Abstract:
A way of controlling access to golf cart starter keys, (referred herein as user-keys) is described. A specially coded and specially shaped key, the user-key is given to a golf cart renter once an appropriate rental fee has been paid. In order to start the golf cart, the renter must insert the user-key into a control unit, which is located in the dashboard. When the user-key is properly inserted, the golf cart starts. Furthermore, the user-key is locked inside the control unit and can no longer be removed by the renter, thereby preventing the renters from misappropriating the user-key. When the renter completes the round of golf, he returns the golf cart, along with the unremovable user-key, to the golf club. Only the specially coded removal key in the golf club&#39;s possession can remove the user-key from the control unit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of The Invention 
     Applicant&#39;s invention relates to the field access control devices. Specifically, applicant&#39;s invention is a novel method of access control for golf carts. 
     2. Background Information 
     Currently, access to golf carts are controlled by metal keys. Individuals obtain a metal key after paying the golf cart rental fee. However, golfers often fail to return the keys after finishing their rounds. Sometimes, the keys are simply forgotten and left in the cart. Other times, renters deliberately remove the keys so that they can keep and/or duplicate the keys for future free access to the golf carts. 
     Unauthorized access to golf carts creates several major problems for country clubs around the world. First, the stolen and/or duplicate keys allow golfers to use the golf carts without paying a rental fee. Second, because some facilities charge golf cart access on an individual rather than a per cart basis, two golfers can have access to the golf cart while only paying the rental fee for one golfer. Third, unauthorized access of golf carts increases the legal liability of the country club because the club cannot prevent unauthorized persons such as minors or highly intoxicated individuals from access to the golf carts. Finally, unauthorized use of golf carts increases the carts&#39; maintenance costs such as washing, hours-based maintenance, battery replacement, damage repair, and wear and tear. All of the above factors result in significant revenue loss for country clubs around the world. 
     Inventions currently in the marketplace cannot solve the above problems. In order to prevent users of bus or gym lockers from removing and retaining locker keys for repeated future use, many lockers use a “captured” key principle. The locker key is secured in the keyhole until a user inserts payment in, for example, the form of coins. Once payment is inserted, the key is released from the keyhole and the user can lock the locker and remove the key. When the user reinserts the key to unlock the locker and gain access to his property, the key is captured by the keyhole until additional payment is inserted. 
     The above invention relies on the fact that the need to retrieve the property placed in the locker induces the keyholder to reinsert the key, thereby providing the opportunity for the lock mechanism to recapture the key. For golf carts, the inducement to reinsert the key will not occur until the first unauthorized access is attempted, rewarding the key-napper with at least one free use of the golf cart. Therefore, the gym locker key capture mechanism is unsuited for golf carts. 
     Another type of access control can be found in the protocol and mechanism used for safety deposit boxes. To open a safety deposit box, two keys, one in the possession of the safety deposit box renter and the other in the possession of a bank employee, must be used simultaneously to unlock the box. Applying this concept to golfcarts is impractical because it would require a country club employee to be present every time a golf cart is started up, thereby increasing the labor costs for country clubs. 
     Specialized magnetic lock and key combinations are sometimes used to prevent unauthorized copying of the key. The combination consists of a key with very small embedded magnets that can magnetically attract or repel magnetized tumbler elements in the lock. Once the appropriate tumbler elements have been attracted, the key can be rotated in the lock. Such a magnetic key cannot be easily duplicated. This concept, when applied to golf carts, would prevent renters from duplicating the keys. However, the inability to duplicate keys would only increase the number of stolen keys. Because stolen keys will continue to allow unauthorized golf cart access, not to mention requiring a costly replacement fee for each key, a magnetic lock and key combination will not give country clubs more control of their golf carts. 
     Finally, some country clubs control access to their golf carts by using radio controlled devices to activate or deactivate the golf carts. Although controlling golf cart access by remote control can limit unauthorized use of the carts, the radio controlled mechanism may break down easily. Furthermore, in order to prevent unauthorized access to golf carts, the country club must first know that the golf cart is being used by unauthorized personnel before it can deactivate the golf cart. In other words, the access control is not immediately effective. Because country clubs cannot immediate prevent a golf cart from being used by unauthorized personnel, radio controlled devices do not provide ideal golf cart access control. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a novel single access control system that allows an authorized individual a single time access to a locked or deactivated device. 
     It is another object of the present invention to provide a single access control system that will physically capture a user-key so that the key can only be removed by using a special key removal tool. 
