Remote, wetness signaling system

ES 2 283 451 T3

DESCRIPTION

System for remote detection of humidity status.

The present invention relates to a status signaling device or system, which can be used with a selected item. In particular aspects, the present invention can provide a moisture signaling device or system, and the device or system can be used with absorbent articles such as dresses, diapers, children's learning pants, feminine hygiene products, incontinence garments and the like.

Conventional signaling systems have been incorporated into conventional articles to alert a caregiver to changes in the condition of the articles. For example, conventional marking systems have been incorporated into disposable absorbent articles, such as diapers and incontinence garments. Absorbent articles have typically utilized absorbent pads or other absorbent structures sandwiched between a layer of a backsheet and a liquid-permeable cover layer. The absorbent structures have incorporated superabsorbent materials combined with fibrous matrices composed of natural and synthetic fibers. For example, absorbent structures have included superabsorbent particles mixed with cellulosic wood pulp fluff.

Typically, signaling systems have been used to alert the user of a change in the moisture of the absorbent structure. Some conventional signaling devices have included a mechanism that undergoes a change in color or other changes in visual appearance when the absorbent material has become wet. For example, absorbent articles have used decorative or graphic patterns that become visible or disappear when the article has become wet. Other conventional devices have incorporated a perishable component that can be broken to signal a wet condition of the absorbent. Still other conventional components have utilized active electronic systems, which have been incorporated into the selected absorbent article. Electronic devices have included power supplies and have used auditory or visual indicating devices, such as buzzers or lights. Certain particular provisions have also used radio transmitters to send the humidity alert to a remote radio receiver.

Conventional devices and systems, such as those described above, have not been sufficiently satisfactory. Systems that have used color change mechanisms or other visual change mechanisms are easily obscured by coating layers, such as sheets or fabric layers. When such systems are arranged so that they are easily visible, the systems have been indiscriminate and indiscreet, and have unwantedly released humidity information to persons other than the caregiver. Systems that have used a perishable component have had similar drawbacks. Systems that have used a power source located within the associated article have proven undesirable to consumers. As a result, there has been a continuing need for improved techniques and systems for signaling a change in the internal location of a selected item.

Document WO 99/33037, on which the independent claims have been characterized, discloses a system for remote detection of a fluid. The system includes a resonance circuit located in a position in which the fluid must be detected. The presence of fluids alters the ability of the circuits to receive energy from a remote oscillator. This produces changes in the oscillator circuit, which are detected and used as an indication of the presence of fluid in the resonance circuit.

US 5,903,222 discloses a detector in a diaper garment for detecting wet conditions in a diaper or underwear. The detector comprises a capacitive sensor attached to an outer surface of the garment to be monitored.

US 5,570,082 discloses a system for detecting moisture in a diaper. The system comprises a coil (5) located in a diaper. The resonance behavior of the coil changes depending on the presence / absence of liquid. A remote receiver detects the generation of a resonance that is a harmonic of a coil-induced resonance by means of a remote transmitter.

US 5,463,377 discloses an apparatus for detecting the presence of liquid in a garment, including an electrically passive sensor adapted to come into contact with liquid and an electrically active remote sensor.

According to the present invention, a system such as claimed in claim 1, and a method such as claimed in claim 10 are disclosed.

The control system includes an interrogator that is located in an operative proximity to the article and is configured to provide input power with a predetermined input frequency. A situation signaling device is located in the controlled part of the article. The status signaling device includes a sensor that can indicate a change of state that occurs when the controlled part of the article changes from a first condition to a different second condition. A passive repeater ("transponder") is arranged in operative communication with the sensor. The repeater is configured to receive input power from the interrogator and

ES 2 283 451 T3 to generate data in the indicator when the controlled part is in the second position. The repeater is configured to transmit an output energy to the exterior of the article. The output energy includes at least a portion of the input energy, and the output energy is configured to carry the indicator data. An output receiver is configured to electronically acquire output power and indicator data from the repeater. A detector is connected to the output receiver and can react to a threshold value of the data indicator. An annunciator is arranged in communication with the detector and is configured to announce the presence of the threshold value of the data indicator.

The situation signaling device can be unobtrusive and can provide the caregiver with humidity information, without at the same time providing the information to other casual observers. The technique and apparatus of the invention may avoid the use of a power source located within the associated article, and may be less susceptible to the generation of unwanted eddy currents.

