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Description  |
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TECHNICAL FIELD
This invention relates to a system for controlling removal of a
specifically identified article from a facility by a specifically
authorized user.
BACKGROUND
Article inventory control (AIC) systems, in general, authorize, track, and
control movement of a given article within a facility by a given user. An
example is a library circulation control system. In this case, a user
could identify himself or herself with an identification card containing
magnetically or optically detectable data (e.g., a barcode). The articles,
books in the collection of the library, typically would have a similar
identifying label. Usually a computerized user database contains
identification data on all registered patrons of the library, and a
similar article database contains identification data on all books in the
library. When someone desires to remove a book from the library, the
library circulation control system will first verify that the person is an
authorized patron of the library, i.e., that the person is authorized to
check out any book, or any of a particular class of books. The system will
then verify that the particular book may be removed from the library,
e.g., that it is not "on reserve." If both the user and the book are
authorized by the system, the book may be removed, ("checked out") by that
user. This authorization is often a visual or audible signal to library
personnel. Additionally, but not required, the system could maintain data
which correlates the specific user with the specific books checked out,
and may issue fine notices, usage reports, and the like.
To prevent unauthorized removal of articles by users of facilities,
electronic article surveillance (EAS) systems may also be employed. An
electronic article surveillance system is defined as a system which
comprises:
(1) a remotely interrogatable marker attached to a given article;
(2) means for interrogating and sensing the marker within an interrogation
zone, thereby determining presence of the article; and
(3) means for preventing removal of the article by a user of the facility.
For the purposes of this invention, the term "removal" is understood to
include the ability of the user to gain access to an article, to move an
article from one point to another within a facility, to bring an article
into a facility, or to remove an article from a facility. The last of
these is a common use of EAS systems. However, an EAS system as defined
above can control, for example, the routing of articles from one portion
of a factory assembly line to another.
Many EAS systems employ a magnetic "marker" attached to an article, with
appropriate marker interrogation and sensing apparatus located at one or
more locations in the facility. Typically, removal of an article is
prevented by restricting movement of the article within or from the
facility, as with a lockable exit gate. The gate is locked in response to
an alarm signal when a marker is detected within an interrogation zone
located immediately before the exit. In the library example used above,
the marker may comprise a piece of magnetic material adapted to be
inserted in the book spine or attached inside the book cover.
Typically, EAS systems employ permanently or reversibly deactivatable
markers and the apparatus associated with them. Such markers are also
known as "dual status" markers. Permanently deactivatable markers are
preferred where it is appropriate in certain circumstances for an article
to pass through the interrogation zone without preventing removal. For
example, in a retail store, if an article of merchandise has been
purchased in a particular department, the marker may be deactivated at
that point so that an interrogation zone in another department will not
activate the marker. Reactivatable markers are appropriate, for example,
in libraries where patrons who check out a book for an extended period of
time may subsequently visit the library with that book during that period.
In this case, the system should not prevent subsequent removal of the book
until the book has been returned, the marker reactivated, and the book
returned to circulation.
Integration of the functions of the two systems described above into a
single system is known in the art. For example, U.S. Pat. No. 3,665,449
(Elder et al.) at column 15, lines 62-67 generally suggests that automated
library checkout systems may be combined with EAS systems. More
specifically related to the present invention, U.S. Pat. No. 4,141,078
(Bridges, Jr. et al.) discloses an automated library circulation control
system which provides for patron identification via a card reader, book
identification via an optical reader, modification and interrogation of
computer data files, an electromagnetic device for magnetizing and
demagnetizing a magnetic strip in each book, detection of unauthorized
removal of books from the library, and other functions. The disclosure of
U.S. Pat. No. 4,141,078 (Bridges, Jr. et al.) is incorporated by reference
into this application.
Application of this type of integrated system may be difficult, especially
in libraries in which one or both of the individual systems are in current
operation. For example, some existing EAS systems cannot distinguish
individual markers, only whether a sensitized marker is present. Thus a
single library might employ markers which are identical, even on different
types of books in the collection. The marker therefore may not already
contain coded inventory data which could identify the type of article to
which it is attached. A library with such an EAS system in place, but no
computerized inventory control system, would have to add a unique
inventory control marker to each book. Each book generally must be
uniquely identified, including the identification of multiple copies of a
single title, some of which may be in general circulation while one is on
reserve.
