U.S. patent number 3,848,229 [Application Number 05/273,529] was granted by the patent office on 1974-11-12 for electronic lock system.
This patent grant is currently assigned to Arthur D. Little, Inc.. Invention is credited to John T. Fowler, Robert R. Perron.
United States Patent |
3,848,229 |
Perron , et al. |
November 12, 1974 |
ELECTRONIC LOCK SYSTEM
Abstract
An electronic lock system in which a coded data word is stored
in a key and, upon insertion of the key into a lock, compared with
a master code, a positive comparison providing actuation of the
lock. Lack of correspondence between the key code and the master
code causes actuation of an alarm and can also cause seizure of the
key in the lock. Digital circuitry is employed in both the key and
lock and is configured to permit easy alteration of the stored code
to greatly enhance system security. Only four interconnections need
couple the key to the lock and the stored key code can be
selectively altered to further enhance system security.
Inventors: |
Perron; Robert R. (Beverly,
MA), Fowler; John T. (Winthrop, MA) |
Assignee: |
Arthur D. Little, Inc.
(Cambridge, MA)
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Family
ID: |
26830610 |
Appl.
No.: |
05/273,529 |
Filed: |
July 20, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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132671 |
Apr 9, 1971 |
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Current U.S.
Class: |
235/382;
902/4 |
Current CPC
Class: |
G07C
9/00182 (20130101); G07C 2009/00761 (20130101) |
Current International
Class: |
G07C
9/00 (20060101); H04q 009/00 () |
Field of
Search: |
;340/149A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pitts; Harold I.
Attorney, Agent or Firm: Stein and Orman
Parent Case Text
REFERENCE TO RELATED APPLICATIONS
This application is a continuation of Ser. No. 132,671 filed Apr.
9, 1971 and now abandoned.
Claims
We claim:
1. An electronic lock system comprising:
a key including a structural member adapted for engagement with an
associated lock and an electronic data memory therein having a
plurality of interconnected stages operative to store an
electrically alterable multiple bit key code and terminal means for
coupling said key to an associated lock by which said key code can
be conveyed from said electronic data memory in response to a clock
signal;
a lock adapted for operation with said key and including a
receptacle for receiving the structural member of said key in
operative engagement therewith;
an electronic data memory for storing a multiple bit master
code;
means for comparing said key code stored in said key data memory
with said master code stored in said master code memory;
clock means for providing a clock signal to said key data memory to
cause readout of said key code to said comparison means for
comparison of said key code with said master code;
said comparison means being operative to provide an output
indication upon receipt of a key code from said key data memory
corresponding to said master code; and
logic means receiving said output indication from said comparison
means and operative in response thereto to provide an output
signal.
2. An electronic lock system according to claim 1 wherein:
said comparison means is also operative to provide a second output
indication upon receipt of a key code from said key data memory
which does not correspond to said master code;
and said logic means is operative in response to said second output
indication to provide a second output signal.
3. An electronic lock system according to claim 1 wherein said lock
includes means operative after comparison of said key code with
said master code for reentering a key code into the electronic data
memory of said key.
4. An electronic lock system according to claim 1 wherein said lock
includes:
means for detecting the presence of said structural member in
operative position with said lock receptacle and for providing a
signal indication of key presence; and
means operative in response to said key presence signal indication
to initiate comparison of said key code with said master code.
5. An electronic lock system according to claim 2 wherein said lock
includes means within said receptacle for preventing removal of
said key therefrom during comparison of said key code with said
master code.
6. An electronic lock system according to claim 5 wherein said
removal preventing means is operative in response to said second
output indication from said comparison means to capture said key in
said lock receptacle upon non-identity between said key code and
master code.
7. An electronic lock system according to claim 2 wherein said
comparison means is operative to compare said key code and said
master code on a bit by bit basis and to provide said second signal
indication upon detection of a bit of said key code which does not
compare with the corresponding bit of said master code.
8. An electronic lock system according to claim 1 wherein said key
data memory is of a data capacity to store predetermined data in
addition to said key code;
and wherein said lock includes:
a second electronic data memory for storing said predetermined
additional data received from said key;
decoding means coupled to said second data memory and operative to
provide an output signal in response to said predetermined data in
said second data memory; and
gate means operative in response to the presence of both said
output indication from said comparison means and said output signal
from said decoding means to provide a utilization signal.