The present invention will be more fully understood and its additional advantages will become more apparent upon reference to the following detailed description of the invention and the drawings, in which:

Figure 1 representatively shows a top plan view, partially in section, of an outer side of an article incorporating an apparatus and method of a preferred embodiment of the invention;

Figure 2 representatively shows a front view of the outer side of an article that has been placed on a wearer and incorporates an apparatus and method of a preferred embodiment of the invention;

Figure 3 representatively shows a schematic front view of the outer side of the article illustrated in Figure 2, in which a part of a modular assembly has been partially cut away to illustrate the relative positions of the coil of a repeater and of the coil of an interrogator mounted on the article;

Figure 3A representatively shows a partial, schematic, cross-sectional view, taken along section 3A-3A of Figure 3;

Figure 4 representatively shows a schematic block diagram of an apparatus and method of a preferred embodiment of the invention;

Figure 5 representatively shows a schematic block diagram of an electronic sensor and passive repeater that can be used with the present invention;

Figure 5A representatively shows a schematic block diagram of a module assembly that may be used with the present invention, and may include the associated interrogator and annunciator, with or without a remote call transmitter;

Figures 6A and 6B representatively show a schematic circuit diagram of an electronic module assembly that may be used with the present invention;

Figure 7 representatively shows a schematic block diagram of a remote calling unit, which can be used with the present invention;

Figures 8A and 8B representatively show a schematic diagram of a remote calling unit circuit, which may be used with the present invention.

In the context of a disposable absorbent article, such as a disposable diaper, the various aspects and embodiments of the invention will be described. However, it is clearly apparent that the present invention can be used with other items, such as hats, dresses, shoe covers, feminine hygiene items, infant learning pants, incontinence garments, and packaged items. Disposable items are typically intended for limited use and are not intended to be laundered or cleaned in any way for reuse. For example, a disposable diaper is discarded once it has become soiled by the user.

It should also be noted that, when used in the present discussion, the expressions "comprises", "comprising" and other derivatives of the expression of the root term "comprehend" are intended to be open expressions that specify the presence of any expressed characteristics, elements, integrators, stages or components, but do not rule out the presence or addition of one or other various characteristics, elements, integrators, stages, components, or groups thereof.

The present description of the invention will be expressed in terms of its various components, elements, constructions, configurations, arrangements and other characteristics that may also be individually or collectively referenced by the expression "aspect / s" of the invention, or other similar expressions. It is considered that the various forms of the disclosed invention may incorporate one or more of its various features and aspects, and that such features and aspects may be used in any desirable operative combination thereof.

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Referring to Figures 1 through 3A, the present invention may provide a feature article (20) having a controlled portion (22) and a status signaling device (24) to communicate a change in status. the controlled part. In a desired aspect, the change in situation may occur within the article. The situation signaling device includes a sensor (26) that can indicate a change of situation that occurs when the controlled part (22) of the article (20) changes from a first condition to a different second condition. In a particular aspect of the invention, a passive electronic repeater (28) may be connected to the sensor (26) cooperatively. In other aspects, the repeater (28) may be configured to receive an input of electromagnetic energy that has been provided to the repeater at a predetermined input frequency, and the repeater (28) may be configured to respond with operational data from the indicator when the controlled party (22) is in the second situation.

One aspect of the process of the invention may provide a method for communicating a change in status of a controlled portion (22) of an article (20). The method comprises the provision of a situation signaling mechanism (24) in the article (20). The status signaling mechanism includes a sensor (26) that can indicate a change of state that occurs when the controlled portion (22) of the article (20) changes from a first condition to a different second condition. In a particular aspect of the method, a passive electronic repeater (28) may be provided to operatively cooperate with the sensor (26). In other aspects, repeater 28 may be configured to receive input electromagnetic energy that has been provided to the repeater at a predetermined input frequency. The repeater (28) may be configured to respond with operational data on the indicator when the controlled portion (22) of the article is in the second condition.

The present invention can also provide a control method and apparatus for signaling a predetermined situation in an article (20) having a controlled portion (22). The control technique or system includes an interrogator (30) that may be located in operative proximity to the item, and may be configured to provide input power with a predetermined input frequency. A situation signaling device (24) is placed in the controlled part (22) of the article. The situation signaling device includes a sensor (26) that can indicate a change of situation that occurs when the controlled part (22) of the article (20) changes from a first condition to a different second condition. A passive repeater (28) is in operative communication with the sensor (26). In a particular aspect of the invention, the repeater can be an electronic repeater. The repeater (28) may be configured to receive input power from the interrogator (30), and may be configured to generate data on the indicator when the controlled part (22) is in the second condition. The repeater (28) may be configured to communicate an output power to the exterior of the article (20). The output energy includes at least a portion of the input energy, and the output energy may be configured to carry the indicator data. An output receiver (34) may be configured to electronically acquire the output power and indicator data from the repeater (28). A detector (36) may be connected to the output receiver (34) and may react to a threshold value of the indicator data. An annunciator (38) may be in communication with the detector (36) and may be configured to announce the presence of the threshold value of the indicator data.