Furthermore, present EAS systems generally are not designed to receive
removal authorization signals from AIC systems added later. Thus, for
complete article removal control in such a facility, it is necessary to
have separate article inventory control and article surveillance systems,
and usually a manual, labor intensive, connection between the two. In a
library, such a connection might be a circulation clerk who, seeing a
flashing light on the AIC system indicating book removal authorization,
physically passes a book through a marker deactivation device of the EAS
system. Another possibility is for the circulation clerk to manually
bypass the removal prevention means, e.g., physically passing the book
around the interrogation device and handing the book to the patron on the
other side of the lockable gate. Since the patron would pass through the
interrogation zone without any marked books, the gate would remain
unlocked and thus allow the patron to exit the library.
SUMMARY OF THE INVENTION
The invention is an article removal control system for enabling removal of
a given article only by a given authorized user from a facility which has:
(a) an article inventory control system which responds to inputs including
user identification data and article identification data to issue an
article removal authorization signal, and
(b) an electronic article surveillance system which controls removal of the
article by detecting within an interrogation zone a sensitized
electronically detectable marker secured to the article;
the article removal control system comprising:
(c) an article removal authorization signal receiver and
(d) means responsive to the article removal authorization signal for
initiating removal of the given article, comprising
(1) a measurer of a characteristic of the given article,
(2) a receiver of a coded input signal representing the measured
characteristic,
(3) a comparer of the measured characteristic and the coded input signal,
which produces a verification signal if they are substantially equal, and
(4) an enabler which upon receipt of the verification signal enables the
initiation of the removal of the given article.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic block diagram of a preferred embodiment of the
invention and associated components.
FIGS. 2 and 3 are detailed schematic block diagrams of components of FIG.
1.
FIG. 4 is a detailed schematic block diagram of the terminal component of
FIG. 1.
FIG. 5 is a perspective view of a preferred embodiment of the terminal
component of FIG. 4.
FIG. 6 is a side cut-away view of a preferred embodiment of the transmitter
component of FIG. 1.
FIG. 7 is a side cut-away view of a preferred embodiment of the receiver
component of FIG. 1.
DETAILED DESCRIPTION
FIGS. 1-4 are schematic diagrams in which major components of a preferred
embodiment of the invention are located within a portion of a facility
generally indicated as 100. Within the facility is at least one article
110, attached to which are an article identification code 220, an
electronic article surveillance (EAS) marker 310, and an article
characteristic code 460. The codes 220 and 460 could be parts of a single
label, similar to a Universal Product Code (UPC) label.
The article inventory control (AIC) system 200 and electronic article
surveillance (EAS) system 300 may exist within the facility prior to the
installation of the inventive system, or may be installed at or about the
same time.
The AIC system 200 includes a user identification card 210. In general,
this system identifies a user (not shown) through the user identification
card 210, and similarly identifies the article 110 through the article
identification code 220. The article identification code could be
permanently affixed to the article itself, embedded or inscribed on the
article, or affixed to a tag adapted to be attached to the article. The
AIC system determines if the identified user is allowed to remove the
identified article from the facility. If so, the AIC sends an article
removal authorization signal 270 to the terminal 400. If not, removal of
the article is prevented as described below. Other functions of the AIC
system not required here, such as storage of the time and date of use,
etc., may also be performed before the article removal authorization
signal 270 is sent to the terminal.
The EAS system 300 interrogates the EAS marker 310 with interrogation
signal 322, receives a sensed signal 324, and, upon receipt of a verified
article removal authorization signal 710, allows the user to remove the
article from the facility.
The inventive system comprises, in this preferred embodiment, at least one
terminal 400. In general, the terminal 400 converts user and article
identification data 412 and 422, respectively, into transmitted user and
article identification signals 232 and 242, respectively, which are passed
to the AIC system 200 for the identification of the user and article as
described above.
Other inputs to the terminal 400 are an article characteristic measurement
432 and a coded article characteristic measurement 442. In the embodiment
shown in FIG. 1, the source of the coded article characteristic
measurement is the article characteristic code 460 attached to the article
110. The coded article characteristic measurement 442 is entered at the
terminal by the user 120. This embodiment is preferred but not required;
the coded article characteristic measurement 442 could be introduced to
the terminal automatically in a manner similar to that used for the user
or article identification data 412 or 422, respectively. The embodiment
shown requires interaction between a user and the terminal 400, which can
be used to improve the security of the total system.