     It is another object of the present invention to provide a single access control system in which the user-key is difficult to duplicate due to both the mechanical tolerances of the key and the varied combination of magnetic polarity and field strength of the magnets embedded in the key. 
     It is another object of the present invention to provide single access control system that requires a special key removal tool that is difficult to duplicate due to mechanical tolerances of the key removal tool and the varied combination of magnetic polarity and field strength of the magnets embedded in the key-removal tool. 
     It is a further object of the present invention to provide specially coded user-keys that permits tracking golf cart usage back to the last user. 
     It is another object of the present invention to provide user-keys that are specially coded so as to enable inventory tracking by the owner of the single access control system. 
     It is a further object of the present invention to provide user-keys that are physically sized and shaped to help deter theft and accidental pocketing. 
     It is a further object of the present invention to provide specially coded user-keys that will reduce cross-facility compatibility and potential misuse by adjacent facility renters, staff, or other individuals. 
     In satisfaction of these and related objectives, Applicant&#39;s present invention provides a novel method and mechanism that allows a single access to a device. Currently, Applicants&#39;s invention is being used on golf carts only. 
     Applicant&#39;s invention, the single access control system and method, has three major components: the user-key, the control unit, and the combination removal and staging key. The user key comprises of a flat, steel cap perpendicularly attached to a generally elongated body. The elongated body is irregularly shaped in cross section to allow differently shaped keys to reduce cross facility compatibility. To prevent further cross facility compatibility, the size and shape of the steel cap can also be varied. User-key is larger than conventional metal keys to prevent accidental pocketing. 
     A plurality of magnets are embedded along the longitudinal axis of the elongated body of the user-key in a certain orientation and spacing such that, when the user-key is inserted into the control unit, the magnets line up with a plurality of hall-effect sensors located in the control unit. Furthermore, a notch is located near the distal end of the user key so that, when the user-key is inserted into the key receptacle, the notch provides a place for the user-key capture-plunger (to be described in the following paragraphs) to latch on and secure the user-key to the control unit, thus preventing unauthorized removal of the user-key. 
     The control unit comprises a generally flat face plate, a receptacle for key insertion, a leaf spring-capture-plunger assembly, a mechanism used to electronically activate the locked device (in the preferred embodiment a relay to activate the golf cart), a circuit board, and two sets of hall-effect sensors. 
     When properly installed, the face plate of the control unit is the only surface that is seen by the user. A base plate is attached generally perpendicularly to the back side of the face plate. The appropriate electrical circuit used in operating the control unit is imprinted in a circuit board attached to the base plate. A plurality of electrical devices such as transistors and resistors are attached to the circuit board. Furthermore, two sets of hall-effect sensors, comprised of a plurality of sensors per set, are also attached to the circuit board. One set of hall-effect sensors is located directly behind the face plate while the other set of hall-effect sensors is located against the side surface of the key receptacle facing towards the circuit board. 
     The key receptacle is located at one side of the control unit. The opening of the receptacle is located at the surface of the face place, and the body of the receptacle extends some distance away from the face plate. The inside perimeter of the key receptacle is irregularly shaped to conform to the outside contours of the user-key so that, when user-key is inserted into the key receptacle, user-key fits snugly inside the key receptacle. Finally, a small, generally circular hole is drilled near the end of the key receptacle farther from the face plate, on the same side as the hall-effect sensors. 
     A leaf spring is flexibly attached to the side surface of the key receptacle facing towards the circuit board. The leaf spring is a thin, flexible piece of material generally made of plastic. In the preferred embodiment, the leaf spring is roughly shaped like an axe, with the handle portion attached to the key receptacle at the end nearer to the face plate and with a generally circular hole drilled in the approximate center of the axe head portion. In future embodiments, the location and geometry of the spring function may vary to meet unique physical requirements. 
     A user-key capture-plunger floats freely within a solenoid. The user-key capture-plunger is secured to and extends through the generally circular hole located in the axe head portion of the leaf spring and is removably inserted into the circular hole drilled on one side of the key receptacle. This user-key capture-plunger is pushed out of the hole at the side of the key receptacle when a user-key is inserted. When the notch of the user-key lines up with the hole at the side of the key receptacle, the user-key capture-plunger then springs back into place into the key receptacle with the aide of the leaf spring. The user-key capture-plunger thus captures the user-key and prevents key removal without the proper key removal instrument. 
     In future embodiments, the circuit board may be potted solid to prevent corrosion brought about by the golf cart&#39;s constant exposure to the outside environment. 