In particular aspects, the invention can include a transmission of high frequency energy from the coil of a transmitting antenna to a receiving coil embedded in a non-metallic substrate. In particular arrangements, the invention can provide a device for indicating changes in resistance that appear between electrodes that are embedded in the substrate. A feature of the invention may include an indication of a change in resistance with the use of a wireless connection through a non-metallic substrate. For example, a desired configuration may indicate a wet condition caused by the introduction or revealed presence of an electrically conductive material, such as urine or other conductive liquid. Another feature may include detecting a change in resistance by measuring the amount of energy reflected from a tuned circuit matched to a tuned matched circuit. An additional feature may include wireless sensing of moisture from a non-metallic material substrate that results in a change in resistance experienced by embedded electrodes that can be detected by measuring the amount of reflected energy from an embedded tuned circuit. Still another feature of the invention can provide a system that ultimately signals a change in resistance on a remotely located monitor via wireless means.

Aspects or features of the invention, alone and in combination, can provide various advantages. Such advantages may include, for example, non-intrusive control of changes in electrical impedance or electrical conductivity using a wireless approach. The method and apparatus can provide wireless detection of electrical impedance and humidity condition through a non-metallic substrate, and can provide wireless signaling of change in electrical impedance and humidity condition. In a particular arrangement, the change in impedance may include a change in electrical resistance. The change in electrical impedance in a controlled substrate can be detected by measuring changes in energy reflected from the part engaged to an external, coupled and tuned circuit. The method and apparatus of the invention may not have a direct electrical connection between the external electronic sensing devices and their embedded part. As a result, there can be no deterioration of the electrical contacts that could otherwise interconnect said components. Any energetically activated circuits are electrically isolated from the interior of the article. As a result, there cannot be a substantial risk of eddy currents or leakage. The method and apparatus of the invention can provide a characteristic magnetic coupling between its nested portion and a separate outer sensing portion. The nested part may be easily incorporated into a selected garment or other non-metallic substrate, and the nested part may comprise a simple two-way circuit.

ES 2 283 451 T3 tuned components. Additionally, the method and apparatus of the invention may include an external portable detection mechanism, and an alert signal transmission mechanism. A wireless alert signal can be sent to a remote monitor.

Referring to Figures 1 and 2, the selected article, such as diaper article (20), shown representatively, may include a constitutive layer (102) of the backsheet, a constitutive layer (100) of the liquid-permeable topsheet and an absorbent body (90) sandwiched between the layer (102) of the backsheet and the layer (100) constituting the topsheet. In particular aspects, the constitutive layer of the backsheet can be substantially impermeable to liquids. In other aspects the constitutive layer of the backsheet may be water vapor permeable or "breathable".

In desired configurations, the article may provide a first waist part, such as the back or back part shown (80) of the waist, and a second waist part, such as the front part (82) shown. Of the waist. Additionally, the article may have an intermediate or crotch portion 84 that interconnects the first and second waist portions 80 and 82, respectively. A gathering system can be used using elastomers or with elements of a gasket, such as a system that includes elastics (86) on the legs and / or elastics (88) on the waist, to help improve the fit and reduce wear. leaks. An operative fastening system, such as that provided by the known system having fastening elements (98), can be used to interconnect the first waist part (80) with the second waist part (82) to hold the article on. the user. The attachment system may be operatively configured to join the first rear waist portion (80) in an overlapping relationship with the second front waist portion (82) in a back-to-front arrangement to thereby encircle the body. and keep the diaper secure on the user during use. Optionally, the fastening system may utilize fasteners (98) that are configured to join the front portion (82) of the waist in an overlapping relationship with the rear portion (80) of the waist in a forward arrangement. back to keep the diaper secure. In such optional arrangements, the front waist area can be identified as the first waist portion (80) and the rear waist portion can be identified as the second waist portion (82). It should be clearly apparent that fully fabricated items such as children's learning pants, feminine hygiene garments, incontinence garments, and other fully fabricated three-dimensional items may not include fasteners.

Figures 1 and 2 show typical views of the representative disposable diaper (20). In Figure 1, some parts of the structure are partially cut away to show more clearly the interior construction of the diaper article, and the surface of the diaper on the body side, which is in contact with the wearer, which is in the part away from the viewer. The outer edges of the diaper define a periphery with longitudinally extending side edge margins extending laterally along the end edge margins. Side edges define diaper leg openings, and are optionally curvilinear and contoured. The extreme edges are shown straight but can optionally be curvilinear.

With respect to the indicated surfaces of the article, the various interior, or body-side surfaces, are configured to face the wearer's body when the article is positioned around the wearer. The indicated outer surfaces of the article are configured to face away from the wearer's body when the article is positioned around the wearer.

The various components of the article may be attached to each other using various conventional fastening techniques and mechanisms, such as adhesives, ultrasonic bonding, heat bonding, welding, stitching, snaps, captive pins, rivets, buttons, and the like, as well as combinations thereof. The clamping mechanisms can be arranged in any configuration or operating arrangement.

