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BACKGROUND OF THE INVENTION
The present invention relates generally to the field of security access
systems and, more particularly, to a computerized cost effective entry
control system which provides high levels of security, convenience and
flexibility.
Individual push-button operated locks have been used to secure doors of
dwellings as well as vehicles. Such locks are described in U.S. Pat. Nos.
3,953,769; 4,149,212; and 4,477,806, each of which discloses a stand-alone
push-button lock programmed at the location of the lock to respond to an
access code.
The only push-button system known to the present inventor for securing a
large number of access locations was manufactured by Tool Research
Engineering of Santa Ana, Calif., under the name "Digikey". The Digikey
system has a keypad at access locations with no local storage or
processing capabilities. The keypads are connected together as an
operating unit by a large number of wires leading to a central control
computer.
In the Digikey system, a four-digit number entered on a keypad at the
access location is transmitted to the central computer which determines
whether the number is a valid access code. If the number is valid, a
signal from the computer unlocks the door. In a hotel installation, the
valid access code is chosen by a guest when he checks in. To do so, he
enters a four-digit number on a keypad at the front desk. The number is
then stored in the central computer at the front desk for subsequent use
in opening the door. As far as applicant is aware, there is no provision
in the Digikey system for deviating from a four-digit entry code, and only
one code can be stored for each room.
Other systems for controlling accesses in large building complexes involve
the use of machinereadable "card keys" which may or may not resemble
mechanical keys. Such devices are described in U.S. Pat. Nos. 3,622,991;
3,694,810; 4,157,534 and 4,415,893. The use of physical keys of any type
involves some disadvantages. While some of the physical key systems
disclosed in the patents above have storage and comparison capabilities at
each controlled access, many are cumbersome in their implementation. For
example, the devices of U.S. Pat. Nos. 3,622,991 and 4,157,534 require
extensive hardwire networks or microwave transmission devices for
communication. U.S. Pat. No. 4,415,893 is somewhat distinct in stressing
the desirability of retaining the mechanical parts of a conventional door
lock, with the pin tumbler replaced by an electronic reading cylinder of
identical size. This is proposed for the purpose of maintaining the "feel"
of a mechanical lock. The patent clearly teaches away from the development
of a keyless system.
To some extent, keyless systems isolate the locking mechanism from direct
manipulation by an unauthorized person; however, other problems arise.
Specifically, the problems of electronic meddling or tampering at various
levels are introduced. In that regard, with the widespread use of portable
computers, it may be a relatively simple matter for an unauthorized person
to couple a computer to an electronic access control system. That
likelihood becomes a particularly significant problem with regard to a
data-bus system as contemplated by the present invention. Accordingly, a
considerable need exists for an economical access control system that is
expedient to install, effective in operation and relatively safe with
regard to the host of possible techniques for an improper entry. The need
is complicated in installations as hotels where access by service and
cleaning people must be accommodated and halls are freely accessible to
all persons. Additionally, persons authorized to enter rooms change daily
and must be accommodated rapidly during a brief contact as at the front
desk of a hotel.
SUMMARY OF THE INVENTION
The present invention relates to a system for securing a building complex,
e.g. a hotel, having a control or desk location and a plurality of
lockable access locations, including at least one control station, located
for example at a hotel front desk. The desk station communicates with
remote access units at the access locations (doors) by an address bus. As
disclosed, each remote access unit is somewhat independent, having a
keypad, a memory and a testing capability. A network bus enables
bidirectional communication between the desk station and the remote access
units. Communication is with data words that normally indicate an address
code (specifying destination) and an access code. A communication bus
transmits data words to store access codes at designated locations, i.e. a
remote station access unit.
In operation, the keypad at a remote station is actuated to develop an
entry access code which is compared with the stored test access codes at
the remote station. With a favorable comparison, an entry signal is formed
to unlock the access door.
