     Electronic device  12  can take many forms. For example, electronic device  12  can take the form of a portable electronic device. In some examples, the portable electronic device can include housing  15 . Housing  15  can enclose and provide support for components of the portable electronic device. Housing  15  can also provide support for at least a large and prominent display occupying a substantial portion of a front face of the portable electronic device. The display can be used to present visual content. The visual content can include still images, visual, textual data, as well as graphical data that can include icons used as part of a graphical user interface, or GUI. 
     In some cases, at least a portion of the display can be touch sensitive. By touch sensitive it is meant that during a touch event, an object (such as a finger, stylus, and so on) can be placed in contact with or in proximity to an upper surface of the display. The particulars of the touch event (location, pressure, duration, and so forth) can be used to provide information to the portable electronic device for processing. In some embodiments, in addition to or in place of information being provided to the portable electronic device, information can be provided by the portable electronic device in a tactile manner using, for example, haptic actuators. It should be appreciated however that this configuration is by way of example and not by way of limitation as the electronic device can be widely varied. In one example, the portable electronic device is a tablet computer such as, for example, the iPad™ manufactured by Apple Inc. of Cupertino, Calif. 
     Article  10  can be widely varied and can take many forms such as, for example, an accessory or accoutrement of electronic device  12 . As an accessory, article  10  can be configured as a cover, a stand, a dock, a hanger, an input/output device and so on. In a particularly useful form, article  10  can take the form of a protective cover that can include a member, such as a flap, that can be positioned over the display of the portable electronic device. Like the electronic device  12 , the article  10  can also include housing  17  that can enclose and provide support for components of the article  10 . 
     Either one or both of article  10  and electronic device  12  can include attachment features. For example, article  10  can include attachment system  13  and electronic device  12  can include corresponding attachment system  14 . Attachment system  13  can cooperate with corresponding attachment system  14  to attach article  10  and electronic device  12  in a releasable manner. When attached to each other, article  10  and electronic device  12  can operate as a single operating unit. On the other hand, in the detached mode, article  10  and electronic device  12  can act separately, and if desired, as two individual parts. Attachment systems  13  and  14  can be configured in such a way that article  10  and electronic device  12  can attach to each other in a desired and repeatable manner. In other words, attachment systems  13  and  14  can repeatedly align article  10  and electronic device  12  together such that they are consistently in a pre-determined position relative to one another. 
     The attachment features can be widely varied. The attachment can be provided by various types of couplings including mechanical, electrical, static, magnetic, frictional, and/or the like. In one embodiment, the attachment cannot be seen from the outside of the article and/or electronic device. For example, the article and device can not include external visible attachment features that adversely affect the look and feel or ornamental appearance (e.g., snaps, latches, etc.), but rather attachment features that cannot be seen from the outside of the article or device and thus do not affect the look and feel or ornamental appearance of the article or device. By way of example, the attachment features can be provided by attraction surfaces that do not disturb the external surfaces of the article or device. In one embodiment, at least a portion of the attachment features utilize magnetic attraction to provide some or all of the attaching force. 
     The attachment systems can include one or more attachment features. If multiple features are used, the manner in which they secure can be the same or different. For example, in one implementation, a first attachment feature utilizes a first attachment means while a second attachment feature utilizes a second attachment means that is different than the first attachment means. For example, the first attachment means can utilize a friction coupling while the second attachment means can utilize magnetism. In another implementation, a first attachment feature utilizes a first attachment means while a second attachment feature utilizes the same or similar attachment means. For example, the first and second attachment means can be provided by magnets. Although, the attachment means can be similar it should be appreciated that the configuration of the features can be different depending on the needs of the system. Further, any number and configuration of attachment means can be used. 
     In the illustrated embodiment, the attachment systems  13  and  14  each include at least a first set of corresponding attachment features  13   a / 14   a  and a second set of corresponding attachment features  13   b / 14   b . Attachment feature  13   a  can cooperate with corresponding attachment feature  14   a  to attach article  10  and electronic device in a releasable manner. In one particular implementation this is accomplished with magnetic attraction. Further, attachment feature  13   b  can cooperate with corresponding attachment feature  14   b  to further attach article  10  and electronic device in a releasable manner. In one particular implementation this is accomplished with magnetic attraction. By way of example, attachment features  13   a / 14   a  can be provided at a first location while attachment features  13   b / 14   b  can be provided at a second location. 
     In a specific example, attachment feature  14   a  can, in cooperation with attachment feature  13   a , secure electronic device  12  to article  10 . In another example, attachment feature  13   b  can secure article  10  to the electronic device  12  using attachment feature  14   b . It should be noted that the attachment systems  13  and  14  of this example can be separate or they can cooperate together to produce the attachment. If they cooperate, attachment features  14   a  and  14   b  correspond to or mate with one or more attachment features  13   a  and  13   b . In any case, the attachment features in any of these examples can be accomplished through mechanical, static, suction, magnetic attachment and/or the like. 
     The placement of the attachment systems and the attachment features within the attachment systems can be widely varied. Regarding electronic device  12 , attachment system  14  can be placed on front, back, top, bottom, and/or sides. Attachment features  14   a  and  14   b  can be placed any location within attachment system  14 . Accordingly, attachment features  14   a  and  14   b  can be placed anywhere relative to the housing and/or the display. In one example, the attachment features  14   a  and  14   b  can provide engagement along one or more of the sides of the housing (e.g., top, bottom, left, right). In another example, attachment features  14   a  and  14   b  can provide engagement at the back of electronic device  12 . In yet another example, attachment features  14   a  and  14   b  can provide engagement at the front (e.g., where, if present, a display is located) of electronic device  12 . In some cases, a combination of attachment features can be located at different regions of electronic device  12  as for example at the sides and front. In one embodiment, attachment system  14  including attachment features  14   a  and  14   b  do not disturb the surfaces of electronic device  12 . Similarly, attachment system  13  and in particular attachment features  13   a  and  13   b  do not disturb the surfaces of article  10 . 
     In accordance with one embodiment, the attachment features can include magnetic elements. The magnetic elements can be configured to help in positioning article  10  relative to electronic device  12  into a mating arrangement. The magnetic elements can further help to secure article  10  and electronic device  12  into a mating engagement. It should be noted that the engagement of article  10  and electronic device  12  can be reversed by the application of an appropriate releasing force that allows article  10  and electronic device  12  to separate back into individual objects. However, the magnetic elements can permit the article  10  and electronic device  12  to subsequently resume the mating engagement without the requirement of fasteners of any sort, mechanical or otherwise. In this way, the magnetic elements provide a repeatable and consistent engagement between article  10  and electronic device  12 . 
     Article  10  and electronic device  12  can further include components  16  and  18  respectively. Components  16  and  18  typically depend on the configuration of article  10  and electronic device  12  and can, for example, be mechanical or structural components used to provide support or they can be operational/functional components that can provide a specific set of operations/functions. The components can be dedicated to their respective devices or they may be configured for coupling with aspects of the corresponding article or device (e.g., wired or wireless). Examples of structural components can include frames, walls, fasteners, stiffeners, movement mechanisms (hinge), etc. Examples of operational components can include processors, memory, batteries, antennas, circuitry, sensors, display, inputs, and so on. Depending on their desired configuration, the components can be external (i.e., exposed at the surface) and/or internal (e.g., embedded within housing). 
       FIGS. 2A and 2B  are simplified perspective views of article  20  that can be releasably attached to electronic device  22  via a magnetic attachment system, in accordance with one described embodiment. Article  20  and electronic device  22  can generally correspond to those discussed with regards to  FIG. 1 . In one embodiment, the magnetic attachment system can be embodied as magnetic surface  24  (shown by broken lines or shading) and more particularly as magnetic surface  24  at the sides of electronic device  22 . Magnetic surface  24  can provide a magnetic field that can cooperate with a corresponding attachment feature in article  20  when placed in proximity to one another. The magnetic field can establish a net magnetic attractive force that can pull article  20  and electronic device  22  together into the mating engagement along engagement surface  26  as shown in  FIG. 2B . 
     In other words, the magnetic field provided by magnetic surface  24  can have properties such that the net magnetic attractive force between article  20  and electronic device  22  is substantially perpendicular to engagement surface  26 . Moreover, the magnetic field can result in the net magnetic attractive force between article  20  and electronic device  22  being applied uniformly along engagement surface  26 . In order to release article  20  and electronic device  22 , a releasing force can be applied to the two conjoined objects in order to overcome a net magnetic attractive force provided by the magnetic attachment system. 
     It also should be appreciated that although only one side wall is shown, in some cases different sidewalls and possibly a combination of sidewalls may be used depending on the needs of the attachment interface. It should be noted that the use of magnetic attachment precludes the need for mechanical attachments such as fasteners. Moreover, the lack of mechanical attachments and the uniformity of the overall magnetic attractive force can leave the surfaces of article  20  and electronic device  22  undisturbed helping to create an appearance of oneness by in which article  20  and electronic device  22  can appear as a single, unified entity. The uniformity in appearance can improve the overall aesthetic appeal of both article  20  and electronic device  22 . 
     In one embodiment, a magnetic surface can be created by embedding magnetically attractable elements in the form of the magnetic attachment feature within the sidewalls of electronic device  22  and/or article  20 . That is, the magnetically attractable elements can be disposed within article  20  and electronic device  22  as for example within the housing of electronic device  22 . In this configuration, the housing can be formed of non-magnetic material such as plastic or non-ferrous metal such as aluminum. In this way, magnetic force lines can be configured to work through the walls of the housing. The magnetic attachment features do not disturb the physical appearance of the external surfaces of article  20  and electronic device  22 . The magnetically attractable elements in article  20  and electronic device  22  can be arranged to produce magnetic fields that can cooperate with each other to generate a magnetic attractive force that attaches article  20  and electronic device  22  together in the mating engagement. The magnetic attractive force being configured to generate a magnetic attraction force normal to engagement surface  26  between electronic device  22  and article  20 . 
     The magnetic attractive force between corresponding magnetic elements in article  20  and electronic device  22  can also be uniformly applied along engagement surface  26 . The uniformity of the overall magnetic attractive force along engagement surface  26  can be a result of the uniformity of the separation distance between corresponding magnetic elements in article  20  and electronic device  22 . The uniformity can also be a result of the consistency of magnetic flux density between corresponding magnetic elements in article  20  and electronic device  22 . The uniformity of net magnetic attachment can be facilitated by the surfaces of article  20  and electronic device  22  each forming a well matched fit to each other. For example, one surface can be flat or have a concave geometry whereas the other surface can have a matching conforming convex geometry. In this way, by fitting tightly together, a separation distance between each of the corresponding magnetic elements in article  20  and electronic device  22  can be reduced to a minimum. The conformity of surface shapes can also enhance the overall look and feel of article  20  and electronic device  22  by reducing or eliminating the appearance of a seam at engagement surface  26 . This seamless quality can provide an illusion of a single entity when article  20  and electronic device  22  are attached to each other. 
     In addition to enhancing the overall look and feel, the consistency of the separation distance between the magnetic elements can render the attachment force between article  20  and electronic device  22  uniform along engagement surface  26 . In this way, the engagement force can be uniformly distributed across engagement surface  26  preventing buckling, weak spots, and so on that might otherwise affect the overall integrity of the engagement between article  20  and electronic device  22 . 
       FIGS. 3A and 3B  are simplified perspective views of article  30  that can be releasably attached to an electronic device  32  via magnetic attachment system  34  and corresponding attachment system  36 . It should be noted that this particular embodiment is similar to the embodiment described in  FIGS. 2A, 2B  except that the magnetic surfaces that were previously located at the side walls are now located on a face of electronic device  32  and, optionally, an opposing face on article  30 . For example, in the case of an electronic device including a display, the magnetic elements of magnetic attachment system  34  can be embedded behind the display surface. 
       FIG. 3B  shows article  30  and electronic device  32  magnetically attached to each other to form cooperating system  38 . As part of system  38 , electronic device  32  and article  30  can cooperate with each other to provide features not available by article  30  or electronic device  32  separately. For example, article  30  can take the form of a cover that can provide protective features. In one embodiment, protective cover can be used to support and protect electronic device  32  while being transported or stored (e.g., cover the display surface). Due to the releasable nature of the magnetic attachment between magnetic attachment systems  34  and  36 , article  30  can be easily detached when electronic device  32  is to be used and subsequently re-attached when desired. 
     The placement of the magnetic elements can be such that only certain magnetically sensitive elements within electronic device  32  are affected by the magnetic field generated by the embedded magnetic elements. For example, a Hall Effect sensor can be used to detect whether or not article  30  is magnetically attached to and covering all or a portion of the display of electronic device  32  using the magnetic field generated by a magnetic element located in article  30 . On the other hand, a magnetically sensitive element in electronic device  32  such as a compass that relies upon an external magnetic field (i.e., such as that provided by the Earth), must not be unduly affected by magnetic field lines generated by the embedded magnetic elements. Therefore, the magnetic elements can be limited to those locations in electronic device  32  positioned away from magnetically sensitive elements such as the compass. 
       FIGS. 4A and 4C  are simplified perspective views of article  40  that can be releasably attached to electronic device  42  via a magnetic system  44 . This embodiment is similar to that shown in  FIGS. 2A, 2B and 3A, 3B  in that magnetic system  44  can include multiple magnetically attractable elements and that article  40  and electronic device  42  generally correspond to those mentioned in previous Figures. For example, one set of magnetically attractable magnetic elements  44   a  can be placed relative to a side of article  40  and electronic device  42  while a second set of magnetically attractable elements  44   b  can be placed relative to a face of article  40  and electronic device  42 . As shown in  FIG. 4B , cooperating system  46  can be formed by placing article  40  and electronic device  42  in proximity to each other such that magnetic elements  44   a  on the sides of article  40  and electronic device  42  magnetically attract each other in addition to magnetic elements  44   b  located at the face of electronic device  42  and article  40 . The overall magnetic attraction generated at the side and face can be sufficient to retain article  40  and electronic device  42  in a mating engagement to form cooperating system  46 . 
     In one embodiment, as shown in  FIG. 4C , cooperating system  46  is presented in an open configuration in which article  40  is used as a cover for electronic device  42  that can be opened and closed. That is, article  40  can act as a protective cover of electronic device  42 . In this embodiment, article  40  can include binding  48  that attaches along the side of electronic device  42  and flap  50  that attaches to the front face of electronic device  42  and more particularly, top face  52 . Top face  52  can correspond to a display. In one implementation, flap  50  can move relative to binding  48 . The moving can be widely varied. In one example, flap  50  can pivot relative to binding  48 . The pivot can be widely varied. In one example, the pivot can be enabled by a hinge mechanism. In another example, the pivot can be enabled by a fold. Furthermore, the flap can be rigid, semi-rigid or flexible. In this manner, article  40  can form an open configuration where flap  50  is positioned away from electronic device  42  (display  52  can be viewed) and a closed configuration where flap  50  is positioned adjacent electronic device  42  (display  52  is covered as represented by closed embodiment of  FIG. 4B ). 
     In one embodiment, binding  48  is only located on one side while flap  50  is only located at top face  52 . In so doing, the other surfaces of electronic device  42  are left exposed. As a result, the beauty of the electronic device may be shown off while the article is attached to the electronic device. Further, it may leave better access for I/O and connectivity related functionality (e.g., buttons, connectors, etc.). 
     Although the purpose of the magnetic elements is similar, i.e., attach article to electronic device, it should be appreciated that these mechanisms can widely vary. In some cases, the magnetic fields may be configured differently. By way of example, the side mounted magnetic surface may provide a first magnetic force and the front facing magnetic surface may provide a second magnetic force that is different than the first magnetic force. This may be in part due to different holding requirements as well as different surface areas, i.e., available space, and its effect on internal components of the electronic device. In one example, the side mounted magnetic surface provides a greater holding force for securing the article to the electronic device, i.e., it is the primary securing force while the front facing magnetic surface is the secondary securing force. 
     In one example, flap  50  includes multiple sections that are semi-rigid and bend relative to one another so as to make the flap movable and flexible. In one embodiment, flap  50  can be folded into one or more different configurations, and in some cases can be held in these configurations using a magnetic system similar to what is described above. These and other embodiments will be described in greater detail below. Moreover, it should be appreciated that the described embodiments are not limited to covers and that other configurations can be used including for example as an accessory device used as a hanging apparatus, as a support mechanism for the electronic device to improve viewing the display and as a support mechanism for or inputting touch events at a touch sensitive portion of the display, and so on. 
     The electronic device and article can take many forms. For the remainder of this discussion, the electronic device is described in terms of a handheld portable computing device. Accordingly,  FIG. 5  shows a top perspective view of electronic device  100  in accordance with the described embodiments. Electronic device  100  can process data and more particularly media data such as audio, visual, images, etc. By way of example, electronic device  100  can generally correspond to a device that can perform as a smart phone, a music player, a game player, a visual player, a personal digital assistant (PDA), a tablet computer and the like. Electronic device  100  can also be hand held. With regards to being handheld, electronic device  100  can be held in one hand while being operated by the other hand (i.e., no reference surface such as a desktop is needed). Hence, electronic device  100  can be held in one hand while operational input commands can be provided by the other hand. The operational input commands can include operating a volume switch, a hold switch, or by providing inputs to a touch sensitive surface such as a touch sensitive display device or a touch pad. 
     Electronic device  100  can include housing  102 . In some embodiments, housing  102  can take the form of a single piece housing formed of any number of materials such as plastic or non-magnetic metal which can be forged, molded, or otherwise formed into a desired shape. In those cases where electronic device  100  has a metal housing and incorporates radio frequency (RF) based functionality, a portion of housing  102  can include radio transparent materials such as ceramic, or plastic. Housing  102  can be configured to enclose a number of internal components. For example, housing  102  can enclose and support various structural and electrical components (including integrated circuit chips) to provide computing operations for electronic device  100 . The integrated circuits can take the form of chips, chip sets, or modules any of which can be surface mounted to a printed circuit board, or PCB, or other support structure. For example, a main logic board (MLB) can have integrated circuits mounted thereon that can include at least a microprocessor, semi-conductor memory (such as FLASH), and various support circuits and so on. Housing  102  can include opening  104  for placing internal components and as necessary can be sized to accommodate display assembly for presenting visual content, the display assembly being covered and protected by protective layer  106 . In some cases, the display assembly can be touch sensitive allowing tactile inputs that can be used to provide control signals to electronic device  100 . In some cases, the display assembly may be a large prominent display area that covers a majority of the real estate on the front of the electronic device. 
     Electronic device  100  can include a magnetic attachment system that can be used to magnetically attach electronic device  100  to at least one other suitably configured object. The magnetic attachment system can include a number of magnetic attachment features distributed within and in some cases connected to housing  102 . For example, the magnetic attachment system can include first magnetic attachment feature  108  and second magnetic attachment feature  110  located on different sides of electronic device  100 . In particular, first magnetic attachment feature  108  can be located in proximity to side wall  102   a  of housing  102 . Second magnetic attachment feature  110  can be located within opening  104  near side wall  102   b  of housing  102 . In those embodiments where electronic device  100  includes a display with cover glass substantially filling opening  104 , second attachment feature  110  can be placed beneath the cover glass. 
     The placement of first magnetic attachment feature  108  at side wall  102   a  can facilitate the use of magnetic attachment feature  108  to magnetically attach electronic device  100  to another suitably configured object such as another electronic device or an accessory device. Accordingly, without loss of generality, first magnetic attachment feature  108  will henceforth be referred to as device attachment feature  108 . 
     The placement of second magnetic attachment feature  110 , on the other hand, can facilitate the use of second magnetic attachment feature  110  to secure aspects of another device attached to electronic device  100  by way of device attachment feature  108 . In this way, the overall attachment between the other device and electronic device  100  can be more secure than attaching through first attachment feature  108  alone. Accordingly, and again without loss of generality, second attachment feature  110  will henceforth be referred to as securing attachment feature  110 . 
     Although not expressly shown, it is understood that the various magnetic attachment features of the magnetic attachment system can be located at any appropriate location of housing  102 . For example, magnetic attachment features can be located at an interior bottom surface of housing  102  or along sides  102   c  and  102   d  of housing  102 . 
     As shown in  FIG. 6 , device attachment feature  108  and securing attachment feature  110  can each include one or more magnetic elements. In one example, device attachment feature  108  can multiple magnetic elements that can magnetically interact with each other to provide magnetic field  112  (only a portion of which is shown). In other words, the properties (shape, field strength, and so on) of magnetic field  112  can be based upon the interaction of the magnetic fields generated by each of the magnetic elements. In this way, the properties of magnetic field  112  can be altered simply by arranging the properties (i.e., physical layout, relative size, and constituent magnetic polarities) of each of the magnetic elements. For example, each of the magnetic elements can have varying sizes and can be disposed along an axis. In this way, the magnetic properties of each of the plurality of magnetic elements can act together to establish the overall properties of magnetic field  112 . 
     In some cases, the portion of magnetic field  112  that is used in the magnetic attachment between device attachment feature  108  and another device can be enhanced with the use of a magnetic shunt (not shown). The magnetic shunt can be formed of magnetically active material, such as steel or iron, and be placed in a position that causes magnetic field lines that would otherwise be directed away from the attachment region to be at least partially re-directed towards the attachment region. The re-direction of the magnetic field lines can have the effect of increasing the average magnetic flux density in the attachment region. 
     Device attachment feature  108  can operate in an active state as in well as an inactive state. Magnetic flux density B 112  can equal or exceed a magnetic flux density threshold B threshold  inside the exterior surface of housing  102  but not outside in the inactive state. In other words, magnetic flux density B 112  of magnetic field  112  at an exterior surface of housing  102  is less than a magnetic flux density threshold B threshold . Magnetic flux density threshold B threshold  representing a magnetic flux value below which magnetically sensitive devices (such a magnetic strip on a credit card) can remain substantially unaffected. In addition, the presence of a magnetically active material (such as steel) in the region outside of electronic device  100  will not by itself trigger device attachment feature  108  to transition from the inactive state to the active state. 
     As noted above, when device attachment feature  108  is inactive, magnetic flux density B 112  of magnetic field  112  at the exterior surface of side  102   a  of housing  102  is less than magnetic flux density threshold B threshold . More particularly, with regards to device attachment feature  108 , magnetic flux density B 112  can vary as a function of distance x (i.e., B=B 112  (x)) from the magnetic elements. Therefore, when device attachment feature  108  is inactive, magnetic flux density B 112  ( x ) can satisfy Eq. (1).
 