9. An electronic lock system comprising:
a key having a structural member adapted for engagement with an
associated lock and including therein:
a first electronic data memory having a plurality of interconnected
stages operative to store an electrically alterable multiple bit
key code;
a second electronic data memory having a plurality of
interconnected stages operative to store a predetermined multiple
bit code different than said key code; and
comparator means coupled to said first and second electronic data
memories and operative to compare said predetermined code in said
second data memory with an enable code provided by said lock and to
provide in response to correspondence between said enable code and
said predetermined code a command signal to said first data memory
to cause readout of said key code stored therein to said lock;
a lock adapted for operation with said key and including:
a receptacle for receiving the structural member of said key in
operative engagement therewith;
an electronic data memory for storing a multiple bit master
code;
means for comparing said key code with said master code and to
provide a signal indication upon receipt of a key code which
corresponds to said master code; and
logic means receiving said signal indication from said lock
comparing means and operative to provide an output signal in
response thereto.
10. An electronic lock system according to claim 9 wherein:
said lock comparing means is also operative to provide a second
signal indication upon receipt of a key code from said key data
memory which does not correspond to said master code;
and said logic means is operative in response to said second signal
indication to provide a second output signal.
11. An electronic lock system according to claim 10 wherein said
lock comparing means is also operative to provide said second
signal indication in response to non-comparison between said enable
code and said predetermined code.
12. An electronic lock system comprising:
a key adapted for insertion into an associated lock;
a multiple bit shift register within said key operative to store an
electrically alterable multiple bit key code representing key
identity and operative in response to clock signals from said lock
to convey said key code from said shift register to said lock and
to receive a key code from said lock;
a lock adapted for operation with said key and including
a receptacle for receiving said key in operative engagement
therewith;
circuitry operative to provide an output signal upon correspondence
between said key code and a master code, said circuitry
comprising:
means for detecting the presence of said key in operative
engagement with said lock receptacle and for providing a signal
indication of key presence;
timing means operative in response to said signal indication of key
presence for providing clock pulses for controlling operation of
said circuitry;
a master code register for storing a multiple bit master code;
digital comparator means operative to compare said key code
received from said shift register and said master code received
from said master code register and to provide a signal indication
upon correspondence between said key code and master code; and
logic means operative in response to said signal indication from
said digital comparator means to provide an output signal.
13. An electronic lock system according to claim 12 wherein:
said digital comparator means is also operative to provide a second
signal indication upon receipt of a key code from said key data
memory which does not correspond to said master code;
and said logic means is operative in response to said second signal
indication to provide a second output signal.
14. An electronic lock system according to claim 13 wherein said
logic means includes:
a first AND gate coupled to the output of said digital comparator
and to said timing means and operative to provide an output signal
upon detection of non-correspondence between said master code and
said key code;
a second AND gate;
a flip-flop maintained in one binary state by the presence of a
signal derived from said key detection means and providing in this
binary state an output signal to said second AND gate;
said flip-flop being operative in response to the output signal
from said first AND gate to switch to its second binary state
causing removal of the flip-flop output signal to said second AND
gate;
alarm circuitry operative upon detection of the output signal of
said first AND gate to provide an output indication of
non-correspondence between said master code and said key code;
and
decoding means for recognizing the last bit of said master code to
denote the end of the code comparison process and to provide an
enabling signal for said second AND gate to cause production of
said logic means output signal.
15. An electronic lock system according to claim 14 wherein said
timing means includes means for providing first clock pulses and
second clock pulses delayed with respect to said first clock pulses
by a predetermined amount, said first clock pulses being employed
to control data bit transitions in said logic circuitry, said
second clock pulses being employed to control data bit comparisons
in said logic circuitry.
16. An electronic lock system according to claim 14 wherein said
lock includes:
means for storing a new master code; and
means for transferring said new master code to said key shift
register and to said master code register.
17. An electronic lock system according to claim 14 wherein said
lock includes:
means for storing a new master code;
a second flip-flop coupled to the output of said second AND gate
and operative to remain in one binary state in the presence of an
output signal from said second AND gate and an opposite binary
state in the absence of an output signal from said second AND gate;
and
a third AND gate coupled to the output of said second flip-flop and
to said timing means and operative to provide a gating signal to
said new code storage means to transfer said new master code to
said master code register and to said key shift register.
18. An electronic lock system according to claim 12 wherein said
key shift register is of a data capacity to store a multiple bit
code longer than said key code, said key code being stored in said
shift register as part of the stored code.