In the disclosed embodiment, addressed access codes are routed in
serial-message data words (including address data) and are transmitted
over split data buses to and from remote stations. The remote stations are
divided into groups (by floor) with a separate common apparatus for each
group. Each group apparatus is responsive to those messages which
designate it. Each group control apparatus also monitors the status and
activity at the access units to which it is assigned and may disable one
or more of the stations upon detection of a threatening activity pattern.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features of the present invention may be more fully
understood from the following detailed description, taken together with
the accompanying drawings, wherein similar reference characters refer to
similar elements throughout and in which:
FIG. 1 is a block and pictorial diagram depicting a system constructed
according to the present invention;
FIGS. 2A and 2B are representations of data word formats utilized in the
system of FIG. 1;
FIG. 3 is a detailed block diagram of an access unit of the system of FIG.
1;
FIG. 4 is a block diagram of a floor unit of the system of FIG. 1; and
FIG. 5 is a block diagram of a control station unit of FIG. 1.
DESCRIPTION OF THE DISCLOSED EMBODIMENT
Referring initially to FIG. 1, the components of the system are represented
somewhat as they are physically located at an installation, as for example
in a hotel. That is, the system is described in an installation for
securing guest rooms in a hotel. However, the applicability of the system
to other building complexes will be apparent, specifically apartment
buildings, industrial complexes, government installations and so on.
In the system as represented in FIG. 1, a desk station DS is located at the
front desk of a hotel for cooperative use by arriving guests and a desk
clerk. The desk station DS is connected through a communication unit CU to
access units located at the individual hotel rooms. The access units are
similar, comprising structure as illustrated in some detail in an access
unit A1 (lower left). The access units carrying a designation A1, A2, A3
and so on are located in one floor group while access units B1, B2, B3 and
so on are located in another floor group. Thus, the alphabetic designation
letter indicates the floor group for each access unit.
As indicated in FIG. 1, a large number of individual access units normally
will be involved in an installation. As described in detail below, the
access units of each floor are grouped together and function as groups
somewhat independently through the communication unit CU.
In operation, actions jointly performed at the desk station DS by a guest
and the desk clerk formulate and register an access code in the access
unit located at the room assigned to the guest. Generally, the registered
access code is known only to the guest.
To enter his assigned room, the guest actuates the access unit with his
access code to form representative signals that are compared with
representations of the registered test access code. On coincidence, the
door is released or unlocked.
As disclosed in detail below, the system also permits access to individual
rooms by service and cleaning personnel as well as management. Specific
access codes are registered at the access units for use by hotel
personnel. Such use may be restricted to specific hours of the day.
The system also incorporates structure for detecting threatening patterns
that suggest misconduct or skullduggery at the access units. With the
occurrence of a threatening pattern, various actions may occur. Such
patterns may alert management personnel or may secure an individual room
or a block of rooms as with a "lock-out" for a time.
In accordance with the operation of the system, a detailed activity log is
maintained in the form of data on individual incidents at access units. In
that regard, a central station unit CS (upper right) includes computing
capability along with memory for the activity log. Vacated rooms also may
be cleared of guest access codes from the central station unit CS.
Preliminary to considering the system of FIG. 1 in somewhat greater detail,
the following chart of signals is provided as a reference for signal
designations used herein.
______________________________________
Signals
Designation Description
______________________________________
asterisk sign (*)
Start access code entry
numeral sign (#)
End access code entry
El-En Comparison approval
T Time of day
LO Lock out - seal entry
RE Re-enter - panel signal
AC Accepted - panel signal
RD Ready - panel signal
WA Wait - panel signal
0 0 number
1 1 number
2 2 number
3 3 number
4 4 number
5 5 number
6 6 number
7 7 number
8 8 number
9 9 number
A * instruction
B # instruction
C Non-digit
D Impossible digit
NA No access, results from lack
of favorable comparison
GO Door open signal
______________________________________
In the system of FIG. 1 the desk station DS incorporates a small keypad 10
and a desk terminal 11. The two are interconnected by a cable 12. The desk
terminal 11 is also connected to the communication unit CU by a cable 14.
A cable 16 interconnects the communication unit CU and the central station
CS. Generally the desk terminal 11 and the central station unit CS may
comprise similar structures. Specifically, they may take the form of a
personal computer as an Epson HX or an IBM PC. Note that physically, the
central station unit CS and the communication unit CU are interconnected.
