Patent Publication Number: US-9424701-B2

Title: Electronic lock and key assembly

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/706,291, filed Dec. 5, 2012, which is a continuation of U.S. application Ser. No. 13/159,326, filed on Jun. 13, 2011, which is a continuation of U.S. application Ser. No. 11/855,031, filed on Sep. 13, 2007, now U.S. Pat. No. 7,958,758, which claims priority under 35 U.S.C. §119(e) from U.S. Provisional Patent Application No. 60/888,282, filed Feb. 5, 2007 and U.S. Provisional Patent Application No. 60/825,665, filed Sep. 14, 2006. The disclosures of each of the foregoing applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to lock and key assemblies. More specifically, the present invention relates to an improved electronic lock and key assembly. 
     2. Description of the Related Art 
     Electronic locks have a number of advantages over normal mechanical locks. For example, electronic locks may be encrypted so that only a key carrying the correct code will operate the lock. In addition, an electronic lock may contain a microprocessor so that, for example, a record can be kept of who has operated the lock during a certain time period or so that the lock is only operable at certain times. An electronic lock may also have the advantage that, if a key is lost, the lock may be reprogrammed to prevent the risk of a security breach and to avoid the expense associated with replacement of the entire lock. 
     One drawback of certain electronic locks is that they use a power supply to function properly. Typically, locks of this type are unable to use conventional alternating current (AC) power supplies, such as from wall outlets, due to the inherit lack of security and mobility of such power supplies. Batteries may be used instead, but batteries require constant replacement or recharging. If a battery dies, a lock might fail to function and thereby create a significant security risk. Electromagnets may also be employed, but the bulk of such devices in some instances limits the potential use of electronic locks to larger-scale applications. 
     One solution to these drawbacks is to place a power source such as a battery in the key instead of in the lock. This arrangement allows the lock to remain locked even in the absence of a power supply. Placing a battery in the key also allows the battery to be charged more easily because keys are generally more portable than locks. 
     When batteries are used in the key, electrical contacts are typically employed to transfer power and data from the key to the lock. However, electrical contacts suffer from the drawback of being susceptible to corrosion, potentially leading to failure of either the key or the lock. Moreover, if separate inductors are used instead to transfer both power and data, magnetic interference between the inductors can corrupt the data and disrupt power flow to the lock. 
     SUMMARY OF THE INVENTION 
     Various embodiments of the present invention overcome these problems by providing a key having a power coil and a data coil and an electronic lock having a power coil and a data coil. When the key engages the lock, the power coils preferably are coaxial and the data coils are substantially parallel to one another. This configuration allows at least a portion of a magnetic field induced by the power coils to be substantially orthogonal to a magnetic field induced by the data coils. Because orthogonal magnetic fields have little effect on one another, inductors or other coils may be used in place of electrical contacts with minimal interference between power and data signals. 
     A preferred embodiment is, a locking device including a key which includes a key power coil and a key data coil. The locking device also includes an electronically-actuatable lock which includes a lock power coil and a lock data coil. The key power coil and the lock power coil are coaxial and at least partially overlap one another when the key engages the lock. The key data coil lies in a first plane, the lock data coil lies in a second plane. The first plane and the second plane are substantially parallel to one another. 
     Another preferred embodiment is a locking device including a key which includes a key power coil and a key data coil. The locking device also includes an electronically-actuatable lock which includes a lock power coil and a lock data coil. The key power coil and the lock power coil are inductively coupled when the key engages the lock. The key data coil and the lock data coil are inductively coupled when the key engages the lock. At least a portion of a data magnetic field created by inductively coupling the lock data coil and the key data coil is substantially orthogonal to a power coil magnetic field created by inductively coupling the lock power coil and the key power coil. 
     Yet another preferred embodiment is a method for communicating with an electronic lock. The method includes inductively coupling a key power coil with a lock power coil. The method also includes inductively coupling a key data coil with a lock data coil, such that at least a portion of a power magnetic field generated by inductive coupling of the key power coil and the lock power coil is substantially orthogonal to at least a portion of a data magnetic field generated by inductive coupling of the key data coil and the lock data coil. The method further includes transmitting data between the key data coil and the lock data coil. The data is operative to move a lock to an unlocked position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects and advantages of the present electronic lock and key assembly are described below with reference to drawings of certain embodiments, which are intended to illustrate, but not to limit, the present invention. The drawings contain twelve (12) figures. 
         FIG. 1  is a side view of an electronic lock and key assembly with certain features, aspects and advantages of the present invention. 
         FIG. 2  is a perspective view of the electronic lock and key assembly of  FIG. 1 . 
         FIG. 3  is a cross-sectional side view of the lock of  FIG. 1  in the locked position. 
         FIG. 4  is a cross-sectional side view of the lock of  FIG. 1  in the unlocked position. 
         FIG. 5  is a cross-sectional side view of the key of  FIG. 1 . 
         FIG. 6  is a perspective view of the key of  FIG. 1  sectioned along a vertical plane extending through a longitudinal axis of the key. 
         FIG. 7  is a perspective view of the key of  FIG. 1  sectioned along a vertical plane extending through an intermediate portion of the key and generally normal to the longitudinal axis. 
         FIG. 8  is a cross-sectional side view of the lock and key assembly of  FIG. 1  in a coupled position wherein a male probe of the key is inserted into a female receptacle of the lock. 
         FIG. 9  is a cross-sectional side view diagram of magnetic fields in accordance with certain embodiments of the present invention. 
         FIG. 10  is an exemplary block diagram of circuit components in accordance with certain embodiments of the present invention. 
         FIGS. 11A-1 and 11A-2  illustrate an exemplary schematic diagram of circuit components in accordance with certain embodiments of the present invention 
         FIGS. 11B-1 and 11B-2  illustrate an exemplary schematic diagram of circuit components in accordance with certain embodiments of the present invention. 
         FIGS. 12-1 and 12-2  depict still another exemplary schematic diagram of circuit components in accordance with certain embodiments of the present invention. 
         FIGS. 13A-1 and 13A-2  illustrate an exemplary schematic diagram of circuit components in accordance with certain embodiments of the present invention. 
         FIGS. 13B-1 and 13B-2  illustrate an exemplary schematic diagram of circuit components in accordance with certain embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the description below certain relative terms such as top, bottom, left, right, front and back are used to describe the relationship between certain components or features of the illustrated embodiments. Such relative terms are provided as a matter of convenience in describing the illustrated embodiments and are not intended to limit the scope of the technology discussed below. 
     Overview of the Key and Lock System 
       FIGS. 1 and 2  illustrate one preferred embodiment of an electronic lock and key system, which is generally referred to by the reference numeral  10 . The electronic lock and key system  10  includes a lock  100  and a key  200 , which are configured to engage one another and to selectively move the key  200  between a locked position and an unlocked position. The lock and key system  10  may be used to permit access to a location or enclosure in a variety of applications, such as a cabinet or other such storage compartment, for example, which may store valuable contents. Certain features, aspects and advantages of the lock and key system  10  may be applied to other types of lock applications, such as selectively permitting access to buildings or automobiles, for example, or for selectively permitting operation of a device. Thus, although the present lock and key system  10  is disclosed herein in the context of a cabinet or storage compartment application, the technology disclosed herein may be used with, or adapted for use with, other suitable lock applications, as well. 
     The illustrated electronic lock and key system  10  is configured to use electronic means to verify the identity of the key and to actuate the internal mechanism of the lock  100 . When the key  200  engages the lock  100 , data transfer and power transfer is enabled between the lock  100  and the key  200 . The lock  100  is then preferably permitted to be actuated by the key  200  to move from a locked position to an unlocked position and permit access to the space or location secured by the lock  100 . In the illustrated arrangement, the direction of power transfer preferably is from the key  200  to the lock  100 , as is described in greater detail below. However, in alternative arrangements, the direction of power transfer may be reversed or may occur in both directions. 
     The illustrated lock  100  is preferably used in a cabinet, or other such storage compartment, and is configured to selectively secure a drawer or door of the cabinet relative to a body of the cabinet. However, as will be appreciated, the lock  100  may be used in, or adapted for use in, a variety of other applications. The lock  100  is preferably mounted to the cabinet in such a way so as to allow only a front portion of the lock  100  to be accessible when the cabinet is closed. The lock  100  includes an outer housing  102  with a cylinder  104  that is rotatable within the outer housing  102  when actuated by the key  200 . An exposed end of the cylinder  104  is configured to support a lock tab (not shown). The lock tab is configured to cooperate with a stop. The lock  100  is associated with one of the drawer (or door) of the cabinet and the cabinet body, and the stop is associated with the other of the drawer (or door) of the cabinet and the cabinet body. The lock tab rotates with the lock cylinder  104  to move between a locked position, wherein the lock tab mechanically interferes with the stop, to an unlocked position, wherein the lock tab does not interfere with the stop. Such an arrangement is well-known to one of skill in the art. In addition, other suitable locking arrangements may be utilized. 