The topsheet (100), the backsheet (102), the absorbent body (90), and other components of the article are connected or otherwise associated with each other in an operative manner. The various components can be operatively attached to each other, for example, with suitable fastening mechanisms (not shown) such as adhesive bonding, ultrasonic bonding, heat bonding, captive pins, stitching, and any other known fastening technique as well as combinations thereof. For example, a uniform continuous layer of adhesive, a layer of adhesive with a certain pattern or configuration, a pattern of spray applied adhesive or adhesive in the form of a set of separate lines, swirls or dots of construction adhesive, can be used to interconnect, clamp and / or fix together in a suitable manner, the various component parts of the article.

The absorbent body (90) provides an absorbent retention portion, such as that provided by the absorbent pad representatively shown, comprised of selected hydrophilic fibers and high absorbency particles. The retention part is configured to contain and store absorbed liquids and other residual materials. The absorbent body may be located and sandwiched between the topsheet (100) and the backsheet (102) to form the diaper (20) or other absorbent article. The absorbent body is constructed in such a way that it is generally compressible and conformable, does not irritate the skin of the user, and is capable of absorbing and retaining body exudates. It should be understood that, for the purposes of this invention, the absorbent body structure may comprise a single, integral piece of material, or alternatively, it may comprise a series of separate, individual pieces of material that are operatively fastened together. .

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Various types of wettable, hydrophytic and fibrous fibers can be used to form the component parts of the absorbent body (90). Examples of suitable fibers may include naturally produced organic fibers comprised of an inherently wettable material, such as cellulosic fibers; synthetic fibers composed of cellulose or cellulose derivatives such as rayon fibers; inorganic fibers composed of inherently wettable materials, such as fiberglass; synthetic fibers made of inherently wettable thermoplastic polymers, such as certain polyester or polyamide fibers; and synthetic fibers composed of a non-wettable thermoplastic polymer, such as polypropylene fibers that have been hydrophilized by suitable means. The fibers can be hydrophilized, for example, by treatment with silica, treatment with a material that has a suitable hydrophilic fraction and is not easily removable from the fiber, or by sheathing the hydrophobic, non-wettable fiber with a hydrophilic polymer. during or after fiber formation. For the purposes of the present invention, it is considered that selected blends of the various types of fibers mentioned above may also be used.

The absorbent body structure (90) may comprise a matrix of hydrophilic fibers, such as a cellulose fluff web, mixed with particles of high absorbency material. In particular arrangements, the absorbent body (90) may comprise a mixture of superabsorbent particles that form a hydrogel and fibers of a synthetic meltblown polymer, or a mixture of superabsorbent particles with a coform fibrous material, comprising a mixture of fibers natural and / or synthetic polymer fibers. The superabsorbent particles can be substantially homogeneously mixed with the hydrophilic fibers, or they can be non-uniformly mixed.

To improve retention of the high absorbency material, the absorbent body structure (90) may include an outer wrap or a wrap sheet, which may be positioned immediately adjacent to and around the absorbent body. The wrap sheet may be attached to the absorbent structure and various other components of the article. The wrapping sheet may be a layer of absorbent material or a substantially non-absorbent material, which covers the main body-side surfaces and / or the outer-side surfaces of the absorbent body. The wrap sheet can enclose substantially all of the peripheral edges of the absorbent body to form a complete wrap around it. Alternatively, the wrap sheet may provide an absorbent wrap that lines the major body-side surfaces and the exterior side surfaces of the absorbent body, and substantially encloses only the lateral edges of the absorbent body sides.

For example, the entire wrap sheet, or at least the body side layer of the wrap sheet, may comprise a web of meltblown fibers, such as meltblown polypropylene fibers. Another example of an absorbent wrap may comprise a low porosity cellulosic web, such as a cellulosic member composed of about 50/50 blend of hardwood / softwood fibers.

In the various aspects and configurations of the invention, the fastening mechanism between the selected first fastener component and the selected second fastener component may be adhesive, cohesive, mechanical, or combinations thereof. In the context of the present invention, a mechanical fastening system is a system that includes first and second cooperative elements that are mechanically coupled to each other to provide the desired protection.

Desirably, the first and second components of the fastener include complementary elements of a mechanical fastener that cooperatively engage each other. The components of the mechanical fasteners can be arranged by mechanical fasteners, such as hooks, buckles, snaps, buttons, and the like, which include cooperative and complementary mechanical interconnect components.

As shown in the illustrated arrangements, for example, the mechanical fastening system may be a hook and loop type fastening system. Such fastening systems typically include fasteners that have a male component in the form of a "hook" or hook-like, and include a cooperating, "loop," or loop-like female component, which engages and engages. removably interconnects with the hook component. Desirably, the interconnect is selectively removable and can be reassembled. For example, conventional systems of this type are available under the trademark VELCRO. The hook element may be provided with a single point hook configuration, a hook configuration with a series of points or by a generally continuous expanded head configuration, such as that provided by a mushroom head type hook element. . The loop element can be provided by means of a woven fabric, a non-woven fabric, a knitted fabric, a perforated or open layer, and the like, as well as combinations thereof. The various arrangements and variations of such attachment systems have been collectively referred to as hook and loop attachment systems.