The terminal compares the article characteristic measurement 432 with the
coded article characteristic measurement 442. If the two agree (within
suitable tolerances), it is presumably verified that the entire article
110, and only that article, is physically present at the terminal, and not
just the article identification code 220 (which might have been removed
from the article, if possible), or more than one article (which would
produce a different article characteristic measurement 432). When both
this agreement and the article removal authorization signal 270 are
present, the terminal issues the verified article removal authorization
signal 710 to the EAS system 300.
In this way, communication between the separate systems 200 and 300 is
established. The result is that the EAS system permits a given article to
be removed from the facility only by a given authorized user, as
determined by the AIC system.
Signals 232, 242, and 270, however, present special difficulties. As stated
earlier, many present AIC systems are not adapted to communicate with
other systems to provide the benefits of this invention, especially if the
AIC system is not designed and/or installed contemporaneously with an EAS
system. As disclosed below, this invention utilizes existing AIC signals
in the integration of AIC and EAS functions without requiring significant
modifications to the AIC system or "hardwired" connections between the two
systems. In order to disclose this, additional description of the AIC and
EAS systems is useful.
FIG. 2 is a schematic block diagram of a typical prior art article
inventory control system 200. As stated above, inputs to this system are
the transmitted user identification signal 232, and the transmitted
article identification signal 242. The output from the system is the
article removal authorization signal 270. The transmitted user
identification signal 232 is evaluated by a user identifier 230 (e.g., a
database is searched), and a determination is made whether the user is
known to the system. If so, a verified user identification signal 234 is
issued to an article removal authorizer 250. Similarly, the transmitted
article identification signal 242 is evaluated by an article identifier
240 (e.g., another database is searched), and a determination is made
whether the article is known to the system. If so, an article
identification signal 244 is issued to the article removal authorizer 250.
The article removal authorizer 250 uses both verified identification
signals 234 and 244 to decide if the user is authorized to remove the
article from the facility. (Additional considerations, not shown, may
include the time of day, number of previous removal requests by a given
user in a day, and the like.) If so, an article removal authorization
signal 270 is produced. If any of the evaluations, determinations, etc.,
above indicate an unauthorized user and/or unauthorized article, the
article removal authorization signal 270 is not produced.
FIG. 3 is a schematic block diagram of a typical electronic article
surveillance system 300, including modifications according to this
invention. As stated above, this system sends the interrogation signal 322
to the EAS marker 310 and receives the sensed signal 324 from the EAS
marker 310. It also receives the verified article removal authorization
signal 710 from the terminal 400. Typically, the interrogation signal 322
results in an alternating magnetic field of known intensity and frequency
in an interrogation zone. The sense signal 324 is induced as a result of
the alternating magnetization in the marker in response to the
interrogation signal 322, and comprises multiple harmonics of the
interrogation signal. When an activated EAS marker 310 is interrogated and
sensed by an interrogator/sensor 320, an activation status signal 330 is
created. This signal is used by removal preventer 350 to decide if the
article to which the activated marker is attached may be removed from the
facility.
The embodiment shown in FIG. 3 is suitable for use with permanently
deactivatable markers. Accordingly, the EAS system 300 further comprises
deactivator 340, which receives the verified article removal authorization
signal 710 The total system operates as described above, and additionally
the receipt of signal 710 energizes the deactivator, which in turn emits
deactivation signal 34 to the marker 310. Typically, deactivation signal
342 is a high intensity non-alternating magnetic field. Once marker 310 is
permanently deactivated, sensed signal 324 will not be produced upon
subsequent interrogation, and thus the activation status signal 330 will
be the same as if no marker was sensed at all. Therefore, the removal
preventer 350 will not prevent the user to remove the article.
An embodiment similar to the above is suitable for EAS systems employing
reactivatable markers. In this case, there will be at least two signals
received by the EAS system from the terminal. One signal would be the
verified article removal authorization signal 710, which would be used,
for example, to allow a library user to remove a book from the library
upon "check out." Upon receipt of this signal, the system would operate as
described above, except the marker will be only temporarily deactivated. A
second signal (not shown) would energize a reactivator, which would emit a
suitable signal to restore a temporarily deactivated marker to active
status. This would be used, for example, to allow a library user to return
a book to the library upon "check in."