     Mechanical Aspects of the Key and Lock System 
       FIGS. 3 and 4  illustrate a cross-sectional view of the lock  100  of the electronic lock and key assembly  10  of  FIGS. 1 and 2 . With additional reference to the  FIGS. 3 and 4 , the portion of the lock  100  on the left hand side of the FIGS. will be referred to as the front of the lock and the portion on the right hand side of the FIGS. will be referred to as the rear or back of the lock  100 . As described above, the lock  100  includes the housing  102  and the cylinder  104 . The cylinder  104  is configured to be rotatable within the housing  102  by the key  200  when the lock  100  and the key  200  are properly engaged. The lock  100  further includes a cartridge  106 , which includes a mechanism configured to selectively permit the cylinder  104  to rotate within the housing  102 . The lock  100  further includes a mating portion  108  which is configured to mate with the key  200  and an attack guard portion  110  which is configured to protect the lock from unwanted tampering. 
     The housing  102  of the lock  100  preferably is a generally cylindrical tube with a head portion  112  and a body portion  114 . The diameter of the head portion  112  is larger than the diameter of the body portion  114  such that the head portion  112  forms a flange of the housing  102 . The head portion  112  also includes an annular groove  174  or key recess. Axially-extending slots  176  open into the annular groove  174  ( FIG. 2 ). The groove  174  and slots  176  are used in engaging the key  200  with the lock  100  and are described in greater detail below. The head portion  112  is further configured to house a seal member, such as an O-ring  116 , which is positioned to create a seal between the housing  102  and the cylinder  104 . Thus, the lock  100  is suitable for use in wet environments. 
     The lock housing  102  also includes a body portion  114  which extends rearwardly away from the head portion  112 . The rearward end of the body portion further includes a threaded outer surface  115  which is configured to receive a nut (not shown). The nut is used to secure the lock  100  to a cabinet or other storage compartment. The body portion  114  also includes at least one, and preferably a pair of opposed flattened surfaces  113  or “flats” ( FIG. 2 , only one shown), which are provided to reduce the likelihood of rotation of the housing  102  in a storage container wall or door. Alternatively, other mechanisms may be used to inhibit rotation of the housing  102  other than the flattened surfaces  113 , as will be apparent to one of skill in the art. 
     With continued reference to  FIGS. 3 and 4 , the body portion  114  further includes an internal groove  120  configured to secure the lock cylinder  104  from rotation relative to the lock housing  112  when the lock  100  is in a locked position. The groove  120  preferably is open towards an interior passage  121  of the body portion  114 , which houses a portion of the lock cylinder  104 . The groove  120  extends axially along the body portion  114  and is formed partially through a thickness of the body portion  114  in a radial direction. 
     The body portion  114  further includes a tab  122  that extends slightly rearward from the rearward end of the body portion  114 . The tab  122  acts as a stop to limit the rotation of a lock tab (not shown) secured to the cylinder  104 . 
     The housing  102  is further configured to include a break-away feature incorporated into the structure of the housing  102 . The head portion  112  is formed with the body portion  114  in such a way that if someone attempted to twist the housing  102  of the lock  100  by grasping the head portion  112 , the head portion  112  is capable of breaking free of the body portion  114 , preferably at a location near the intersection of the head portion  112  and the body portion  114  of the housing  102 . This feature is advantageous in that it increases the difficulty of opening or disabling the lock  100  by grasping the housing  102 . That is, if a person were to attempt to grasp the head portion  112  and it were to break away then there would no longer be an easily graspable surface with which to try to rotate the lock  100  mechanically, without use of the key  200 , because the head portion  112 , which is external to the cabinet, would no longer be coupled to the body portion  114 , which is internal to the cabinet. The break-away feature between the head portion  112  and the body portion  114  may be created simply by a structure that concentrates stresses at the head portion  112 /body portion  114  junction. Alternatively, the housing  102  may be deliberately weakened at or near the head portion  112 /body portion  114  junction, or at any other desirably or suitable location. Other anti-tampering solutions apparent to one of skill in the art may be employed as well. 
     With continued reference to  FIGS. 3 and 4 , as described above, the lock cylinder  104  includes a portion referred to as the cartridge  106 . The cartridge  106  includes a solenoid  126  with two adjacent slide bars  128 . The slide bars  128  are spaced on opposing sides of the solenoid  126  and are configured to magnetically attract to the solenoid  126  when the lock  100  is in the locked position. The slide bars  128  preferably are constructed with a neodymium-containing material, which may be encapsulated in a stainless steel material for corrosion protection and wear resistance. When the lock  100  is moved to an unlocked position, the solenoid  126  is configured to reverse polarity such that the slide bars  128  are magnetically repelled from the solenoid  126 , as is described in greater detail below. Preferably, the slide bars  128  are movable along an axis that is parallel to (which includes coaxial with) a longitudinal axis of the lock  100 . 
     The cartridge  106  is surrounded by a tamper-resistant case  124  that houses a circuit board  134  configured to receive instructions when the key  200  engages with the lock  100 . The circuit board  134  is configured to recognize the proper protocol required to unlock the lock  100 . The circuit board  134  is further configured to actuate the solenoid  126  to reverse the polarity of the solenoid  126  and repel the slide bars  128  away from the solenoid  126 . The details of the circuit board  134  and a preferred method of communication between the key  200  and the lock  100  are discussed in greater detail below. The interior of the case  124  preferably is filled with a filler material, such as an epoxy, to occupy empty space within the case  124  and protect and maintain a desired position of the components within the case  124 , such as the circuit board  134  and wires  160 . 
     The lock cartridge  106  further includes two slide tubes  136  which are positioned on opposite sides of the solenoid  126  and are configured to at least partially encapsulate the slide bars  128  and are further configured to provide a smooth, sliding surface for the slide bars  128 . The slide tubes  136  each include an aperture  138  configured to receive at least a portion of a bolt  130 , or side bar, of the lock  100  when the lock  100  is in an unlocked position. 
     The bolt  130  is preferably a relatively thin, generally block-shaped structure that is movable between a locked position, in which rotation of the lock cylinder  104  relative to the housing  102  is prohibited, and an unlocked position, in which rotation of the lock cylinder  104  relative to the housing  102  is permitted. Preferably, the bolt  130  moves in a radial direction between the locked position and the unlocked position, with the unlocked position being radially inward of the locked position. 
     The bolt  130  includes two cylindrical extensions  131 , which extend radially inward toward the cartridge  106 . When the solenoid  126  is actuated to repel the slide bars  128  such that the apertures  138  are not blocked by the slide bars  128 , the extensions  131  of the bolt  130  may enter into the case  124  through the apertures  138  as the bolt  130  moves radially inward. 
     The bolt  130  is preferably of sufficient strength to rotationally secure the cylinder  104  relative to the housing  102  when the bolt  130  is in the locked position, wherein a portion of the bolt  130  is present within the groove  120 . The bolt  130  has a sloped or chamfered lower edge  129 , which in the illustrated embodiment is substantially V-shaped. The lower edge  129  is configured to mate with the groove  120 , which preferably is of an at least substantially correspondingly shape to the lower edge  129  of the bolt  130 . The V-shaped edge  129  of the bolt  130  interacting with the V-shaped groove  120  of the housing  102  urges the bolt  130  in a radially inward direction towards the cartridge  106  in response to rotation of the cylinder  104  relative to the housing  102 . That is, the sloped lower edge  129  and groove  120  cooperate to function as a wedge and eliminate the need for a mechanism to positively retract the bolt  130  from the groove  120 . Such an arrangement is preferred at least in part due to its simplicity and reduction in the number of necessary parts. However, other suitable arrangements to lock and unlock the cylinder  104  relative to the housing  102  may also be used. 
     When the lock  100  is in an unlocked condition and the slide bars  128  are spaced from the solenoid  126 , as shown in  FIG. 4 , the bolt  130  is free to move radially inward (or upward in the orientation of  FIG. 4 ) into the cartridge  106 , thus allowing the cylinder  104  to rotate within the housing  102 . Preferably, one or more biasing members, such as springs, tend to urge the bolt  130  toward a locked position. In the illustrated arrangement, two springs  132  are provided to produce such a biasing force on the bolt  130 . 