19. An electronic lock system comprising:
a key having a structural member adapted for insertion into an
associated lock;
an electronic data memory within said structural member and having
plural interconnected stages each operative to store a bit of an
electrically alterable multiple bit code representing key
identity;
a plurality of first terminals on said structural member connected
to said electronic data memory and operative to couple said member
to an associated lock;
a lock adapted for operation with said key and including:
a receptacle for receiving the structural member of said key
therein;
a plurality of second terminals within said receptacle for coupling
to respective ones of said first terminals of said key with said
key in said receptacle;
logic circuitry coupled to said second terminals and having an
electronic data memory for storing a multiple bit master code;
first logic means operative with said key inserted in said
receptacle to compare the key code stored in said key data memory,
and to provide an output indication of correspondence between said
key code and master code; and
second logic means operative in response to said output indication
from said first logic means to provide an output signal.
20. An electronic lock system according to claim 19 wherein:
said first logic means is also operative to provide a second output
indication upon receipt of a key code from said key data memory
which does not correspond to said master code;
and said second logic means is operative in response to said second
output indication to provide a second output signal.
21. An electronic lock system comprising:
a key including
a structural member adapted for engagement with an associated
lock;
an electronic shift register disposed in said structural member and
operative to store an alterable multiple bit code representing key
identity and to read out said code in response to clock pulses from
said lock; and
a plurality of first terminals disposed in predetermined
disposition on said structural member and connected to said shift
register, said first terminals including a clock terminal, a data
input terminal and a data output terminal;
a lock including
a receptacle for receiving the structural member of said key and
having a plurality of second terminals operative to couple to
respective ones of said first terminals of said key;
means in said receptacle for detecting the presence of a key and
for providing an output indication of key presence; and
circuitry for decoding said key code and including
clock means operative in response to an output indication from said
key detection means for providing clock pulses for controlling the
key decoding process;
a master code register for storing a multiple bit master code;
a digital comparator operative in response to said clock pulses to
receive said master code and said key code and to provide a signal
indication upon detection of correspondence between said key code
and master code; and
logic means operative in response to said signal indication from
said digital comparator to provide an output signal.
22. An electronic lock system according to claim 21 wherein:
said comparator is also operative to provide a second signal
indication upon receipt of a key code from said key shift register
which does not correspond to said master code;
and said logic means is operative in response to said second signal
indication to provide a second output signal.
23. An electronic lock system comprising:
a key adapted for use with an associated lock and having an
electronic data memory therein with a plurality of interconnected
stages operative to store an electrically alterable multiple bit
key code and terminal means for coupling said key to an associated
lock by which said key code can be conveyed from said electronic
data memory in response to a command signal;
a lock adapted for operation with said key and including receptacle
means for receiving said key in operative association
therewith;
an electronic data memory for storing a multiple bit master
code;
means for providing a command signal to said key data memory to
cause readout of said key code to comparison means for comparison
of said key code with said master code;
means operative to compare said key code stored in said key data
memory with said master code stored in said master code memory and
to provide a signal indication upon receipt of a key code from said
key data memory corresponding to said master code; and
logic means operative in response to said signal indication from
said comparison means to provide a utilization signal upon
correspondence between said key code and said master code.
Description
FIELD OF THE INVENTION
This invention relates to lock systems and more particularly to an
electronic lock system employing active digital electronic
circuitry in both the key and lock.
BACKGROUND OF THE INVENTION
Electronic locks have been proposed in which an electronic circuit
in a lock is energized to activate the lock by use of a key
containing circuitry cooperative with the lock circuit. The
circuitry employed in a key has generally been of a type in which a
plurality of coded interconnections are provided to appropriately
energize an associated lock circuit. Such key circuitry, however,
usually contains a fixed code which is alterable only by rewiring
of the key circuit. There is little versatility of coding in such
conventional systems. In addition, the configuration of the key
circuit can be ascertained by appropriate analysis and the code
thereby duplicated. As a further disadvantage, such keys usually
require a relatively large number of interconnections with the
lock, with attendant increase in system cost and complexity.