     In the preferred embodiment, the staging key and the removal key are combined into one “L” shaped unit called the combination removal and staging key. However, in future embodiments, the staging key and the removal key may be separately maintained. The staging key is generally elongated in shape and can have a cross section of the same size and shape as the cross section of the user-key or can have a cross section smaller than the cross section of the user-key. However, the staging key lacks the notch at the end of the user-key, and thus can be inserted and removed at will, without the user-key capture-plunger preventing the removal of the staging key. A plurality of magnets, corresponding generally in location, polarity, and field strength as the user-key, are embedded into the staging key. In the preferred embodiment, where the present invention is used for golf carts, the staging key is given to caddies so that they may drive the golf cart to the renters, whereupon the staging key is removed and the user-key inserted, thus readying the golf cart for rental use. 
     The removal key, which is attached to the staging key in the preferred embodiment, is also generally rectangular in shape. Unlike the user-key and the staging key, however, the removal key is rectangular and larger in cross section. Thus, the removal key will never be mistakenly inserted into the key receptacle. A plurality of magnets possessing a variety of polarities and field strengths are embedded into the removal key so that, when lined up with the plurality of hall-effect sensors located immediately behind the face plate, the hall-effect sensors will cause the release of the user-key capture-plunger so that the user-key can be removed. In addition to the magnets positioned to activate the hall-effect sensors, the removal key also contains a magnet to capture the user-key. The user-key has a flat top that is made of iron or steel. In the preferred embodiment, the top is made of steel. As the removal key is passed over the steel cap of the user-key, and as the hall-effect sensors cause the release of the user-key, the user-key is pulled out of the key receptacle by the magnetic attraction between the steel cap and the magnet embedded in the removal key. 
     The present invention, in its preferred embodiment, is installed by first removing the original golf cart key-switch assembly. Then, the control unit of the present invention is inserted into the same place left empty by the prior art unit by connecting the electrical units of the present invention to the battery pack used to power the golf carts and by physically securing the face plate to the golf cart. Twelve volts of direct current are needed to operate the present invention. 
     Once the present invention is installed, the renter of the golf cart obtains a properly encoded user-key after paying the rental fee. To operate the golf cart, the user-key is inserted into the key receptacle of the control unit. Once the key is properly inserted, the user-key capture-plunger secures the key in the key receptacle so that the user-key cannot be removed except by a specially coded removal key. When the user-key capture-plunger captures the user-key, the magnets in the user-key are properly aligned with the hall-effect sensors located next to the key receptacle. Magnetic interaction between the magnets in the user-key and the hall-effect sensors activates the electrical circuit in the control unit which, in turn, activates the golf cart power system. The golf cart is now ready for use. 
     At the end of the rental time, the golf cart is returned to the club house with the user-key still attached to the golf cart. A caddy now can remove the user-key by using the removal key. Proper use of the removal key involves passing the removal key in front of the face plate and allowing the magnets embedded in the removal key to interact magnetically with the hall-effect sensors located behind the face plate. These hall-effect sensors cause a circuit to be activated so that the user-key capture-plunger is magnetically pulled back from its resting position partially inside the key receptacle. Once pulled back, the user-key capture-plunger can no longer prevent the removal of the user-key. The magnet embedded in the removal key and located directly over the steel cap now magnetically attracts the steel cap out of the key receptacle and thus removes the user-key from the key receptacle. 
     The staging key can be used when the caddy drives the golf cart from one place to another for maintenance purposes or when the caddy brings the golf cart from the garage to the individual who rented the golf cart. The staging key functions just like the user-key except it does not require a removal key to remove it from the control unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the prior art golf cart in its environment, with the prior art golf cart activation module enlarged for ease of identification. 
     FIG. 2 is an electrical schematic of the prior art golf cart key-switch assembly. 
     FIG. 3 is a frontal perspective view of the control unit of the preferred embodiment. 
     FIG. 4 is an exploded rear perspective view of the control unit of the preferred embodiment. 
     FIG. 5 is an electrical schematic of the control unit of the preferred embodiment. 
     FIG. 6 is a side view of the user-key. 
     FIG. 6A is a partial cross section view of the proper placement of the user-key in the key receptacle immediately prior to the user-key&#39;s capture by user-key capture-plunger. 
     FIG. 7 is a partial cross section view of the user-key, key receptacle, and user-key capture-plunger assembly after user-key has been properly inserted and captured. 
     FIG. 8 is a cross sectional view of the combination removal and staging key. 