     When the lock  100  is in a locked condition, the bolt  130  is extended radially outward into engagement with the groove  120 . The bolt  130  is prevented from inward movement out of engagement with the groove  120  due to interference between the extensions  131  and the slide bars  128 . When the lock  100  is in the unlocked position, the slide bars  128  are moved away from the solenoid  126  due to a switching of magnetic polarity of the solenoid  126 , which is actuated by the circuit board  134 . The bolt  130  is then free to move radially inward towards the center of the cylinder  104  and out of engagement with the groove  120 . At this point, the rotation of the cylinder  104  within the housing  102  may cause the bolt  130  to be displaced from engagement with the groove  120  due to the cooperating sloped surfaces of the groove  120  and the lower edge  129  of the bolt  130 . The cylinder  104  is then free to be rotated throughout the unlocked rotational range within the housing  102 . When the cylinder  104  is rotated back to a locked position, that is, when the lower edge  129  of the bolt  130  is aligned with the groove  120 , the bolt  130  is urged radially outward by the springs  132  such that the lower edge  129  is engaged with the groove  120 . Once the extensions  131  of the bolt  130  are retracted from the case  124  to a sufficient extent, the slide bars  128  are able to move towards the solenoid  126  to once again establish the locked position of the lock  100 . 
     Although  FIG. 3  and  FIG. 4  show a housing  102  with only one groove  120 , it will be appreciated by one skilled in the art that multiple grooves  120  may be provided within the housing  102 . Such a configuration may be advantageous in that multiple bolts  130  may be provided, or if it is desirable to have multiple locked positions using a single bolt  130  interacting with one of several available grooves  120 . 
     With continued reference to  FIGS. 3 and 4 , the lock  100  further includes an attack guard portion  110  configured to inhibit access to the cartridge  106  such as by drilling, for example, from the exposed portions of the lock, such as the head portion  112 . The illustrated attack guard portion  110  includes a radial array of pins  140  and an attack ball  142 , which are located along the longitudinal axis of the lock  100  between the mating portion  108  and the cartridge  106 . In the illustrated arrangement, the attack ball  142  is generally centered relative to the longitudinal axis of the lock  100  and is surrounded by the pins  140 . 
     The pins  140  are preferably made from a carbide material, but can be made of any suitable material or combination of materials that are capable of providing a suitable hardness to reduce the likelihood of successful drilling past the pins  140  and attack ball  142 . The pins  140  are inserted into the cylinder  104  to a depth that is near the outer extremity of the attack ball  142 . It is preferred that a small space is provided between the outer end of the attack ball  142  and the end of the carbide pin  140  to allow for the passage of the wires  160 , which is discussed in greater detail below. The pins  140  are provided so as to add strength and hardness to the outer periphery of the cylinder  104  adjacent to the attack ball  142 . 
     The attack ball  142  is preferably made of a ceramic material but, similar to the carbide pins, can be made of any suitable material that is of sufficient hardness to reduce the likelihood of successful drilling of the lock cylinder  104 . The attack ball  142  is preferably generally spherical shape and lies within a pocket on substantially the same axis as the cartridge  106 . Preferably, the attack ball  142  is located in front of the cartridge  106  and is aligned along the longitudinal axis of the lock  100  with the pins  140 . The attack ball  142  is configured to reduce the likelihood of a drill bit passing through the cylinder and drilling out the cartridge  106 . It is preferable that if an attempt is made to drill out the cylinder  104 , the attack ball  142  is sufficiently hard as to not allow the drill bit to drill past the ball  142  and into the cartridge  106 . The shape of the attack ball  142  is also advantageous in that it will likely deflect a drill bit from drilling into the cartridge  104  by not allowing the tip of the drill bit to locate centrally relative to the lock  100 . Because the attack ball  142  is held within a pocket, it advantageously retains functionality even if cracked or broken. Thus, the attack guard portion  110  is configured to substantially reduce the likelihood of success of an attempt to drill out the cartridge  106 . In addition, or in the alternative, other suitable arrangements to prevent drilling, or other destructive tampering, of the lock  100  may be used as well. 
     One advantage of using the pins  140  and the attack ball  142  is that the entire lock cylinder  104  does not have to be made of a hard material. Because the lock cylinder  104  includes many features that are formed in the material by shaping (e.g., casting or forging) or material removal (e.g., machining), it would be very difficult to manufacture a cylinder  104  entirely of a hard material such as ceramic or carbide. By using separate pins  140  and an attack ball  142 , which are made of a very hard material that is difficult to drill, the lock cylinder  104  can be easily manufactured of a material such as stainless steel which has properties that allow easier manufacture. Thus a lock cylinder can be made that is both relatively easy to manufacture, but also includes drill resistant properties. 
     With continued reference to  FIGS. 3 and 4 , the lock  100  includes a mating portion  108  located near the front portion of the lock  100 . The mating portion  108  preferably includes a mechanical mating portion  144  and a data and power mating portion  146 . The mechanical mating portion  144  includes a tapered cylindrical extension  148  that extends in a forward direction from the lock cylinder  104  and is configured to be received within a portion of the key  200  when the lock  100  and the key  200  are engaged together. At the base of the extension  148  are two recesses  150  configured to mate with two extensions, or protrusions, on the key  200 , which are described in greater detail below. The recesses  150  are configured to allow the key  200  to positively engage the cylinder  104  such that torque can be transferred from the key  200  to the cylinder  104  upon rotation of the key  200 . 
     The data and power mating portion  146  includes a mating cup  152 , a data coil  154 , and a power coil  156 . The cup  152  is configured to receive a portion of key  200  when the lock  100  and the key  200  are engaged together. The cup  152  resides at least partially in an axial recess  158  which is located in a front portion of the lock cylinder  104  and further houses the attack ball  142 . The cup is at least partially surrounded by the power coil  156 , which is configured to inductively receive power from the key  200 . The cup  152  preferably includes axial slots  161  configured to allow power to transmit through the cup  152 . 
     The data coil  154  is located towards the upper edge of the cup  152  and, preferably, lies just rearward of the forward lip of the cup  152 . The data coil  154  is generally of a torus shape and is configured to cooperate with a data coil of the key  200 , as is described in greater detail below. Two wires  160  extend from the cup  152 , through a passage  162 , and into the lock cartridge  106 . The wires  160  preferably transmit data and power from the data and power mating portion  146  to the solenoid  126  and the circuit board  134 . 
     The power coil  156  is preferably aligned with a longitudinal axis of the lock  100  so that a longitudinal axis passing through the power coil  156  is substantially parallel (or coaxial) with a longitudinal axis of the lock  100 . The data coil  154  is preferably arranged to generally lie in a plane that is orthogonal to a longitudinal axis of the lock. Such an arrangement helps to reduce magnetic interference between the transmission of power between the lock  100  and the key  200  and the transmission of data between the lock  100  and the key  200 . 
     As described above, the lock cylinder  104  is configured to support a lock tab, which interacts with a stop to inhibit opening of a cabinet drawer or door, or prevent relative movement of other structures that are secured by the lock and key system  10 . The lock cylinder  104  includes a lock tab portion  164  adapted to support a lock tab in a rotationally fixed manner relative to the lock cylinder  104 . The lock tab portion  164  includes a flatted portion  166  and a threaded portion  168 . The flatted portion  166  is configured to receive a lock tab (not shown) which can slide over lock tab portion  164  and mate with the flatted portion  166 . One or more flat surfaces, or “flats,” on the flatted portion  166  are configured to allow the transmission of torque from the cylinder  104  to the lock tab (not shown). The threaded portion  168  is configured to receive a nut (not shown), which is configured to secure the lock tab (not shown) to the cylinder  104 . 
       FIGS. 5-7  illustrate a preferred embodiment of the key  200  configured for use with the preferred lock  100  of the electronic lock and key assembly  10 . The key  200  is configured to mate with the lock  100  to permit power and data communication between the key  200  and the lock  100 . In the illustrated arrangement, the key  200  is further configured to mechanically engage the lock  100  to move the lock from a locked to an unlocked position or vise versa. 
     The key  200  includes an elongate main body section  204  that is generally rectangular in cross-sectional shape. The key  200  also includes a nose section  202  of smaller external dimensions than the body section  204 . An end section  206  closes and end portion of the body section  204  opposite the nose section  202 . The nose section  202  is configured to engage the lock  100  and the body section  204  is configured to house the internal electronics of the key  200  as well as other desirable components. The end section  206  is removable from the body section  204  to permit access to the interior of the body section  204 . 
     With continued reference to  FIGS. 5-7 , the nose section  202  includes a tapered transition portion  208  which extends between a cylindrical portion  210  of the nose section  202  and the body section  204 . The cylindrical portion  210  houses the power and data transfer portion  212  of the key  200 , which is discussed in greater detail below. 
