CA1340420C - Electronic lock system with portable access device - Google Patents

Abstract

A lock in a secure entry system for use with a source of DC power having high frequency pulse width with modulation thereon comprising a housing and a key container mounted in said housing movable between accessible and inaccessible positions. Circuitry is provided within the housing for controlling the movement of the key container and is adapted to be connected to the source of DC power.
The circuitry includes a filter having a capacitor. The circuitry is capable of receiving the high frequency pulse width modulated DC power. The capacitor serves to supply at least some of the power required by the circuitry during the time the pulse width modulation is occurring on the DC
power supplied. A latch mechanism is provided to prevent opening of the key container to an accessible position by hammer blows applied to the housing.

Description

ELECTRONIC LOCK SYSTEM
WITH PORTABLE ACCESS DEVICE
This invention relates to an electronic lock. 1~ ~0 ~ 0 In United States Letters Patent No. 4,609,780 there is disclosed an electronic secure entry system, apparatus and method. In that apparatus and system, a battery is pro-vided in the apparatus and system for operating the elec-tronics within the lock box. A card is provided for use with the lock box. In one embodiment, a keyboard is provided as an integral part of the lock box in which the private code of the user can be inserted. In another embodiment a card is provided which is separate from the lock box and which can be utilized to insert a private code by communicating with the electronics in the box by sensor coils carried by the box. In co-pending Canadian patent application, Serial No. 545,119, filed August 21, 1987 (now Canadian patent No. 1,274,894) there is disclosed an electronic access card which can be utilized with a lock box of the type described in U.S. Patent No. 4,609,780, but which carries its own electronics and a battery type power supply. In Canadian application Serial No. 545,118 filed August 21, 1987 there is disclosed an electronic access card of the type disclosed in application Serial No.
545,119 but with a visual display. In connection with the foregoing, it has been found that it is desirable to provide additional features for an electronic lock box and access device which are not within the capabilities of the lock box and access devices of the type hereinbefore dis-closed. As for example, it is desirable to provide aaccess device which has minimal, if any, power requirements when it is not being operated. There is therefore a need for a new and improved electronic lock box, access device, system and method.
In general, it is an object of the present invention to provide an electronic lock box, access device, system and method in which the power required for operating the lock - 2 - 1~4042~

box is substantially supplied from the power supply in the access device.

Another object of the invention is to provide a lock box, access device, system and method in which the timekeeping function is supplied by the access device.

Another object of the invention is to provide a lock box, access device, system and method in which information is conveyed by the use of high frequency pulse width modula-tion of the DC power.

Another object of the invention is to provide a lock box, access device, system and method of the above character in which modulation is in the form of pulse width modulation.

Another object of the invention is to provide a lock box for use in a secure entry system in which the lock box is provided with a safety means to prevent access to the container in the lock box by hammer blows applied to the lock box.

Another object of the invention is to provide a secure entry system having lock boxes and access devices and in which the power supply is provided in the access device and in which normally open switch means is provided in the access device for preventing power from being supplied by the access device until the access device is mated with a lock box.
Another object of the invention is to provide a access device for use in a secure entry system in which the access device is provided with the sole timekeeping function.

Another object of the invention is to provide a access device for use in a secure entry system in which the access device is provided with the sole power supply.

- 3 ~ 1 3 4 0 i 2 3 Additional objects and features of the invention will appear from the following description in which the pre-ferred embodiments are set forth in detail in conjunction with the accompanying drawings.

Figure 1 is a front elevational view of a lock box with a access device disposed therein incorporating the present lnvent lon .

Figure 2 is a side elevational view of the lock box and access device shown in Figure 1.

Figure 3 is a rear elevational view partially in cross section of a lock box shown in Figures 1 and 2 with the rear cover removed.

Figure 4 is a side elevational view in cross section of the lock box shown in Figure 2 and showing in broken lines the position of the key container in an open position.
Figure 5 is an enlarged cross-sectional view of a portion of the lock box shown in Figure 3.

Figure 6 is a cross-sectional view taken along the line 6-6 of Figure 5.

Figure 7 is a block diagram of the electronics utilized in the lock box using a CMOS memory with a keep alive battery and showing the manner in which it is connected to the access device.

Figure 7A is a curve showing high frequency pulse width modulation applied to the D.C. voltage utilized in the lock box and access device shown in Figure 7.
Figure 7B is a curve showing the voltage across the capacitor C1 in the lock box in Figure 7.

.. , . . , .,~ _.

~ 4 - i~ 40~20 Figure 8 is a block diagram of an alternate embodiment of the electronics utilized in the lock box using a EEPROM
memory with no battery in the lock box and showing it connected to the access device and in which the access device is shown with the rear cover removed.

Figure 9 is a block diagram of the electronic circuitry utilized in the access device.

In general, the secure entry system of the present inven-tion is comprised of a plurality of lock boxes, each having housing and a container therein movable between accessible and inaccessible positions. Circuitry is provided within the housing for controlling the movement of the key con-tainer. A plurality of access devices are provided. Eachaccess device has a keyboard. A battery is mounted in the access device and electronic circuitry is provided in the access device coupling the battery to the keyboard means and means is carried by each lock box and by each access device for establishing electrical contact between the access device and the box for supplying power from the battery in the access device to the circuitry in the lock box to operate the circuitry in the lock box.