     FIG. 9 is a partial cross section view of the proper placement of the combination removal and staging key when used to remove the user-key. 
     FIG. 9A is a partial cross section view of the proper method of removing the user-key from the key receptacle after the user-key is released by user-key capture-plunger. 
     FIG. 10 is a cross section view of the proper placement of the combination removal and staging key when the staging key is used to activate the golf cart. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Applicant&#39;s invention can be used on any device for which locks and keys are used to limit access. However, because Applicant has only implemented the current invention on golf carts as of the time of this application, the following detailed description of the preferred embodiment is for golf carts only. 
     FIG. 1 shows the prior art golf cart key-switch assembly  21  installed in golf cart  20 . From the user&#39;s perspective, only key switch  22  and face plate  22   a  can be seen when operating golf cart  20 . 
     FIG. 2 is an electrical schematic of the prior art golf cart key-switch assembly  21 . Golf cart key-switch assembly  21  consists of key switch  22  embedded in face plate  22   a . Electrical switch  23  is attached to key switch  22  and is oriented generally perpendicularly to face plate  22   a . Connectors  23   a  and  23   b  connect electrical switch  23  to the electrical circuits of golf cart  20 . Connector  23   a  links electrical switch  23  to relay  24 . Relay  24  controls the activation of golf cart electronics. Relay  24  is connected to golf cart electronics module  25  and ground  26 . Connector  23   b  links electrical switch  23  to power source  27 , which, in the case of golf carts, is a 36 volt DC battery assembly. 
     Turning to the present invention, FIG. 3 shows a front perspective view of control unit  30  of the preferred embodiment of single access control system. Control unit  30  consists of various subcomponents, with the major subcomponents being face plate  31 , keyhole  33 , key receptacle  34 , leaf spring  35 , solenoid  36 , relay  37 , circuit board  38 , and power connector  39 . With the exception of face plate  31 , detailed descriptions of each subcomponent will be described in later sections of this detailed description. A detailed description of face plate  31  will be given at this time. 
     Face plate  31  is a generally rectangular plate made of metal, plastic, or any other hard material. Two round openings,  32   a  and  32   b , are drilled into the lower portion of face plate  31  so that face plate  31  can be secured to golf cart  20 . Further, two mounting ears,  41   a  and  41   b , are located on the upper part of face plate  31 . Mounting ears  41   a  and  41   b  facilitate the installment of control unit  30  onto golf cart  20 . In the preferred embodiment, keyhole  33  and key receptacle  34  are located on one side of control unit  30 . However, so long as the design elements described in the following pages are met, keyhole  33  and key receptacle  34  can be located anywhere or in any relative position on face plate  31 . 
     Two key control indicators,  40   a  and  40   b , are located on face plate  31 . In essence, key control indicators  40   a  and  40   b  are LEDs used to indicate the activation and deactivation of golf cart  20 . In the preferred embodiment, when user-key  100  (as will be subsequently described) is properly inserted into key receptacle  34  and golf cart  20  is activated, one key control indicator,  40   a  or  40   b , lights up. When removal key  112  (as will be subsequently described) is properly used for user-key  100  removal and golf cart  20  deactivation, both key control indicators  40   a  and  40   b  light up. Once user-key  100  has been removed from control unit  30 , both key control indicators  40   a  and  40   b  are turned off. Although two LEDs are used in the preferred embodiment of the present invention, other means such as no display, a single LED, a liquid crystal display, or any other digital or analog display can be used to indicate the activation or deactivation of golf cart  20 . 
     FIG. 4 shows an exploded rear perspective view of control unit  30 . Face plate  31  is attached to golf cart  20  by any conventional fastening means. In the preferred embodiment, face plate  31  is attached to golf cart  20  by inserting screws  50  and  51  (not shown) through round openings  32   a  and  32   b  and boring screws  50  and  51  (not shown) into the instrument panel of golf cart  20 . Base plate  52  is attached generally perpendicularly to the back side of face plate  31 . In the preferred embodiment, the depth of base plate  52  is less than the length of face plate  31 . However, as long as the design requirements disclosed in this detailed description of the invention are met, base plate  52  can be longer in depth than the length of face plate  31 . 
     Base plate  52  provides a surface onto which circuit board  38  is attached. Although, in the preferred embodiment, circuit board  53  is attached to base plate  52  via a plurality of nuts  54 , bolts  55 , and washers  56 , circuit board  38  can be attached to base plate  52  by glue or any other conventional means. 