Regardless of the type of marker chosen, removal of articles by users
determined to be authorized by the article inventory control system is
accomplished by requiring an appropriate activation status signal 330 as
described above.
FIG. 4 is a schematic block diagram of the terminal 400. The terminal
receives the user identification data 412, the article identification data
422, the article characteristic measurement 432, the coded article
characteristic measurement 442, and the article removal authorization
signal 270. The terminal sends the user identification signal 232, the
article identification signal 242, and the verified article removal
authorization signal 710. A user of the facility who desires to remove an
article from the facility enters his or her user identification data into
the terminal, e.g., by typing an identification number on an alphanumeric
keypad. Similarly, the article identification data is entered into the
terminal, e.g., by using an optical scanner to read a barcode on the
article. A user identification receiver 410 receives the user
identification data 412 and sends an internal user identification signal
414 to the user identification transmitter 510. Similarly, an article
identification receiver 420 receives the article identification data 422
and sends an internal article identification signal 424 to the article
identification transmitter 520. Either or both of these processes could
involve a translation of the input signals 412 and 422 into a different
encoding format, such as from ASCII to BCD.
The user identification transmitter 510 receives the internal user
identification signal 414 and sends the transmitted user identification
signal 232 to the user identifier 230 of the AIC system 200, described
above (FIG. 2). Similarly, the article identification transmitter 520
receives the internal article identification signal 424 and sends the
transmitted article identification signal 242 to the article identifier
240. Either or both of these processes could involve a translation of the
internal signals 414 and 424 into a different encoding format, such as
ASCII to BCD. It is mandatory that the user and article identification
signals 232 and 242 be compatible in coding (e.g., ASCII) and form (e.g.,
audible tone, varying voltage level, etc.) to the signals which the AIC
system is designed to accept.
The article characteristic measurement is made by an article characteristic
measurer 430, which also produces a measured article characteristic signal
434. The coded article characteristic receiver 440 receives the coded
article characteristic measurement 442 representing the same
characteristic, but the latter is coded in a form that is not necessarily
understandable to the user. For example, with a keypad as described above,
the user may enter an alphanumeric or other code printed on a label
attached to the article. Alternatively, if the code is in the form of a
barcode, or the like, it may also be automatically entered. The code gives
the value of the characteristic as measured before the article was made
available for removal from the facility. In response, the terminal
produces a coded article characteristic signal 444, and the measured
characteristic verifier 450 compares the measured and coded signals 434
and 444 to verify that only the actual article, and not just a tag
containing the article identification code 220 for example, is in fact
present at the terminal. This comparison produces a characteristic
verification signal 452, which is one input to an article removal enabler
700. The use of a verified measured characteristic of the article is
preferred for its accuracy over non-measurement based systems such as that
taught in U.S. Pat. No. 4,141,078 (Bridges, et al.), e.g., at column 6,
lines 6-14.
The other input to the article removal enabler 700 is an internal article
removal authorization signal 614. This signal is produced by an article
removal authorization receiver 610, which receives the article removal
authorization signal 270 from the article removal authorizer 250 of the
AIC system 200, as described above. As with the user and article
identification transmitters 510 and 520, the article removal authorization
receiver 610 could translate the article removal authorization signal 270
into a different encoding format, such as from ASCII to BCD. It is
likewise mandatory that the article removal authorization receiver 610 be
capable of receiving and understanding the article removal authorization
signal 270 which the AIC system is designed to emit, including coding
(e.g., ASCII) and form (flashing light, RS-232C, 20 mA current loop,
etc.).
The article removal enabler 700 performs a logical "and" function,
requiring both signals 452 and 614 to be present before issuing the
article removal authorization authorization signal 710 to deactivator 340
of the EAS system 300. Thus, the issuance of the signal 710 identifies to
the EAS system that (1) the user is authorized to remove the article
according to the article removal authorization signal 270, and (2) the
article is in fact present at the terminal according to the measured
characteristic verification signal 452.
In certain applications, it may be convenient to remove the user
identification transmitter 510 and/or the article identification
transmitter 520 from the terminal 400 and physically locate either or both
near the AIC system 200. Similarly, the article authorization receiver 610
may be removed from the terminal 400 and located near the EAS system.