More particularly, as shown in the drawings Figures 1-7, the electronic lock box and access device system 16 con-sists of an electronic lock box 17 and a access device 18 which as shown in Figure 1 can be disposed in the lock box 17 and is removably mounted therein.
The electronic lock box 17 consists of a housing formed of a suitable material such as die cast zinc or aluminum. The housing 21 is provided with parallel spaced apart side walls 22 and 23 and a top wall 24. The bottom side of the housing 21 is provided with a rectangular opening 26 which opens into a rectangular box-shaped recess 27 that extends to an intermediate wall 28 of the housing 21 which is 13404~0 spaced apart and parallel to the top wall 24. The housing 21 is provided with a rectangular opening 29 which is closed by a cover plate 30 seated in a generally rectangu-lar recess 31 which is formed in the side walls 22, 23, the top wall 24 and in the intermediate wall 28. The cover plate 30 is held in place by suitable means such as non-removable screws 32 threaded into bosses 33 formed in the housing 21.

The housing 21 is also provided with a front wall 34 which extends generally in a plane spaced apart from and parallel to the rear cover plate 33. The front wall 34, the side walls 22 and 23 and the cover plate 30 define a generally rectangular compartment 36 accessible through the rectangu-lar opening 29. A forwardly facing recess or cavity 37which has a generally rectangular configuration is provided in front of the front wall 34 and is adapted to receive the access device 18. The rear side of the recess or cavity 37 is formed by the front wall 34. Upper and lower walls 39 and 41 extending perpendicular to the front wall 34 define the upper and lower extremities of the recess or cavity 37.
The walls 39 and 41 are provided respectively by upper lower protrusions 42 and 43 formed as an integral part of the housing 21. The sides of the recess or cavity 37 are open for a reason hereinafter described. However, the upper and lower extremities of the sides of the recess 37 are closed off by upper spaced apart parallel ribs 44 and 45 and lower spaced apart parallel ribs 46 and 47. As shown particularly in Figure 1, these ribs 42, 43, 46 and 47 serve to retain the access device 18 within the recess or cavity 37 when the access device is removably positioned in the lock box 17 as hereinafter described.

Spring loaded contacts 48 and 49 are carried by the housing 21. The contacts 48 and 49 are comprised of pins 51 which are provided with conical tips 52 and a flanged head 53.
The pins are seated in a block 54 of a suitable insulating ~340420 .~

material such as a plastic. The pins 51 extend downwardly through holes 56 provided in the blocks 54 and have the flanged heads 53 disposed within recesses 57 also provided in the block 54. The blocks 54 are placed in the housing 21 through recesses 55 extending from the rear which are formed in the upper protrusion 42. Springs 58 are disposed in the recesses 57 and yieldably urge the pins 51 in a downward direction. The upper extremities of the springs 58 engage inserts 59 formed of a suitable insulating material so that the springs 58 and the pins 51 are insu-lated from the housing 21.

The spring-loaded contacts 48 and 49 as shown, are adapted to be engaged by the access device 18 to make electrical contact therewith. Once the access device 18 has been slid into the cavity or recess 37 it will be retained therein by the spring-loaded contacts as well as by the ribs 44, 45, 46 and 47. Because of the sides of the recess 37 are open, the access device 18 can be readily engaged by the hands from the sides and pushed upwardly against the spring loaded contacts to remove it from the recess 37 when desired.

The housing 21 is provided with upstanding generally cylindrical bosses 61 and 62 formed integral with the top wall 24. The bosses 61 and 62 are provided with cylindri-cal holes 63 and 64 with a reinforcing rib 65 therebetween.
The holes 63 and 64 are adapted to receive a U-shaped shackle 66. As can be seen one end 66a of the shackle 66 extends into the hole 64 and terminates in a position above the wall 24. The other end 66b of the shackle 66 extends through the hole 63 and through the top wall 24 and into the compartment 36. The end 61b is provided with a conical tip 67 and with a recess 68 which is spaced above the conical tip 62. The recess 68 is defined by a generally flat surface 69 and a truncated conical surface 71. The recess 68 is adapted to receive the free end of an L-shaped leaf spring 72. 13 4 0 ~ ~ ~

The lower extremity of the L-shaped leaf spring 72 is secured to an upstanding ear 73 formed on a sheet metal chassis 74 which has a generally L-shaped configuration.
The chassis 74 is secured within the compartment 36 adjac-ent the side wall 31 and secured to the housing 21 by suitable means such as push nuts 76 engaging posts 77 formed integral with the housing. The lower extremity of the leaf spring 72 is secured to the ears 73 by suitable means such as rivets (not shown). The leg portion 72a of the leaf spring 72 is provided with a hole 78 through which the portion 66b of the shackle 66 extends. The spring force normally applied by the leaf spring 72 is such that the leg portion 72a is normally engaged by the flat 69 provided on the portion 66b of the shackle 66 and serves to normally retain the shackle 66 in a latched position so that it cannot be removed from the housing 21.