     On the outer surface of the cylindrical portion are two radiused tabs  214  which are configured to rotationally locate the key  200  relative to the lock  100  prior to the key  200  engaging the lock  100 . The tabs  214  extend radially outward from the outer surface of the cylindrical portion  210  and, preferably, oppose one another. 
     The cylindrical portion  210  further includes two generally rectangular extensions  216  that extend axially outward and are configured to engage with the recesses  150  of the lock  100  ( FIG. 3 ) when the key  200  engages the lock  100 . The rectangular extensions  216  are configured to couple the nose section  202  of the key  200  to the lock cylinder  104  and to transmit torque from the key  200  to the cylinder  104  when the key  200  is rotated. 
     The cylindrical portion  210  comprises a recess  218  that opens to the front of the key  200 . Located within the recess  218  is the power and data transfer portion  212  of the key  200 . Preferably, the power and data transfer portion  212  is generally centrally located within the recess  218  and aligned with the longitudinal axis of the key  200 . The power and data transfer portion  212  includes a power coil  220  and a data coil  222 . The power coil  220  is generally cylindrical in shape with a slight taper along its axis. The power coil  220  is positioned forward of the data coil  222  and, preferably, remains within the recess  218  of the cylindrical portion  210 . The power coil  220  is configured to be inductively coupled with the power coil  152  of the lock  100 . The data coil  222  is generally toroidal in shape and is located at the base of the recess  218 . The data coil  222  is configured to be inductively coupled with the data coil  154  of the lock  100 , as is described in greater detail below. 
     With continued reference to  FIGS. 5-7 , in the illustrated arrangement, the nose section  202  is a separate component from the body section  204  and is connected to a forward end of the body section  204  of the key  200 . The nose section  202  mates with the body section  204  and is sealed by a suitable seal member, such as O-ring  224 , which inhibits contaminants from entering the interior of the key  200 . The nose section  202  is secured to the body section by two fastening members, such as screws  226  ( FIGS. 1 and 5 ). Similarly, the end section  206  is a separate component from the body section  204  and is coupled to a rearward end of the body section  200 . The end section is substantially sealed to the body section  204  by a suitable seal member, such as O-ring  230 , which is configured to inhibit contaminants from entering the interior of the key  200 . Thus, the key  200  preferably is suitable for use in wet environments. The end section  206  is secured to the body section  204  by a fastening member, such as screw  232 , which is configured to retain the end section  206  to the body section  204 . 
     The body section  204  includes three externally-accessible input buttons  228  extending from the body section  204  (upward in the orientation of  FIG. 5 ). The input buttons  228  are in electrical contact with a processing unit  229  of the key  200 , which preferably includes a processor and a memory. The input buttons  228  permit data to be entered into the key  200 , such as a wake-up or programming code, for example. Preferred functional features of the key  200  are described in greater detail below with reference to  FIGS. 9-12 . 
     With reference to  FIGS. 6 and 7 , the key  200  further includes a plurality of axially-extending cavities  236 . The illustrated key  200  includes four cavities  236 . The axial cavities  236  extend through at least a significant portion of the length of the body section  204  and are preferably circular in cross-sectional shape. The axial cavities  236  are adapted to house battery cells (not shown) that provide a source of power within the key  200 , which provides power to the lock  100  when the key  200  and the lock  100  are engaged. The cavities  236  are preferably arranged in a side-by-side manner and surround a longitudinal axis of the key  200 . The key  200  preferably includes a power source (discussed below) and is adapted to be rechargeable. Preferably, the key  200  includes a recharge port (not shown), which are configured to mate with an associated recharge port of a recharger (not shown) when it is desired to recharge the key  200 . 
     With reference to  FIGS. 2 and 8 , the key  200  is shown about to engage the lock  100 , and engaging the lock  100 , respectively. When the key  200  engages with the lock  100 , desirably, certain mechanical operations occur and certain electrical operations occur. When engaging the key  200  with the lock  100 , the key  200  is rotationally positioned relative to the lock  100  such that the tabs  214  of the key  200  are aligned with the slots  176  ( FIG. 2 ) of the lock  100 . The key  200  is then displaced axially such that the tabs  214  pass through the slots  176  and the cylindrical portion  210  of the key  200  is positioned within the housing  102  of the lock  100 . The key  200  is sized and shaped such that the tabs  214  are located within the annular groove  174 , which has a shape that closely matches the profile of the tabs  214 . In this relative position, the key  200  is able to rotate within the housing  100 , so long as the key  200  is a proper match for the lock  100  and the lock is moved to the unlocked position, as is described in greater detail below. 
     Furthermore, when the key  200  engages the lock  100 , the cylindrical extension  148  of the lock  100  is received within the recess  218  of the key. The recess  218  is defined by a tapered surface which closely matches a tapered outer surface of the cylindrical extension  148 . The cooperating tapered surfaces facilitate smooth engagement of the lock  100  and key  200 , while also ensuring proper alignment between the lock  100  and key  200 . Furthermore, the rectangular extensions  216  of the key  200  insert into the recesses  150  of the lock  100  to positively engage the key  200  with the lock  100  so that rotation of the key  200  results in rotation of the lock cylinder  104  within the housing  102 . 
     When the key  200  engages the lock  100 , the power coil  220  of the key  200  is aligned for inductive coupling with the power coil  156  of the lock  100 . Also, the data coil  222  of the key  200  is aligned for inductive coupling with the data coil  154  of the lock  100 . Preferably, the power coil  220  of the key  200  is inserted into the cup portion  152  of the lock  100  and thus the power coil  156  of the lock  100  and the power coil  220  of the key  200  at least partially overlap along the longitudinal axis of the lock  100  and/or key  200 . Furthermore, preferably, the data coil  154  of the lock  100  and the data coil  222  of the key  200  come into sufficient alignment for inductive coupling when the key  200  engages the lock  100 . That is, in the illustrated arrangement, when the key  200  engages the lock  100 , the data coil  222  of the key  200  and the data coil  154  of the lock  100  are positioned adjacent one another and, desirably, are substantially coaxial with one another. Furthermore, a plane which passes through the data coil  222  of the key  200  preferably is substantially parallel to a plane which passes through the data coil  154  of the lock  100 . Desirably, the spacing between the data coils  154  and  222  is within a range of about 30-40 mils (or 0.03-0.04 inches). Such an arrangement is beneficial to reduce interference between the power transfer and the data transfer between the lock  100  and key  200 , as is described in greater detail below. However, in other arrangements, a greater or lesser amount of spacing may be desirable. 
     In the illustrated embodiment of the lock and key system  10 , when the key  200  engages the lock  100  there are two transfers that occur. The first transfer is a transfer of data and the second transfer is a transfer of power. During engagement of the key  200  and the lock  100 , the data coils  222  and  154 , in the illustrated embodiments, do not come into physical contact with one another. Similarly, the power coil  200  of the key  200  and power coil  156  of the lock  100 , in the illustrated embodiment, do not come into physical contact with one another. The data is preferably transferred between the data coil  222  of the key  200  and the data coil  154  of the lock  100  by induction, as described in connection with  FIG. 9  below. The power is also transferred between the power coil  200  of the key  200  and the power coil  156  of the lock  100  preferably once again by induction, as is also described in connection with  FIG. 9  below. When engagement between the key  200  and the lock  100  has been made, a data protocol occurs which signals to the circuit board  134  that the proper key  200  has been inserted into the lock  100 . Power is transferred from the key  200  to the lock  100  to activate the solenoid  126 , which permits the lock  100  to be unlocked by rotation of the key  200 . 
     Electrical Aspects of the Key and Lock System 
       FIG. 9  depicts a magnetic field diagram  400  in accordance with certain embodiments of the present invention. In the magnetic field diagram  400 , a cross-section view of a power coil  402 , interior power coil  418 , first data coil  406 , and second data coil  408  are depicted in relation to a power magnetic field  404  and a data magnetic field  410  generated by the coils  406  and  408 . In the depicted embodiment, the configuration of the power coil  402 , interior power coil  418 , first data coil  406 , and second data coil  408  causes the power magnetic field  404  to be orthogonal or substantially orthogonal to the data magnetic field  410  at certain locations. This orthogonal relationship facilitates data transfer between the data coils  406 ,  408  with little or no interference from the power magnetic field  404 . The coils  402 ,  406 ,  408  and  418 , as illustrated, correspond with the power and data coils of the lock  100  and key  200  of  FIGS. 1-8 . In particular, the power coil  402  corresponds with the lock power coil  156 , the interior power coil  418  corresponds with the key power coil  220 , the data coil  406  corresponds with the lock data coil  154  and the data coil  408  corresponds with the key data coil  222 . However, it will be apparent to one of skill in the art that the physical relationships between the coils may be altered in alternative embodiments from the locations shown in  FIGS. 1-8 ; however, preferably the interference reduction or elimination concepts disclosed herein are still employed. 