However, it is preferred to incorporate or duplicate the deactivation
and/or reactivation functions directly into the terminal 400. In this
case, the article authorization receiver 610 is not removed from the
terminal 400, and article removal authorization signal 710 is wholly
internal to the terminal 400. However, the removal preventer 350 would
still stand alone and include a duplicate interrogator/sensor 320
operating as described above.
FIG. 5 shows a preferred embodiment of the terminal suitable for use in a
library. The embodiment of FIG. 5 includes the preferred configuration
discussed above, in which certain interrogation, sensing, and deactivation
functions of the EAS system are additionally incorporated into the
terminal. In this embodiment, the article 110 is a book, map, or other
member of the collection of the library; a user of the facility is
typically referred to as a "patron" of the library; and the EAS system 300
typically includes as the removal preventer 350 a gate which is normally
locked. Typically, the patron, carrying the book, passes through an
interrogation zone immediately before exiting from the library or an
individual department of the library; if the electronic article
surveillance system interrogates and senses an activated marker attached
to the book (i.e., the marker was not temporarily deactivated as part of
the book check out procedure), the gate is held shut, thereby preventing
egress, and perhaps also activating a visible or audible alarm.
In the embodiment of FIG. 5, the terminal 800 receives the user
identification signal 412 by means of an optical sensor 802. The patron
places an identification card flat on the book shelf 804 and against the
front face of card rail 803, which holds the card in the proper
orientation. The identification card, in this embodiment, has user
identification data encoded on it in the form of a barcode or other means
which can be optically detected. Optical sensor 801 detects the presence
of the card and enables optical sensor 802. The use of two optical sensors
is not required, but is preferred to ensure that ambient light does not
trigger optical sensor 802 when an identification card is not present.
Such triggering can cause spurious signals which may be improperly
interpreted by the terminal or the AIC system. As the card is passed by
the patron from right to left, the barcode on the identification card is
read, and the user identification data 412 received.
The optical sensors could be replaced by devices known in the art for
receiving and decoding magnetically encoded data on the identification
card. A similar process of reading the encoded data would be use, such as
passing the card over a "card reader" sensor built into the shelf of the
terminal.
The article identification data 422 is also received by the terminal. The
book is placed flat on book shelf 804 and firmly against the back rail
805. Card rail 803 is movable and spring loaded so that the book lowers it
temporarily below shelf 804. The book is passed from right to left over
the optical sensors 801 and 802 until it lies in the corner formed by the
book shelf 804, the back rail 805, and the side rail 806, thereby covering
optical sensor 807. This embodiment requires that the article
identification code 220 be attached to the book in a position which will
enable the barcode on the marker to be read by optical sensor 802 when the
book is held flat on the book shelf 804.
If the optical sensors are replaced by devices known in the art for
receiving and decoding magnetically encoded data on the identification
card, as described above, and it is desired to use the same device for
receiving the article identification data 422 as the user identification
data 412, the article identification code 220 also must be magnetically
encoded. However, it is not necessary that the user and article
identification receivers 410 and 420 be identical.
When the book is passed completely from right to left, it covers optical
sensor 807, which activates the characteristic measuring component 808.
The terminal monitors optical sensor 807 and aborts the checkout process
if the book is removed. In this position, the book is suitably positioned
to allow the terminal to measure a characteristic of the book. In the
preferred embodiment shown, the characteristic measured is the thickness
of the book along the dimension perpendicular to the book shelf. The
preferred means for measuring thickness is an ultrasonic ranging
measurement of the distance from the characteristic measuring component
808 and the book. A preferred means for ultrasonic ranging is available
from the Polaroid Company and is identified as "OEM Ranging Kit" with
product code IP44491. Following the directions provided with this product,
the ultrasonic ranging means is adjusted to measure within .+-.1.6
millimeters over a range of 11.5 to 25 centimeters.
Subtraction of the distance between the characteristic measuring component
808 and the book, from the known distance between the same point and the
book shelf 804, yields the thickness of the book. In the preferred
embodiment, this thickness, pre-measured before the book was placed in
circulation, is coded into a hexadecimal value and attached to the book so
that the user may read it as article characteristic code 460. The user
enters the hexadecimal code by means of the user declaration keypad 809.
This embodiment is preferred as it requires interaction between the patron
and the system, which is believed to increase the security of the entire
system. The terminal thus receives measured and entered values of the same
characteristic.