 B   112 ( x=x   o   +t )&lt; B   threshold,   Eq. (1)
 
where t is thickness of housing  102  at side  102   a , and
         x o  is distance from interior of side  102   a  to the magnetic elements.
 
When device attachment feature  108  is inactive, any magnetic flux leakage in the near region outside of electronic device  100  (i.e., B 112 (x&gt;x o +t)) is low enough that there is little likelihood that magnetically sensitive devices in the near region are adversely affected. However, it should be noted that even in the inactive state, magnetic field  112  can have a value of magnet flux B 112 (x=x o +t) that satisfies Eq (1), and yet is sufficiently high to interact with the magnetic field of another device placed in relatively close proximity thereto. In this way, the other appropriately configured magnetic attachment feature in the other device can be used to activate device magnetic attachment feature  108  even though Eq. (1) is satisfied.
       

     The properties of magnetic field  112  can include at least field strength, magnetic polarity, and so on. The properties of magnetic field  112  can be based upon the combination of the magnetic fields from each of the magnetic elements included in magnetic attachment feature  108  The combined magnetic fields can form in the aggregate magnetic field  112 . For example, the magnetic elements can be arranged in such a way that the combination of the respective magnetic fields results in magnetic field  112  having desirable magnetic field properties (such as field strength). For example, the combination of one arrangement of magnetic elements can result in magnetic field  112  having characteristics (such a polarity and strength) that are for the most part symmetric about a particular axis (such as a geometric center line). 
     On the other hand, the magnetic elements can be arranged in such a way that the combination of the magnetic fields of the magnetic elements can result in magnetic field  112  having at least one property that is anti-symmetric about the center line. For example, a magnetic element on one side of the centerline can be positioned with a North magnetic pole pointing up whereas a corresponding magnetic element on the other side of the centerline can be arranged with a South magnetic pole pointing up. Hence, the magnetic properties of magnetic field  112  can be adjusted in any manner deemed appropriate to provide a desired mating engagement. For example, the magnetic properties of magnetic field  112  can be modified by arranging the magnetic elements in such a way that magnetic field  112  can cooperatively interact with another magnetic field (from another magnetic attachment system, for example). The cooperative interaction between the two magnetic fields can result in the two objects being magnetically attached to each other in a well-defined, precise, and repeatable manner. 
     The properties of magnetic field  112  can be stable. By stable it is meant that the properties of the magnetic field can remain essentially unchanged for an extended period of time. Hence, a stable version of magnetic field  112  can be created using magnetic elements having properties that are essentially constant (or nearly constant) over an extended period of time or at least any changes in one component is offset by a corresponding change in another component. The magnetic elements can be physically arranged in a fixed or at least substantially fixed configuration with respect other magnetic elements. For example, the magnetic elements can each have fixed sizes and polarities arranged in a specific order relative to each other providing the desired properties (shape, strength, polarity, etc.) of magnetic field  112 . Hence, depending upon the properties and the nature of the magnetic elements, the shape of magnetic field  112  can remain substantially unchanged over the extended period of time (such as the anticipated operating life of electronic device  100 ). 
     In some embodiments, however, the properties of magnetic field  112  can be varied by modifying a magnetic or other physical property of at least one of the magnetic elements. When at least one magnetic element has magnetic properties (e.g., a polarity or field strength) that can be modified, the resulting magnetic field can also be modified. Accordingly, in some embodiments at least one of the magnetic elements can be characterized as having dynamic magnetic properties. By dynamic it is meant that at least one magnetic property, such as polarity, can be modified. In this way, the magnetic field properties of the resulting magnetic field can also vary. The resulting magnetic field, in turn, can alter the magnetic characteristics of magnetic field  112  that, in turn, can alter how the magnetic attachment system causes the objects to magnetically attach to each other (alignment, orientation, centering, and so forth). An electromagnet is one example of such a magnetic element whose magnetic properties can be modified as desired. Other examples include a malleable non-magnetic substrate impregnated with magnetic dopant (such as magnetite). In this way, the malleable substrate can be formed into a physical shape that can affect the nature of the magnetic field produced by the magnetic dopant material. 
     Turning now to other aspects of the magnetic attachment system, securing attachment feature  110  can include one or more of magnetic elements  116 . When a plurality of magnetic elements is used, the arrangement of the plurality of magnetic elements  116  can be widely varied and can magnetically interact with a cooperating feature on another device. In one embodiment, the plurality of magnetic elements  116  associated with securing feature  110  can assist in securing at least a portion of another device otherwise attached to electronic device  100  by way of device attachment feature  108 . 
     At least some of the plurality of magnetic elements  116  can have a fixed size and polarity (along the lines of a simple bar magnet) whereas other of the plurality of magnetic elements  116  can have magnetic properties that can vary (such as an electromagnet) while still others can be shaped to provide specific magnetic characteristics. For example, at least one of the plurality of magnetic elements  116  can be positioned and shaped (if need be) to interact with a magnetically responsive circuit included in the other device. Hence, the magnetically responsive circuit can respond to the presence (or absence) of a particular magnetic element(s) of securing feature  110 . An example of the magnetically responsive circuit is described above with regards to the Hall Effect sensor  118 . 
     It should be noted that the magnetic field generated by magnetic elements  116  should not extend so far that magnetically sensitive circuits within electronic device  100  (such as Hall Effect sensor  118 ) are adversely affected. This is particularly important since the magnetic field is not generally contained within housing  102  since at least a portion of the magnetic field must extend in the z direction in order to interact with the magnetically active portion of other devices. Therefore, the magnetic field in {x,y} must be limited in extent to avoid magnetically sensitive circuits such as Hall Effect sensor  118  and compass  120 . 
     In a particular implementation, the magnetic elements of device attachment feature  108  can be grouped into distinct magnetic regions. In this way, the magnetic fields from the magnetic regions can superpose to form magnetic field  112 . The magnetic regions can include various magnetic elements that can be arranged into groups represented by magnetic elements  126  and  128 . By grouping the magnetic element into separate magnetic regions, the ability of the magnetic attachment system to provide a magnetic field having desired characteristics can be substantially enhanced. Magnetic elements  126  and  128  can interact with each other to form magnetic field  112 . In the one embodiment, the interaction can take the form of combination of magnetic properties of each of magnetic elements  126  and  128 . In some cases, the arrangement of magnetic elements  126  and  128  can be related to each other in order to provide magnetic field  112  with desired characteristics. For example, magnetic elements  126  can  128  can be arranged in such a way relative to one another that magnetic field  112  is anti-symmetric (or symmetric) about a horizontal center line of magnetic attachment feature  108 . In another embodiment, magnetic field  112  can be anti-symmetric (or symmetric) about a vertical center line of attachment feature  108 . In still another embodiment, magnetic field  112  can be anti-symmetric (or symmetric) both horizontally and vertically. 
       FIG. 7A  shows electronic device  100  in proximity to object  200  having magnetic attachment feature  202 . Magnetic attachment feature  202  of object  200  can include magnetic elements each generating an individual magnetic field that can interact with the other to form in the aggregate a resulting magnetic field. The resulting magnetic field can have magnetic characteristics (such as field strength and shape) that can interact with magnetic field  112  of electronic device  100  to attach electronic device  100  and object  200  together in a well-defined, precise, and repeatable manner without mechanical fasteners and nor require external assistance. It should be noted that magnetic field  208  can be about 2500 Gauss whereas magnetic field  112  can be on the order of about 1400 Gauss when device attachment feature  108  is inactive. 
     Object  200  can take many forms including an accessory, peripheral, electronic device or the like. In one embodiment, object  200  can take the form of an electronic device along the lines of electronic device  100 . Accordingly, electronic device  100  and electronic device  200  can be magnetically attached to each other using device attachment feature  108  and magnetic attachment feature  202  to form a cooperative electronic system. The cooperative electronic system can be one in which electronic elements in electronic device  100  and corresponding electronic elements in electronic device  200  cooperate with the other to perform functions that cannot be performed by either of the electronic devices separately. In one embodiment, information can be passed between electronic devices  100  and  200 . 
     More specifically, magnetic attachment feature  202  can include at least magnetic elements  204  and  206  each of which can generate magnetic fields that cooperate with each other to provide magnetic field  208  (only a portion of which is shown). The properties of magnetic field  208  can be based upon the interaction of each of the plurality of magnetic elements  204  and  206 . In this way, magnetic field  208  can have properties based upon the physical layout, relative size, and constituent magnetic polarities of each of the plurality of magnetic elements  204  and  206 . For example, magnetic elements  204  and  206  can be disposed along a center line and have magnetic properties that superpose to provide magnetic field  208  with desired properties. Magnetic flux density B 208  of magnetic field  208  of object  200  can vary as a function of distance x (i.e., B=B 208  (x)) from magnetic elements  204  and  206 . 
     When object  200  takes the form of an electronic device such as electronic device  100 , then magnetic flux density B 208  satisfies Eq. (1). However, when object  200  takes the form of an accessory device, then unlike magnetic flux density B 112  of electronic device  100 , which satisfies Eq. (1), magnetic flux density B 208  (x) of accessory device  200  can satisfy Eq. (2).
 