     The power coil  402  of certain embodiments is a solenoid. The solenoid includes windings  420  which are loops of wire that are wound tightly into a cylindrical shape. In the depicted embodiment, the power coil  402  includes two sets of windings  420 . Two sets of windings  420  in the power coil  402  reduce air gaps between the wires and thereby increase the strength of a magnetic field generated by the power coil  402 . 
     The depicted embodiment of the power coil  402  does not include a magnetic core material, such as an iron core, although in certain embodiments, a magnetic core material may be included in the power coil  402 . In addition, while the power coil  402  is depicted as a solenoid, other forms of coils other than solenoids may be used, as will be understood by one of skill in the art. 
     The power coil  402  may form a portion of a lock assembly, though not shown, such as any of the lock assemblies described above. Alternatively, the power coil  402  may be connected to a key assembly, such as any of the key assemblies described above. In addition, the power coil  402  may be connected to a docking station (not shown), as described in connection with  FIG. 10 , below. 
     The power coil  402  is shown having a width  414  (also denoted as “W P ”). The width  414  of the power coil  402  is slightly flared for the entire length of the power coil  402 . The overall shape of the power coil  402 , including its width  414 , determines in part the shape of the magnetic field emanating from the power coil  402 . In certain embodiments, a constant or approximately constant width  414  of the power coil  402  does not change the shape of the power magnetic field  404  substantially from the shape illustrated in  FIG. 9 . 
     The power coil  402  further includes a casing  462  surrounding the power coil  402 . In one embodiment, the casing  462  is a non-conducting material (dielectric). The casing  462  of certain embodiments facilitates the power coil  402  receiving the interior power coil  418  inside the power coil  402 . The casing  462  prevents electrical contact between the power coil  402  and the interior power coil  418 . Thus, in the embodiment described with reference to  FIGS. 1-8 , the cup  152  of the lock  100  may be constructed from, or include, an insulation material. Furthermore, other physical structures interposed between adjacent coils may be made from, or include, insulating materials. 
     In alternative embodiments, the casing  462  is made of a metal, such as steel. The strength of a metal casing  462  such as steel helps prevent tampering with the power coil  402 . However, magnetic fields typically cannot penetrate more than a few layers of steel and other metals. Therefore, the metal casing  462  of certain embodiments includes one or more slits or other openings (not shown) to allow magnetic fields to pass between the power coil  402  and the interior power coil  418 . 
     The interior power coil  418  mates with the power coil  402  by fitting inside the power coil  402 . In certain embodiments, the interior power coil  418  has similar characteristics to the power coil  402 . For instance, the interior power coil  418  in the depicted embodiment is a solenoid with two windings  420 . In addition, the interior power coil  418  may receive a current and thereby generate a magnetic field. The interior power coil  418  is also covered in a casing material  454 , which may be an insulator or metal conductor, to facilitate mating with the power coil  402 . Furthermore, the interior power coil  418  also has a width  430  (also denoted “W i ”) that is less than the width  414  of the power coil  402 , thereby allowing the interior power coil  418  to mate with the power coil  402 . 
     In addition to these features, the interior power coil  418  of certain embodiments includes a ferromagnetic core  452 , which may be a steel, iron, or other metallic core. The ferromagnetic core  452  increases the strength of the power magnetic field  404 , enabling a more efficient power transfer between the interior power coil  418  and the power coil  402 . In addition, the ferromagnetic core  452  in certain embodiments enables the frequency of the power signal to be reduced, allowing a processor in communication with the power coil  418  to operate at a lower frequency and thereby decrease the cost of the processor. 
     The interior power coil  418  may form a portion of a lock assembly, though not shown, such as any of the lock assemblies described above. Alternatively, the interior power coil  418  may be connected to a key assembly, such as any of the key assemblies described above. In addition, the interior power coil  418  may be connected to a docking station (not shown), as described in connection with  FIG. 10 , below. 
     A changing current flow through the interior power coil  418  induces a changing magnetic field. This magnetic field, by changing with respect to time, induces a changing current flow through the power coil  402 . The changing current flow through the power coil  402  further induces a magnetic field. These two magnetic fields combine to form the power magnetic field  404 . In such a state, the power coil  402  and the interior power coil  418  are “inductively coupled,” which means that a transfer of energy from one coil to the other occurs through a shared magnetic field, e.g., the power magnetic field  402 . Inductive coupling may also occur by sending a changing current flow through the power coil  402 , which induces a magnetic field that in turn induces current flow through the interior power coil  418 . Consequently, inductive coupling may be initiated by either power coil. 
     Inductive coupling allows the interior power coil  418  to transfer power to the power coil  402  (and vice versa). An alternating current (AC) signal flowing through the interior power coil  418  is communicated to the power coil  402  through the power magnetic field  404 . The power magnetic field  404  generates an identical or substantially identical AC signal in the power coil  402 . Consequently, power is transferred between the interior power coil  418  and the power coil  402 , even though the coils are not in electrical contact with one another. 
     In certain embodiments, the interior power coil  418  has fewer windings than the power coil  402 . A voltage signal in the interior power coil  418  is therefore amplified in the power coil  402 , according to known physical relationships in the art. Likewise, a voltage signal in the power coil  402  is reduced or attenuated in the interior power coil  418 . In addition, the power coil  402  may have fewer windings than the interior power coil  418 , such that a voltage signal from the interior power coil  418  to the power coil  402  is attenuated, and a voltage signal from the power coil  402  to the interior power coil  418  is amplified. 
     The power magnetic field  404  is shown in the depicted embodiment as field lines  434 ; however, those of skill in the art will understand that the depiction of the power magnetic field  404  with field lines  434  is only a model or representation of actual magnetic fields, which in some embodiments are changing with respect to time. Therefore, the power magnetic field  404  in certain embodiments is depicted at a moment in time. Moreover, the depicted model of the power magnetic field  404  includes a small number of field lines  434  for clarity, but in general the power magnetic field  404  fills all or substantially all of the space depicted in  FIG. 9 . 
     Portions of the field lines  434  of the power magnetic field  404  on the outside of the power coil  402  are parallel or substantially parallel to the axis of the power coil  402 . The parallel nature of these field lines  434  in certain embodiments facilitates minimizing interference between power and data transfer, as is described below. 
     The first data coil  406  is connected to the power coil  402  by the casing  462 . The first data coil  406  has one or more windings  422 . In one embodiment, the first data coil  406  is a toroid comprising tightly-wound windings  422  around a ferromagnetic core  472 , such as steel or iron. The ferromagnetic core  472  of certain embodiments increases the strength of a magnetic field generated by the first data coil  406 , thereby allowing more efficient transfer of data through the data magnetic field  410 . In addition, the ferromagnetic core  472  in certain embodiments enables the frequency of the data signal to be reduced, allowing a processor in communication with the first data coil  406  to operate at a lower frequency and thereby decreasing the cost of the processor. 
     Though not shown, the first data coil  406  may further include an insulation material surrounding the first data coil  406 . Such insulation material may be a non-conducting material (dielectric). In addition, the casing  462  covering the power coil  402  in certain embodiments also at least partially covers the first data coil  406 , as shown. The casing  462  at the boundary between the first data coil  406  and the second data coil  408  may also include a slit or other opening to allow magnetic fields to pass between the first and second data coils  406 ,  408 . 
     The first data coil  406  has a width  416  (also denoted as “W d ”). This width  416  is greater than the width  414  of the power coil  402  in some implementations. In alternative embodiments, the width  416  may be equal to or less than the width  414  of the power coil  402 . 
     The second data coil  408  in the depicted embodiment is substantially identical to the first data coil  406 . In particular, the second data coil  408  is a toroid comprising tightly-wound windings  424  around a ferromagnetic core  474 , such as steel or iron. The ferromagnetic core  474  of certain embodiments increases the strength of a magnetic field generated by the second data coil  408 , thereby allowing more efficient transfer of data through the data magnetic field  410 , allowing a processor in communication with the second data coil  408  to operate at a lower frequency and thereby decreasing the cost of the processor. 
     The second data coil  408  in the depicted embodiment has a width  416  equal to the width  414  of the first data coil  406 . In addition, the second data coil  408  may have an insulating layer (not shown) and may be covered by the casing  454 , as shown. However, in certain embodiments, the second data coil  408  has different characteristics from the first data coil  406 , such as a different number of windings  424  or a different width  416 . In addition, first and second data coils  406 ,  408  having different widths may overlap in various ways. 