The keypad 10 includes a numeric keyboard 18 which may take the form of a
conventional push-button telephone array with twelve buttons designated
with the numerals 0 through 9 and the symbols asterisk (*) and number sign
(#). The disclosed embodiment employs a hexidecimal signal format wherein
a standard code represents the numerals 0 through 9, A, B, C and D.
______________________________________
Code Decimal Number Representation
______________________________________
0000 0 0 number
0001 1 1 number
0010 2 2 number
0011 3 3 number
0100 4 4 number
0101 5 5 number
0110 6 6 number
0111 7 7 number
1000 8 8 number
1001 9 9 number
1010 A * instruction
1100 B # instruction
1101 C Non-digit
1110 D Impossible digit
______________________________________
The signal representations for 0-9, (*) (A) and (#) (B) can be produced at
the access unit. However, the signal representations for (C) and (D) may
not be so produced. The utilization of the signals C and D is treated in
detail below.
The desk terminal 11 incorporates a full computer keyboard 19 and a CRT
display 20. The keyboard 18 of the keypad 10 is used by an arriving guest
to enter his personally selected access code which is registered at the
access unit of his assigned room. The desk clerk uses the keyboard 19 for
entering the number of the room assigned to the guest along with
appropriate guest information and control data. The assigned room number
serves (directly or indirectly) as an address for communicating the access
code to the access unit of the assigned room. Accordingly, the access code
selected by the guest is passed through the communication unit CU to a
communication bus, e.g. L1 or L2, from which it is accepted by the
designated access unit.
To consider an operating example, assume a guest uses a number significant
to him as his access code, e.g. "2478613". Also assume the guest is
assigned the room number "101", associated with the access unit Al which
is shown in FIG. 1 in some detail. Proceeding from those assumptions, a
data word is formulated in the desk terminal 11 including the room number
"101" and the access code number "2478613". The data word is transmitted
through the cable 14 to a communication system 21, then through the floor
unit FA to a serial bus L1. Note that the communication unit CU
incorporates a floor unit for each group of access units collected by
floors, e.g. floor units FA, FB, and so on.
The appearance of a data word addressed to the access unit A1 on the bus L1
is detected by a monitor 22 located in the access unit A1. The monitor 22
identifies an address ("101") as designating a data word for the access
unit A1 and accepts the data from the bus L1 to store the access code in a
register 23.
With the selected access code stored in the register 23, the guest can
unlock the assigned room by freshly entering the assigned access code
("2478613") using a keypad 24 at the access unit A1. Specifically, access
codes entered at the keypad 24 are compared with test access codes held in
the register 23. Both are applied to a comparator 26 and upon coincidence,
the comparator 26 releases a lock 27. The monitor 22 then reports the
occurrence of that event by formulating a data word which is communicated
for registration in an activity log of the central station unit CS.
Specifically, a data word is communicated by the bus L1, the floor unit
FA, the bus 32, the communication system 21 and the cable 16 to the unit
CS.
Note that in the operation of the system, the controlled access or door
(not shown) associated with the access unit A1, and specifically the lock
27, can be released only by a person entering a proper access code at the
keypad 24.
As explained above, the apparatus of the desk station DS and the central
station CS are in bidirectional communication with the access units, e.g.
units A1, A2, A3 as well as units B1, B2, B3 and so on. Such communication
is by address-bearing data words communicated on data buses as well known
in the prior art. However, in spite of such communication the central
control facilities are not able to unlock the doors. That operation can be
accomplished only at the individual access units. Furthermore, with a
proper access code inserted, each access unit is capable of unlocking a
door independently of the remainder of the system. Each access unit relies
on its own memory and need not communicate with other components of the
system to actuate the associated lock. Accordingly, security and operation
at individual doors may be maintained even if other components of the
system fail. It is also noteworthy, as explained in detail below, that
access codes can be set in the register 23 to incapacitate the keypad 24
from forming the requisite access code.
As indicated above, communication with access units involves the buses L1,
L2 and so on which receive data words incorporating an address for the
designation in accordance with well known computer bus techniques. In that
regard, data words are formulated by the desk terminal 11, the control
station CS and each of the access units. Specifically for example, data
words are formed in the monitor 22 of access unit Al. The formulation of
such data words is treated in detail below; however, consideration will
now be directed to the data word formats as illustrated in FIGS. 2A and
2B.