 B   208 ( x=x   1   +s ) B   threshold   Eq. (2)
 
where s is thickness of housing  212  at side  212   a , and
         x 1  is interior separation distance.
 
In this way, accessory device  200  can magnetically interact with electronic device  100  further removed from electronic device  100  than would otherwise be possible. Hence, accessory device  200  can be placed near but not necessarily close to electronic device  100  in order for electronic device  100  and object  200  to magnetically attach to each other in a well-defined, predictable, and repeatable manner.
       

     In addition to magnetic attachment feature  202 , accessory device  200  can further include magnetic attachment feature  216  that can be used to interact with securing attachment feature  110 . Magnetic attachment feature  216  can include a variety of magnetically active components. Some of the magnetic elements can take the form of magnetic elements arranged to cooperatively interact with corresponding magnetic elements in securing attachment feature  110 . Other of the magnetic element can be more passive in nature in that they provide a mechanism for completing a magnetic circuit with magnetically active elements in securing attachment feature  110 . An example of a magnetically passive element is a ferromagnetic material, such as iron or steel, that can be interact with a magnetic element actively providing an associated magnetic field. In this way, the ferromagnetic material can interact with the magnetic field to complete a magnetic circuit between the passive element in attachment feature  216  and the active element in securing attachment feature  110 . 
       FIG. 7B  shows that accessory device  200  can be used to provide support functions and services for electronic device  100 . By allowing a portion of magnetic field  208  having magnetic flux density B 208  satisfying Eq. (2) to extend into region  214 , magnetic attractive force F net  between device attachment feature  108  and accessory attachment feature  202  can be created where net attractive force F net  satisfies Eq. (3a) and Eq. (3b).
 
 F   net −( L   total )· B   2 /μ 0   Eq. (3a)
 
 B/B   0   =f ( x   sep )  Eq. (3b)
 
where L total  is total surface area of magnetic elements
         B is total magnetic flux density (B 208 +B 112 )   x sep  is separation distance between magnetic elements,   B 0  is magnetic flux density at surface of magnetic regions.       

     Net magnetic attraction force F net  due to the interaction of magnetic field  208  and magnetic field  112 , attachment feature  202  can be used to activate device attachment feature  108 . Moreover, when device attachment feature  108  is activated, magnetic flux density B 112  now satisfies Eq. (4).
 
 B   112 ( x=x   o   t )&gt; B   threshold,   Eq. (4) in active state.
 
     This increase in magnetic flux density B 112  in region  214  can result in a substantial increase in net magnetic attractive force F net  between accessory device  200  and electronic device  100 . Moreover, since net attractive force F net  varies with total magnetic flux density B (B 208 +B 112 ) and flux density B in general can vary inversely with the separation distance (i.e., Eq. 3(b)), as electronic device  100  and accessory device  200  approach each other and separation distance x sep  decreases to a limiting value consistent with physical contact of electronic device  100  and accessory device  200 , the increase in net attractive force F net  can increase sharply in a relatively short amount of time. This sharp increase in net attractive force F net  can cause the devices to quickly snap together in what can be referred to as “snapping into place” as shown in  FIG. 7C  showing cooperating system  300  in the form of electronic device  100  magnetically attached to accessory device  200  along engagement surface  218 . It should be noted that in a representative embodiment, the magnetic elements in device attachment feature  108  can be N52 type magnets whereas magnetic elements in attachment feature  216  can be N35 type magnets. Moreover, the net magnetic attractive force can be on the order of about 10 newtons to at least 20 newtons where it can require about 3 newtons to activate device attachment feature  108 . 
     The overall magnetic attractive force F NET  between device  100  and device  200  at engagement surface  218  can be derived as the summation of all the net magnetic attractive forces F neti  for all actively coupled magnetic elements. In other words, the overall net magnetic attractive force F NET  satisfies Eq. (5).
 
 F   NET =Σ 1   n   F   neti   Eq. (5)
 
where F neti  is the net magnetic attractive force for each of n components. In one embodiment, net magnetic attractive force F neti  is substantially perpendicular to that portion of engagement surface  218  intersected by magnetic field  112  and magnetic field  208 .
 
     In order to assure that overall magnetic attachment force F NET  is uniform along the engagement surface between device  100  and device  200 , the separation distances between each corresponding magnetic element in attachment features  108  and  202  are well controlled. The separation distance can be well controlled by, for example, shaping the magnetic elements to conform to the shape of the devices. For example, if device  100  has a spline (curved) shaped housing, the magnetic elements in device  100  can be shaped to conform to the curved shape. In addition, the magnetic elements can be formed in such a way that the magnetic vectors of corresponding magnetic elements align with each other. In this way, the magnitude and direction of the net magnetic attractive force can be controlled as desired. 
     One result of the aligning of the magnetic vectors is that the direction of the net magnetic force between each magnetic element can be well controlled. Moreover, by reducing the separation distance between corresponding magnetic elements to a minimum, the net attractive magnetic force F neti  between each magnetic element can be maximized. In addition, maintaining a substantially uniform separation distance between the various magnetic elements, a correspondingly uniform magnetic attachment force can be provided along engagement surface  218 . Moreover, by appropriately adjusting the corresponding magnetic vectors, F net  can be applied normally to the engagement surface. 
     In addition to minimizing the separation distance between corresponding magnetic elements, the magnetic flux density between the corresponding magnetic elements can be increased by using magnetic shunts. A magnetic shunt formed of magnetically active material such as iron or steel can be placed on or near a magnetic element having the effect of directing magnetic flux lines in a desired direction. In this way, for example, magnetic flux lines that would otherwise propagate in a direction away from a corresponding magnetic element can be partially re-directed towards a desired direction, such as towards a magnetic attachment region between the devices thereby increasing the overall magnetic flux density. Hence, increasing the available magnetic flux density between the magnetic elements can result in a substantial increase in the net magnetic attractive force. 
       FIG. 8A  shows an embodiment of attachment feature  110 . In particular, attachment feature  110  can be part of housing  102 . In particular, attachment feature can include magnetic elements  402  that can be mounted to ledge  404  of housing  102  Magnetic elements  402  can be widely varied. For example, magnetic elements  402  can be spatially arranged as an array on ledge  404  to be used to attach and secure at least a portion of an accessory device to a particular aspect of electronic device  100 . For example, when the accessory device takes the form of a flap, the magnetic elements  402  can be used to magnetically secure the flap to electronic device  100  to cover at least a portion of a display. The size and shape of the array can also be widely varied. In the embodiment shown in  FIG. 8A , the array can be rectangular and sized to encompass a substantial portion of ledge  404 . 
       FIG. 8B  shows a plurality of magnetic elements  410  that can be incorporated into an accessory device as part of attachment feature  216 . Some but not all of the plurality of magnetic elements  410  can correspond to magnetic elements  402  and be used to magnetically attach accessory  200  to electronic device  100 . In another embodiment, all or most of the plurality of magnetic elements  410  can be used to secure portions of accessory device  200  together to form other support structures that can be used in conjunction with electronic device  100 . In one embodiment, magnetic element  414  can be used to activate a magnetically sensitive circuit such as Hall Effect sensor  118 . 
       FIGS. 9A-9C  show representative magnetic attachment feature  500  in accordance with a described embodiment. Magnetic attachment feature  500  can, for example, correspond to device attachment feature  108  shown  FIG. 6  and  FIGS. 7A-7C . In the inactive state, the magnetic elements within magnetic attachment feature  500  can be positioned away from housing  102  to minimize the magnetic field lines that propagate through  102 . On the other hand, in the active state, the magnetic elements can move towards housing  102  in order to increase the number of magnetic field lines that propagate through housing  102  thereby satisfying Eq. (2). 
     The manner in which the magnetic elements moves can be widely varied. For example, the magnetic elements can rotate, pivot, translate, slide or the like. In one example, the magnetic elements can be positioned within a channel that allows the magnetic elements to slide from a first position corresponding to the inactive state to a second position corresponding to the active state. 
     In the particular embodiment shown in  FIGS. 9A-9C , attachment feature  500  can include magnetic element  502  having magnetic properties that can remain stable over a period of time. For example, it can be desired that the magnetic attachment properties remain stable over the expected operating life of electronic device  100 . In this way, the magnetic field formed by the interaction of the magnetic fields of each of the magnets will also remain stable. The stability of the magnetic field can result in a very repeatable attachment process. This repeatability is particularly useful when electronic device  100  undergoes numerous and repeated attachment cycles (attach/detach) with other appropriately configured objects such as accessory device  200  that requires a consistently accurate placement. 
     In the representative embodiment shown, magnetic element  502  can take many forms. For example, magnetic element  502  can take the form of a number of magnets arranged in a specific order and configuration having stable magnetic properties (such as polarity and intrinsic magnetic strength). However, in order to satisfy Eq. (1) when magnetic attachment feature  500  is inactive, magnetic element  502  must remain at least distance x=(x 0 +t) from the exterior of housing  102 . In other words, in order to satisfy Eq. (1), the dimensions of device attachment feature  500  must take into consideration at least the magnetic properties and physical layout of magnetic element  502 . 
     Accordingly, magnetic element  502  can be attached to retaining mechanism  504  arranged to exert retaining force F retain . Retaining force F retain  can be used to retain magnetic element  502  at a position within device attachment feature  500  resulting in little or no magnetic flux leakage outside of electronic device  100  (i.e., Eq. (1) is satisfied) when device attachment feature  500  is inactive. In one embodiment, retaining mechanism  504  can take the form of a spring arranged to provide retaining force F retain  according to Eq. (6):
 
 F   retain   =k·Δx   Eq. (6)
 
where k is spring constant of retaining mechanism  504 , and
         Δx is spring displacement from equilibrium.       

     For example,  FIG. 9B  shows representative magnetic attachment feature  500  in an active state. By appropriately configuring magnetic element  502  and those in accessory attachment feature  204 , the resulting magnetic interaction of the magnetic field of magnetic element  502  and that generated by accessory attachment feature  204  can create a net attractive magnetic force at least as great as that required to activate magnetic attachment feature  500 . In other words, the net attractive magnetic force can have a magnitude at least that of activation force F act  satisfying Eq. (7) thereby overcoming retaining force F retain  causing magnetic element  502  to move from the inactive position (i.e., x=0) to the active position (i.e., x=x 0 ),
 
 F   act   ≥F   retain (Δ x=x   o )  Eq. (7).
 