SUMMARY OF THE INVENTION
In accordance with the present invention, a highly reliable and
secure electronic lock system is provided in which active data
storage means are provided within a key containing a readily
alterable coded data word corresponding to a master code stored in
an associated lock circuit. Upon insertion of the key into the
lock, the data stored in the key is compared with a master code in
the lock, identity therebetween causing actuation of the lock. In
the event that there is not exact comparison between the master
code and the key code, an alarm can be actuated and the key seized
within the lock to prevent its removal therefrom. By immediate
actuation of an alarm in the event of detection of one or more
incorrect bits of the key code, there is little opportunity to
attempt duplication of the key code and thereby materially
enhancing the security of the system. Analysis of the data storage
circuitry within the key will not reveal the data code stored
therein and even if the stored data were read out by interrogation
of the key, the data can be selectively coded such that it would
be, in practice, substantially impossible to analyze and decode the
data content thereof.
In a typical embodiment of the invention, the key contains a
multiple bit shift register for storing the key code and is
typically of the integrated circuit type having extremely low
energy requirements. Power is provided by a small battery source
located within the key. Alternatively, the shift register can be of
the nonvolatile type requiring no external power, in which case no
battery need be employed. Only four connections are required
between the key and the associated lock; one for transferring data
from the key to the lock, one for transferring data from the lock
back into the key, a ground connection and a clock line. Such
connection can be made by various electrical contact elements
suited to particular system requirements or, as an alternative,
connection can be made inductively.
DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood from the following
detailed description taken in conjunction with the accompanying
drawings, in which:
FIG. 1 is a simplified block diagram representation of a lock
system according to the invention;
FIG. 2 is a block diagram of an alternative key circuit embodying
the invention;
FIG. 3 is a partial block diagram of an alternative lock circuit
embodying the invention;
FIG. 4 is a more detailed block diagram of a lock system according
to the invention; and
FIG. 5 is a pictorial view, partly in section, illustrating a
typical key configuration embodying the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1 there is shown an electronic key 10 having a
memory 12 powered by a suitable energy source such as a battery 14.
The memory is typically a shift register of the low power type
constructed by monolithic integrated circuit techniques and is,
therefore, of extremely small physical configuration capable of
being readily mounted in a small key member. The battery is
typically a low power mercury battery also adapted for mounting in
the key member and capable of energizing memory 12 for a long
period of time. The power requirements of an integrated circuit
shift register are sufficiently small that the effective life of
battery 14 is determined more from the shelf life thereof rather
than the power drain. The key 10 is cooperative with an electronic
lock 16 and is coupled thereto by three lines, labeled data out,
data in and clock. The data out line carries data from memory 12 to
the lock circuit, the data in line carries data from the lock
circuit back into memory 12, and the clock line carries clock
pulses for shifting of data in and out of memory 12. In actual
implementation, a ground line would also interconnect key 10 and
lock 16.
The lock circuit 16 includes a data gate 18 connected to a memory
20, and operative to couple data from memory 12 to memory 20, and
to recirculate data from memory 12 back into memory 12 for
restorage of a key code therein. The memory 20 has an output
thereof coupled to a comparator 22 which also receives data from a
master code generator 24. The output of comparator 22 is connected
to logic circuitry 26 which provides a first output signal for
actuation of associated utilization means, and a second output
signal for providing an alarm indication in the event that an
improper key code is employed.
Memory 20 and associated components of the lock 16 can also be
typically implemented by integrated circuits. Timing of data from
the key to the lock circuit is accomplished by means of a clock 28
providing clock signals to memory 12 and to a control circuit 30
which governs operation of memory 20 and also provides master
timing signals to the lock system. An insertion detector 32 is
provided in the lock for sensing the presence of key 10 therein and
for providing in response to key detection a start signal to clock
28 for initiation of the key identification process. As will be
described, the insertion detector 32 can also cause mechanical
clamping of the key within the lock to prevent its premature
withdrawal during the code recognition cycle and also to capture
the key in the event that an improper key code is detected.
In operation, a multiple bit data word specifying a key code is
stored in memory 12 representative of a unique key identity, this
code being identical to a master code provided by generator 24
located in the lock circuitry. The key code contained within memory
12 is compared with the master code, positive identity between the
two codes enabling actuation of the lock. Non-correspondence
between one or more bits of the key code and the master code causes
actuation of an alarm indicating an attempt to utilize an improper
key. Upon insertion of key 10 into lock 16, the presence of the key
as determined by insertion detector 32 causes enabling of clock 28.
Clock pulses from clock 28 are applied to memory 12 and cause
readout of the data stored therein to data gate 18 and thence to
memory 20.