FIG. 2A illustrates the format for data words that are addressed to
individual access units. FIG. 2B illustrates the format for data words
that are generated at the access units to report a specific operation or
pattern. Such words may be addressed to the associated floor unit, the
central station unit CS or the desk station DS.
In most installations, it is likely that primarily communications to the
access units (FIG. 1) will be to register an access code, as for a fresh
guest. Likewise, presumably most communications from access units will be
to report a door was opened at a specific time using a specific access
code. That information is placed in the memory of the central station unit
CS to constitute the activity log. Of course, other important
communications will be expected to occur from time to time.
Considering FIG. 2A, an illustrative data word 30 is represented to include
a number of specific fields as follows:
______________________________________
Field Data Digits
______________________________________
FA1 Source address identification
2
FA2 Destination address identification
4
FA3 Access code 10
FA4 User code (e.g. guest or staff)
2
FA5 Flag code 2
FA6 Time 10
______________________________________
The somewhat similar data word 31 formualted at the access units is
illustrated in FIG. 2B and includes individual fields as follows:
______________________________________
Field Data Digits
______________________________________
FC1 Source address identification
4
FC2 Destination address identification
2
FC3 Access code 10
FC4 User code 2
FC5 Flag code 2
FC6 Time 10
______________________________________
In the disclosed embodiment, the digits are hexidecimal as indicated in the
above chart as represented by the numerals: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
A, B, C and D. The numerals A and B are manifest as instruction digits
signaled by an asterisk (*) or a number sign (#). The numerals C and D
have special purposes as will now be considered.
The fields FA3 and FC3 for accommodating access codes may constitute from
four to ten hexidecimal digits. Consequently, the guest is afforded
flexibility in his selection of an individual access code. For access
codes of less than ten digits, signal representations for the numeral C
are inserted automatically by the keypad 24 to fill the unused digits. For
example, a selected access code of "2478613" would be signal represented
as a ten-digit code "CCC2478613", the initial digits "C" actually being
non-digits which designate unused digit locations.
The fields FA4 and FC4 identify the uses involved or special codes for
certain data words, along with the flag fields FA5 and FC5. The time stamp
fields FA6 and FC6 manifest Julian clock values and are provided by any of
several clocks in the system as disclosed below.
The data words 30 are formulated in the desk terminal 11 or the somewhat
similar central station CS which, as indicated above, incorporate a
microprocessor. Essentially, data words are formulated or generated at
various locations in the system using well known techniques of the prior
art. Data words simply may be compiled in a hexidecimal register as
illustrated in FIGS. 2A and 2B, then stepped from the register in a serial
format. Parallel data paths are also employed. Thus, with respect to the
word of FIG. 2A as formed in the terminal 11 (FIG. 1), the format is
generated in a buffer register by control functions and data entry
performed on the keyboard 19. Again, note that the field FA3 (access code)
is developed by the guest using the numerical keyboard 18 on the keypad
10.
Thus, in accordance with operations well known in the prior art, a code key
on the keyboard 19 may be actuated to indicate a command for forming the
data word 30. Specifically, with the command, the source address
identification is drawn from a table storage and entered in field FAl
(FIG. 2A). Using the keyboard 19, the operator indicates the destination
address identification which is set to occupy the field FA2 in the
compiling register. A look-up table may be involved. Next, the operator
actuates a key in the desk terminal 11 to receive the access code from the
keypad 10. In the illustrative embodiment format, the guest is requested
to strike the asterisk (*) button followed by the digits of his access
code which is then followed by the number symbol (#) key. Representative
signals are provided from the keypad 10 to the desk terminal 11 for
registration as the field FA3 of the data word.
The operator (desk clerk) uses the keyboard 19 to identify the user, e.g.
guest or staff, which data is registered as FA4 and a flag is provided to
indicate various circumstances, for example, that the access code is being
assigned to a guest.
To terminate the word-generation operation, the operator actuates a code
key prompting the registration of the time as the field FA6.