     However, only another magnetic attachment feature that generates a magnetic field having properties that “match” the magnetic field properties of magnetic element  502  can activate magnetic attachment feature  500 . Therefore, as shown in  FIG. 9C , the presence of object  506  formed of magnetically active material (such as steel) located at the exterior surface of housing  102  (i.e., x=x 0 +t) cannot activate magnetic attachment feature  500 . More specifically, in one embodiment, the net magnetic attractive force generated between object  506  and magnetic attachment feature  500  less than 2 NT, whereas activation force F ACT  can be on the order of about 3 NT. 
     More specifically, in order to transition from the inactive to the active state, the magnetic force created between magnetic element  502  and object  506  must be greater than activation force F act . However, since the magnetic flux density of the magnetic field generated by magnetic element  502  at the exterior surface of housing  102  is less than B threshold , any magnetic force generated between object  506  and magnetic element  502  is substantially less than F retain  and therefore fails to satisfy Eq. (7). Hence, magnetic element  502  remains fixed in place at about x=0 and magnetic attachment feature  500  cannot undergo the transition from the inactive to the active state. 
     It should be appreciated that the spring can be widely varied. For example, it may vary depending on the type of movement. Examples include tension, compression, torsion, leaf and the like. In one particular implementation, leaf springs are used. 
     It should also be noted that in some embodiments, magnetic element  502  can be fixed in such a way that no spring is needed. In these embodiments, although Eq. (1) may not be satisfied, it can nonetheless be a practical arrangement. 
       FIG. 10  shows an embodiment of device attachment feature  600  in accordance with one embodiment of the present invention. Attachment feature  600  can correspond to element  208  in  FIG. 6  and  FIGS. 7A-7C . This embodiment is similar to the embodiment shown in  FIGS. 9A-9C  except that instead of a single mechanism, multiple mechanisms and more particularly a pair of mechanisms in the form of magnetic element  602  and magnetic element  604  are used. In particular,  FIG. 10  shows device attachment feature  600  in the active state. More specifically, spring  606  attached to magnetic element  602  and spring  608  attached to magnetic element  604  are each extended by distance Δx. 
     In this system, the two mechanisms cooperate to form the magnetic field. They can move independently or they can be connected together and move as a unit. The spring forces and the magnetic forces can vary. For example, system can be symmetric or asymmetric. The arrangement of magnetic elements may be similar or different. Again being symmetric or asymmetric. The configuration may depend on the needs of the system. 
     The magnetic attachment system can take many forms each of which provides for a repeatable and precise magnetic attachment mechanism that can be used to attach multiple suitably configured objects together. 
       FIGS. 11A-11B  show a specific implementation of device attachment feature  108  in the form of device attachment feature  700  in accordance with one embodiment. The device attachment feature can correspond to element  108  shown in  FIG. 6  and  FIGS. 7A-7C . In some cases, device attachment feature  700  can be used in conjunction with springs  606  and  608  as shown in  FIG. 10 . As shown in  FIG. 11A , device attachment feature  700 . In particular, device attachment feature  700  is shown in the inactive state having magnetic elements in the form of magnetic assembly  702  that can be enclosed within an enclosure. In this way, a retaining mechanism (not shown) attached to magnetic assembly  702  can exert associated retaining force F retain . Retaining force F retain  can be used to maintain magnetic assembly  702  at a position consistent with device attachment feature  700  being in the inactive state (i.e., satisfying Eq. (1)). 
     Magnetic assembly  702  can each include individual magnets. In the described embodiment, the individual magnets can be arranged in a structure in which the polarities of the magnets can be oriented to form a coded magnetic structure. The coded magnetic structure can be formed of a sequence of magnetic polarities and in some cases magnetic strength. In other words, the sequence of magnetic polarities can be represented, for example, as {+1, +1, −1, +1, −1, +1, −1, −1}. For this particular example, “+1” indicates the direction and strength of the magnet. Hence, a positive sign “+” can indicate that the corresponding magnet is aligned having a magnetic vector in a particular direction, a negative sign “−” can indicate a magnetic vector in an opposite direction and “1” indicates a strength of one unit magnet. 
     When a plurality of magnets of the same polarity are placed next to each other, the magnetic fields from each of the plurality of magnets can combine such that the plurality of magnets can be considered equivalent to a single magnet, the single magnet having the combined properties of the plurality of magnets. For example, the coded magnetic sequence {+1, +1, −1, +1, −1, +1, −1, −1} representing eight individual magnets can be considered equivalent to the coded magnetic sequence {+2, −1, +1, −1, +1, −2} embodied as an array of six individual magnets. In one embodiment, the magnets in a first and last position can possess the same magnetic strength as the other magnets in the array but twice their respective size. On the other hand, the magnets in the first and last position can have about the same size as the other magnets but possess twice the magnetic strength of the other magnets. In any case, the equivalency of magnetic properties can provide for a more compact coded sequence of magnets. The smaller size can help reduce weight as well as preserve the amount of valuable internal real estate required to house the magnetic attachment feature. In addition, since magnetic flux density is directly related to that area through which magnetic field lines propagate, as the area through which a given magnetic flux propagates decreases, the resulting magnetic flux density increases. 
     In one embodiment, magnetic assembly  702  can include individual magnets  712   a ,  712   b , and  712   c  having relative sizes of 2L, 1L, and 1L, respectively, where “L” represents a unit length. It should be noted that as discussed above a magnet having a relative size of “2L” can be embodied as either a single magnet having a physical length of “2L”, two magnets side by side each having a length “1L” with the magnetic poles aligned with each other, or a magnet of unit length L having twice the magnetic strength of the other magnets. Accordingly, for the remainder of this discussion, with regards to the terms 2L and 1L, “L” can represent a unit length and the relative strength of the magnet can be represented by the associated digit. For example, a magnet having a relative magnetic strength of “1” but a length of “2L” can be considered equivalent to a magnet having a relative strength of “2” and a length of “1L”. In this way, both the relative magnetic strengths, and orientation can be used to form the coded magnetic structure. 
     For example, magnet  712   a  can have an overall length of approximately twice that of magnets  712   b  or  712   c . On the other hand, magnet  712   a  can have the same length as magnets  712   b  and  712   c  but have an inherent magnetic strength twice that of magnets  712   b  and  712   c . In yet another embodiment, magnet  712   a  can be an equivalent magnet formed of two (or more) constituent magnets having their respective polarities aligned. 
     In one embodiment, magnets  712   a, b, c  can each be spaced apart from each other a predetermined distance. For example, in one implementation, the magnets can be spaced equidistant from each other. This spacing is, of course, predicated upon the desired magnetic properties of the magnetic field generated. In another embodiment, those magnets having anti-aligned polarities can be magnetically attached to each other. In this way, the magnetic bond formed between the adjacent magnets can be used to maintain the integrity of the sequence of magnets in the magnetic assembly. However, those magnets having aligned polarities must be held together by an externally applied force to overcome the repulsive magnetic force generated between the two aligned magnets. 
     In addition to size and positioning, the magnetic polarities of magnets  712   a, b, c  can be selected based upon the desired properties of the magnetic field generated. In the embodiment shown, however, the magnetic elements are magnetically coupled to each other end to end thereby reducing the amount of space required and increasing the magnetic flux density by reducing an overall region in which the magnetic field lines are propagated. 
     In particular, magnetic assembly  702  can have a specific magnetic polarity pattern set in which each of magnets  712   a, b, c  are oriented in such a way that their N or S magnet poles are aligned (or anti-aligned) in a particular manner. For example, the magnets in magnetic assembly  702  can be arranged to form first coded magnetic structure {+1, −1, +1} in which the magnetic poles of magnets  712   a, b, c  are aligned according to first magnetic polarity pattern {P1, P2, P1} by which it is meant that the magnetic pole of magnet  712   a  is anti-aligned relative to magnet  712   b  which in turn is anti-aligned with magnet  712   c.    
     Magnetic assembly  702  can also include individual magnets  714   a, b, c  and having relative sizes of 1L, 1L, and 2L, respectively. Furthermore, magnets  714   a, b, c  can be arranged to have their respective magnetic poles aligned in accordance with second magnetic polarity pattern {P2, P1, P2} that is the inverse (or complement) of first magnetic polarity pattern {P1, P2, P1}. In terms of coded magnetic structure, magnets  714   a, b, c  can be aligned according to second coded magnetic sequence {−1, +1, −1} that is the inverse, or complement, of first coded magnetic structure {+1, −1, +1}. This anti-symmetric relationship between magnets  712   a, b, c  and  714   a,b,c  provides a magnetic field that is anti-symmetric with respect to center line  716 . 
       FIGS. 11A and 11B  also show specific implementation of accessory attachment feature  800  that can, for example, correspond to element  202  shown in  FIG. 6  and  FIGS. 7A-7C . Magnetic assemblies  802  can include a number of magnetic elements. The magnetic elements can be arranged in such a way that the combined magnetic field matches the magnetic field of magnetic assembly  702 . 
     Magnetic assembly  802  can include magnets  802   a ,  802   b , and  802   c  each being about the same size as corresponding magnet  712   a ,  712   b , and  712   c  in magnetic assembly  702 . However, in order to maximize net attraction force F net  and drive the magnetic interaction between the magnetic fields to a desired equilibrium, magnets  802   a, b, c  are aligned based upon second magnetic polarity pattern {P2, P1, P2}. Magnetic assembly  802  can also include magnets  804   a ,  804   b , and  804   c  each being about the same size as corresponding magnets  714   a ,  714   b , and  714   c . Moreover, in keeping with the overall goal of the magnetic interaction between the magnetic fields to equilibrate at the desired configuration of the devices, magnets  804   a, b, c  can be aligned according to first magnetic polarity pattern {P1, P2, P1}. 
       FIG. 11B  shows device attachment feature  700  in the active state due to the magnetic interaction between magnetic assemblies  702  and  802 . In particular, since the arrangement of magnetic elements between attachment feature  700  and those in accessory attachment feature  800  “match”, then the magnetic interaction between the magnetic fields can cause magnetic assemblies  702  to move from the inactive state (i.e., x=0) to the active state (i.e., x=x 0 ). 
       FIG. 12  illustrates a sequence of relative shift positions for the magnetic structure of magnetic assembly  702  and the complementary magnet structure of magnetic assembly  802 . Magnetic assembly  702  is shown to be encoded with coded magnetic sequence {+2, −1, +1, −1, +1, −2}. Magnetic assembly  802  is shown to be encoded with complementary coded magnetic sequence {−2, +1, −1, +1, −1, +2}. For this example, the magnets can have the same or substantially the same magnetic field strength (or amplitude), which for the sake of this example is provided a unit of 1 (where A=Attract, R=Repel, A=−R, A=1, R=−1). In this example, magnetic assemblies  702  and  802  are moved relative to each other one “1L” length at a time (note that the anti-symmetry about center line  716  of the coded magnetic sequence allows that the results of a leftward shift mirror the results of a rightward shift, therefore, only a rightward shift is shown). 
     For each relative alignment, the number of magnets that repel plus the number of magnets that attract is calculated, where each alignment has a total force in accordance with a magnetic force function based upon the magnetic field strengths of the magnets. In other words, the total magnetic force between the first and second magnet structures can be determined as the sum from left to right along the structure of the individual forces, at each magnet position, of each magnet or magnet pair interacting with its directly opposite corresponding magnet in the opposite magnet structure. Where only one magnet exists, the corresponding magnet is zero, and the force is zero. Where two magnets exist, the force is R for equal poles or A for opposite poles for each unit magnet. 
     The total magnetic force can be computed for each of the figures and shown with each figure along with the relative shift value. Accordingly, using a specific coded magnetic sequence {+2, −1, +1, −1, +1, −2} can result in net magnetic attractive force F net  varying from −3 (i.e., 3R) to +8 (i.e., +8 A) where the peak occurs when magnetic assemblies  702  and  802  are aligned such that their respective codes are also aligned. It should be noted that the off peak net magnetic force can vary from −3 to +4. As such, the net magnetic force can cause magnetic assemblies  702  to generally repel each other unless they are aligned such that each of their magnets is correlated with a complementary magnet (i.e., a magnet&#39;s South pole aligns with another magnet&#39;s North pole, or vice versa). In other words, magnetic assemblies  702  and  802  highly correlate when they are aligned such that they substantially mirror each other. 
     It should also be noted that when magnetic assemblies  702  and  802  are 180° out of phase (i.e., something akin to top to bottom misalignment also referred to as upside down) the net magnetic force generated can be on the order of  8 R. Hence, it is highly unlikely that devices being magnetically attached to each other using magnetic assemblies  702  and  802  can be attached upside down. 
       FIG. 13  illustrates graph  900  of function F NET (L). Function F NET (L) describes net magnetic force F NET  as a function of shift displacement (L) shown in  FIG. 12  for the coded magnet structures in magnetic assembly  702  and magnetic assembly  802 . It should be noted that the symmetric nature of the coded magnetic structures in magnetic assemblies  702  and  802  about center line  716  provides that function F NET (L) is also anti-symmetric about center line  716 . In this way, the results of  FIG. 12  can be plotted on the right side of center line  716  and reflected about center line  716  to populate the left side of graph  900 . 
     As shown in  FIG. 13 , function F NET (L) has a global maximum value when magnetic assemblies  702  and  802  correlate at a position corresponding to center line  716 . In other words, function F NET  (L=0) reaches a maximum (i.e., 8 A) when all magnetic elements in magnetic assemblies  702  and  802  having opposite polarities align with each other. Any other configuration (i.e., F NET  (L≠0) results in net magnetic force F NET  being less than the global maximum value (of 8 A). It should further be noted, however, that function F NET (L) has at least two local maxima values (i.e., F NET (L=±3)) that permits a weak attachment between magnetic assemblies  702  and  802 . However, a strong, durable attachment can only occur when device magnetic attachment feature  700  associated with magnetic assembly  702  is properly activated. Therefore, by establishing activation force F ACT  satisfying Eq. (8), a “false activations” of device magnetic attachment feature  700  or a weak attachment between magnetic assemblies  702  and  802  can be avoided.
 
 F   NET ( L =local maxima)≤ F   ACT   ≤F   NET ( L =global maximum)  Eq. (8).
 
It should also be noted that activation force F ACT  is related to retaining force F retain  through Eq. (6). In this way, Eq. (6) and Eq. (8) in view of function F NET (L) can be used to determine a suitable value for spring constant k.
 