A configuration using a selectively removable, inter-engageable mechanical fastening system can, for example, position the first fastening component, at least, on the intended mating or protecting surface of the tab (98) of the element. attachment and may position the cooperating second attachment component on the intended engagement surface of the member (96) intended for placement. For example, with the hook and loop fastener shown representatively, the fastener component that is attached

ES 2 283 451 T3 to the intended mating surface or protection surface of the tab (98) of the fastening element may include a hook-type mechanical coupling element, and the complementary fastening element, which is operatively attached and coupled to the element (96) of the intended engagement zone, it may include a loop-type fastening element.

Also, it should be clearly apparent that, in the various configurations of the invention, the relative positions and / or the materials of the first fixation element and its second complementary fixation component may be interchanged. Accordingly, the fastener component, which is coupled to the provided engagement surface of the fastener tabs (98), may include the loop-type fastener; and the second ancillary attachment component, which is operatively attached and coupled to the intended element of the coupling zone, may include the hook-type coupling elements.

An example of an element of a coupling hook suitable for the various configurations of the invention is a micro (hook element arranged in a material that is distributed under the designation VELCRO HTH 829, and is available from VELCRO USA, Inc., a company which has offices in Manchester, New Hampshire The micro-hook material has fasteners in the form of sharp elements of the pointed hook type. The hook elements can be configured with a hook height that is in the range of about 0.030-0.063 cm (about 0.012-0.025 inches); and a hook width that is within a range of about 0.007-0.022 cm (about 0.003 to 0.009 inches). The hook elements are molded onto a layer of a base substrate that is about 0.0076-0.008 cm (about 0.003-0.0035 inches) thick. Another suitable type of fastening hook element can be found in a 3M CS200 material, which can be supplied by "Minnesota Mining and Manufacturing (3M) Company", a company having offices in St. Paul, Minnesota. Other suitable hook materials can be supplied by various distributors, such as VELCRO USA, Inc. and 3M Company.

In the various configurations of the invention, the material of the loop can be arranged by a non-woven, woven or knitted fabric, as well as combinations thereof. For example, a suitable fabric for the loop material may be comprised of a 2 bar warp woven fabric, of the type that can be supplied by Guilford Mills, Inc., of Greensboro, North Carolina, under the trade designation # 34285. , as well as other types of knitted fabrics. Also other suitable loop materials may be supplied by the 3M Company, which distributes a fabric of nylon woven loops under its brand name SCOTCHMATE. 3M Company also distributes a linerless loop web with adhesive on the back of the web and a 3M knit loop tape.

The loop material may also include a nonwoven fabric having continuous bonded areas that define a series of discrete, unbonded areas. The fibers or filaments within the discrete unbonded areas of the fabric are dimensionally stabilized by the continuously bonded areas, which enclose or surround each unbound area, so that a backing or backing layer is not required. film or adhesive backing. The unbonded areas are specifically designed to allow the spaces between fibers or filaments within the unbound area to remain sufficiently open or wide to accommodate and engage the hook elements of the supplemental hook material. In particular, a nonwoven fabric or web having a seamless configuration may include a continuous filament nonwoven web formed from a single component or from multi-component spunbonding. At least one surface of the nonwoven fabric may include a series of discrete areas unbonded, enclosed, or surrounded by continuous bonded areas. The continuous bonded zones dimensionally stabilize the fibers or filaments that make up the nonwoven web by joining or fusing together the parts of the fibers or filaments that extend outside the unbonded zones in the bonded zones, leaving no However, the fibers or filaments within the unbonded areas, substantially free from bonding or fusion. Desirably, the degree of bonding or fusion within the bonded areas is sufficient to render the nonwoven web non-fibrous within the bonded areas, leaving the fibers or filaments within the unbonded areas act as "loops" to receive and engage the hook elements. Suitable examples of suitable non-point bonded fabrics are described in US Patent No. 5,858,515.

The loop material used in the various configurations of the invention need not be limited to discrete or isolated patches on the outer surface of the article. Rather, the loop material may be arranged by a substantially continuous outer fibrous layer that is assembled, integrated, or otherwise attached to extend over a predetermined surface area of ​​the desired article. For example, the outer fibrous layer may be arranged to extend substantially above the total uncovered surface of an outer covering of the type of fabric used with the article.

In the various configurations of the invention, the coupling force between the selected first component of the fastener and its intended and cooperating second component of the fastener must be sufficiently large and durable to provide adequate protection of the article on the wearer, during Its use.

Referring to Figures 1, 3 and 3A, the controlled portion (22) can be any desired area of ​​the selected item. For example, the provided controlled portion (22) may be a predetermined area of ​​the absorbent body (90) in the article. In desired arrangements, the controlled portion of the absorbent body may be a section that is intended to absorb and retain urine and other body fluids.