The data being shifted out of memory 12 is also recirculated via
data gate 18 back into memory 12 to reload the key code for
subsequent use. Upon loading of the data word into shift register
20, comparator 22 is operative to compare the data contents of
register 20 with that of master code generator 24 and to provide
output signals to logic 26 indicative of whether or not the coded
data from key 10 is identical to the master code pattern.
Comparison of the key code with the master code can be accomplished
on a bit by bit basis or on the entire code word after it is
shifted into comparator 22. If upon comparison between the master
code and the key code there is identical correspondence of all bits
therebetween, logic 26 provides an output signal to actuate the
associated lock or other utilization means. It will be appreciated
that the lock 16 can be associated with any utilization means which
is to be key operated, such as a locking mechanism for a door,
vault or the like, or electrical apparatus. If there is a lack of
correspondence between one or more bits of the master code and the
key code, logic 26 provides an alarm signal indicative of an
erroneous key code. The alarm signal can immediately actuate an
alarm indicator or can be employed with suitable counting circuitry
to permit a selected number of decoding attempts before an alarm is
actuated. Delayed alarm actuation is useful, for example, to
prevent a transient condition such as momentary contact loss from
causing an alarm.
The security of the present system is considerably enhanced by the
feature wherein any attempt to employ an incorrect key code will
serve to actuate an alarm. There is thus no opportunity to try
different possible key codes in an attempt to actuate the lock, as
the first wrong code will cause an alarm indication. It is possible
to cause readout of data stored in memory 12 to ascertain its data
content and thereby reproduce the key code. However, a key code can
be employed as part of the data in memory 12 such that
interrogation thereof will not reveal the key code. For example,
data stored in memory 12 can be configured such that the code
itself is contained at predetermined bit positions within a longer
stored word and coding schemes can be selected which are extremely
difficult if not practically impossible to decode. The length of
the data word stored in memory 12 also serves to enhance security
of the system; for example a 32 bit memory permits 2.sup.32
possible coding combinations.
System security can be further enhanced by use of a key which
communicates data to the lock circuit only upon receipt by the key
of a proper interrogation code. Such a technique is illustrated in
FIG. 2 which shows a first memory 34 coupled to a comparator 36
which, in turn, is coupled to a second memory 38. Each of the
memories 34 and 38 are typically integrated circuit shift registers
as described above. The memory 34 contains a predetermined code
word which is compared in comparator 36 with an enable code which
can be provided by the lock circuit. Upon detection by comparator
36 of identity between the enable code and the code stored in
memory 34, a read command is provided to memory 38 to cause readout
of a different code stored in memory 38. The code word from memory
38 is operative to actuate the lock after identity is established
between this code and the master code stored in the lock circuit,
as described above.
Upon interrogation of the key by an enable code which does not
compare with the preprogrammed data in memory 34, comparator 36 can
provide an alarm signal to the associated lock circuit. An alarm
indication can also be provided as above upon non-identity between
the master code in the lock and the code from memory 38. The
technique of FIG. 2 thus affords a dual encoding arrangement which
is of a higher order of security than the coding arrangement of
FIG. 1. Additional levels of coding can also be readily provided
according to the principles of this invention since small, low
power digital circuitry can achieve the key function.
In addition to storage in the key of a key identification code for
gaining access to the associated lock, the key can also contain
additional data representing the identity of the particular key, an
account number or the like. The system disclosed in FIG. 1 can be
modified as indicated in FIG. 3 to accommodate such additional
identification data. Referring to FIG. 3, data from a key is
composed of a first word representing the key code and a second
word representing other data such as a key number. This data is
applied from the key to a pair of memory stages. The key code word
is stored in memory 20a while the other identification code is
stored in 20b. The key code is compared with the master code in
comparator 22 in the same manner as described hereinabove.
The output of the comparator is applied to one input of an AND gate
23. The output of memory 20b is applied to a decoder 25, the output
of which is applied to the second input of AND gate 23. The code
processing cycle is governed by a counter 21 operative in response
to clock signals from clock 28, the counter providing a timing
sequence sufficient for loading data from the key into memories 20a
and 20b. Upon identification of the key code in comparator 22, an
output signal is provided by AND gate 23 for actuation of the lock.