The terminal then compares the measured and entered values of the
characteristic, and if the two agree (within acceptable tolerances), the
terminal concludes that only the specifically identified book is present
at the terminal, and issues characteristic verification signal 452. If
only the barcode were passed across the optical sensor 802, or if more
than one book were stacked beneath the characteristic measuring component
808, the measured thickness of the book would not agree with the coded
measurement entered by the user.
Another suitable characteristic is the weight of the article. In this
embodiment, the terminal would incorporate a scale to produce the measured
characteristic, and compare this value to a pre-coded, user-entered weight
measurement as described above.
The preferred embodiment of the terminal shown in FIG. 5 utilizes user and
article identification transmitters 510 and 520 which are physically
separated from the terminal, and also a physically separated article
removal authorization receiver 610, as described above. Thus, the terminal
passes the user identification signal 414 and the article identification
signal 424 to the transmitters 510 and 520 using any means known in the
art, typically common wire. As described above, if the article inventory
control system authorizes the removal of the book from the library, the
terminal receives the authorization signal 614 from the receiver 610. This
too may be received through any means known in the art.
FIG. 6 is a side cut-away view of a preferred embodiment of an optical
transmitter 500, which incorporates the functions of both the user and
article identification transmitters 510 and 520. This embodiment is
suitable for AIC systems which employ a barcode reader 530 as an element
of both the user identifier 230 and the article identifier 240. The
optical transmitter is connected with the terminal 800 by a common cable
540 which carries user identification signal 414 and article
identification signal 424 through any convenient signal transmission
means. Cable 540 terminates on circuit board 541, which includes light
emitting diode (LED) 542. Cover 501 is preferably designed to hold barcode
wand 530 in close proximity to LED 542.
The circuit of circuit board 541 is designed to replicate, by flashing LED
542, the barcode signal detected by optical sensor 802. Thus, the barcode
wand 530 receives the same user and article identification data 412 and
422, in the same form, as if the barcode wand 530 had been physically
present in the terminal 800 at the location of optical sensor 802. A
preferred circuit is described in Application Note 1008 (published by the
Hewlett-Packard Company in January 1981), modified to operate on a 5 vdc
power supply and use a LED as the output device instead of a direct wired
connection to a barcode circuit. This circuit is effective for use with
the barcode wand 530 of a model 9410B Portable Bar Code Reader supplied by
the Interface Mechanisms Company. The optical sensor 802 is preferably a
model HBCS-1100, and the LED 542 is preferably a model HEMT-6000, both
supplied by the Hewlett-Packard Company. Other models of barcode reader
may require other similar circuits and/or modifications.
FIG. 7 is a side cut-away view of a preferred embodiment of an audio
receiver 600, which incorporates the functions of the article
authorization receiver 610. This embodiment is suitable for AIC systems
which employ an audio generator (not shown) as an element of the
authorization signal producer 260. Such a generator would typically
produce an audible tone in which is encoded in some manner the article
removal authorization signal 270. The encoding method could involve one or
more frequencies, or the duration of the audio signal, or some
combination. FIG. 7 also shows cable 640, which carries received removal
authorization signal 270 through any convenient signal transmission means.
The cable 640 terminates on circuit board 641, and connects the audio
receiver with the terminal 800.
The circuit of circuit board 641 preferably is designed to produce a
voltage pulse whenever an audible signal is detected by microphone 642.
Thus, if the terminal is adapted to receive this voltage pulse, it
operates as if the authorization signal producer 260, which produced the
audible tone, is directly connected to it. A preferred design incorporates
a frequency-sensitive circuit, known in the art as a "bi-quad" RC active
bandpass filter, tuned to the specific audible signal produced by
authorization signal producer 260. Typically, this audible signal is
between 0.9 and 4.0 kHz. A preferred microphone is model MC1606 supplied
by the Armaco Company. It is useful to use a parabolic reflector in
conjunction with the microphone to focus the microphone in the direction
of the audible signal source of the AIC system. Other frequency sensitive
circuits and components may be suitable for other audible signals.
While certain representative embodiments and details have been shown to
illustrate this invention, it will be apparent to those skilled in this
art that various changes and modifications may be made in this invention
without departing from its true spirit or scope, which is indicated by the
following claims.
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