Solenoid operated means 79 is provided for moving the leaf spring 72 from the normal latched position to an unlatching position and consists of a plunger 81 which is movably mounted in a coil 82. The coil 82 is secured to an up-standing ear 83 provided on the chassis 74 by suitable means such as screws (not shown). The plunger 81 extends through a hole 84 provided in the ear 83 and is adapted to engage the leaf spring 72 to move the upper extremity of the same to the left as viewed in Figure 3 to move the leaf spring to an unlatched disengaging position in which the hole 78 is moved into alignment with the portion 66b of the shackle 66 permitting the shackle 66 to be removed from the housing 21. The plunger 81 is provided with a head portion 81b which limits the travel of the plunger so as to prevent the plunger from moving the leaf spring into a position which would move the hole 78 out of registration with the portion 66b of the shackle 66. After the solenoid 79 is deenergized it returns to its normal position, permitting the leaf spring 72 to return to its normal latching posi-tion. When it is desired to reinsert the shackle 66, the conical tip 67 will cam the leaf spring 72 out of the way to permit the portion 66b of the shackle to enter the hole 78 before it again seats in the recess 68 as the shackle 66 is pushed downwardly into the housing 21.

A key container 86 which can serve as access means is removably mounted in the rectangular recess 27 provided in the bottom of the housing 21. The key container 86 is formed of a suitable material such as chromium plated steel and is formed of a U-shaped member 87. A top plate 88 is mounted in the upper extremities of the U-shaped member 87 in a suitable manner. Thus by way of example, the top plate 88 can be provided with spaced apart ears 89 provided on opposite sides of the same which extend through slots 90 and 91 provided in the U-shaped member 91. The U-shaped member 91 with the top plate 88 forms the key container which is open at opposite ends and provides a space 93 therein which is adapted to receive one or more keys of a conventional type.

An upstanding pin 94 is mounted in the top plate 88 by suitable means such as a press fit. The pin 94 is provided with a conical tip 96 adapted to extend through a hole 97 provided in the intermediate wall 28. A C-ring 98 is mounted on the pin 94 adjacent the conical tip 96. The pin 94 is also provided with an annular recess 99 which is formed by a tapered or truncated conical surface 101 which adjoins a champer 103. A flat surface 102 is provided as a part of the recess 99 and is adapted to be engaged by a leg portion 104a of an L-shaped leaf spring 104. The leg portion 104a is provided with a hole 105 through the pin 94 is adapted to extend. The leaf spring 104 has its upper extremity secured to an ear 106 provided on the chassis 74 by suitable means such as rivets (not shown).

Solenoid operated means 107 is provided for moving the leaf spring 104 between pin latching and pin unlatching posi-tions and consists of a plunger 108 which is mounted in a coil 109 secured to another ear 111 provided on the chassis 74 by suitable means such as screws (not shown). When the solenoid 107 is energized, the plunger 108 is moved to the right of Figure 3 to engage the leaf spring 104 to move it from the dotted line position shown in Figure 3 to the solid line position and from a latched to an unlatched position permitting the key compartment 87 to be moved downwardly under the force of a coil spring 112 provided on the pin 94 disposed between the top wall 88 of the key container 86 and the lower or bottom side of the intermedi-ate wall 28. The spring 112 yieldably urges the key container or access means 86 from an inaccessible position to an accessible position as shown by the dotted lines in Figure 4 to permit removal of a key or keys from the recess or compartment 93. Outward movement of the key container 86 is limited when the ring 98 is engaged by the leg portion 104a of the leaf spring 104. This permits the key container to be moved into a position so that the keys contained within the space 93 are readily accessible while still preventing the key container from being separated from the housing 21.
Additional safety latch means 116 is provided for prevent-ing the key container from being opened by tampering. The safety latch means 116 consists of a safety latch plate 117 slidably mounted on top of the intermediate wall 28 and being generally confined for movement from one side to the other of the housing 21 and being captured by an L-shaped member 118 provided as a part of the chassis 74. The latch plate 117 is generally rectangular in shape as shown in Figure 6 and is provided with a substantially centrally disposed hole 121 which is generally rectangular in con-figuration but which has one side which is facing the side-wall 22 which has a semi-circular configuration. The pin lO- 13~0420 94 extends through the hole 101 and is provided with an annular recess 123 which has straight sides in which the safety latch plate 117 travels so that the latch plate 117 can move between pin engaging and pin disengaging positions with respect to the cutout 121 and the annular recess 123.
The forward extremity of the latch plate 117 is provided with a downwardly extending protrusion 124 which has been formed in the latch plate that is adapted to seat in a cutout or recess 126 formed in the intermediate wall 28 of the housing 21. Means is provided for urging the forward extremity of the latch plate 117 in a downward position as viewed in Figure 5 and also for yieldably urging the latch plate 117 to the left as viewed in Figure 5 and consists of a large L-shaped leaf spring 128 which has a leg 129 which is secured to the ear 111 by suitable means such as rivets (not shown). The leaf spring 128 is also provided with another leg 131 which overlies the latch plate 117 and is provided with a large rectangular cutout 132 through which the pin 96 extends. The outer extremities of the leg 131 are secured to the forward extremity of the latch plate 117 by suitable means such as rivets 133. The leaf spring 128 is provided with a hole 134 through which the plunger 108 for operating the leaf spring 104 extends.