Failure to detect a proper key code will prevent a lock actuation
output. In the embodiment of FIG. 3 failure to detect a proper code
in memory 20b will also prevent lock actuation. It is evident that
an output signal from decoder 25 representative of the additional
identity code stored in the key can be employed to record such key
identity, for example to denote the time that a particular key was
employed with the associated lock.
A more particular embodiment of the invention is illustrated in
FIG. 4. The key includes and has disposed therein a shift register
40 typically of the monolithic integrated circuit type and capable
of storing a predetermined number of data bits which comprise a key
code. Register 40 is powered by a suitable battery 42 which is also
of small physical size to fit within a key element. Data from shift
register 40 is communicative with the lock circuit by way of a data
gate 44 operative to recirculate data back into shift register 40
to retain the same key code, or to load register 40 with new data
to provide a new key code, as will be described.
Data from register 40 is applied to a digital comparator 46 which
also receives information from a master code register 48. Register
48 contains a master code word as provided by a master code
selector 50, which is used for comparison with the key code
contained in the shift register 40. System timing is governed by a
clock 52 which is started upon receipt of a start signal from a key
insertion detector 32, such as described above. Detector 32 also
energizes key clamp 33 which captures the key in the lock during
the identification cycle. A clock provides two output signals,
labeled respectively .phi..sub.1 and .phi..sub.2, which are clock
pulses recurring at the same clock rate but shifted in phase one
from the other by a predetermined amount, typically 180.degree..
The clock pulses .phi..sub.1 are advanced in phase from the clock
pulses .phi..sub.2 and are employed to control data bit
transitions, while the delayed clock pulses .phi..sub.2 are
employed to control bit comparisons. Thus it will be appreciated
that bit comparisons are accomplished at the midpoint of a bit
interval to assure that such comparisons are performed after
transients which may occur during bit transitions.
The clock pulses .phi..sub.1 are applied to register 48 and also to
a counter 54 operative to count the number of bits shifted out of
register 48. By means of a counter decoder 56, the last bit shifted
out of register 48 is recognized to denote the end of the code
comparison process. The key insertion detector 32 is operative to
clamp the key in the lock to prevent its premature removal prior to
completion of the decoding process. Detector 32 also provides a
signal to flip-flop 58 to set the flip-flop to one logical state,
the output signal thereof being applied to one input of an AND gate
62. Data in key register 40 and master register 48 are clocked out
bit by bit by clock pulses .phi..sub.1 and are compared bit by bit
in comparator 46. The comparator is operative to provide a first
output, say zero, if the bit from the key register is identical to
the bit from the master register, and to provide a second output,
say one, if there is not correspondence between the received data
bits. The output of comparator 46 is coupled to an AND gate 60
which also receives the clock pulses .phi..sub.2, the output of
gate 60 being applied to the reset input of flip-flop 58. The
output of flip-flop 58 is coupled to one input of an AND gate 62,
the other input of which is the output signal from counter decoder
56 for enabling gate 62.
Upon correspondence between a data bit from key register 40 and a
date bit from master register 48, AND gate 60 will remain disabled
and no reset signal will be applied to flip-flop 58. Thus,
flip-flop 58 remains in its set state so long as there is identity
between the key code and the master code providing an output signal
to gate 62. Upon detection of the last bit of the master code by
decoder 56, an output signal is provided therefrom to AND gate 62
to enable the gate and cause a signal for lock actuation. The
signal from decoder 56 is also employed to release key clamp 33 to
permit removal of the key from the lock. The output signal from
gate 62 is the system output signal for activating the associated
lock or other utilization means upon detection of a proper key
code.
If, during comparison of any bit of the key code, a lack of
identity is found between this bit and the associated bit of the
master code in register 48, the output signal from comparator 46
will cause enabling of AND gate 60 and consequent resetting of
flip-flop 58 which causes removal of the flip-flop output signal to
gate 62. No actuation signal can be provided by reason of the
disabling of gate 62. An output signal from gate 60 is provided
only upon detection of an error between a bit of the key code and a
corresponding bit of the master code, and this output signal is
also employed to activate an alarm circuit 64 to indicate detection
of an erroneous key code. Upon sensing of an alarm condition, a
stop signal can be generated by alarm circuitry 64 to stop clock 52
and discontinue the decoding process and to prevent release of the
key clamped in the lock by clamp 33.