       FIGS. 14 and 15  show other embodiments where magnetic elements can be arranged vertically and horizontally. In addition, the magnetic elements can be sized to have polarities that also extend both horizontally and vertically. For example, arrangement  1000  shows two rows of magnetic elements where each magnetic element extends height H in the vertical direction. In the arrangement shown, each vertically arranged magnetic element has the same magnetic polarity forming equivalent magnetic structure  1002 . In other words, both arrangement  1000  and arrangement  1002  can be both be characterized as having the coded magnetic sequence {+2, −2, +2, −2, +2, −2}. 
       FIG. 15  shows a top view of magnetic array configured as two dimensional coded magnetic sequence  1004  in accordance with the described embodiments. Two dimensional coded magnetic sequence  1004  can be used to extend the combined magnetic field over an area that extends in both the x and y directions. This extended area can result in an overall increase in the area available to propagate magnetic field lines that can result in an increase in magnetic flux and a commensurate increase in net magnetic attractive force. In addition to providing an improved magnetic attachment, two dimensional coded magnetic sequence  1004  can approximate non-integer values of magnetic properties, such as magnetic strength. For example, with magnetic sequence  1004 , the magnetic fields of the various components can combine to approximate the coded magnetic sequence {+1.5, −1.5, +1.5, −1.5, +1.5, −1.5}. Furthermore, two dimensional coded magnetic sequence  1004  can assist in providing a vertical alignment in addition to a horizontal alignment. 
     For the remainder of this discussion, various embodiments of accessory device  200  are discussed. 
     In one embodiment, accessory device  200  can include a number of protective elements that can be used to protect certain aspects of electronic device  100 . For example, accessory device  200  can take the form of a protective cover. The protective cover can include a flap pivotally connected to a hinge assembly. The hinge assembly can, in turn, be coupled to electronic device  100  by way of accessory attachment feature  202 . In this way, the flap portion can be used as a protective cover to protect aspects of electronic device  100  such as a display. The flap can be formed of various materials such as plastic, cloth, and so forth. The flap can be segmented in such a way that a segment of the flap can be lifted to expose a corresponding portion of the display. The flap can also include a functional element that can cooperate with a corresponding functional element in electronic device  100 . In this way, manipulating the flap can result in an alteration in the operation of electronic device  100 . 
     The flap can include magnetic material that can be used to activate a magnetically sensitive circuit in electronic device  100  based upon, for example, the Hall Effect. The magnetically sensitive circuit can respond by generating a signal that can, in turn, be used to alter an operating state of electronic device  100 . Since the cover can be easily attached directly to the housing of the tablet device without fasteners, the cover can essentially conform to the shape of electronic device  100 . In this way, the cover will not detract or otherwise obscure the look and feel of electronic device  100 . 
     In one embodiment, accessory device  200  can be used to enhance the overall functionality of electronic device  100 . For example, accessory device  200  can be configured to act as a hanging apparatus. When magnetically attached to electronic device  100 , accessory device  200  can be used to hang electronic device  100 . In this way, electronic device  100  can be used as a display for presenting visual content such as art, movies, photos and so forth on a wall or suspended from a ceiling. As a hanging apparatus, accessory device  200  can be used to hang electronic device  100  from a wall or a ceiling. Electronic device  100  can be easily removed by simply exerting a releasing force sufficient to overcome the net magnetic attractive force F NET . Accessory device  200  can be left in place and be used to reattach electronic device  100  (or another device) at a later time. 
     In one embodiment, accessory device  200  can also take the form of a holding mechanism for attaching objects that are not by themselves equipped to magnetically attach to electronic device  100 . For example, accessory device  200  can be configured to carry a stylus or other such input device. The stylus can be used to provide inputs to the electronic device. In some cases, accessory device  200  can provide a signal to electronic device  100  indicating the presence of the stylus. The signal can cause electronic device  100  to enter into a stylus recognition state, for example. More particularly, when accessory device  200  is magnetically attached to electronic device  100 , electronic device  100  can activate a stylus input state in order to recognize stylus type inputs. When accessory device  200  is removed, electronic device  100  can de-activate the stylus input state. In this way, the stylus can be conveniently attached/detached to electronic device  100  when needed. 
     Accessory device  200  can take the form of a support that can be used to enhance the functionality of electronic device  100 . For example, accessory device  200  can be configured to act as a display stand on which a display of electronic device  100  can be viewed at a comfortable viewing angle such as 75°. In other words, when placed upon a horizontal surface such as a table or desk, accessory device  200  can support electronic device  100  in such a way that the visual content presented at the display can be viewed at about a viewing angle of approximately 75°. 
     Accessory device  200  can also take the form of a support that can be used to enhance the functionality of electronic device  100  in a keyboard state. In the keyboard state, accessory device  200  can be used to present a touch pad surface at an angle that is ergonomically friendly. In this way, input touch events can be applied (to a virtual keyboard, for example) at an angle that does not overtax a user&#39;s wrist, hands, arms, etc. 
     The remainder of this discussion will describe particular embodiments of devices that can use the magnetic attachment system. In particular,  FIG. 16A  and  FIG. 16B  show electronic device  100  presented in terms of tablet device  1100  and accessory device  200  is shown as cover assembly  1200  each in perspective top views These elements may generally correspond to any of those previously mentioned. In particular,  FIGS. 16A and 16B  show two perspective views of tablet device  1100  and cover assembly  1200  in the open configuration. For example,  FIG. 16A  shows device attachment feature  108  included in tablet device  1100  and its relationship to tablet device  1100 .  FIG. 16B , on the other hand, is the view presented in  FIG. 16A  rotated about 180° to provide a second view of attachment feature  202  and its relationship with cover assembly  1200 . 
     Tablet device  1100  can take the form of a tablet computing device such as the iPad™ manufactured by Apple Inc. of Cupertino, Calif. Referring now to  FIG. 16A , tablet device  1100  can include housing  1102  that can enclose and support device attachment feature  108 . In order to not interfere with the magnetic field generated by device attachment feature  108 , at least that portion of housing  1102  nearest device attachment feature  108  can be formed of any number of non-magnetic materials such as plastic or non-magnetic metal such as aluminum. Housing  1102  can also enclose and support internally various structural and electrical components (including integrated circuit chips and other circuitry) to provide computing operations for tablet device  1100 . Housing  1102  can include opening  1104  for placing internal components and can be sized to accommodate a display assembly or system suitable for providing a user with at least visual content as for example via a display. In some cases, the display assembly can include touch sensitive capabilities providing the user with the ability to provide tactile inputs to tablet device  1100  using touch inputs. The display assembly can be formed of a number of layers including a topmost layer taking the form of transparent cover glass  1106  formed of polycarbonate or other appropriate plastic or highly polished glass. Using highly polished glass, cover glass  1106  can take the form of cover glass  1106  substantially filling opening  1104 . 
     Although not shown, the display assembly underlying cover glass  1106  can be used to display images using any suitable display technology, such as LCD, LED, OLED, electronic or e-inks, and so on. The display assembly can be placed and secured within the cavity using a variety of mechanisms. In one embodiment, the display assembly is snapped into the cavity. It can be placed flush with the adjacent portion of the housing. In this way, the display can present visual content that can include visual, still images, as well as icons such as graphical user interface (GUI) that can provide information the user (e.g., text, objects, graphics) as well as receive user provided inputs. In some cases, displayed icons can be moved by a user to a more convenient location on the display. 
     In some embodiments, a display mask can be applied to, or incorporated within or under cover glass  1106 . The display mask can be used to accent an unmasked portion of the display used to present visual content and can be used to make less obvious device attachment feature  108  and securing attachment feature  110 . 
     Tablet device  1100  can include various ports that can be used to pass information between tablet device  1100  and the external environment. In particular, data port  1108  can facilitate the transfer of data and power whereas speakers  1110  can be used to output audio content. Home button  1112  can be used to provide an input signal that can be used by a processor included in tablet device  1100 . The processor can use the signal from home button  1112  to alter the operating state of tablet device  1100 . For example, home button  1112  can be used to reset a currently active page presented by the display assembly. 
     In one embodiment, accessory device  200  can take the form cover assembly  1200 . Cover assembly  1200  can have a look and feel that complements that of the tablet device  1100  adding to overall look and feel of tablet device  1100 . Cover assembly  1200  is shown in  FIGS. 16A and 16B  attached to tablet device  1100  in an open configuration in which cover glass  1106  is fully viewable. Cover assembly  1200  can include flap  1202 . In one embodiment, flap  1202  can have a size and shape in accordance with cover glass  1106 . Flap  1202  can be pivotally connected to accessory attachment feature  202  by way of a hinge assembly (not shown). The magnetic attachment force between attachment feature  202  and device attachment feature  108  can maintain cover assembly  1200  and tablet device  1100  in a proper orientation and placement vis-a-vis flap  1202  and cover glass  1106 . By proper orientation it is meant that cover assembly  1200  can only properly attach to tablet device  1100  having flap  1202  and cover glass  1106  aligned in a mating engagement. The mating arrangement between cover glass  1106  and flap  1202  is such that flap  1202  covers substantially all of cover glass  1106  when flap  1202  is placed in contact with cover glass  1106  as shown in  FIG. 17A  below. 
       FIGS. 17A and 17B  show cover assembly  1200  and tablet device  1100  magnetically attached to each other.  FIG. 17A  shows a closed configuration in which cover glass  1106  is fully covered by and in contact with flap  1202 . Cover assembly  1200  can pivot about hinge assembly  1204  from the closed configuration of  FIG. 17A  to an open configuration of  FIG. 17B . In the closed configuration, inner layer  1206  of cover assembly  1200  can come in direct contact with cover glass  1106 . In one embodiment, inner layer  1206  can be formed of material that can passively clean cover glass  1106 . The passive cleaning by inner layer  1206  of cover glass  1106  can be accomplished by movements of those portions of inner layer  1206  in contact with cover glass  1106 . In a particular embodiment, inner layer  1206  can be formed of a microfiber material. 
     In order to transition from the closed to the open configuration, releasing force F release  can be applied to flap  1202 . Releasing force F release  can overcome the magnetic attractive force between attachment feature  216  in flap  1202  and attachment feature  110  in tablet device  1100 . Hence, cover assembly  1200  can be secured to tablet device  1100  until releasing force F release  is applied to flap  1202 . In this way, flap  1202  can be used to protect cover glass  1106 . For example, cover assembly  1200  can be magnetically attached to tablet device  1100 . Flap  1202  can then be placed upon and magnetically secured to cover glass  1106  by the magnetic interaction between magnetic attachment features  110  and  216 . Flap  1202  can be detached from cover glass  1106  by the application of releasing force F release  directly to flap  1202 . Releasing force F release  can overcome the magnetic attraction between magnetic attachment features  110  and  216 . Hence, flap  1202  can then move away from cover glass  1106  unhindered. 
     In order to maintain a good magnetic attachment between flap  1202  and magnetic attachment feature  110 , flap  1202  can include a number of magnetic elements. Some of the magnetic elements in flap  1202  can interact with corresponding magnetic elements in magnetic attachment feature  110 . The net magnetic attractive force generated between the magnetic elements can be strong enough to prevent inadvertent release of flap  1202  from cover glass  1106  during normal handling. The net magnetic attractive force, however, can be overcome by releasing force F release . 
       FIG. 18  shows a top view of a specific embodiment of cover assembly  1200  in the form of segmented cover assembly  1300 . Segmented cover assembly  1300  can include body  1302 . Body  1302  can have a size and shape in accordance with cover glass  1106  of tablet  1100 . Body  1302  can be formed from a single piece of foldable or pliable material. Body  1302  can also be divided into segments separated from each other by a folding region. In this way, the segments can be folded with respect to each other at the folding regions. In one embodiment, body  1302  can be formed layers of material attached to one another forming a laminate structure. Each layer can take the form of a single piece of material that can have a size and shape in conformance with body  1302 . Each layer can also have a size and shape that correspond to only a portion of body  1302 . For example, a layer of rigid or semi-rigid material about the same size and shape of a segment can be attached to or otherwise associated with the segment. In another example, a layer of rigid or semi-rigid material having a size and shape in accordance with body  1302  can be used to provide segmented cover assembly  1300  as a whole with a resilient foundation. It should be noted that the layers can each be formed of materials having desired properties. For example, a layer of segmented cover assembly  1300  that comes in contact with delicate surfaces such as glass can be formed of a soft material that will mar or otherwise damage the delicate surface. In another embodiment, a material such as micro-fiber can be used that can passively clean the delicate surface. On the other hand, a layer that is exposed to the external environment can be formed of a more rugged and durable material such as plastic or leather. 
     In a specific embodiment, segmented body  1302  can be partitioned into a number of segments  1304 - 1310  interspersed with thinner, foldable portions  1312 . Each of the segments  1304 - 1310  can include one or more inserts disposed therein. By way of example, the segments can include a pocket region where the inserts are placed or alternatively the inserts may be embedded within the segments (e.g., insert molding). If pockets used, the pocket region can have a size and shape to accommodate corresponding inserts. The inserts can have various shapes but are most typically shaped to conform to the overall look of segmented body  1302  (e.g., rectangular). The inserts can be used to provide structural support for segmented body  1302 . That is, the inserts can provide stiffness to the cover assembly. In some cases, the inserts may be referred to as stiffeners. As such, the cover assembly is relatively stiff except along the foldable regions that are thinner and do not include the inserts (e.g., allows folding) making segmented cover assembly  1300  more robust and easier to handle. In one embodiment segments  1304 ,  1306 , and  1310  can be related to segment  1308  in size in the proportion of about 0.72 to 1 meaning that segments  1304 ,  1306  and  1310  are sized in width to be about 72% of the width of segment  1308 . In this way, a triangle having a appropriate angles can be formed (i.e., about 75° for display stand and about 11° for keyboard stand discussed below). 
     Segments  1306 ,  1308 , and  1310  can include inserts  1314 ,  1316 , and  1318 , respectively (shown in dotted lines form). Inserts  1314 - 1318  can be formed of rigid or semi-rigid material adding resiliency to body  1302 . Examples of materials that can be used include plastics, fiber glass, carbon fiber composites, metals, and the like. Segment  1304  can include insert  1320  also formed of resilient material such as plastic but also arranged to accommodate magnetic elements  1322  some of which can interact with magnetic elements in table device  1100  and more specifically attachment feature  110 . 
     Due to the ability of segmented body  1302  to fold and more particularly the various segments to fold with respect to each other, most of magnetic elements  1322  can be used to magnetically interact with magnetically active insert  1324  embedded in insert  1318 . By magnetically binding both active insert  1324  and magnetic elements  1322  various support structures can be formed some of which can be triangular in shape. The triangular support structures can aid in the use of tablet device  1100 . For example, one triangular support structure can be used to support tablet device  1100  in such a way that visual content can be presented at a desirable viewing angle of about 75° from horizontal. However, in order be able to appropriately fold segmented cover  1300 , segment  1308  can be sized to be somewhat larger than segments  1304 ,  1306  and  1310  (which are generally the same size). In this way, the segments can form a triangle having two equal sides and a longer third side, the triangle having an interior angle of about 75°. 