The operation of the safety latch means 116 may now be briefly described as follows. If someone is attempting to tamper with the lock box 117 in order to gain access to the key container or key compartment 86 by striking the lock box with a hammer such efforts will be futile because of the operation of the safety latch means. In the event a hammer blow is placed on the right hand side of the housing 21, as for example, against the side wall 23 of the housing as shown in Figure 5, the hammer blow will accelerate the housing to the left as viewed in Figure 5. When this occurs, the inertia of the mass of the safety latch plate 117 inhibits movement of the latch plate 117 to the left with the housing. Thus, as the housing moves to the left, .. , ~.. . .

:~ 34942~

the projection or protrusion 124 carried by the latch plate 117 will drop into the recess 126 provided in the housing.
At the same time the pin 94 moves in the cutout 121 in the latch plate 117 so that the flat surface 102 carried by the pin 94 overlies the upper surface of the latch plate 117.
This will prevent the pin 96 from becoming disengaged in the event the force supplied by the hammer blow is suffi-cient to cause the lower extremity of the leaf spring 104 to be accelerated to the right as viewed in Figure 5 because of its mass to release the pin 96. Thus it can be seen that even if this should occur, the safety latch plate 117 because of its greater mass than the leaf spring 104 and its associated inertia will move to a latching position with respect to the recess 126 before any unlatching can 15 occur with respect to the leaf spring 104 and the pin 96.

In the event that the housing 21 has been struck with a hammer blow which is sufficient to cause operation of the safety latch means 116, access to the key container 86 20 cannot be obtained until the safety latch means has been released. This can be readily accomplished merely by pushing up on the key container 16 in Figure 5. As soon as this upward movement commences, the leaf spring 104 will snap into place in the recess 99 to again latch the pin 96 25 and the key container 86 in a closed or inaccessible position. This latching of the leaf spring 104 will occur prior to unlatching of the safety latch means 116 because of the additional clearance provided in the annular recess 123. Continued upward movement of the key container 86 30 with the pin 96 thereon causes the enlarged portion of the pin 96 to come into engagement with the safety latch plate 117 to move the protrusion 124 carried thereby out of the recess 126. As soon as this occurs, the yieldable force provided by the leaf spring 128 moves the leg 131 and the 35 protrusion 124 carried thereby to the dotted line position shown in Figure 5 and permitting movement of the latch plate 117 to the left with respect to the housing 21 under -- 12 - 13~0420 the force of the leaf spring 128 so that the surface 102 of the pin 94 no longer overlies the latch plate 117. Thus it can be seen that the key container latch is reset before the safety latch 116 is reset.

The safety latch 116 remains in this position throughout operation of the electronic lock box and only comes into play when a hammer blow of sufficient force strikes the right-hand side of the housing 21 as viewed in Figure 5.
Hammer blows into other parts of the housing 21 in differ-ent directions will not and cannot cause accidental opening of the key container latch 86 because the forces would be in the wrong direction to cause the leaf spring 104 to release the pin 94.
The safety latch means has been designed so that it actuate with a relatively low force so that it is sure to become effective before any force can be applied which would be efficient to cause release of the key container latch.
20 Thus the safety latch means serves as means for providing inadvertent opening of the key container by tampering. The safety latch means is constructed in such a manner so that it can be readily reset.

25 The lock box 17 and the access device 18 are provided with cooperative switch means for connecting the battery in the access device 18 to the circuitry in the access device when the access device is inserted into the lock box 17. Such means consists of a circular permanent magnet 141 which is 30 seated in a recess 142 provided in the chassis 74. The magnet 141 is held in place by a tab 143 forming a part of the chassis 74. Because the housing 21 is formed of a non-magnetic material, magnetic lines of force from the magnet 141 pass through the front wall 34 of the housing 21 and 35 are adapted to operate a reed switch S-1 provided in the access device 18 (see Figure 2).

.

- 13 - 134042d An encapsulated electronics module 146 is provided in the compartment 36. It is provided with a printed circuit board (not shown) which is encapsulated therein. The electronics module 146 is provided with recesses 147 and 5 148 which are formed to accommodate a speaker 151 mounted on the rear cover plate 30. Holes 152 are provided in the cover plate 30 to permit the transmission of sound therethrough from the speaker 151. A circular ring 153 of a suitable resilient material such as rubber is mounted on the exterior side of the cover plate 30.

Means is provided for preventing the lock box from scratch-ing or marring doors and other objects on which the lock box is hung. Such means takes the form of a guard 161 15 formed of a suitable material such as rubber or plastic which surrounds the lower extremity of the housing 21 as shown particularly in Figures 3 and 4. A bumper strip 162 is provided on the exterior surface of the cover plate 30 near the top thereof and is also formed of a suitable 20 material such as rubber or plastic. A shroud 164 encloses the exposed portion of the shackle 66 exterior of the boss and is also formed of a suitable material such as a trans-parent plastic.

25 The access device 18 is provided with a molded plastic case 171 which has a rear removable cover plate 172. The case 171 encapsulates a printed circuit board (not shown). As shown in Figure 8, a battery compartment 173 has been provided within the case 171 and is of a size so that it is 30 capable of receiving an alkaline battery of J size provid-ing a six volt output and having a capacity of 500 miliamphere hours. As also shown in Figure 8, the reed switch S1 is disposed within the encapsulated case 171.
The battery 174 is provided with a case formed of an 35 insulating material which will not short out the components on the printed circuit board. The electronic circuitry which is provided within the case 171 is connected to - 14 - 134042~

output terminals 176 and 177 provided on the top side of the access device 18 and are adapted to be engaged by the spring-loaded contacts 48 and 49 of the lock box.