Signals representative of the composed data word pass from the desk
terminal 11 (FIG. 1) through the cable 14 in a serial fashion to the
communication system 21. A bus 32 from the communication system 21
supplies the data word 30 to each of the floor units FA, FB and so on. The
data word is accepted by the designated floor unit (address of field FA2),
registered and passed on to the appropriate bus for an access unit.
Specifically for example, if the floor unit FA is addressed, it supplies
the code word to the bus L1. Consequently, each of the access units A1,
A2, A3 and so on, receives the data word; however, only the specific
access unit addressed (field FA2, room portion) accepts the data word.
Specifically for example, if the access unit A1 is addressed (FIG. 1), the
monitor 22 detects the address in accordance with well known prior-art
techniques and accepts the code word in the register 23. Subsequently,
from that register, the access code (field FA3) will be supplied to the
comparator 26 as a test access code along with a fresh entry access code
(generated by the pad 24) to determine whether or not the lock 27 should
be released.
In addition to the operations as described above for registering access
codes in a floor unit and an access unit, the data word is supplied from
the desk terminal 12 to the control station CS where it is registered in
the activity log. It is to be noted that the central station unit CS
incorporates the same capability to that explained and illustrated for the
desk station DS. In that regard, it may be convenient to formulate entry
codes for service personnel at the location of the central station unit
CS. Such codes may be formed by data words as explained above. As
explained below, such codes occupy different portions of the register 23.
That is, as explained in detail below, the register 23 contains several
access codes designated for use by specific persons and in certain cases
designated for use during limited times. Note that the central station
unit CS also incorporates control capability for interfacing data of the
activity log and clearing access codes of departing guests. Again, details
of the unit CS are treated below.
Considering the hierarchy of communication, the floor units FA, FB and so
on receive data words on the bus 32 to accept those which are specified
(by destination field FA2, FIG. 2A) for the assigned floor. Such data
words are then passed on to the access units of the floor. Depending on
specific implementations, on receiving a data word, a floor unit may
modify or refine the data word, as for compatibility in accordance with
well known techniques of the prior art. In any event, a data word is
applied to the appropriate floor bus, e.g. bus L1 or L2 from the floor
unit.
From the bus L1 for example, the designated access unit, e.g. access unit
A1, recognizes its address and accepts the data word to register the
access code along with a designation of time use restraints indicated by
the fields FA4 and FA5. As explained above with reference to FIG. 1, the
access code is set in a register 23. Also, the register 23 incorporates
several individual registers for several individual access codes. Those
registers have time gates which restrict their effective use to specific
times of the day. In that manner, service and housekeeping personnel are
accommodated limited access to rooms. The specific designation in that
regard is carried by the fields FA4 and FA5 (FIG. 2A).
To review and summarize the operation of the system, assume a situation for
the operating sequence attendant the registration of a guest and the
subsequent use of his access code. The keypad 18 is positioned for use by
the guest while the desk terminal 11 serves the desk clerk. As indicated
above, by the two people interacting, a data word is formulated which
includes an access code known only to the guest and input through the
keypad 10.
On command, the data word is transmitted from the desk terminal 11 to the
control station unit CS and through the communication unit CU to the
access unit at the assigned room for the guest. As indicated above, the
control station unit CS incorporates a substantial memory for a
comprehensive activity log.
Assume, for example, that the guest is assigned the room 101 associated
with the access unit A1. Accordingly, the individual access code, e.g.
"2478613" (actually CCC2478613), selected by the guest is set in the
register 23. Accordingly, the guest has the "key" for access to the room.
Moving to the assigned room, the guest actuates the keypad 24 which would
normally be mounted in or adjacent to the door jam of the assigned room.
Specifically, queued by the signal lights 38, the guest simply keys in the
access code as previously explained beginning with the asterisk (*)
followed by "2478613" and ending with the number sign (#) to indicate
completion.