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The controlled situation can be any desired characteristic of the controlled part (22). For example, the controlled situation can be a humidity level, a level of light, sound, heat or the like, as well as combinations thereof. In the example of the representatively shown article, the controlled characteristic may be the moisture of the controlled portion of the absorbent.

Sensor 26 can indicate the desired change in situation by employing various operating techniques. The sensor can include, for example, a chemical sensor, a mechanical sensor, an electronic sensor, or the like, as well as combinations thereof. The chemical sensor can be configured to respond, undergoing a chemical reaction, a color change, or other change in its chemical characteristics. The mechanical sensor can physically dissolve, break, disperse, or undergo any other physical transformation. The electronic sensor can include any type of electrical or electronic circuit with passive or active components. Passive components can include resistors, capacitors, inductors, thyristors, diodes, connecting cables, antennas, and the like, as well as combinations thereof. Active components can include transistors, solar cells, batteries, integrated circuits, solid-state circuits, and the like, as well as combinations thereof.

In the example of the representatively shown arrangement, sensor 26 may be an electronic sensor. More particularly, the sensor (26) may be configured to indicate the change in situation by providing a change in electronic impedance that occurs when the controlled portion (22) of the absorbent body changes from the first condition to the second condition. In desired arrangements, the first condition can be a substantially dry condition and the second condition can be a wet condition. Accordingly, the passive repeater (28) may be configured to respond with selected indicator data when the absorbent body (90) is, for example, in the second wet condition. The situation signaling device can thus provide a humidity signaling device.

In a particular aspect, sensor 26 can provide a variable resistive impedance. In another aspect, sensor 26 can provide a varying capacitive impedance. The impedance of the sensor (26) may be configured to change when the controlled portion (22) of the article changes from its first condition to its second condition. In more particular arrangements, the impedance of the sensor 26 may change as the controlled portion 22 of the article changes from its first substantially dry condition to its second wet condition.

Repeater 28 is passive to the extent that it does not include a conventional power supply, such as a battery, solar cell, coiled spring, electric generator, or other conventional mechanisms that are ordinarily considered to be a source of power. Accordingly, the passive repeater may include a passive electronic device, a passive mechanical device, a passive optical device, a passive chemical device, or the like, as well as combinations thereof.

In desired embodiments, the repeater (28) is a passive electronic repeater that includes an operative coupler, configured to communicate the indicator data to the exterior of the article (20). In the example of the representatively shown arrangement, the method and apparatus of the invention includes an electrical coupler. The method and apparatus may use a capacitive coupler, an inductive coupler, a light coupler, a heat coupler, a sound coupler, a reflector, or the like, as well as combinations thereof. In the representative example shown, the method and apparatus include an inductive coupler.

An interrogator (30) is configured to provide the desired input power with the predetermined input frequency. The interrogator can, for example, be configured to provide the input power at any operating frequency. In desired aspects, the input frequency can be an operating frequency in the electromagnetic spectrum. The frequency of the input energy can be, for example, an audio frequency or other sonic frequency, a radio frequency, a microwave frequency, an infrared frequency, an optically visible frequency, an ultraviolet frequency or other higher or lower frequencies, as well as combinations thereof. The interrogator (30) can be a component that is integrally mounted to the article in an operative position. Alternatively, the interrogator may be provided by a component that is disposed spaced from the article, and is selectively positioned in operative proximity to the article. Desirably, the interrogator may be provided by a component that is selectively positioned, or that may be positioned in cooperative proximity to the repeater (28).

In a particular aspect, the input energy can be radio frequency (RF) and the radio frequency can be at least a minimum of about 0.1 MHz. Alternatively, the radio frequency can be at least about 5 MHz, and optionally can be at least about 7 MHh to provide improved performance. In other aspects, the radio frequency may not exceed a maximum of about 50 MHz. Alternatively, the radio frequency may be no more than about 15 MHz, and optionally no more than about 12 MHz, to provide improved effectiveness.

The desired selection of the input frequency can provide particular benefits. For example, higher frequencies may allow the use of smaller electronic components. Lower frequencies can reduce the amount of power required to generate the desired input power.

The repeater (28) may be configured to return a portion of the input power to the interrogator (30) and thereby communicate the indicator data to the outside of the item (20). In particular aspects, the repeater

ES 2 283 451 T3 may be configured to use a sonic, optical and / or electromagnetic technique or device to return the desired part of the input energy to the interrogator (30). In a desired aspect, repeater 28 may be configured to electronically return a portion of the input power to the interrogator.