The upper rear side of the case 171 is provided with a space in which a label 181 is placed. The label 181 carries a bar code 182 as well as a secure entry number 133 and a call-in date 184. The cover plate 172 is provided with spaced parallel notches 186 near its lower end. It also provides space for a label 187 that carries operating instructions for the access device 18.

The front side of the access device 18 (see Figure 7) is provided with a keyboard 191 which is of the type described in co-pending application Serial No. 899,533, filed on August 22, 1986. The keyboard 191 is provided with two holes, 192 and 193 through which light emitting diodes of the type hereinafter described can be viewed. As shown the keyboard 191 contains key pads 194 for the numbers 0 through 9. It also includes a "battery test" key pad 196 which underlies the hole 192 and a "clear/start" key pad 197 which underlies the hole 193. Also included is a "set 24 hour use" key pad 198, a "set daytime only" key pad 199, a "send" key pad 201, a "remove lock box" key pad 202, an "update card" key pad 203, and an "obtain key" key pad 204.

The electronics for the lock box 17 is shown in block diagram form in Figure 7 and shows the manner in which the electronics is connected to the contacts 176 and 177 of the access device or access device 18 through the spring-loaded contacts 48 and 49 provided in the lock box 17. The electronics, as shown in Figure 7, includes a micropro-cessor 221 which can be any standard eight bit micropro-cessor having low power requirements. A battery Bl is provided in the housing 21 of a lithium type which provides back-up power for the memory 222 which is of a conventional type as, for example a CMOS static memory. The battery Bl 134042~
also provides back-up power to a crystal controlled clock 223 which is provided with a crystal 224. The clock 223 is used to provide time and date information for the lock box 17 as hereinafter described.

As hereinbefore described, the access device 18 is provided with a reed switch S1. The reed switch is normally open and controls the energization of the contacts 176 and 177 provided on top of the access device 18. The reed switch Sl is normally in an open position and thus no power is provided to the contacts 176 and 177 during the time the reed switch is in this position. This serves to prevent any accidental short circuits in the event the contacts 176 and 177 come into contact with the conductor when the 15 access device 18 is not inserted into a lock box as, for example, when carried in a pocket of a user. When the access device 18 is inserted into the lock box as shown in Figures 1 and 2, the reed switch S1 is actuated by the magnet 141 to cause power to be supplied to the contacts 20 176 and 177. Typically the voltage supplied from the contacts 176 and 177 is approximately 5 - 1/2 volts and is approximately twice that supplied by the lithium battery Bl inside the lock box. A diode D1 is provided in the circuitry in Figure 7 which is reverse biased and serves to 25 assure that the electronics in the lock box will be oper-ated from the power provided by the battery 174 in the access device. As soon as the access device is removed from the lock box, the memory 222 and the clock 223 will revert to being operated by the back-up lithium battery B1.
A diode D2 is provided which is in series with the diode D1 and is reversed biased to prevent voltage from being supplied from the lithium battery B1 to other parts of the electronics when the access device 18 is removed from the 35 lock box 17. This reduces the drain on the battery B1 and ensures that the battery B1 will have a long lifetime.

- 16 - 1~4~420 The contacts 176 and 177 are energized when the access device 18 is placed within the lock box and DC power 225 is supplied to a filter comprised of a diode D3 and a capacitor C1 for filtering the power supplied from the battery in the access device 18 which supplies power to the various components in the electronics in the lock box.
Zener diodes D4 and D5 serve as protection diodes to protect the electronic circuitry in the lock box. In addition to the DC power 225 being supplied on the conduc-tors 226 and 227 from the contacts 176 and 177, a highfrequency pulse width modulated digital data signal 228 is supplied on a conductor 229 from the conductor 226 to a decoder detector 231. The modulated digital data signal 228 is achieved by turning the DC power on and off at a high frequency as, for example, at the 32 kilohertz fre-quency selected in the present invention to provide two different types of series of interruptions to transfer digital data information in the form of "O's" and "l's".
Thus, for example, as shown in Figure 7A, the "0" can be in the form of four interruptions, each having a width of time tl which at 32 kilohertz corresponds to 16 microseconds and eight or twelve of such interruptions of time interval tl to transmit a "1".

During the times of these interruptions, the capacitor C1 serves to supply the necessary continuous power to the lock box electronics during each interval tl during the presence of high frequency pulse width modulation of the DC power from the access device. During the time intervals t2 shown in Figure 7A, the six volt DC power is supplied to the line 229 and at the same time the capacitor C1 is recharged.
The microprocessor 221 therefore receives uninterrupted power either from the battery in the access device or from the capacitor C1 in the lock box. At the same time the microprocessor 221 will receive any of the high frequency data in the signal 228 on the line 229. This high fre-... .. . . ~ . .

- 17 - 134042d quency data is unfiltered and unaffected by the capacitor C1.

In connection with the foregoing, it is desirable to keep the time tl relatively small so as to minimize the amount of power required from the capacitor C1. The time t2 should be sufficiently large to permit the recharging of the capacitor C1. In addition, it is desirable to keep the time tl relatively small to minimize the voltage ripple on the capacitor C1 as represented by the voltage Vc shown in Figure 7B which is approximately 5.5 volts. It can be seen that during the time tl that the voltage on the capacitor decreases by a slight amount by approximately 20 to 25 millivolts and then is rapidly recharged to the 5.5 volt level during the time t2.