With the entry of the access code, a representative signal is supplied from
the keypad 24 to the comparator 26. The operation commands the register 23
to supply the test access codes to the comparator 26 as described in
detail below. Thus, the comparator 26 compares the fresh entry access code
with the previously stored test access codes. If a match occurs, the
comparator 26 provides a coincidence signal to release the lock 27 and
enable access to the room. Concurrently, the access unit A1 actuates the
monitor 22 to transmit a "valid entry" message to be logged at the central
station unit CS. The message is carried in a data word (FIG. 2B) that
identifies the matching access code, states the time and so on.
Recognizing that some selectivity may be exercised in various installations
and embodiments, it is generally contemplated that in most systems, every
data word formulated in the system will be sequentially stored in memory
on the activity log of the central station unit CS.
While most keypad operations at the individual access units are expected to
produce a favorable comparison and open the door, unfavorable comparisons
are likely to be common. If the entry access code (entered on the keypad
24) does not match any of the test access codes stored in the register 23,
an "invalid entry" message is sent to the control station CS through the
communication unit CU. That data word contains the attempted access code
to enable logic in the control station CS to evaluate a question of
whether the entry was merely an honest mistake or resulted from an
unauthorized person attempting to enter the room. After a preselected
number of invalid entries, or after entries that are deemed dangerous, the
central station CS transmits a message inhibiting the access unit. For
some patterns of improper entries, several access units may be inhibited.
Certain of the inhibiting operations are performed by the floor units FA,
FB and so on, as described in greater detail below. Again, such details in
specific embodiments and individual installations may vary considerably.
At this point FIG. 3 will be considered to pursue further details of the
access units specifically the access unit A1. Initially, it should be
understood that the individual access units, e.g. units A1, A2 and so on,
may not communicate directly with each other. Rather, the units
communicate exclusively through the floor units to the desk station DS and
the central station CS. Limited communication is accomplished by
restricting the contents of the destination address identification (FIG.
2B, field FC2). For example, data word messages generated by access units
for transmission on an associated bus identify the central controller CS
as the ultimate designation. As disclosed in greater detail below, the
formation of a data word at each of the access units mandatorily
designates the control station CS as the ultimate addressee.
Referring to FIG. 3, the detailed structure of a typical room access unit
is illustrated. Note that certain elements of FIG. 3 have been described
above and bear similar reference numerals. Specifically, the keypad 24
(upper left) is actuated to enter fresh access codes for comparison (in
the comparator 26, upper central) with stored test access codes from the
memory or register 23 (FIG. 3, upper right) as previously discussed. In
FIG. 3, the principal parallel data paths involving these elements are
enlarged for distinction from paths for serial binary control and
operating data signals.
When a guest actuates the keypad 24 the activity initially prompts the
creation of a "start" signal represented as an asterisk (*) which signal
is set up for application in parallel to a data path 42 and sensed by a
clearing circuit 44 which resets or clears an access code register 46. The
access code digits follow, then the end digit (#) is formed.
Following a somewhat instantaneous clearing operation with the start digit
(*), the digits of the freshly entered access code from the keypad 24 are
supplied to the access register 46. Thus, the access code is set in the
register 46 preparatory to a strobe comparison with the previously
registered test access codes contained in the register 23. Note that the
so-called total register 23 actually comprises memory locations for
holding several authorized test access codes. Specifically, access code
memories M1 through Mn are illustrated in FIG. 3. At this point, consider
some details of the test access codes, their operation and the manner in
which the memories M1 through Mn are set to contain those test access
codes.
Each of the memories M1--Mn is associated with a time gate G1--Gn
respectively. The time gates may limit the hours of the day when test
access signals can be supplied from a memory to an associated comparator.
In a structural configuration, the time gates G1--Gn may simply comprise a
digital gang "and" gate set for qualification at predetermined hours of
the day by a time signal.
The code for the registered guest is available for comparison from the
memory M1 under control of a time gate G1 during any time of the day.
However, the test codes for use by service personnel are available from
the memories M2--Mn only during predetermined hours under control of time
gates G2--Gn respectively. For example, a maid-service test code in the
memory M3 might be used for comparisons only from 9:00 a.m. until 3:00
p.m. under control of the time gate G3. Accordingly, the time gates G1--Gn
are coupled to receive timing signals T from a clock 53. Note that the
data paths for entering the test access codes in the memories M1 through
Mn are described below. Also, it will be recalled that more than one of
the memories may be dedicated for the storage of guest access codes. Other
memories may be designated for maintenance service, management and so on.