     Referring now to FIGS. 4 and 5 in combination, a variety of electrical components are attached to circuit board  38  by soldering or any other conventional means. The electrical components include relay  37 ; diodes  57  and  58 ; transistors  60  and  61 ; hall-effect sensors  63 ,  64  and  65 ; hall-effect sensors  69 ,  70 , and  71 ; and resistors  73 ,  74 ,  75 , and  76 . Diodes  57  and  58  are flyback control diodes. Although not shown in the preferred embodiment, diodes  57  and  58  can be replaced by other conventional voltage transient suppressors, such as capacitors. Transistors  60  and  61  control solenoid  36  and relay  37 , respectively. Hall-effect sensors  63 ,  64  and  65  are field density and polarity sensitive. They are used in the user-key  100  removal process and are located against the back side of face plate  31 . Each sensor is tuned to respond to a different field density and polarity corresponding to their counterpart magnets embedded in removal key  112  (see FIGS.  8  and  9 ). Although three hall-effect sensors are used in the preferred embodiment, the number of hall-effect sensors can be increased or decreased as needed. LEDs  67  and  68  are used as indicators for user-key insertion and removal. Hall-effect sensors  69 ,  70 , and  71  are field density and polarity sensitive. They are used in the golf cart  20  activation/user-key  100  (see FIGS. 6 and 6A) insertion process. Each sensor is tuned to respond to a different density and polarity corresponding to the density and polarity of its counterpart magnet in user-key  100  and staging key  111 . Hall-effect sensors  69 ,  70 , and  71  are placed against the side of key receptacle  34  facing circuit board  38 . Although three hall-effect sensors are shown in the preferred embodiment, the number of hall-effect sensors can be increased or decreased as needed. 
     Power connector  39  is attached to circuit board  38 . Power connector  39  connects control unit  30  to the power source of golf cart  20  via power cords  53   a  and  53   b . Power connector  39  taps 12 volts of direct current from golf cart  20 &#39;s battery pack. 
     Solenoid  36  can be attached to circuit board  53  or base plate  52  via any conventional means. In the preferred embodiment, solenoid  36  is attached to base plate  52  by using screws  78  and  79 . User-key capture-plunger  77  is retractable into solenoid  36 . 
     Key receptacle  34  can be attached to circuit board  53  or base plate  52  via any conventional means. In the preferred embodiment, key receptacle  34  is attached to base plate  52 . Key receptacle  34  is a generally elongated rectangular box with an irregularly shaped inside perimeter. The inside perimeter of key receptacle  34  is irregularly shaped so that only an user-key  100  with the exact complementary irregularly shaped outside contour can fit into key receptacle  34 . Thus the irregular shape of the inside perimeter of key receptacle  34  ensures proper positioning of magnets  106 ,  107 , and  108  located in user key  100  and magnets  113 ,  114 , and  115  located in staging key  111  prevents unauthorized access and cross facility access to golf cart  20 . 
     Leaf spring  35  is flexibly attached to key receptacle  34 . Leaf spring  35  can be attached to key receptacle  34  by any conventional means. In the preferred embodiment, leaf spring  35  is attached to key receptacle  34  by means of screw  80 . Although, in the preferred embodiment, leaf spring  35  is made of a thin flexible piece of plastic, leaf spring  35  can be made of any thin flexible material. Leaf spring  35  is shaped like an axe, with the tip of the long handle portion attached to key receptacle  34  at a point near face plate  31 . The axe head portion of leaf spring  35  is square shaped, with orifice  81  drilled in approximately the middle of the square. Orifice  81  allows user-key capture-plunger  77  to be secured to and passed through leaf spring  35 . A second orifice  82  (not shown) is located at the side of key receptacle  34  and directly aligned with orifice  81 . This second orifice  82  allows user-key capture-plunger  77  to pass though the side wall of key receptacle  34  and extend into the inside perimeter of key receptacle  34 , thereby securing user-key  100  when user-key  100  has been properly inserted, while preventing user-key capture-plunger  77  from extending too far into key receptacle  34 . 
     In alternative embodiments, the entire electrical assembly of control unit  30  may be potted solid to prevent moisture accumulation and corrosion due to the constant exposure to the outside atmosphere. 
     FIG. 5 shows the electrical schematic of circuit board  38 . This electrical schematic diagram can be further subdivided into two major sections. Section  90  controls the golf cart starter mechanisms. Section  91  controls the user-key removal system. Voltage is applied at junctions  92  and  93 . 