The decoder detector 231 is of a conventional type and detects and decodes the signal supplied on the conductor 229 to provide a clock signal on the conductor 232 to the microprocessor 221 and a data signal on the conductor 233 also supplied to the microprocessor 221. During the time that the access device 18 is transmitting data or commands to the lock box 17, a filter comprised of the capacitor C1 and the diode D3 filters out the high frequency signal being supplied. Thus the power being supplied to the components of the electronics is free of the high frequency components.

The microprocessor 221 is connected to control logic 234 by a conductor 236. The control logic 234 is of a type disclosed in U.S. Patent No. 4,609,780. The control logic 234 is connected by conductors 237 and 238 to the solenoid 82 and 109 provided for the shackle 66 and the key con-tainer 86 respectively. The microprocessor 221 in addition to supplying signals to the control logic 234 supplies signals to a DTMF (dual tone multifrequency) block 241 which energizes the speaker 151. As explained in U.S.

- 18 - 1~40420 Patent No. 4,609,780, the DTMF block 241 is utilized for transmitting data stored in the memory 222 of the lock box to a central computer. As explained previously in U.S.
patent 4,609,780, the data contained in the memory 222 is 5 converted to DTMF tones and transmitted to a central computer along with other information such as the serial number of the lock box, the time and date of the trans-mission and the serial number of the owner of the lock box and the serial number of the sender of the data and the identification number and time and date of each key con-tainer opening.

In Figure 9 there is shown the electronics for the access device, largely in block diagram form. As shown therein, 15 the schematics include the keyboard 191, the operation of which is well known and is generally described in applica-tion Serial No. 545,119 filed on August 21, 1987. The keyboard or key pad 191 is connected to a microprocessor 251 of a conventional type. It also can be an eight bit 20 microprocessor having low power requirements. It is provided with a crystal 252 which is utilized for providing the timing to the microprocessor and is also utilized for creating the high frequency signal 225 hereinbefore de-scribed which is utilized for communicating with the lock 25 box 17.

The circuitry for the access device 18 includes two bat-teries Bl and B2 with the battery Bl providing an approxi-mately 6 volt output and the battery B2 providing an approximately 3 volt output. The battery Bl can be the large alkaline type battery 174 hereinbefore described, whereas the battery B2 can be a relatively low power lithium-type battery having a long life. The battery B2 is designed to operate the microprocessor and the electronics 35 within the access device and is designed to operate at very low power so that the lithium battery B2 should be capable of meeting the power requirements of the access device for - 19 - 1~40420 a period of 5 to 6 years. The larger battery B1 or 174 is utilized for supplying power to the lock box and is a replaceable battery which can be replaced when needed.
Thus the battery B1 is usually replaceable, whereas the battery B2 is not intended to be replaceable except at the factory.

A battery test circuit is provided for testing the battery B1 to ascertain when it should be replaced. The battery test circuit is activated when both the battery test button 196 and the clear/start button 197 are depressed simulta-neously. This requirement for simultaneous depression of these two buttons is provided to ensure that operation of the battery test button by itself could not possibly occur accidentally in the pocket of a user and activate the test circuit and inadvertently drain the battery B1.

Upon simultaneous depression of the buttons 196 and 197 a battery test signal is supplied by the microprocessor 251 to a conductor 253 through a resistor R8 to turn on a transistor Q4. When the transistor Q4 turns on current flows through the collector and through the resistors R1 and R2. The resistors R1 and R2 serve as a voltage divider which is connected by a conductor 254 to a comparator A1.
The comparator A1 utilizes the three volt output from the lithium battery B2 as its reference. Since the lithium battery has a long life, the voltage output form it is very stable and serves as a reliable reference for the comparator A1. The six volt battery voltage of the battery B1 is measured against the three volts provided by the battery B2. If the output from the battery B1 is relative-ly high in excess of three volts, the output from the comparator A1 goes up and supplies a signal to a green light emitting diode D2 and resistor R7 identified in Figure 9. The resistive values of the resistors R1 and R2 are chosen to be relatively low to reflect the same type of load that the battery B1 would receive in operating the , ~
.

- 20 - 134042~

lock box. If the light emitting diode D2 does not light up, this indicates that the battery Bl should be replaced.

AS the pads or buttons of the keyboard 191 are depressed to supply appropriate commands to the access device, this information is supplied to the microprocessor 251. The 32 kHz high frequency output 228 from the crystal 252 is supplied by a conductor 256 to an OR gate as shown in Figure 9. This 32 kHz frequency signal is gated by a gating signal supplied to the OR gate to an output conduc-tor 257 from the microprocessor 251. As shown, the OR gate is supplied with a three volt signal and thus has a DC
output which swings from O to 3 volts which is supplied through a conductor 258 to a comparator A2. The comparator A2 iS provided for translating the O to 3 volts swings provided by the OR gate to O to 6 volt swings so that it can be used with the 6 volt output from the alkaline battery 174 or Bl. The comparator A2 is provided with a 1.5 volt reference and provides a high frequency pulse width modulated signal on the DC which swings between O and 6 volts.