Note that, as explained below, attempted use of an access code stored in
one of the time restricted memories may signal a caution pattern.
Generally, the memories M1--Mn are set for a specific use and are
individually addressed by the fields FA4 or FA5 (FIG. 2A). For example,
the memory M1 is used for a test access code assigned to a guest.
Specifically, test access codes are received in the memories M1--Mn of the
addressed access unit A1 through the bus L1 (FIG. 1, also indicated in
FIG. 3, lower right). The bus L1 is connected to the monitor 22 which
includes "in" and "out" sections. The "in" section 49 of the monitor may
take the form of a structure well known in the prior art for detecting and
accepting address-designated data words. The access codes of such data
words are then passed into a specific memory through an address unit 51.
Thus, the field FA4 (FIG. 2A) is sensed by an address block 51 for an
instruction to gate the received access code to a specific one of the
memories M1--Mn.
As indicated above, the monitor 22 (lower right) also includes an "out"
section 52 which provides data from the access unit back to the central
station unit. Essentially, the monitor may take the form of an addressable
bus coupling as well known in the prior art of data processing. Its
operation in the access unit A1 of FIG. 3 is described in detail below
along with other apparatus involved in the receipt, formulation and
transmission of data words.
With one or more access codes entered in the memories M1--Mn (all need not
be filled), consider the basic comparative operation to test an entered
code as generally explained above with respect to FIG. 1. Assume an access
code is entered at the keypad 24 (FIG. 3, upper left) designated by a
start signal (asterisk "*") and concluded by an end signal (number sign
"#"). The start signal (*) is detected by the clearing circuit 44 to purge
the access code register 46. The individual digits of the freshly entered
access code are then registered in the access register 46. With the
occurrence of the end signal (#), a comparison strobe generator 54 (FIG.
3, central) is actuated keying the comparator 26 through a line 56 to
sequentially actuate a series of individual comparators C1, C2, C3 and Cn
coupled respectively to the memories M1, M2, M3 and Mn. Accordingly, the
comparators C1--Cn operate in the reverse order of their designation to
individually compare the access codes contained in the register 46 with
the contents of the memories M1--Mn.
Upon detecting equality of access codes (entered code versus test code),
each of the comparators C1--Cn generates an equality signal E1, E2, E3 or
En respectively. The absence of an equality signal from a comparator
signals the next comparator in the sequence to act. If none of the
comparators detect equality, a binary signal NA is provided at the output
from the comparator block 26 to a conductor 60. With the occurrence of the
signal NA in the conductor 60, an erroneous or improper entry of an access
code is manifest. Conversely, the generation of any of the signals E1--En
manifests a successful comparison indicating that the entry access code
coincided with one of the test access codes stored in the memories M1--Mn.
Note that both events are reported for registration in the activity log of
the central station unit CS.
Upon a favorable comparison indicating the determination of a proper code,
the access door is released. Upon the determination of an improper code,
security measures may be taken, for example a lock-up of the access units
thereby sealing the associated entry for a time. Initially, consider the
structural elements and operations attendant the failure of coincidence as
manifest by the signal NA in the conductor 60.
Access code failures manifest by the signal NA in the conductor 60 actuate
an error counter 62 and an error message generator 64. The error counter
62 tallies comparison failures and may be set to various numbers depending
on the nature of the installation. When the counted errors reach the
predetermined level, the counter 62 provides a signal to a lock-out binary
65 to produce a lock-out signal LO for controlling the access entry. The
binary 65 has two states as manifest by signals LO and LO'. The signal LO
indicates "lock-out" while the signal LO' indicates "no lock-out". The use
of the signal LO' to inhibit striking the door lock is treated in detail
below. Note that the room lock-out binary 65 receives a time signal T and
can be variously programmed to clear or be reset after a specific
interval.
As indicated, signals manifesting an erroneous entry are also supplied to
an "and" gate 63 (FIG. 3, top center) which receives the freshly entered
access code from the register 46 through an error message generator 64.
Consequently, with the failure of an im | | |