In one mode of operation, the master code stored in register 48 is
recirculated back into this register so that the code is available
for subsequent data comparison. Similarly, the code in shift
register 40 is recirculated therein by means of data gate 44 so
that the same key code can later be employed. To further enhance
the security of the novel lock system, however, the invention is
also operative in another mode wherein the code residing in shift
register 40 and master code register 48 is replaced with a new
code. Such new code can be replaced on a regular basis or from time
to time depending on particular security requirements.
To employ such a new code, the output signal of gate 62 provided
upon identity between the key code and the master code, is applied
via a switch 63 to set a flip-flop 66, one output of which is
employed to energize a timing circuit 67 which, in turn, provides a
start signal to clock 52. The other output of flip-flop 66 is
applied to an AND gate 68 which also receives clock signals
.phi..sub.1. The output of gate 68 is applied to the clock input of
a new code register 70 which has stored therein a new data code
provided by a new code selector 72. The output of new code register
70 is applied to data gate 44 for coupling of such new data into
key shift register 40. The new data is also applied to the master
code register 48 for use in a subsequent data comparison. In this
latter mode of operation, clock 52 is enabled for only a sufficient
period of time determined by timing circuit 67 to permit shifting
in the new code data into the key shift register 40 and to prevent
reinstitution of the digital comparison process until the key is
again inserted into the lock at a subsequent time.
The new code selector 72 can be implemented in several different
ways and can include a binary word generator which is manually
actuable such as by an array of switches, or automatically actuable
for example by means of a computer. By use of a digital computer a
new key code can be provided from a random number sequence
generated by the computer such that the code is readily
identifiable only in computer memory and need not be known to
operating personnel in order to alter the key code. The master code
can be updated immediately after completion of a particular
decoding process or, alternatively, can be updated on a periodic
basis. For example, in some circumstances it is desirable to
reprogram the key code immediately after use of the key and to
reprogram the master code on a daily basis to permit use of the key
only once per day.
The key can be implemented in a variety of mechanical
configurations to suit particular operating requirements. The key
can, for example, be in a form much like an ordinary mechanical key
as illustrated in FIG. 5. In this instance the key 80 is formed of
a nonconductive material such as an epoxy and has the storage
register 82 encapsulated therein. The battery in the form of a
small button cell is contained within a battery compartment located
in the handle portion of key 80, access thereto being provided by a
removable cover 84. Electrical connection is provided at the distal
end of key 80 by means of four conductive bands 86 provided on the
end thereof each being of generally U-shaped configuration as
illustrated.
The key is inserted within a keyway 88 of an associated lock, the
contact bands 86 being cooperative with an electrical connector 87
disposed at the inner end of the keyway to provide connection
between the key and the lock circuitry. Also disposed at the inner
end of the keyway is a microswitch 90 which includes an actuation
arm 92 disposed for actuation by the end of key 80 upon its
insertion into the lock. The switch 90 is part of insertion
detector 32 (FIG. 1) and is operative to provide a key insertion
signal to the system clock for commencement of the key decoding
process. A notch 94 is provided in one side of key 80 and is
cooperative with a rod 94 associated with solenoid 96 to prevent
removal of the key during the decoding process. The solenoid 96 is
typically energized by a signal from key insertion detector 32.
As described hereinabove, an alarm signal is provided by the
invention in the event that there is lack of comparison between the
key code and the master code of the lock. Premature withdrawal of
the key could also cause an alarm condition and to prevent such an
occurrence, the key is clamped within the lock by solenoid 96 until
completion of the decoding cycle. The key can also be retained in
the lock in the event that an erroneous code is detected to prevent
its removal in such event. The key code can be arranged such that
the first bit to be read out of the key is always of ground
potential such that ground potential exists on all terminal
contacts 86 when the key is not in use, to thereby prevent
accidental shorting of the key which could destroy the stored data.
The key terminals could alternatively be deactivated when the key
is not in use by a suitable switch arrangement.
From the foregoing it will be evident that an electronic lock
system has been provided which is both reliable and highly secure
and which can be constructed in an efficient and commerically
realistic manner. Various modifications and alternative
implementations will occur to those versed in the art without
departing from the spirit and true scope of the invention. For
example, data can be conveyed from the key memory to the lock in a
parallel rather than a serial manner, and various levels of coding
can be provided to suit the desired level of security. The
electronic circuitry and its mechanical housing can take a wide
variety of forms adapted to specific installation requirements.
Accordingly, it is not intended to limit the invention by what has
been particularly shown and described, except as indicated in the
appended claims.
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