The signal from the conductor 257 to the OR gate is in digital form as shown in Figure 9. The signal supplied by the comparator A2 is supplied by a conductor 259 to two base current limiting resistors R3 and R4 which are con-nected to the bases of transistors Ql and Q2 in which Ql is a PNP transistor and Q2 is a NPN transistor connected in a push-pull configuration. As can be seen, the transistors Ql and Q2 are connected to the 6 volt battery supply and can only be energized when the reed switch Sl is operated to supply output signals to the contacts 176 and 177 provided on the exterior of the access device 18. When the reed switch Sl is open when the access device 18 is not in the lock box 17, even though the output of the comparator A2 is attempting to turn on the transistor Q2 no base current can flow nor can collector current flow because the . .

13~0~20 , reed switch Sl is open. As soon as the access device 18 is placed in the lock box 17, the reed switch Sl closes. The positive 6 volts is normally connected to the contact 176 but the negative contact 177 is not energized until it is connected to ground when the transistor Q2 is turned on thereby creating approximately 6 volts across the contacts 176 and 177. If a signal is present on the output of the comparator A2 which contains data or a command from the microprocessor 251, the transistors Ql and Q2 are turned off in an appropriate manner to create a high frequency power signal across the contacts 176 and 177. This power signal is deciphered by the lock box electronics hereinbefore described and decoded by the microprocessor in the lock box to determine the operations to be performed.

The microprocessor 251 is provided with a second output 263 in addition to the output 257 which is connected to a resistor R5 to the base of a transistor Q3. The micropro-cessor 251 supplies an output on the line 263 each time a key is depressed on a keyboard 191. When the transistor Q3 is turned on it drives a red light emitting diode Dl through a current limiting resistor R6. A resistor R5 limits the base current for the transistor Q3.

The contacts 176 and 177 are connected by the conductors 261 and 262 to the transistors Ql and Q2. A conductor 266 is connected to the conductor 262 which is connected to ground through two resistors R8 and R9 with a "program in'~
line 267 being connected between the resistors R8 and R9 and to the microprocessor 251. This circuitry permits data to be sent to the microprocessor 251 to program the micro-processor, as for example, the serial number identity of the access device and other information important to the operation of the access device. This permits the micropro-cessor 251 to be programmed from an external programmer bysupplying information in pulse width modulated form. The microprocessor 251 can be readily placed in a receive mode 1~04~0 ..

or in a program mode by pressing the clear/start button 197 and then by depressing the send button 201. This places the access device in the program mode and places it in a condition in which it can accept data and decode that data to update its memory as well as other functions. This "program in" line 267 is only used to initialize the access device with the serial number and other pertinent bits of information that it needs for its operation. The access device thereafter can be updated from the keyboard 191 as described in co-pending application Serial No. 545,119 filed on August 21, 1987.

Another embodiment of the electronic circuitry for a lock box 17 which does not require the use of an internal battery is shown in Figure 8. In the embodiment of the circuitry for the lock box shown in Figure 7, the circuitry shown required the use of an internal back-up battery because of the static CMOS ram which was used for the memory 222. As is well known to those skilled in the art, such a memory requires a continuous application of power to it to maintain the memory. In Figure 8, in place of the static CMOS ram memory 222 there is provided a memory 271 which does not require the use of a back-up battery. It is an EEPROM (electrically erasable programmable read-only memory). This type of memory as is well known to those skilled in the art is provided with a memory which can be erased and rewritten and which does not require any back-up power for maintaining the data in the memory. Also to eliminate the need for a battery in the electronic circuitry of the lock box, the clock and time keeping function performed by the clock in the lock box 17 is removed from the lock box and this function is performed by the access device 18. Thus the need for the crystal con-trolled clock 223 provided in Figure 7 is eliminated. This clock and time keeping function as it is performed by the access device 18 as hereinafter be described. The remain-13~ 'l2i~
. , der of the circuitry shown in Figure 9 is substantially identical to that which is shown in Figure 7.

Similarly, the circuitry for the access device which is used for performing the timekeeping function for the lock box is substantially identical to that shown in Figure 8 with the exception that the microprocessor is provided with an internal real time clock which is incorporated in the firmware to provide time and date information.

Operation and use of the access device 18 and the lock box 17 shown in Figures 7 and 9 may now be briefly described as follows. Let it be assumed that it is desired to obtain access to a key container. To accomplish this the access device 18 is inserted into the lock box in the manner hereinbefore described. The user's four digit private code is then inserted into the access device and the "obtain key" button is depressed. During that transaction the access device transmits to the lock box who the person is, the serial number of the access device and the update code and also the function code for opening the key container.
The access device responds to that information by actuating the solenoid for releasing the key container and also records the time and date and the identity of the access device for later transmission.

Operation and use of the access device 18 and the lock box 17 shown in Figures 8 and 9 may now be briefly described as follows. Let it be assumed that it is desired to obtain access to a key container. To accomplish this the access device 18 is inserted into the lock box 17 in the manner hereinbefore described. The user's four digit private code is then inserted into the access device and the obtain key button is depressed. During that transaction the access device in addition to telling the box who the person is, the serial number of the access device and the update code and the function code for opening the key container, the - 24 - 1340~20 access device will also send an additional series of l's and 0's that would supply the time and date information to the lock box. The time and date information would be supplied to the access device at the time of initialization of the access device. There is no capability for the user to change the time and date in the access device.