     In order for current to flow through section  90 , user-key  100  must be inserted into key receptacle  34  as shown in FIG.  7 . The magnetic fields in magnets  106 ,  107 , and  108  embedded in user-key  100  activate hall-effect sensors  69 ,  70 , and  71 , respectively, thereby completing the circuit in section  90 . While in the preferred embodiment relay  37  is used to maximize interchangeability with alternative golf cart activation electrics of varying voltages, polarities, and so forth, in future embodiments, the function of relay  37  may be performed by a sold-state or other electro-mechanical component best suited to a specific cart electronic design. Once the circuit in section  90  is completed, current flows between junctions  92  and  93  to relay  37 . Relay  37  primarily consists of inductor  94  and key switch  95 . The magnetic effects of inductor  94  activates key switch  95 , which in turn activates the electrical systems of golf cart  20  via relay  24 , thereby allowing someone to drive golf cart  20 . Key switch  95  remains in the “on” position as long as current flows through inductor  94 . Diode  58  is connected in parallel to relay  37  and reduces electrical surges when user-key  100  is removed. Resistor  74  and LED  68  are connected in series with respect to each other, but are connected in parallel with respect to diode  58  and relay  37  and act to signal the completion of circuit section  90 , the proper insertion of user-key  100 , and the activation of golf cart  20 . Finally, electrical current is controlled by passing through transistor  61 , which is switched on or off by current flowing through resistor  73  and hall-effect sensors  69 ,  70 , and  71 . 
     Section  91  controls the deactivation of golf cart  20 . When removal key  112  (see FIGS. 9 and 9A) is properly positioned in front of face plate  31 , the magnetic fields of magnets  116 ,  117 , and  118  embedded in removal key  112  activate hall-effect sensors  73 , 64  and  65 , respectively, and allow current flow through resistor  76  to transistor  62 . This switches on transistor  62  to allow electrical current flow through solenoid  36 , which mainly consists of magnetic core inductor  96 . Magnetic core inductor  96  magnetically pulls user-key capture plunger  77  out of notch  104 , thereby releasing user-key  100 . Diode  57  is connected parallel to solenoid  36  and reduces electrical current from flowing back towards junction  92  when current stops following through inductor  96 . Resistor  75  and LED  67  are connected in series with respect to each other and in parallel with respect to diode  57  and solenoid  36 . LED  67  signals the correct placement of removal key  112  and the completion of circuit section  91 . Finally, electrical current is controlled by transistor  62  which is switched on or off by, resistor  76 , and hall-effect sensors  63 ,  64 , and  65 . 
     The completion and activation of the circuit in section  91  leads to the deactivation of section  90 . When solenoid  36  causes user-key capture-plunger  77  to release user-key  100 , user-key  100  can then be removed. When user-key  100  is retracted from key receptacle  34 , magnets  106 ,  107 , and  108  no longer cause hall-effect sensors  69 ,  70 , and  71  to complete the circuit in section  90 . When current no longer flows through relay  36 , key switch  95  automatically is returned to the “off” position, thereby shutting down the electrical system of golf cart  20 . 
     Although the preferred embodiment of the present invention uses magnets and hall-effect sensors to complete the above described circuit, other methods of completing the above circuit can also be used. Conventional magnetic key cards, optical codes, or touch memory, along with their respective code reader, can be used to complete the above described circuit. Further, any conventional means, whether mechanical, electrical, or a combination of both, can be used to capture magnetic key cards, optical codes, or touch memory to prevent renters from using the magnetic key cards, optical codes, or touch memory more than once. Although it is contemplated that the means for preventing renters from using the key cards or bar codes more than once is through a magnetic key card or bar code capturing key receptacle, any means that will prevent renters from using golf cart  20  more than once can be adapted to the present invention. When properly implemented, magnetic key cards, optical codes, or touch memory can further regulate access to golf cart  20 , the number of rounds of golf the user(s) are authorized to use golf cart  20 , and the length of time the user(s) are authorized to use golf cart  20 . When the number of renters exceeds that which has been authorized or when the rounds played exceeds the number for which rental fee has been paid, or when the allotted time has expired, golf cart  20  is automatically shut down. All of the above will give golf clubs better control to the access of golf carts, thereby increasing their revenue. 