     When a current is transmitted through either the first data coil  406  or the second data coil  408 , the first data coil  406  and the second data coil  408  are inductively coupled, in a similar manner to the inductive coupling of the power coil  402  and the interior power coil  418 . Data in the form of voltage or current signals may therefore be communicated between the first data coil  406  and the second data coil  408 . In certain embodiments, data may be communicated in both directions. That is, either the first or second data coil  406 ,  408  may initiate communications. In addition, during one communication session, the first and second data coils  406 ,  408  may alternate transmitting data and receiving data. 
     Data magnetic field  410  is depicted as including field lines  442 , a portion of which are orthogonal or substantially orthogonal to the data coils  406 ,  408  along their width  416 . Like the field lines  434 ,  436  of the power magnetic field  404 , the field lines  442  of the data magnetic field  410  are a model of actual magnetic fields that may be changing in time. The orthogonal nature of these field lines  442  in certain embodiments facilitates minimizing the interference between power and data transfer. 
     In various embodiments, at least a portion of the data magnetic field  410  is orthogonal to or substantially orthogonal to the power magnetic field  404  at certain areas of orthogonality. These areas of orthogonality include portions of an interface  412  between the first data coil  406  and the second data coil  408 . This interface  412  in certain embodiments is an annular or circumferential region between the first data coil  406  and second data coil  408 . At this interface, at least a portion of the data magnetic field  410  is substantially parallel to the first data coil  406  and second data coil  408 . Because the data magnetic field  410  is substantially parallel to the data coils  406 ,  408 , the data magnetic field  410  is therefore substantially orthogonal to the power magnetic field  404  at portions of the interface  412 . 
     According to known relationships in the physics of magnetic fields, magnetic fields which are orthogonal to each other have very little effect on each other. Thus, the power magnetic field  404  at the interface  412  has very little effect on the data magnetic field  410 . Consequently, the data coils  406  and  408  can communicate with each other with minimal interference from the potentially strong power magnetic field  404 . In addition, data transmitted between the data coils  406 ,  408  does not interfere or minimally interferes with the power magnetic field  404 . Thus, data may be sent across the data coils  406 ,  408  simultaneously while power is being sent between the power coil  402  and the interior power coil  418 . 
       FIG. 10  depicts a key circuit  510  and a lock circuit  530  in accordance with certain embodiments of the present invention. In the depicted embodiment, the key circuit  510  is shown in proximity to the lock circuit  530 . The relative locations of the key circuit  510  and the lock circuit  530  shows that in certain implementations components of the key circuit  510  interface with components of the lock circuit  530 . Moreover, the key circuit  510  may in certain embodiments be contained in a key assembly such as any of the keys described above. Likewise, the lock circuit  530  may be contained in a lock assembly such as any of the locks described above. 
     The key circuit  510  includes a processor  502 . The processor  502  may be a microprocessor, a central processing unit (CPU), a microcontroller, or other type of processor. The processor  502  in certain embodiments implements program code. By implementing program code, the processor  502  sends certain signals to the lock circuit  530  and receives signals from the lock circuit  530 . Such signals may include power signals, data signals, and the like. 
     A memory device  526  is in communication with the processor  502 . The memory device  526  in certain embodiments is a flash memory, hard disk storage, an EEPROM, or other form of storage. The memory device  526  in certain embodiments stores program code to be run on the processor  502 . In addition, the memory device  526  may store data received from the processor  502 . 
     Data stored on the memory device  526  may include encryption data. In one embodiment, the encryption data includes one or more encryption keys that when communicated to the lock circuit  530  effectuate unlocking a lock. Several different encryption schemes may be used, as will be appreciated by one having skill in the art. 
     Data stored by the memory device  526  may also include audit data. Audit data in some implementations is data received from the lock circuit  530  or generated by the key circuit  510  that identifies past transactions that have occurred between the lock and other keys. For instance, audit data may include ID numbers of keys used to access the lock, including keys which unsuccessfully used the lock. This data allows security personnel to monitor which individuals have attempted to access the lock. The audit data may further include several other types of information as will be understood by one of skill in the art. 
     A data coil  512  is in communication with the processor  502  through conductors  504  and  506 . The data coil  512  may be any of the data coils described above. The data coil  512  in certain embodiments receives data from the processor  502 . This data may be in the form of a voltage or current signal which changes with respect to time, such that certain changes in the signal represent different symbols or encoded information. Because the signal changes with respect to time, a magnetic field is generated in the data coil  512  which induces a magnetic field in a corresponding data coil  532  in the lock circuit  530 . The magnetic field in the data coil  532  further induces a voltage or current signal, which contains the same information or substantially the same information as the voltage or current signal generated in the data coil  512 . Thus, the data coil  512  facilitates communication between the key circuit  510  and the lock circuit  530 . 
     In certain embodiments, the data coil  512  receives data in a like manner from the data coil  532  of the lock circuit  530 . A voltage or current signal induced in the data coil  512  is sent to the processor  502 , which processes the information conveyed in the voltage or current signal. The data coil  512  may also send and receive information to and from a docking station (not shown), which is described more fully below. 
     One or more switches  516  are in communication with the data coil  512  and with the processor  502 . The switches  516  in certain embodiments are transistor switches, relays, or other forms of electronic switches which selectively direct current flow to different parts of the key circuit  510 . In the depicted embodiment, switches  516  direct current flow between the data coil  512  and the processor  502 . The switches  516  therefore selectively allow the processor  502  to both send and receive data. 
     A power coil  514  is in communication with the processor  502  via conductors  508  and  510 . The power coil  514  in certain embodiments transmits power to the key circuit  530 . In certain implementations, the power coil  514  may be any of the power coils described above. In one implementation, the power coil  514  receives an alternating current (AC) signal. This AC signal induces a magnetic field in a corresponding power coil  534  in the lock circuit  530 . In one embodiment, the AC signal oscillates at an appropriate frequency to effectuate optimal power transfer between the key circuit  510  and the lock circuit  530 . For example, the oscillation may occur at 200 kilohertz. Alternatively, the oscillation may occur at a different frequency which may be chosen so as to minimize interference with other circuit components. 
     One or more switches  518  are in communication with the power coil  514  and a processor  502 . Like the switches  516 , the switches  518  may be transistor switches, relays or any other form of electronic switch. The switches  518  in certain embodiments allow power to be transmitted to the power coil  514  from the processor  502 . In such embodiments, the switches  518  are closed, allowing current to transfer from the processor  502  to the power coil  514 . The switches  518  may be opened when the power coil  514  is receiving power such as from a docking station. When the switches  518  are open, power received from the power coil  514  in certain embodiments cannot be transmitted to the processor  502 . The switches  518  therefore protect the processor  502  from receiving harmful current signals while simultaneously allowing the processor  502  to transmit power to the power coil  514 . 
     A rectifier circuit  520  is in communication with the power coil  514  via conductors  508  and  510 . The rectifier circuit  520  in certain embodiments includes one or more diodes. The diodes may form a bridge rectifier or other form of rectifier as will be appreciated by those of skill in the art. The diodes of the rectifier circuit  520  rectify an incoming signal from the power coil  514 . Rectification in certain embodiments includes transforming an alternating current signal into a direct current signal by converting the AC signal into one of constant polarity. Rectification may further include smoothing the signal, for example, by using one or more capacitors, and thereby creating a direct current signal that can power circuit components. 
     A recharge circuit  522  is in communication with the rectifier  520 . The recharge circuit  522  in certain embodiments recharges a battery  524  when the key circuit  510  is in communication with a docking station (not shown). The battery  524  may be a lithium iron battery, a nickel cadmium battery or other form of rechargeable battery. The battery may also be an alkaline or other non-rechargeable battery. In addition, the battery  524  may include multiple batteries. In one embodiment, the battery  524  receives power from the recharge circuit  522  in order to recharge the battery. In addition, the battery  524  sends power to the processor  502 , to the memory device  526 , and to other components in the key circuit  530 . 
     In some implementations, the key circuit  510  is capable of communicating with a docking station (not shown) connected to an AC power supply, such as a wall outlet. The docking station in one embodiment has a power coil and a data coil, similar to a power coil  534  and data coil  532  of the lock circuit  530  described below. The docking station receives the data coil  512  and the power coil  514  such that the key circuit  510  can communicate with the docking station. In one embodiment, the power coil  514  receives power from the docking station and transfers this power to the rectifier  520  and recharge circuit  522 , effectuating recharge of the battery  524 . 