It can be seen that by use of lock boxes and access devices of the type hereinbefore described it has been possible in certain embodiments to reduce the dependence on batteries in the lock box to a very small long-life back-up battery when CMOS rams are utilized in the memory and can be eliminated entirely when EEPROMs are utilized for the memory.
In many applications of the electronic lock box, access device system and method, it is typical that a group of identification numbers would be utilized for providing access to the containers of the lock boxes limited to a single real estate board such as a multiple listing real estate board. In such arrangements, a real estate agent can only obtain access to lock boxes in the system of that real estate board. The agent would not be able to obtain access to lock boxes in the system of another real estate board. This ensures that unauthorized entry from real estate agents of other boards cannot obtain access to the lock boxes of another real estate board.

However, it should be appreciated that there are situations in which it may be desirable to have agents from different real estate boards have access to the lock boxes of other real estate boards. This is particularly true in metro-politan areas which occur on the East Coast and West Coast of the United States in which there are multiple listing real estate boards in close proximity to each other. In such areas, it is often desirable that a real estate agent be able to show properties that are listed under adjacent 13~0 i2~
real estate boards. This capability can be obtained with the present electronic lock boxes, access device system and method by programming the access device or access devices with group identification numbers of the authorized groups.
This could be as few as one or as many as 15 to 20 differ-ent groups. Thus the lock boxes for each group would be programmed with a unique group identity which could be in the form of a three or four digit code. With a access device so programmed, when a real estate agent is attempt-ing to obtain access to a lock box, a access device wheninserted into a lock box will send all of the group identi-fication numbers which have been placed in the access device to the lock box during a transaction. If the lock box group identification number is contained in the trans-mission from the access device or card, the lock box willpermit access to its key container, if the access device also transmits an update code that is current.

To accomplish the entering of group identification numbers into the access device or an access device, the software which is utilized for initializing the access device includes the group identification numbers to which the real estate agent is to have access. With the access device or access device programmed in this manner, a typical trans-mission from the access device to a lock box would be asfollows.
xxxxxxxx xxxx xxxxxxxxxx xxxxxx Group ID S/N Agent Name Time/Date xxx xxx xxxx xxxx xx xx Agent Tel No. Update Check Operate/Function Code Sum Code All of the above can be transmitted in ASCII characters with the group identification utilizing up to eight digits, the serial number utilizing up to four digits, the agent's name up to 10 digits, the time and date, the agent's telephone number, the update code which is in the computer from the group identification number and the serial number - 26 - 1340~23 which tells the lock box whether or not the agent's access device is a current or valid access device. This is followed by a check sum to check the validity of the transmission and a two-digit operate code or function code.
This instructs the lock box as to whether it is to permit opening of the key container or removal of the shackle of the lock box or other desired function. In other words, this last code is a function code.

By programming the access device or access devices 18 in this manner, the agent is unaware of these additional pieces of information being supplied from the access device to the lock box. The agent merely punches in his or her four digit personal access code or ID number and presses the appropriate function key on the access device to accom-plish the desired function as, for example, opening of the key container or removal of the shackle.

It should be appreciated that in connection with the above in the one embodiment of the invention where the time and date information is contained in the lock box the time and date information would not be transmitted from the access device. It is only in those situations where there is no battery in the lock box and no timekeeping function in the lock box that the time and date information is transmitted from the access device.

In the event it is desired to utilize an access device which has been provided with a visual display of the type disclosed in application Serial No. 545,118 filed on August 21, 1987, the lock box during a transaction would supply to the access device the serial number, the agent's telephone number, the agent's name and time and date of each transac-tion. In addition, the box would identify its own serial number, the owner's name and telephone number. The person who owns the lock box in a real estate application might be the listing agent or the broker. Also transmitted could be the time and date of the transmission from the lock box to the access device to provide a record when the lock box was interrogated. In addition, the lock box could also trans-mit its own group identification number.

It is apparent from the foregoing that there has been provided an electric lock box, access device, system and method which has many advantages. They are particularly advantageous in applications where reliance on battery power in the lock boxes is undesirable. The lock box has been constructed in such a manner so the shackles can not be removed and access obtained to the key containers. By the use of group identification numbers, it is possible to permit real estate agents from one board to have access to the lock boxes of one or more additional real estate boards.

.

Claims (3)

1. In a lock for use in a secure entry system, a housing, access means mounted in said housing movable between accessible and inaccessible positions, circuitry within said housing for controlling movement of said access means, said circuitry including means for receiving DC power, said means for receiving DC power including a filter having a capacitor, said circuitry for receiving high frequency pulse width modulation superimposed on said DC power, said capacitor serving to supply at least some of the power required by said circuitry during the time said pulse width modulation is superimposed on said DC power.

2. A lock as in claim 1 wherein said circuitry receives said high frequency pulse width modulated DC power in the form of two separate and different series of interruptions of said DC power and wherein each of said interruptions extends over a period of time which is substantially less than the time required to discharge the charge on said capacitor by a substantial amount.

3. A lock as in claim 2 wherein said circuitry includes a microprocessor and wherein said microprocessor receives its DC power from said means for receiving DC
power.