     One approach to forming at least one triangular support structure can include segment  1304  folding with respect to segments  1306 - 1310  in such a way that most of magnetic elements  1322  embedded in insert  1320  magnetically attract the magnetically active insert  1324 . In this way, segment  1304  and segment  1310  can be magnetically bound together forming a triangular support structure having the appropriate dimensions. The triangular support structure can be used as a stand onto which tablet device  1100  can be placed such that visual content can be displayed at about 75°. In another example, segmented cover  1300  can be folded to form a triangular support structure that can be used as a keyboard support. Segmented cover  1300  can also be folded to form a triangular support structure that can be used to hang tablet device  1100  from a horizontal support piece (such as a ceiling) or a vertical support piece (such as a wall). 
     Cover assembly  1300  can pivotally attach to accessory attachment feature  202  by way of a hinge assembly. The hinge assembly can provide one or more pivots to allow the cover to fold over on the device while the cover assembly is attached to the device through the magnets. In the illustrated embodiment, the hinge assembly can include first hinge portion (also referred to as first end lug)  1328  and a second hinge portion (or second end lug)  1330  disposed opposite the first end lug. First end lug  1328  can be rigidly connected to second end lug  1330  by way of connecting rod  1332  (shown in dotted line form) incorporated into a tube portion of segmented body  1302 . The longitudinal axis of connecting rod  1332  can act as pivot line  1333  about which the segmented body can pivot relative to the hinge assembly. Connecting rod  1332  can be formed of metal or plastic strong enough to rigidly support cover assembly  1300  as well as any objects, such as tablet device  1100 , magnetically attached to magnetic attachment feature  202 . 
     In order to prevent metal on metal contact, first end lug  1328  and second end lug  1330  can each have protective layers  1336  and  1338 , respectively, attached thereto. Protective layers (also referred to as bumpers)  1336  and  1338  can prevent direct contact between first end lug  1328  and second end lug  1330  with housing  1102 . This is particularly important when end lugs  1328 ,  1330  and housing  1102  are formed of metal. The presence of bumpers  1336  and  1338  can prevent metal to metal contact between the end lugs and housing  1102  thereby eliminating the chance of substantial wear and tear at the point of contact that can degrade the overall look and feel of tablet device  1100 . 
     In order to maintain their protective qualities, bumpers  1336  and  1338  can be formed of material that is resilient, durable, and resists marring the finish of the exterior surface of tablet device  1100 . This is particularly important due to the tight tolerances required for good magnetic attachment and the number of attachment cycles expected during the operational life of tablet device  1100 . Accordingly, bumpers  1336  and  1338  can be formed of soft plastic, cloth or paper that can be attached to the end lugs using any suitable adhesive. It should also be noted that in some cases, the bumpers can be removed and replaced with fresh bumpers when needed. 
     First end lug  1328  and second end lug  1330  can be magnetically connected to the electronic device by way of hinge span  1340  that is configured to pivot with respect to the end lugs. The pivoting can be accomplished using hinge posts  1342  (a portion of which can be exposed). Hinge posts  1342  can rotatably secure hinge span  1340  to both first end lug  1328  and second end lug  1330 . Hinge span  1340  can include magnetic elements. The magnetic elements can be arranged to magnetically attach hinge span  1340  to a magnetic attachment feature having a matching arrangement of magnetic elements in the electronic device. In order to fix the magnetic elements in place within hinge span  1340 , hinge posts  1342  can be used to secure magnetic elements located at both ends of hinge span  1340  reducing the likelihood that the magnetic elements in hinge span  1340  will move about having the potential for disrupting the magnetic attachment between hinge span  1340  and the magnetic attachment feature in the electronic device. 
     In order to assure that there is no interference between the magnetic elements in hinge span  1340  and the corresponding magnetic elements in the electronic device, hinge span  1340  can be formed of magnetically inactive material such as plastic or non-magnetic metal such as aluminum. When hinge span  1340  is formed of magnetically inactive metal, such as aluminum, metal to metal contact between hinge span  1340  and housing  1102  of electronic device  1100  can be prevented with the use of protective layer  1344 . Protective layer  1344  can be applied to the surface of hinge span  1340  that faces housing  1102  when hinge span  1340  and electronic device  1100  are magnetically attached to each other. Protective layer  1344  (also referred to as label  1344 ) can be formed of many materials that will not mar the finish of housing  1102 . Such materials can include, for example, paper, cloth, plastic, and so forth. 
       FIGS. 19A and 19B  show a more detailed view of two embodiments of hinge span  1340 . More specifically,  FIG. 19A  shows embodiment  1400  of the hinge span where magnetically inert spacers are used to separate and fix the magnetic elements. In particular, hinge span  1400  can enclose and support magnetic elements  1402  used by magnetic attachment feature  202  to magnetically attach segmented cover assembly  1300  to tablet device  1100 . Magnetic elements  1402  can be arranged in a specific configuration that matches corresponding magnetic elements in device attachment feature  108  in tablet device  1100 . In this way, segmented cover assembly  1300  and tablet device  1100  can precisely and repeatedly attach to each other. 
     In order to maintain repeatable and stable magnetic engagement over an extended period of time, magnetic elements  1402  can remain in a stable configuration. In other words, magnetic elements  1402  in hinge span  1400  should remain in their relative positions and polarities vis-à-vis the corresponding magnetic elements in the magnetic attachment system in tablet  1100  for an extended period of time. This is particularly important when repeated attachment cycles are anticipated to occur over an expected operating life of cover assembly  1300  and/or tablet device  1100 . 
     Hence, to assure the integrity of the magnetic engagement over the course of many attachment cycles, the configuration of magnetic elements  1402  can remain essentially fixed with respect to each other and to the corresponding magnetic elements in device attachment feature  108 . Hence, in order to assure that the physical layout of magnetic elements  1402  remain essentially fixed, filler material  1404  can be inserted between the various magnetic elements in hinge span  1400 . Filler material  1404  can be non-magnetic material such as plastic. Filler material  1404  can be shaped to tightly fit in the interstitial spaces between the magnetic elements. In this way, magnetic elements  1402  remain in a fixed and stable configuration for an extended period of time. 
     On the other hand,  FIG. 19B  shows another embodiment of hinge span  1340  in the form of hinge span  1410  that utilizes the mutual magnetic attraction between physically adjacent magnetic elements for fixing the magnetic elements in place. In this way, the number of component parts is reduced. Furthermore, due to the reduced area taken up by magnetic elements  1402 , the corresponding magnetic flux density can increased. However, end plugs  1412  can be used to fix those magnetic elements located at either end of hinge span  1410  End plugs  1412  can be necessary to overcome a net magnetic repulsive force when the magnetic elements at either end of hinge span  1410  have aligned polarities. In addition to end plugs  1412 , an alternative embodiment can provide for centrally located spacer  1414 . Centrally located spacer  1414  can be formed of magnetically inert material and be used to fix magnetic elements  1402  in place. 
       FIG. 19C  shows that portion of hinge span  1340  that forms part of the engagement surface when segmented cover assembly  1300  is magnetically attached to tablet device  1100 . In particular, label  1344  is shown attached to hinge span  1340  using adhesive such as glue. It should be noted, that label  1344  is arranged to conform to the shape of that portion of housing  1102  that also forms part of the engagement surface. In this way, the separation distance between corresponding magnetic elements can be minimized. 
       FIG. 20A  shows a representative side view of segmented cover assembly  1300  magnetically attached to tablet device  1100 .  FIG. 20B  show representative cross sectional views of segmented cover assembly  1300 /tablet device  1100  along line AA shown in  FIG. 18 .  FIG. 20B  shows a covered configuration and  FIG. 20C  shows a folded back configuration that fully exposes protective layer  1106  of tablet device  1100 . 
       FIG. 21A  shows a cross sectional side view  1500  of hinge span  1340  magnetically attached to housing  1102  having a curved shape. In this embodiment, housing  1102  can have a curved shape and is formed of non-magnetic material such as aluminum. Magnetic element  1502  can be incorporated into device attachment feature  108  in tablet device  1100 . In some embodiments, in order to prevent metal to metal contact, in those embodiments in which magnetic element  1502  is metal, a protective film can be attached to an engagement surface of magnetic element  1502  that prevents magnetic element  1502  from contacting housing  1102  directly. The protective film can be thin enough to be neglected when considering the magnetic engagement force between corresponding magnetic elements. The protective film can be unnecessary if magnetic element  1502  is not formed of metal or if that portion of housing  1102  that contacts magnetic element  1502  is not metal. 
     Magnetic element  1502  can magnetically interact with corresponding magnetic element  1504  in hinge span  1340 . Magnetic element  1504  can have thickness of about 2 mm. The magnetic interaction can create net magnetic attractive force F NET  satisfying Eq. (3a) in which separation distance x sep  is about equal to the total of the thickness t of housing  1102  and thickness “l” of label  1344 . Thickness “l” can be on the order of about 0.2 mm. Therefore in order to minimize separation distance x sep  (and thereby increase F NET ), magnetic element  1502  can be shaped to conform to interior surface  1506  of housing  1102 . Furthermore, label  1344  and magnetic element  1504  can each be shaped to conform to exterior surface  1508  of housing  1102 . In this way, the distance between magnetic element  1502  and magnetic element  1504  can be reduced to about the thickness t of housing  1102  and thickness 1 of label  1344 . 
     In order to further improve net attractive magnetic force F NET  between magnetic elements  1502  and  1504 , magnetic shunt  1510  can be glued to and enclose that portion of magnetic element  1504  facing away from housing  1102 . Magnetic shunt  1510  can be formed of magnetically active material such as steel or iron. The magnetically active material can redirect magnetic flux lines that would otherwise be directed away from magnetic element  1502  towards housing  1102  thereby increasing the total magnetic flux density B TOTAL  between magnetic element  1502  and magnetic element  1504  resulting in a commensurate increase in net magnetic attractive force F NET . Magnetic shunt  1510  can, in turn, be glued to housing  1512  of hinge span  1340 . It should be noted, that in order to assure that only label  1344  contacts exterior surface  1508  of housing  1102  (to avoid metal to metal contact), label  1344  is proud (i.e., protrudes) of housing  1512  of hinge span  1340  by about distance “d”. Nominally, distance d can be on the order of about 0.1 mm. 
     Since net magnetic force F NET  depends in part on separation distance between cooperating magnetic elements, the overall integrity of the magnetic attachment between the magnetic attachment system in tablet device  1100  and the magnetic elements in hinge span  1340  can be affected by the actual separation distance between cooperating magnetic elements as well as the consistency of the separation distance along length L of hinge span  1340 . In order to provide a highly correlated magnetic attractive force along hinge span  1340 , the separation distances between the magnetic elements in hinge span  1340  and those of the magnetic attachment system in tablet device  1100  are well controlled. 
       FIG. 21B  shows cross sectional view  1550  of hinge span  1340  magnetically attached to housing  1102  having a flat surface. In this arrangement, label  1344  and magnet  1554  can each conform to the flat shape of housing  1102 . 
     In order to assure consistency of the net magnetic attractive force along length L of hinge span  1340 , the components of hinge span  1340  can be assembled using fixture  1600  shown in cross section in  FIG. 22A  and in perspective view in  FIG. 22B . Fixture  1600  can have surface  1602  that conforms to the shape of the exterior surface of housing  1102 . In order to assemble hinge span  1340  in a manner that assures consistent magnetic attractive force along the length L of hinge span  1340  (as well as to provide an aesthetically pleasing look), label  1344  can be temporarily attached to surface  1602  of fixture  1600 . Since surface  1602  substantially conforms to the shape of exterior surface  1508 , label  1344  will have a shape that also conforms to the shape of exterior surface  1508 . In one embodiment, a partial vacuum can be created within fixture  1600  that causes label  1344  to attach to surface  1602  under suction. In this way, the assembled hinge span can be detached from surface  1602  by simply removing the partial vacuum. 
     Once label  1344  is secured to surface  1602  of fixture  1600 , magnetic element  1504  can be placed in direct contact with and attached to label  1344  using any appropriate adhesive. In order to reduce separation distance as much as possible, magnetic element  1504  can have a shape that conforms to that of both labels  1344  and surface  1602 . In this way, the conformal shaping of both label  1344  and magnetic element  1504  assures a minimum separation distance between magnetic element  1504  and  1502 . Magnetic element  1504  can then be glued to magnetic shunt  1510  formed of magnetically active materials such as steel to focus magnetic flux towards magnetic element  1502 . Metal shunt  1510  can then be enclosed by and glued to hinge span housing  1512  leaving about d=0.1 mm of label  1344  protruding from housing  1512 . 
     In addition to providing protection to tablet device  1100 , segmented cover assembly  1300  can be manipulated to form useful support structures. Accordingly,  FIGS. 23 through 26  show useful arrangements of cover assembly  1300  in accordance with the described embodiments. 
     For example, as shown in  FIG. 23 , segmented cover assembly  1300  can be folded such that the magnetically active portion of insert  1324  magnetically interacts with magnetic elements  1322 . It should be noted that the magnetic force used to maintain triangular support structure  1700  is about in the range of 5-10 newtons (NT). In this way, triangular support structure  1700  can be prevented from unwrapping inadvertently. Triangular support structure  1700  can be formed that can be used in many ways to augment tablet device  1100 . For example, triangular support structure  1700  can be used to support tablet device  1100  in such a way that touch sensitive surface  1702  is positioned relative to a support surface at an ergonomically advantageous angle. In this way, using touch sensitive surface  1702  can be a user friendly experience. This is particularly relevant in those situations where the touch sensitive surface is used over an extended period of time. For example, a virtual keyboard can be presented at touch sensitive surface  1702 . The virtual keyboard can be used to input data to tablet device  1100 . By using triangular support structure  1700  to support tablet device  1100  at the ergonomically friendly angle, the deleterious effects of repetitive movements can be reduced or even eliminated. 
       FIGS. 24A and 24B  show another folded implementation of segmented cover assembly  1300  in which triangular support structure  1700  can be used to support tablet device  1100  in a viewing state. By viewing state it is meant that visual content (visual, stills, animation, etc.) can be presented at a viewer friendly angle of about 75° from horizontal. In this “kickstand” state, visual content can be presented for easy viewing. A viewable area of tablet device  1100  can be presented at an angle of about 75° which has been found to be within a range of viewing angles considered optimal for a good viewing experience. 
       FIGS. 25A and 25B  show segmented cover assembly  1300  folded into various hanging embodiments. By hanging embodiments, it is meant that by folding segmented cover assembly  1300  into an appropriate triangular shape, tablet device  1100  can be suspended from above as shown in  FIG. 26A  in the form of hanger  1900 . Hanger  1900  can be used to suspend tablet device  1100  from above. For example, hanger  1900  can be suspended directly from a ceiling using a support piece such as a rod. Hanger  1900  can be created simply by folding segmented cover assembly  1300  in a first direction until embedded magnets  1322  magnetically engage magnetically active insert  1324  that can be formed of steel or iron. The magnetic circuit formed by the engagement of embedded magnets  1322  and magnetically active insert  1324  can provide sufficient support for safely suspending tablet device  1100  from any horizontally aligned support structure. 
       FIG. 25B  shows hanger embodiments suitable for hanging tablet device  1100  from a vertically aligned support structure such as a wall. In particular, hanger  1910  can be mechanically attached to a wall or other vertical support structure. Hanger  1910  can then be used to suspend tablet device  1100  along the lines of a wall mount. In this way, tablet device  1100  can be used to present visual content along the lines of a visual display for visual content, or wall hanging for still images such as photos, art, and the like. 
       FIGS. 26A and 26B  show arrangement  2000  where triangular support structure  1700  can be used as a handle. Again by folding segmented cover assembly  1300  such that segmented portions interact with each other to form triangular support structure that can be used as a handle. As such, tablet device  1100  can be picked up as one would pick up a book for viewing. The body of segmented cover assembly  1300  can provide convenient grasping features that can be used to more firmly grasp triangular support structure  1700  when being used to hold tablet device  1100  as a book. 