In the example representatively shown in Figures 1, 4, 5A, 6A, and 6B, the interrogator (30) may include an interrogation coil (52). Additionally, repeater 28 may include a coil 50 of an operational repeater. The repeater coil (50) has an inductive impedance. Similarly, the interrogator coil 52 has an inductive impedance. In particular configurations, the passive repeater (28) may respond through an electronic coupling, which may, for example, include an inductive coupling between the repeater coil (50) and the interrogator coil (52). In various configurations of the invention, the interrogator coil 52 can be interpreted to be an antenna.

The technique of the invention includes placing the interrogation coil (52) in operative proximity to the repeater coil (50). In a desired aspect, the interrogator coil may be positioned in substantially coaxial relationship with the repeater coil (50), and the central axis of the interrogator coil may be aligned to substantially coincide with the central axis of the interrogator. the repeater coil. The input power is supplied to the interrogator coil (52), and the input power is operatively transmitted from the interrogator coil (52) to the repeater coil (50). A certain amount of the output energy that drives the indicator data is received by the interrogator coil (52). In particular aspects, the interrogator coil (52) may receive output energy that is reflected back to the interrogator coil (52) from the repeater coil (50). Operatively, a threshold value of the indicator data is detected, and the presence of a threshold value of the indicator data is operatively signaled. In the various arrangements of the invention, the signaling or the announcement of the threshold value may use any operative display mechanism or technique.

In the representatively shown arrangement, the repeater coil (50) may be a single turn or series of turns coil having a selected diameter (54) (eg, FIG. 5). Additionally, the interrogator coil (52) may also be a single turn or series of turns coil having a selected diameter (56) (eg, Figure 5A). The diameter (54) of the repeater coil and the diameter (52) of the interrogator coil may have a selected ratio. The selected ratio may be configured to increase the coupling coefficient, (k) between the repeater coil (50) and the interrogator coil (52). Increasing the coupling coefficient can increase the efficiency of energy transfer between the coils. The desired diameter of one of the two coils is chosen based on the physical limitations of the article (20), and the wavelength / frequency of the energy intended for operation. For example, in the arrangement shown, it is desirable to initially select the dimension of the repeater coil, based on available space and the ease of positioning the repeater coil in the article.

It can be found that the diameter of the second coil increases the coupling coefficient, (k). In certain aspects, the diameter of the second coil may be based on the diameter of the first coil and the expected separation distance between the two coils. See, for example, FE Terman, "Radio Engineer's Handbook", First Edition, McGraw (Hill Book Company, Inc. New York, 1943, for example, pages 67-73. In the configurations shown, the separation distance is determined primarily by the total thickness of the various layers of material (for example, layers of article -20- and the modulus of system assembly -68-) that are interposed between the coil ( 50) of the repeater and the coil (52) of the interrogator during ordinary operation. When the first and second coils (for example, the repeater coil and the interrogator coil) are located in a separate, substantially coaxial relationship, it can be determined that an increased or maximized coupling coefficient (k) can be provided, when the diameters of the coils are configured according to the following formula:

d = [(d₂)² + 4D²]^1/2 in which:

d2 = relatively smaller coil diameter d1 = relatively larger coil diameter

D = separation distance between the two coils.

In desirable embodiments, when the separation distance (D) can be expected to be about 5mm ± 1.5mm, the diameter (56) of the interrogator coil (52) is about 1.25 times the diameter (54 ) from the repeater coil (50) to provide improved performance. For example, in the representatively shown configuration, the interrogator coil may have a diameter of about 1.25 inches (approximately 3.2 cm) and the repeater coil (50) may have a diameter (54) of 1 inch. approximately (2.54 cm).

Referring to Figures 1, 3A, 4 and 5, repeater 28 may include an electronically tuned circuit that can resonate electronically at the predetermined input frequency, or substantially at the frequency of

ES 2 283 451 T3 entry. Similarly, interrogator 30 may include an electronically tuned resonant circuit that is tuned to resonate electronically at the selected input frequency, or substantially at the input frequency. For example, the interrogator may be tuned with a tuning capacitor 46 of a suitable size. When the interrogator (30) uses RF energy at an input frequency of 10 MHz and a 1-inch (2.54 cm) diameter single-turn repeater coil (50), the interrogator may be tuned to a capacitor 3,900 pF connected in parallel.

In another aspect, the output receiver (34) may include a circuit that can resonate electronically at the predetermined input frequency. In a further aspect, repeater 28 may be configured to supply the desired output power at a predetermined output frequency. In desired embodiments, the output frequency can be substantially equal to the input frequency. In alternative arrangements, the output frequency may be different from the input frequency.

A primary power source (58) is operatively configured to supply the input power. In desired embodiments, the primary energy source is separately arranged and electrically isolated from the article (20). The desired electrical isolation may be provided by wireless communication between the passive repeater (28) and the interrogator (30) and the output receiver (34).