     FIG. 6 shows a side view of user-key  100 . In the preferred embodiment, steel cap  101  is circular in shape. However, to prevent cross-facility compatibility, steel cap can be of different shapes and sizes. User-key  100  has a generally elongated body perpendicularly attached to a flat steel cap  101 . The body of user-key  100  has a proximate end  102  and a distal end  103 , ending in tip  105 . Notch  104  is cut near the distal end  103  of user key  101 . Notch  104  extends cross sectionally some distance into the body of user-key  100 . The body of user-key  100  has an irregularly shaped cross section that can snugly fit into the irregularly shaped inside perimeter of key receptacle  34 . The cross section of user-key  100  is reduced at distal end  103  from notch  104  to tip  105  by means of a cant  105   a . A plurality of magnets—magnets  106 ,  107 , and  108  in the preferred embodiment—are embedded into the body of user-key  100 , along its longitudinal axis. Magnets  106 ,  107 , and  108  differ in polarity and field strength in order to deter unauthorized copying of user-key  100 . For future embodiments of this invention, a greater number of magnets can be embedded into user key  100  to further complicate and prevent unauthorized copying. As the number of magnets embedded inside of user-key  100  increases, the number of hall-effect sensors in control unit  30  should increase accordingly. However, in future embodiments, the number of hall-effect sensors do not have to precisely match the number of magnets embedded in user-key  100 . 
     A number of other features of user-key  100  can reduce cross facility compatibility, prevent accidental pocketing, and allow inventory tracking of user-key  100 . Cross facility compatibility—i.e. using keys from one country club at another country club—can be reduced or prevented by, for example, varying the size and shape of key hole  33  and steel cap  101 , and/or by varying the cross section of user-key  100  and key receptacle  34 . Accidental pocketing of user-key  100  can be prevented by enlarging the size of user-key  100 , making it too bulky to carry in one&#39;s pocket. Finally, inventory tracking of user-key  100  can be achieved by recording the alphanumeric codes located in each user-key  100 . 
     FIG. 6A shows user-key  100  inserted into key receptacle  34  immediately prior to being captured by user-key capture-plunger  77 . As user-key  100  is pushed into key receptacle  34 , tip  105  comes into contact with user-key capture-plunger  77 . User-key capture-plunger  77  is pushed away from key receptacle  34  by the distal end  103  of user-key  100  across the cant  105   a  between tip  105  and notch  104 . When user-key  100  is completely inserted into key receptacle  34 , notch  104  lines up with user-key capture-plunger  77 . Because user-key capture-plunger  77  is attached to leaf spring  35 , user-key capture-plunger  77  springs back into key receptacle  34  to rest snugly inside notch  104 . In this position, user-key capture-plunger  77  prevents golf cart renters from removing user-key  100 . 
     As shown in FIG. 7, when properly inserted, user-key  100  fits snugly into key receptacle  34 . Similarly, user-key capture-plunger  77  should fit snugly inside notch  104 . In addition, magnets  106 ,  107 , and  108  should line up with hall-effect sensors  69 ,  70 , and  71 . Finally, the outside surface of steel cap  100  rests evenly with the outside surface of face plate  31 . This arrangement discourages renters from forcibly prying user-key  100  out of key receptacle  34 . 
     FIG. 8 shows combination removal and staging key  110 . Combination removal and staging key  110  comprises of staging key  111  and removal key  112  attached together in the shape of an “L.” Removal key  112  forms the vertical arm of the “L” and staging key  110  forms the horizontal arm of the “L.” A plurality of magnets-the precise number, position, polarity, and field strength generally corresponding to the number, position, field strength, and polarity of magnets embedded in user-key  100 —are embedded in the staging key  111 , on the side facing the bend of the “L.” In the preferred embodiment, three magnets— 113 ,  114 , and  115 —generally similar imposition, field strength, and polarity to magnets  106 ,  107 , and  108  are embedded in staging key  111 . Likewise, a plurality of magnets—in the preferred embodiment magnets  116 ,  177 , and  118 —capable of activating hall-effect sensors  63 ,  64 , and  65  are embedded in removal key  112  on the side facing away from the bend of the “L.” In addition, magnet  119  is embedded in removal key  112  in order to magnetically attract steel cap  101  (and the entire user-key  100 ) after user-key  100  is released by user-key capture-plunger  77 . 
     The length and thickness of removal key  112  can vary depending on the number of embedded magnets. However, although the length of staging key  111  can vary, it is designed so that it cannot be captured by user-key capture plunger  77 . Furthermore, in order to be able to inset staging key  111  into key receptacle  34 , the cross section of staging key  111  can never be thicker than user-key  100 . The cross section of staging key  111  can either match the outside contours of user-key  100  or it can be so much smaller than the inside contours of key receptacle  34  that it can be inserted into key receptacle  34  despite the fact that its outside contour does not match the inside contour of key receptacle  34 . In the preferred embodiment, the cross section of staging key  111  is rectangular and is smaller than the cross section of user-key  100 . 