     In addition, the data coil  512  may receive data from a corresponding data coil in the docking station. Such information might include, for example, program code to be stored on the memory device  526 , program code to be run on the processor  502 , data to be stored in the memory device  526  including encryption data, data regarding locking codes and the like, as well as ID data, tracking data, and the like. In addition, the docking station may transmit data, codes, or the like to the key circuit  510  which enable the key to be used for a limited time, such as a couple of hours or days. The data coil  512  may also transmit data to the docking station via a corresponding data coil. Such data might also include audit information, tracking information, and the like. 
     The docking station may also be connected to a computer. Programs can be run on the computer which facilitate the docking station communicating with the key circuit  510 . Consequently, the key circuit  510  may be recharged and reprogrammed by the docking station of certain embodiments. 
     Turning to the lock circuit  530 , the lock circuit  530  includes a processor  546 . Like the processor  502  of the key circuit  510 , the processor  546  may be a microprocessor, a central processing unit (CPU), or any other type of processor. The processor  546  in certain embodiments implements program code. By implementing program code, the processor  546  may send certain signals to the key circuit  510  and receive signals from the key circuit  510 . Such signals may include power signals, data signals, and the like. 
     A memory device  548  is in communication with the processor  546 . The memory device  548  in certain embodiments is a flash memory, hard disk storage, an EEPROM, or other form of storage. The memory device  548  in certain embodiments stores program code to be run on the processor  546 . In addition, the memory device  548  may store data received from the processor  546 . 
     Data stored on the memory device  548  may include encryption data. In one embodiment, the encryption data includes one or more encryption keys. When an identical encryption key is received from a key circuit  510  in certain embodiments, the lock circuit  530  unlocks a lock. The memory device  548  may also include audit data. This data allows security personnel to monitor which individuals have attempted to access the lock. 
     A data coil  532  is in communication with the processor  546  through conductors  536  and  538 . The data coil  532  may be any of the data coils described above. The data coil  532  in certain embodiments receives data from the processor  546  and transmits the data to the key circuit  510 . In other embodiments, the data coil  532  receives data from the key circuit  510  via magnetic fields generated by the data coil  512 . 
     One or more switches  544  are in communication with the data coil  532  and with the processor  546 . The switches  544  in certain embodiments are transistor switches, relays, or other forms of electronic switches which selectively direct current flow to different parts of the key circuit  530 . In the depicted embodiment, switches  544  may be used to direct current flow between the data coil  532  and the processor  546 . Like the switches  516  in the key circuit  510 , the switches  544  selectively allow the processor  502  to both send and receive data. 
     A power converter  550  is in communication with the processor  546  and with the power coil  534 . The power converter  550  in one embodiment includes a rectifier circuit such as the rectifier circuit  528  described above. The power converter  550  may further include a low drop-out regulator (described in connection with  FIG. 11 , below). In addition, the power converter may include other circuit components common to power regulation as will be understood by one of skill in the art. 
     In one embodiment, the power converter  550  receives an oscillating power signal from the power coil  534 . The power converter  550  includes a rectifier circuit, similar to the rectifier circuit  520  described above, which converts the oscillating signal into two components, namely an AC component signal and a direct current (DC) component signal. In one embodiment, the AC component signal is provided to a solenoid  552  through conductor  574 , and the DC component signal is provided to the processor  546  through conductor  572 . Consequently, the power converter  550  enables the lock circuit  530  to run on both AC and DC power. 
     The solenoid  552  receives the AC component signal from the power converter  550 . The solenoid  552  in one embodiment is a coil containing one or more windings. The solenoid  552 , upon receiving current from the power converter  550 , generates a magnetic field to actuate an unlocking mechanism in a lock, in a manner similar to that which is described above. 
     A switch  554  is in communication with the solenoid  552  through a conductor  576 . The switch  554  is also in communication with the processor  546  through a conductor  580 . In addition, the switch  554  is in communication with ground  578 . The switch  554  enables or disables the solenoid  552  from receiving current, thereby causing the solenoid  552  to lock or unlock. In one embodiment, the processor  546  sends a signal through the conductor  580  to the switch  554  that closes the switch  554  and thereby creates a conduction path from the solenoid  552  to ground  578 . With the switch closed  554 , the solenoid  552  is able to receive current from the power converter  550  and thereby effectuate unlocking. At other times, the processor  546  will not send a signal  580  to the switch  554  and thereby cause the switch to be open, preventing current from flowing through the solenoid  552  and thereby locking the lock. Alternatively, the processor  546  can send a signal over the signal line  580  to the switch  554  which will cause the switch to remain open. 
     While not shown, in certain embodiments the lock circuit  530  includes a battery in addition to, or in place of, the battery  524  in the key circuit  500 . In such instances, the lock circuit  530  may provide power to the key circuit  510 . This power may recharge the battery  524 . Alternatively, if the key circuit  510  does not have a battery  524 , power transmitted from the battery in the lock circuit  530  may power the key circuit  510 . 
       FIGS. 11A-1-11A-2  (“ FIG. 11A ”) and  11 B- 1 - 11 B- 2  (“ FIG. 11B ”) depict one specific implementation of a key circuit, referred to by the reference numeral  600 , which is substantially similar in structure and function to the key circuit  510  described above.  FIGS. 11A and 11B  depict separate portions of the key circuit  600 , but these separate portions together constitute one key circuit  600 . Certain components of the key circuit  600  are therefore duplicated on each FIG. to more clearly show the relationship between the portion of the key circuit  600  depicted in  FIG. 11A  with the portion of the key circuit  600  depicted in  FIG. 11B . Although the implementation shown in  FIGS. 11A and 11B  is preferred, other suitable implementations may also be used, which may include features alternative or additional to those described above. 
     A processor  602  in the key circuit  600  is in communication with a memory device  626 , similar to the processor  502  and the memory device  526  of the key circuit  510 . In the depicted embodiment, the processor  602  is a microcontroller and the memory device  626  is a flash memory device. While the processor  602  and the memory device  626  are shown on both  FIGS. 11A and 11B , in the depicted embodiment only one processor  602  and one memory device  626  are employed in the key circuit  600 . However, in other embodiments, multiple processors  602  and memory devices  626  may be used, as will be appreciated by one of skill in the art. 
     A data coil  612 , shown in  FIG. 11B , is in communication with the processor  602  through conductors  604  and  606 . The data coil  612  in the depicted embodiment is a coil or solenoid which has a value of inductance (a measure of changing magnetic energy for a given value of current). In one embodiment, the inductance of the data coil  612  is 100 μH (micro-Henries). In certain embodiments, the data coil  612  sends data to and receives data from a lock circuit  700  (shown in  FIG. 12 ). 
     Transistors  616  are depicted as switches in  FIG. 11B . Similar to the switches  516 , the transistors  616  selectively direct current flow between the data coil  612  and the processor  602 . Control signals sent on conductors  662  from the processor  602  selectively allow current to flow through the transistors  616 . When the transistors  616  are activated by control signals from the processor  602 , and when the processor  602  is sending signals to the data coil  612 , the data coil  612  transmits the data. Alternatively, when the data coil  612  is receiving data, the transistors  616  in conjunction with other circuit components direct the data to the processor  602  through the ACDATA line  664 . Consequently, the key circuit  600  can both send and receive data on the data coil  612 . 
     Various encoding schemes may be used to transmit and receive data. For example, a Manchester encoding scheme may be used, where each bit of data is represented by at least one voltage transition. Alternatively, a pulse-width modulation scheme may be employed, where a signal&#39;s duty cycle is modified to represent bits of data. Using different encoding schemes may allow the key circuit  600  to contain fewer components. For example, when a pulse-width modulation scheme is used, such as in  FIGS. 13A and 13B  below, fewer transistors  616  may be employed. By employing fewer components, the key circuit  600  of certain embodiments may be reduced in size, allowing a corresponding key assembly to be reduced in size. In addition, using a relatively simple modulation scheme such as Manchester encoding or pulse-width modulation reduces the need for filters (e.g., low-pass filters), thereby further reducing the number of components in the key circuit  600 . 
     A power coil  614  is in communication with the processor  604  through conductors  608  and  610  (see  FIG. 11B ). In one embodiment, the inductance of the power coil  612  is 10 μH (micro-Henries). Like the power coil  514  of  FIG. 10 , the power coil  614  in certain embodiments transmits power to the lock circuit  700  described in connection with  FIG. 12 , below. 
     In the depicted embodiment, the processor  602  generates two oscillating signals which are provided to the power coil  614 . In the depicted embodiment, the oscillating power signals oscillate at 200 kHz (kilohertz). The relative high frequency of the power signal in certain embodiments facilitates improved rectification of the power signal and therefore a more efficient power transfer. In alternative embodiments other frequencies may be chosen without departing from the scope of the present invention. 