     In those cases where tablet device  1100  includes image capture devices, such as a front facing camera  2002  and rear facing camera  2004 , visual content can be presented by tablet device  1100 . In this way, triangular support structure  1700  can be used as a holder along the lines of a camera handle. As such, triangular support structure  1700  can provide a convenient and effective mechanism for aiding in the image capture process. For example, when used to capture images, tablet device  1100  can be firmly held by way of triangular support structure  1700  and rear facing camera  2004  can be pointed at a subject. The image of the subject can then be presented by tablet device  1100  at the display shown in  FIG. 25B . In this way, both front facing camera  2002  and/or rear facing camera  2004  can be used to capture still images or video such as in a video chat or simply view a video presentation. As part of a video chat, a visual chat participant can easily carry on a video conversation while using triangular support structure  1700  to hold tablet device  1100 . 
       FIGS. 27A-27C  show configuration  2100  of cover assembly  1300  and tablet device  1100  illustrating what is referred to as a peek mode of operation of tablet device  1100 . More particularly, when segment  1304  is lifted from glass cover  1106 , sensors in tablet device  1100  can detect that segment  1304  and only that segment has been lifted from glass layer  1106 . Once detected, tablet device  1100  can activate only the exposed portion  2102  of the display. For example, tablet device  1100  can utilize a Hall Effect sensor to detect that segment  1304  has been lifted from glass cover  1106 . Additional sensors, such as optical sensors can then detect if only segment  1304  has been lifted or if additional segments have been lifted. 
     As shown in  FIG. 27B , when tablet device  1100  has determined that only segment  1304  has been lifted, then tablet device  1100  can change operating state to “peek” state in which only the exposed portion  2102  of the display actively presents visual content in the form of icons  2104 . Hence, information in the form of visual content such as time of day, notes, and so forth can be presented for viewing on only that portion of display viewable. Once the sensors detect that segment  1304  has been placed back on glass layer  1106 , tablet  1100  can return to the previous operational state such as a sleep state. Furthermore, in another embodiment, when an icon arranged to respond to a touch is displayed, then that portion of a touch sensitive layer corresponding to the visible portion of the display can also be activated. 
     Furthermore, as shown in  FIG. 27C , when additional segments are lifted from cover glass  1106  to further expose second portion  2106  of cover glass  1106 , second portion  2106  of the display can be activated. In this way, in the “extended” peek mode, additional visual information, such as icons  2108 , can be presented in the portions of the display activated. It should be noted that as segments are lifted from cover glass  1106 , additional segments of the display can be activated. In this way, an extended peek mode can be provided. 
     Alternatively, the tablet device  1100  can respond to the signals from the Hall Effect sensor(s) by simply powering up the display when the flap is moved away from the display and power down (sleep) when the display is covered by the flap. In one embodiment, a subset of magnetic elements  1322  can be used in conjunction with corresponding magnetic elements  402  in attachment feature  110  to secure cover assembly  1300  to tablet device  1100  on cover glass  1106 . Furthermore, at least magnet  1326  can be used to activate magnetically sensitive circuit  118 . For example, when segmented cover  1300  is placed upon tablet device  1100  at cover glass  1106 , the magnetic field from magnet  1326  can be detected by magnetically sensitive circuit  118  that can take the form of a Hall Effect sensor. The detection of the magnetic field can cause Hall Effect sensor  118  to generate a signal that can result in a change in the operating state of tablet device  1100 . 
     For example, when Hall Effect sensor  118  detects that segmented cover  1300  is in contact with cover glass  1106  indicating that the display is not viewable, then the signal sent by Hall Effect sensor  118  can be interpreted by a processor in tablet device  1100  to change the current operating state to sleep state. On the other hand, when segment  1304  is lifted from cover glass  1106 , Hall Effect sensor  118  can respond to the removal of the magnetic field from magnet  1326  by sending another signal to the processor. The processor can interpret this signal by again altering the current operating state. The altering can include changing the operating state from the sleep state to an active state. In another embodiment, the processor can interpret the signal sent by Hall Effect sensor  118  in conjunction with other sensors by altering the operating state of tablet device  1100  to a peek mode in which only that portion of the display exposed by the lifting of segment  1304  is activated and capable of displaying visual content and/or receiving (or sending) tactile inputs. 
     In some cases, when segment  1306  is lifted from cover glass  1106  at the same time that Hall Effect sensor  118  indicates that segment  1304  is also lifted, the presence of sensors in addition to Hall Effect sensor  118  can cause the processor to enter into an extended peek mode in which additional display resources corresponding to the additional exposed portion of the display are also activated. For example, if tablet device  1100  includes other sensors (such as optical sensors) that can detect the presence of a particular segment, then signals from Hall Effect sensor  118  in combination with other sensor signals can provide an indication to the processor that a particular portion or portions of the display assembly are currently viewable and can thus be enabled to present visual content. 
       FIG. 28A  shows cover assembly  2200  in accordance with a particular embodiment. Cover assembly  2200  can include segmented cover  2202  attached to pivoting assembly  2204  shown in an exploded view. Pivoting assembly  2204  can include end lugs  2206  and  2208  pivotally connected to each other by way of hinge span  2210  and connecting rod  2212  (which can be enclosed within sleeve  2214  that can in turn be connected to or enclosed within segmented cover  2202  and not seen). In this way, at least two pivot lines  2216  and  2218  can be provided for pivotally moving end lugs  2206  and  2208 , hinge span  2210  and connecting rod  2212 . For example, hinge span  2210  (and end lugs  2206  and  2208 ) can rotate about pivot line  2216  whereas connecting rod  2212  (and end lugs  2206  and  2208 ) can rotate about pivot line  2218 . It should be noted that connecting rod  2212  and hinge span  2210  can pivot independent of each other. The pivoting can occur at the same time or at different times giving pivoting assembly  2204  at least four independent directions of axial rotation. 
     In order to prevent metal on metal contact when hinge span  2210  is magnetically coupled to tablet  1100 , label  2220  can be affixed to an external surface of hinge span  2210  and bumpers  2222  can be affixed to an external surface of end lugs  2206  and  2208 . Label  2220  and bumper  2222  can be formed of material that can undergo repeated contact with housing  102  without marring or otherwise damaging the appearance of housing  102 . Accordingly, label  2220  and bumpers  2222  can be formed of paper, cloth, plastic and adhered to hinge span  2210  and end lugs  2206  and  2208  using an adhesive such as glue. In some cases, the adhesive can have properties that allow for easy replacement of label  2220  and/or bumpers  2222  when needed. 
       FIG. 28B  shows an assembled embodiment of pivoting assembly  2204  showing pivot line  2216  about which end lugs  2206 ,  2208  and connecting rod  2212  (in sleeve  2214 ) can rotate in two axial directions (i.e., clockwise and counter-clockwise). It should be noted that end lugs  2206 ,  2208  and hinge span  2210  can rotate in two axial directions (i.e., clockwise and counter-clockwise) with respect to pivot line  2218 . In this way, end lugs  2206  and  2208  can rotate about pivot line  2216  and pivot line  2218  with a total of four axial directions. 
       FIG. 28C  shows hinge span  2210  illustrating in more detail end pins  2224  and  2226  that can be used to mount hinge span  2210  into end lug  2206  and end lug  2208 , respectively. Although not viewable in this figure, end pins  2224  and  2226  can further be used in conjunction with internal plugs to secure end unit magnetic elements incorporated within hinge span  2210 . This is particularly useful in those situations where the coded magnetic sequence of the magnetic elements incorporated within hinge span  2210  causes the end unit magnetic elements to magnetically repel an adjacent neighbor magnetic element. 
       FIG. 28D  shows an exploded view of hinge span  2210  in accordance with the described embodiments. Magnetic elements  2228  can be configured as a coded magnetic structure in which individual magnetic elements can be arranged in a specific pattern of magnetic polarity, strength, size and so forth. In the embodiment shown, those magnets next to each other having anti-aligned polarity can rely upon their mutual magnetic attraction to maintain their position with the coded magnetic structure. However, magnetic elements placed next to each other having aligned magnetic polarity can require an external force to overcome the mutual magnetic repulsive force in order to maintain their position within the coded magnetic structure. For example, magnetic element  2228 - 1  and  2228 - 2  can each be formed of two magnets having aligned magnetic poles. In this situation, each of the two magnets that form magnetic element  2228 - 1  (and  2228 - 2 ), for example, will have magnetic poles that are aligned and therefore will generate a net magnetic repulsive force between them. Therefore, an externally applied constraint can be applied using, for example, plugs  2232 - 1  and  2232 - 2 , respectively. The magnetic attractive force provided by magnets  2228 - 3  and  2228 - 4  (that are anti-aligned with respect to magnets  2228 - 1  and  2228 - 2 , respectively) can help in stabilizing the coded magnetic structure enclosed within hinge span  2210 . Spacer  2234  formed of magnetically inert material can be used to provide additional physical integrity to the coded magnetic structure formed by magnetic elements  2228 . 
     In order to improve an overall net magnetic attractive force, magnetic shunt  2236  formed of magnetically active material such as steel, can be adhesively attached to a back end of magnetic elements  2228 . The back end placement of shunt  2236  can help to re-direct magnetic field lines that would otherwise propagate away from the engagement surface between hinge span  2210  and housing  1102 . By deflecting the magnetic field lines back towards the engagement surface, the magnetic flux density provided by magnetic elements  2228  at the engagement surface can be commensurably increased resulting in an increased net magnetic attractive force between magnetic elements  2228  and the corresponding magnetic components within housing  1102 . 
     As discussed previously, label  2220  can be adhesively attached to magnetic elements  2228  (and spacer  2234 , if present) which can, in turn, be adhesively attached to magnetic shunt  2236 . Magnetic shunt  2236  can be adhesively attached to opening  2238  in hinge span  2210  leaving label  2220  proud by about a distance “d” which can be on the order of about 0.1-0.2 mm preventing metal to metal contact between hinge span  2210  and housing  1102 . 
     It should be noted that in the keyboard arrangement and display arrangement, hinge span  2210  can experience a shearing force due to the placement of tablet device  1100  on a supporting surface at an angle. The shearing force can be resisted by the net magnetic attractive force generated between hinge span  2210  and the device attachment feature tablet device  1100 . 
       FIG. 29  shows an exploded view of segmented cover  2202 . Bottom layer  2250  can come in direct contact with a protected surface such as a cover glass for a display. Bottom layer  2250  can be formed of a material that can passively clean the protected surface. The material can be, for example, a microfiber material. Bottom layer  2250  can be attached to stiffening layer  2252  formed of resilient material such as plastic. Stiffening layer  2252  can, in turn, be adhesively attached to inserts  2254  to form a laminate structure including adhesive layer  2256 , laminate material  2258  and insert  2254 . Some of inserts  2254  can accommodate embedded components. For example, insert  2254 - 1  can accommodate magnets  2260  some of which can cooperate with corresponding attachment feature  110  embedded in tablet device  1100  for securing segmented cover  2202  to tablet device  1100 . At least one magnet  2260 - 1  can be positioned and sized to interact with a magnetically sensitive circuit (such as a Hall Effect sensor) incorporated within tablet device  1100 . It should be noted that whereas some of magnets  2260  are specifically allocated to interact only with attachment feature  110 , substantially all of magnets  2260  can magnetically interact with magnetically active plate  2262  embedded in segment  2254 - 2  used to form various triangular support structures. In this way, a strong magnetic force can be generated providing a stable foundation for the triangular support structure. 
     An additional laminate structure can be formed of adhesive layer(s)  2256 , laminate material  2258  and top layer  2264 . In some embodiments, an intervening layer of material can be provided having a knitted structure that can aid in the attachment of top layer  2264 . Top layer  2264  can be formed of many materials such as plastic, leather, and so forth in keeping with the overall look and feel of tablet device  1100 . In order to provide additional structural support, top layer  2264  can have edges reinforced by reinforcement bars  2266  that can be formed of plastic or other rigid or semi-rigid material. 
       FIG. 30  shows a partial cross sectional view of segmented cover  2200  shown in  FIG. 29  placed in position upon cover layer  1106  of tablet device  1100 . Of particular note is the relative positioning of magnet  2260 - 1  and Hall Effect sensor  118 . In this way, when segmented cover  2200  is placed upon cover layer  1106 , the magnetic field from magnet  2260 - 1  can interact with Hall Effect sensor  118  that can respond by generating a signal. The signal can, in turn, be processed in such a way that the operating state of tablet device  1100  can change in accordance with the presence of cover  2200 . On the other hand, the removal of cover  2200  can cause the operating state to revert to the previous operating state, or another operating state such as peek mode. It should be noted that the magnetic field density between magnetic element  2260 - 1  and Hall Effect sensor  118  can be on the order of about 500 gauss. However, in those embodiments where cover  2202  is flipped over to the back of housing  1102 , the magnetic flux density at Hall Effect sensor  118  can be on the order of about 5 Gauss. 
       FIG. 31A  shows cross sectional view of hinge span  2210  in active engagement with device attachment feature  2300  incorporated into tablet device  1100 . In particular, magnetic attachment feature  2300  includes at least magnetic element  2302  forming a magnetic circuit with magnetic element  2228  (which is part of the coded magnetic structure incorporated into hinge span  2210 ). Magnetic shunt  2304  can be used to re-direct magnetic field lines that propagate from magnetic element  2302  in a direction other than that of magnetic element  2228 . In this way, the magnetic flux density at engagement surface  2306  can be commensurably increased thereby increasing net magnetic attractive force F net . Magnetic attachment feature  2300  can be incorporated into barrel  2308  in housing  1102  sized to accommodate both magnetic element  2302  and shunt  2304 . In the described embodiment, barrel  2308  can provide support for magnetic element  2302  and shunt  2304 . Barrel  2308  can also direct the motion of magnetic element  2302  and shunt  2304  when magnetic attachment feature  2300  transitions between the active state and the inactive states. 
     In order to ensure that net attractive force F NET  is applied substantially normal to engagement surface  2306 , the magnetization of magnetic element  2228  and magnet element  2302  can be configured such that their respective magnetization vectors M substantially align. By magnetization it is meant that the magnets can be manufactured having magnetic domains that are substantially aligned in the same direction. By aligning the magnetization vectors M 1  and M 2  of magnetic element  2302  and magnetic element  2228 , respectively, net magnetic force F NET  can be generated substantially normal to engagement surface  2306 . 
       FIG. 31B  shows magnetic attachment feature  2300  in an inactive state. When in the inactive state, magnetic attachment feature  2300  is located at least distance x 0  from exterior surface of housing  1102  in order to satisfy Eq. (1). Therefore, barrel  2308  must be able to accommodate the movement of magnetic element  2302  and shunt  2304  from x=0 in the inactive state to about x=x 0  in the active state. 
       FIG. 32  shows a representation of an embodiment of device attachment feature  108  in the form of attachment feature  2400 . In particular, attachment  2400  can include magnetic elements  2402 /shunt  2404  in attached to leaf spring  2406 . Leaf spring  2406  can be secured directly to shunt  2404  by way of fasteners  2408  and end supports  2410  by way of fasteners  2412 . End supports  2410  can be attached to a support structure such as a housing to provide support for attachment feature  2400 . In one embodiment, alignment posts  2414  can be used during assembly to provide alignment for both end supports  2410  and leaf spring  2406 .  FIG. 33  shows a close up view of the support structure  2410 /leaf spring  2406  interface. 
       FIG. 34  shows a flowchart detailing a process  2500  in accordance with the described embodiments. The process can begin at  2502  by providing a first coded magnetic attachment feature in an inactive state. At  2504 , using a second magnetic attachment feature to activate the first coded first magnetic attachment feature. At  2506 , causing a magnetic field from the activated first magnetic attachment feature to interact with a magnetic field from the second magnetic attachment feature. At  2508 , generating a net magnetic attachment force in accordance with the interaction of the magnetic fields. At  2510 , magnetically binding the first and second magnetic attachment features in accordance with the net magnetic attachment force. 