     FIG. 9 shows the proper usage of combination staging and removal key  110  to remove user-key  100  from control unit  30 . Generally, in order to remove user-key  100 , removal key is placed in front of face plate  31 . When embedded magnets  116 ,  117 , and  118  are properly lined up with hall-effect sensors  63 ,  64 ,  65 , respectively, solenoid  36  is activated and user-key capture-plunger  77  is pulled away from notch  104  of user-key  100 . User-key  100  is now no longer held in key receptacle  34  by user-key capture-plunger  77  and can be removed at any time. 
     When magnets  116 ,  117 , and  118  are properly aligned with hall-effect sensors  63 , 64 ,  65 , magnet  119  is also aligned with steel cap  101 . As shown in FIG. 9A, after user-key capture-plunger  77  releases user-key  100 , magnet  119  can pull user-key  100  out of key-receptacle  34  via the magnetic attractive forces between magnet  119  and steel cap  101 . 
     Although only three magnets and three hall-effect sensors are used in the preferred embodiment, future embodiments of the present invention can include a larger number of magnets, each with a different polarity and field strength, and a suitable—but not necessarily equal—number of hall-effect sensors adjusted to respond to the precise polarity and field strength of its counterpart magnet. 
     FIG. 10 illustrates the correct placement of staging key  111 . When inserted into key receptacle  34 , magnets  113 ,  114 , and  115  line up with hall-effect sensors  69 ,  70 ,  71 , respectively, and golf cart  20  is activated. Since staging key portion  111  does not extend beyond user-key capture-plunger  77 , staging key  111  is not captured once it is inserted into key receptacle  34 . Therefore, staging key  111  can be freely removed without the aide of removal key  112 . 
     When staging key  111  is inserted into key receptacle  34 , the position of removal key  112  is such that magnets  116 ,  117 ,  118 , and  119  are facing away from face plate  31 . Such a configuration prevents key removal circuits from being accidentally activated. 
     A conventional golf cart  20  can easily be retrofitted with the present invention. First, the original golf cart key-switch assembly  21  requiring a conventional metallic key is disconnected and removed from golf cart  20 . Second, control unit  30  of the present invention is installed into golf cart  20  by connecting power connector  39  to a 12 volt DC power source provided by the battery pack of golf cart  20 . Then, control unit  30  is affixed to golf cart  20  in the location vacated by the original golf cart key-switch assembly  21  by using, for example, screws  50  and  51  (not shown) or any other conventional device generally used to secure one object to another. 
     Once control unit  30  is installed, golf cart  20  can only be activated by a properly coded user-key  100  or by staging key  111 . A plurality of magnets, each differing in polarity and field strength, are embedded in user-key  100 . A duplicate set of magnets, with each magnet generally matching in location, polarity, and field strength to the magnets embedded in user-key  100 , are embedded in staging key  111 . User-key  100  is given to the golf cart renter(s) after proper rental fees have been paid and the identity of the renter(s) properly recorded. Golf cart  20  is then activated by inserting staging key  111  into key receptacle  34  and brought to the renter(s) by an authorized person. The authorized person deactivates golf cart  20  and removes staging key  111  from key receptacle  34  before turning the control of golf cart  20  over to the renter(s). In order to activate golf cart  20 , the renter(s) must insert user-key  100  into key receptacle  34 . Once inserted, user-key  100  is captured in key receptacle  34  and can no longer be removed by the renter(s). Thus, the renter(s) cannot remove user-key  100  and gain access to golf cart  20  in the future without first paying a rental fee. Furthermore, if the renter(s) somehow damages golf cart  20 , other property, or causes another some injury, his/her/their identity can be retraced via user-key  100  and he/she/they or any other unauthorized individual he/she/they allowed to use golf cart  20  can be held accountable for the damage(s). 
     After the renter(s) finish(es) the round of golf, golf cart  20  is returned to the clubhouse, and authorized personnel can inspect golf cart  20  to ensure no damage was done during the rental period. After such inspection, user-key  100  can be removed from key receptacle  34  by using removal key  112 . 
     Authorized personnel can access golfcart  20  for maintenance purposes by using user-key  100  or staging key  111 . 
     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.