     In one embodiment, the power signals sent over power coil  614  oscillate at a higher frequency than the data signals sent over the data coil  612 . When the power signals oscillate at a higher frequency than the data signals, interference between power and data signals is further minimized, e.g., the signal-to-noise ratio (SNR) is improved. In one embodiment, significant SNR improvements occur when the power signal frequency is greater than 10 times the data signal frequency. 
     Diodes  620  are in communication with the power coil  614  through conductors  608  and  610 . The diodes  620  in the depicted embodiment form a rectifier circuit, similar to the rectifier circuit  520  of  FIG. 10 . The depicted configuration of the diodes  620  constitutes a bridge rectifier, or full wave rectifier. The bridge rectifier receives power from the power coil  614  when, for example, the key circuit  600  is in communication with a docking station. In such instances, the diodes  620  of the bridge rectifier in conjunction with a capacitor  684  convert an incoming AC signal into a DC signal. This DC signal is denoted by voltage Vpp  682  in the depicted embodiment. 
     The voltage Vpp  682  is provided to a recharge circuit  622  (see  FIG. 11A ). The recharge circuit  622  recharges a battery  624  using Vpp  682 . The battery  624  outputs a voltage Vcc  696 , which is sent to various components of the key circuit  600  including to a voltage regulator  690 . The voltage regulator  690  provides a constant voltage to a supervisory circuit  692 , which is in communication with a backup battery  694 . If the battery  624  fails, in certain embodiments, the supervisory circuit  692  provides power to the circuit through the backup battery  694 . Consequently, data stored in the memory device  626  is protected from loss by the supervisory circuit  692  and by the backup battery  694 . 
       FIGS. 12-1 and 12-2  (“ FIG. 12 ”) depict a specific implementation of a lock circuit, generally referred to by the reference numeral  700 , which is substantially similar in structure and function to the lock circuit  530  described above. The lock circuit  700  includes a processor  746 . The processor  746 , like the processor  602 , is a microcontroller. The processor  746  communicates with a memory device  748 , which in the depicted embodiment is a flash memory. Although the specific implementation of the lock circuit  700  illustrated in  FIG. 12  is a preferred implementation of the lock circuit  530 , other suitable implementations may also be used, which may include alternative or additional features to those described above. 
     In the lock circuit  700 , a data coil  732  is in communication with the processor  746  through conductors  736  and  738 . The data coil  732  in the depicted embodiment is a coil or solenoid which has a value of inductance. In one embodiment, the inductance of the data coil  732  is 100 μH (micro-Henries). The data coil  732  receives data from and sends data to the data coil  612  of the key circuit  600 . 
     In one embodiment, data provided by the key circuit  600  and received by the data coil  732  provides a clock signal to the processor  746 , enabling the processor  746  to be synchronized or substantially synchronized with the processor  602  of the key circuit  600 . The clock signal may be provided, for example, when a Manchester encoding scheme is used to transmit the data. In certain embodiments, this external clock signal removes the need for a crystal oscillator in the lock circuit  700 , thereby reducing the number of components and therefore the size of the lock circuit  700 . 
     Transistors  744  are depicted as switches. Similar to the switches  544 , the transistors  744  selectively direct current flow between the data coil  732  and the processor  746 . Control signals sent on conductor  782  from the processor  746  control the transistors  744 , selectively allowing current to flow through the transistors  744 . 
     A power coil  734  is in communication with the processor  746  through conductors  740  and  742 . In one embodiment, the inductance of the power coil  734  is 10 μH (micro-Henries). Like the power coil  532  of  FIG. 10 , the power coil  734  in certain embodiments receives power from the key circuit  600 . In the depicted embodiment, the power coil  734  provides an AC voltage signal to power conversion circuit  750 . 
     Power conversion circuit  750  includes diodes  720 , a capacitor  790 , and a low-dropout regulator  760 . The diodes  720  of the power conversion circuit  750  form a rectifier circuit. The depicted configuration of the diodes  720  constitutes a bridge rectifier, or full wave rectifier. When the diodes  720  receive an AC voltage signal from the power coil  734 , the diodes  720  of the bridge rectifier full-wave rectify the AC voltage signal. This full-wave rectified signal in certain embodiments still contains a changing voltage signal with respect to time, but the voltage signal has a single polarity (e.g., the entire voltage signal is positive). This full-wave rectified signal is provided as voltage Vcc  784  to a solenoid  752 . 
     The capacitor  790  converts the full-wave rectified signal into DC form and provides the DC signal to the low-dropout regulator  760 . The low-dropout regulator  760  stabilizes the signal to a voltage Vdd  772 , which is provided to various components in the lock circuit  700 , including the processor  746 . Consequently, the power conversion circuit  750  provides a changing or AC voltage Vcc  784  to the solenoid  752  and a DC voltage Vdd  772  to various circuit components. 
     The solenoid  752  receives the voltage Vcc  784  from the power converter  750 . The solenoid  752  in one embodiment is a coil containing one or more windings. The solenoid  752 , upon receiving the voltage Vcc  784  from the power converter  550 , generates a magnetic field to actuate an unlocking mechanism in a lock, in a manner similar to that which is described above. 
     A transistor  754  is in communication with the solenoid  752 . The transistor  754  is also in communication with the processor  746  through a conductor  780 . In addition, the transistor  754  is in communication with ground  778 . In certain embodiments, the transistor  754  acts as a switch to enable or disable the solenoid  752  from receiving current, thereby causing the solenoid  752  to lock or unlock the locking device. In one embodiment, the processor  746  sends a signal through the conductor  780  to the transistor  754  that sends current through the transistor  754  and thereby creates a conduction path from the solenoid  752  to ground  778 . With the transistor  754  in this state, the solenoid  752  is able to receive current from the voltage Vcc  784  and thereby effectuate unlocking. However, at other times, the processor  746  will not send a signal  780  to the transistor  754 , such as when the processor  746  did not receive a correct unlocking code. In such case, the processor  746  causes the transistor  754  to remain open, thereby preventing current from flowing through the solenoid. 
       FIGS. 13A-1-13A-2  (“ FIG. 13A ”) and  13 B- 1 - 13 B- 2  (“ FIG. 13B ”) depict another specific implementation of a key circuit, referred to by the reference numeral  800 , which is substantially similar in structure and function to the key circuit  600  described in  FIGS. 11A and 11B  above. In certain embodiments, certain elements of the key circuit  600 , such as circuit components  860 ,  872 , and  874  (shown in  FIG. 13B ), may also be employed in a corresponding lock circuit (not shown). 
     In the depicted embodiment, circuit components  860 ,  872 , and  874  in conjunction with a processor provide circuitry for a pulse-modulation data-encoding scheme. During transmission of data from the key circuit  800 , transistor switches  860  are selectively switched on and off to pulse a data signal to a data coil. When the key circuit  800  is receiving data, the comparator  872  receives the data voltage signal from the data coil. 
     The comparator  872  is used to convert the data voltage signal into a two-bit digital signal which is sent to a processor via data input line  880 . In addition, the comparator  872  (or an operational amplifier used as a comparator) may be used to amplify the voltage signal to a level appropriate for a processor to manipulate. 
     A feedback resistor  874  provides positive feedback to the comparator  872 , such that the comparator  872  attenuates small voltage signals and amplifies large voltage signals. By attenuating and amplifying small and large voltage signals respectively, the comparator  872  and feedback resistor  874  reduce the oscillatory effects of noise on the comparator  872 . Thus, wrong-bit detection errors are reduced. In alternative embodiments, a Schmitt trigger integrated circuit may be employed in place of the comparator  872  and the resistor  874 . 
     While various embodiments of key and lock circuits have been depicted, those of skill will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. 
     The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor can be a microprocessor, conventional processor, controller, microcontroller, state machine, etc. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In addition, the term “processing” is a broad term meant to encompass several meanings including, for example, implementing program code, executing instructions, manipulating signals, filtering, performing arithmetic operations, and the like. 
     In addition, although this invention has been disclosed in the context of a certain preferred embodiment, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiment to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In particular, while the present key and lock system has been described in the context of a particularly preferred embodiment, the skilled artisan will appreciate, in view of the present disclosure, that certain advantages, features and aspects of the key and lock system may be realized in a variety of other applications. Additionally, it is contemplated that various aspects and features of the invention described can be practiced separately, combined together, or substituted for one another, and that a variety of combination and subcombinations of the features and aspects can be made and still fall within the scope of the invention. Furthermore, the systems described above need not include all of the modules and functions described in the preferred embodiments. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiment described above, but should be determined only by a fair reading of the claims that follow.