       FIG. 35  shows a flowchart detailing process  2600  in accordance with the described embodiments. Process  2600  can begin at  2602  by providing a coded magnetic attachment feature in an inactive state. In the inactive state, magnetic flux density at a pre-determined distance for magnetic elements in the coded magnetic attachment feature is less than a threshold value. At  2604 , an external magnetic field is received at the coded magnetic attachment feature. At  2606 , if it is determined that the external magnetic field corresponds to magnetic elements that correlate with the magnetic elements in the coded magnetic attachment feature, then at  2608 , the coded magnetic attachment feature is activated, otherwise, process  2600  ends. 
       FIG. 36  shows a flowchart detailing process  2700  in accordance with the described embodiments. Process  2700  can begin at  2702  by placing an electronic device having a first and an accessory having second coded magnetic attachment features in proximity to each other. At  2704 , if the magnetic elements in the first and second coded magnetic attachment features correlate with each other, then at  2706 , the first coded magnetic attachment feature is activated. When the first coded magnetic attachment feature is activated, then a magnetic flux density of a magnetic field generated by the first coded magnetic attachment feature increases to a value above a threshold. The magnetic field interaction between the magnetic elements in the first and second magnetic attachment features cause the electronic device and accessory to magnetically attach to each other at  2708 . 
       FIG. 37  shows a flowchart detailing a peek mode process  2800  in accordance with the described embodiments. Process  2800  can begin at  2802  by determining if a first portion of a display is uncovered. By uncovered it is meant that visual content presented at the first portion can be viewed. When it is determined that the first portion of the display is uncovered, then at  2804 , only that portion of the display that is determined to be uncovered can present visual content. In other words, a set of icons or other visual content can be displayed in the uncovered portion of the display, where the remainder of the display can remain blank or off. Next at  2806 , visual content is displayed by the activated portion of the display. Next at  2808 , a determination is made if a second portion of the display is uncovered, the second portion being different than the first portion. When it is determined that the second portion of the display is uncovered, then a second portion of the display is activated at  2810 . Visual content is then displayed at the second activated portion at  2812 . 
       FIG. 38  shows a flowchart detailing process  2900  for forming a magnetic stack incorporated into hinge span  1340  in accordance with the described embodiments. Process  2900  for forming the magnetic stack incorporated into hinge span  1340  can begin at  2902  by providing a fixture. The fixture having a shape in accordance with an exterior shape of the housing that defines the electronic device upon which the hinge span will magnetically attach. The fixture can also be connected to a vacuum source that can be used to subsequently secure a protective film at  2904 . The protective film can be used to provide protection against metal to metal contact between the hinge span and the housing of the electronic device. The protective film (also referred to as a label) can be formed of resilient material and have a length consistent with that of the hinge span. Once the label has been secured to the fixture using the vacuum, the label conforms to the contour of the fixture, and thus the shape of the housing of the electronic device. 
     At  2906 , a magnet is attached to the label at a first surface shaped to conform to the fixture (and the housing). In one embodiment, the label and magnet can be glued to each other using adhesive. In another embodiment, the label can have an adhesive inner layer impregnated with glue that can attach the label to the magnet upon curing. At  2908 , a magnetic shunt is glued to the magnet and label assembly. The magnetic shunt can be formed of magnetically active material such as steel. The magnetic shunt can interact with those magnetic field lines from the magnet initially directed away from the engagement surface between the housing and the hinge span. The magnetic shunt can interact with the magnetic field lines by re-directing at least some of the magnetic field lines in a direction towards the magnet and the engagement surface. The re-directed magnetic field lines can increase the magnetic flux density at the engagement surface thereby increasing the net attractive magnetic force between magnetic elements in the electronic device and the hinge span. 
     At  2910 , a hinge span enclosure can be glued to the magnetic shunt. The hinge span enclosure can be used to support and protect the magnetic elements used to magnetically attach the hinge span to the electronic device. It should be noted that the after the attachment of the hinge span enclosure, the label is proud of the hinge span enclosure by which it is meant that the label protrudes a distance “d” from the hinge span enclosure. In this way, there is no contact between the metal hinge span enclosure and the metal housing of the electronic device. 
       FIG. 39  shows a flowchart detailing process  3000  for determining a configuration of magnetic elements in a magnetic stack used in a magnetic attachment system in accordance with the described embodiments. Process  3000  begins at  3002  by providing a first plurality of magnetic elements in accordance with a first configuration. At  3004 , a second plurality of magnetic elements in accordance with a second configuration is provided. By first and second configuration, what is meant is that the first and second plurality of magnetic elements can be arranged in any manner deemed appropriate. For example, the first and second configuration can relate to a physical size, a magnetic polarity, a magnetic strength, a relative position with respect to other magnetic elements, and so on. Next, at  3006 , a net magnetic force is created in one embodiment by positioning each of the first and second plurality of magnetic elements with respect to each other. In so doing, those corresponding magnetic elements having the same polarity will generate a negative (repulsive) magnetic force whereas those corresponding magnetic elements having opposite polarities will generate a positive (attractive) magnetic force. At  3008 , a total value of the net magnetic force for each of the corresponding one of the first and second plurality of magnetic elements is determined. As mentioned above, since some magnetic elements can generate a negative magnetic force whereas others a positive magnetic force for the same position, the total value of the net magnetic force can be either positive, negative, or zero (indicating the positive and negative magnetic forces cancel each other out to give no overall net magnetic force). 
     At  3010 , a difference between a global maximum net total magnetic force and first local maximum net total magnetic force is determined. For example, as shown in  FIG. 13 , the global maximum corresponds with a total net magnetic force of about 8 A (“A” being a unit magnetic attractive force where “8 A” is equivalent to “+8” where “+” indicates attractive force). Moreover, a first local maximum net total value is about 4A and a second local maximum net total value is about 1A. In order to avoid a “false activation” that can result in a weak magnetic attraction, the difference between the global maximum net total magnetic force and the first local maximum net total magnetic force can indicate a probability that the magnetic attachment system will equilibrate at the global maximum net total magnetic force (representing the strongest net magnetic attraction) and the first local maximum net total magnetic force (representing a weak net magnetic attraction). 
     Therefore, if at  3012 , the difference is acceptable (meaning that the global maximum is the likely equilibrium point), then process  3000  stops, otherwise, the configuration of magnetic elements is changed at  3014  and control is passed directly to  3006  for further evaluation. 
       FIG. 40  is a block diagram of an arrangement  3100  of functional modules utilized by an electronic device. The electronic device can, for example, be tablet device  1100 . The arrangement  3100  includes an electronic device  3102  that is able to output media for a user of the portable media device but also store and retrieve data with respect to data storage  3104 . The arrangement  3100  also includes a graphical user interface (GUI) manager  3106 . The GUI manager  3106  operates to control information being provided to and displayed on a display device. The arrangement  3100  also includes a communication module  3108  that facilitates communication between the portable media device and an accessory device. Still further, the arrangement  3100  includes an accessory manager  3110  that operates to authenticate and acquire data from an accessory device that can be coupled to the portable media device. 
       FIG. 41  is a block diagram of an electronic device  3150  suitable for use with the described embodiments. The electronic device  3150  illustrates circuitry of a representative computing device. The electronic device  3150  includes a processor  3152  that pertains to a microprocessor or controller for controlling the overall operation of the electronic device  3150 . The electronic device  3150  stores media data pertaining to media items in a file system  3154  and a cache  3156 . The file system  3154  is, typically, a storage disk or a plurality of disks. The file system  3154  typically provides high capacity storage capability for the electronic device  3150 . However, since the access time to the file system  3154  is relatively slow, the electronic device  3150  can also include a cache  3156 . The cache  3156  is, for example, Random-Access Memory (RAM) provided by semiconductor memory. The relative access time to the cache  3156  is substantially shorter than for the file system  3154 . However, the cache  3156  does not have the large storage capacity of the file system  3154 . Further, the file system  3154 , when active, consumes more power than does the cache  3156 . The power consumption is often a concern when the electronic device  3150  is a portable media device that is powered by a battery  3174 . The electronic device  3150  can also include a RAM  3170  and a Read-Only Memory (ROM)  3172 . The ROM  3172  can store programs, utilities or processes to be executed in a non-volatile manner. The RAM  3170  provides volatile data storage, such as for the cache  3156 . 
     The electronic device  3150  also includes a user input device  3158  that allows a user of the electronic device  3150  to interact with the electronic device  3150 . For example, the user input device  3158  can take a variety of forms, such as a button, keypad, dial, touch screen, audio input interface, visual/image capture input interface, input in the form of sensor data, etc. Still further, the electronic device  3150  includes a display  3160  (screen display) that can be controlled by the processor  3152  to display information to the user. A data bus  3166  can facilitate data transfer between at least the file system  3154 , the cache  3156 , the processor  3152 , and the CODEC  3163 . 
     In one embodiment, the electronic device  3150  serves to store a plurality of media items (e.g., songs, podcasts, etc.) in the file system  3154 . When a user desires to have the electronic device play a particular media item, a list of available media items is displayed on the display  3160 . Then, using the user input device  3158 , a user can select one of the available media items. The processor  3152 , upon receiving a selection of a particular media item, supplies the media data (e.g., audio file) for the particular media item to a coder/decoder (CODEC)  3163 . The CODEC  3163  then produces analog output signals for a speaker  3164 . The speaker  3164  can be a speaker internal to the electronic device  3150  or external to the electronic device  3150 . For example, headphones or earphones that connect to the electronic device  3150  would be considered an external speaker. 
     The electronic device  3150  also includes a network/bus interface  3161  that couples to a data link  3162 . The data link  3162  allows the electronic device  3150  to couple to a host computer or to accessory devices. The data link  3162  can be provided over a wired connection or a wireless connection. In the case of a wireless connection, the network/bus interface  3161  can include a wireless transceiver. The media items (media assets) can pertain to one or more different types of media content. In one embodiment, the media items are audio tracks (e.g., songs, audio books, and podcasts). In another embodiment, the media items are images (e.g., photos). However, in other embodiments, the media items can be any combination of audio, graphical or visual content. Sensor  3176  can take the form of circuitry for detecting any number of stimuli. For example, sensor  3176  can include a Hall Effect sensor responsive to external magnetic field, an audio sensor, a light sensor such as a photometer, and so on. 
     The magnetic attachment feature can be used to magnetically attach at least two objects. The objects can take many forms and perform many functions. When magnetically attached to each other, the objects can communicate and interact with each other to form a cooperative system. The cooperating system can perform operations and provide functions that cannot be provided by the separate objects individually. For example, at least a first object and a second object can be magnetically attached to each other such that the first object can be configured to provide a support mechanism to the second object. The support mechanism can be mechanical in nature. For example, the first object can take the form of a stand that can be used to support the second object on a working surface such as a table. In another example, the first object can take the form of a hanging apparatus. As such, the first object can be used to hang the second object that can then be used as a display for presenting visual content such as a visual, still images like a picture, art work, and so on. The support mechanism can also be used as a handle for conveniently grasping or holding the second object. This arrangement can be particularly useful when the second object can present visual content such as images (still or visual), textual (as in an e-book) or has image capture capabilities in which case the second object can be used as an image capture device such as a still or visual camera and the first object can be configured to act as a support such as a tripod or handle. 
     The described embodiments can take many forms. For example, the attachment can occur between a first and second object where the first object and second object can take the form of electronic devices. The electronic devices can be magnetically attached to each other to form a cooperative electronic system in which the electronic devices can communicate with each other. As part of this communication, information can be passed between the first and second electronic devices. The information can be processed in whole or in part at either the first or second electronic device depending upon the nature of the processing. In this way, the cooperative electronic system can take advantage of the synergistic effect of having multiple electronic devices magnetically attached and in communication with each other. In one implementation, the communication can be carried out wirelessly using any suitable wireless communication protocol such as Bluetooth (BT), GSM, CDMA, WiFi, and so on. 
     The cooperative electronic system can take the form of an array of electronic devices. In one embodiment, the array of electronic devices can act as a single unified display (along the lines of a mosaic). In another embodiment, the array of electronic devices can provide a single or a set of functions (such as virtual keyboard). In still another embodiment, at least one of the electronic devices can take the form of a power providing device that can be attached to the electronic device using the magnetic attachment feature. The power providing device can utilize a mechanical connection such as a power port, or in some cases a magnetically based charging mechanism, to provide current to the electronic device. The current can be used to charge a battery if necessary while providing power to operate the cooperative electronic system. The power provided can be passed from one device to another as in a bucket brigade to even out the power distribution and battery charge levels in the cooperative electronic system. 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a non-transitory computer readable medium. The computer readable medium is defined as any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not target to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings. 
     The advantages of the embodiments described are numerous. Different aspects, embodiments or implementations can yield one or more of the following advantages. Many features and advantages of the present embodiments are apparent from the written description and, thus, it is intended by the appended claims to cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, the embodiments should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents can be resorted to as falling within the scope of the invention.

Metadata:
Filing Date: 20170815
Publication Date: 20190319
Grant Date: 20190319
Priority Date: 20100917
Inventors: LAUDER, ANDREW D.
ROHRBACH, MATTHEW DEAN
COSTER, DANIEL J.
STRINGER, CHRISTOPHER J.
OW, FLORENCE W.
AI, JIANG
IVE, JONATHAN P.
KIBITI, ELVIS M.
TERNUS, JOHN P.
LUBNER, SEAN D.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/1662", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T24/32", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1601", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T24/32", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F7/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/0205", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1637", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "A45C11/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1637", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/0205", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "A45C11/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1662", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1601", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T24/32", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F7/04", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 43982174