With reference to Figures 4, 5, 6A and 6B, a particular aspect of the invention includes the configuration of an output receiver (34) to electronically acquire the predicted data of the indicator, communicated from the repeater (28). In particular arrangements, the output receiver may have the configuration of a directional electronic coupler (60). A detector (36) is connected to resolve the indicator data of the energy that is supplied from the output receiver (34). For example, the supplied energy level may vary by an amount corresponding to the first and second selected conditions of the controlled part (22). In a particular aspect, an electronic sampling device can be used to monitor a value supplied or derived from the indicator data. For example, a comparator 40 can be configured to react to a threshold value of indicator data. An annunciator is operatively connected in communication with detector 36 and is configured to announce the presence of at least one threshold value of indicator data. The mechanism and technique for providing the connected communication may include, for example, a switch 42.

Annunciator (38) may be configured to provide any suitable indicating device desired. For example, the annunciator (38) may be configured to provide an audio indication device. Alternatively, the annunciator may be configured to provide a visual indication device. Optionally, the annunciator may provide another type of indication device, such as a tactile indication device, a vibration indication device, a smell indication device or the like, as well as combinations thereof.

In another aspect, the annunciator (38) may be configured to include a calling device or other rebroadcasting device that can operatively communicate the desired assessment of the indicator data and / or the recognized presence of the threshold value to a further position. remote. Such information can, for example, be communicated in the form of selected signal data. Referring to Figures 4, 5A, 6A, 6B, 7, 8A, and 8B, the rebroadcast device may include a supplemental transmitter (70) that can operably send the desired signal data, and a supplemental receiver (72) which can operatively receive the reissued signal data, supplied from the supplementary transmitter. The supplemental transmitter can be an infrared transmitter, an ultrasound transmitter, an RF transmitter or the like, as well as combinations thereof. Accordingly, the corresponding and cooperative receiver may be an infrared receiver, an ultrasound receiver, an RF receiver or the like, as well as combinations thereof. In the representative example shown, the supplemental receiver may be a radio frequency transmitter, and the supplemental receiver may be a radio frequency receiver. Additionally, the rebroadcast device may include a remote annunciation indicating device that announces the presence of the threshold value of the indicator data. As mentioned elsewhere in this specification, the annunciator of the indicating device may be provided with any suitable display mechanism or technique, as desired.

A desired configuration of a method and apparatus for remotely indicating a wet or dry condition on a non-metallic material or substrate may include an RF wireless connection produced at the selected input frequency. The connection can be made between an external RF source and a passive part of a tuned circuit (i.e. no power source) that is embedded in a non-metallic item, such as a diaper, or other garment (for example, figures 1, 3 and 3A). The RF connection can be implemented by utilizing a stable RF source and the accompanying tuned resonant circuit, which is embedded in the article and electronically coupled to the RF source using interrogator (30). The power supply for the circuits on the outside of the apparatus may be provided by ordinary batteries, such as AAA size batteries or a coin cell. When the controlled portion 22 of the article is moistened with an electrically conductive liquid, such as urine, the wet condition can be detected by detecting changes in electrical resistance that occur in the wet areas of the article. The outside can send another RF signal with a selected second RF frequency to a remotely located call unit to remotely signal the detected humidity condition.

ES 2 283 451 T3

The power supply and associated circuitry of the desired exterior portion of the signaling device may be housed in a suitable system of the module assembly (68). In desired configurations, the module system (68) is remarkably compact and lightweight. For example, the module system (68) may weigh no more than about 15 grams. Additionally, the module system (68) may have dimensions less than about 4 centimeters in width, less than about 4 centimeters in height, and less than 1 centimeter in depth or thickness.

The module assembly (68) may also include a mounting operative device to secure the module system (68) to the selected target article (20). Various types of conventional mechanisms can be used to hold the module assembly (68) on the target article. Such support mechanisms may include, for example, adhesives, snaps, hooks, mechanical inter) coupling attachment systems, hook and loop attachment systems, magnetic attachment systems, or the like, as well as combinations thereof. For example, in the illustrated configuration, the module assembly system (68) may include a hook component, and the target area of ​​the article (20) may include a complementary loop material.

The system may utilize a two-way wireless radio connection between an external RF micro-energy source and the passive repeater (28) that is embedded in the non-metallic substrate of the selected article. A micro-energy RF carrier is transmitted from a small outer coil antenna (approximately 3.2 cm), such as that provided by the interrogator coil (52). In the arrangement shown, a substantially constant RF carrier can be transmitted. Alternatively, the transmission of the RF carrier may not be constant. For example, the transmitted RF configuration may be timed, cycled “on-off”, or otherwise modified. The outer antenna coil may be closely magnetically coupled to the coil of a smaller (approximately 2.5 cm) indoor antenna, such as that provided by the repeater coil (50). The inner coil is desirably embedded in the controlled portion of the absorbent pad. These coils can be interpreted as constituting a transformation coupling between the tuned primary circuit with its outer coil, and the tuned secondary circuit with its embedded coil. The difference in diameters between the primary and secondary coils allows a certain tolerance with respect to misalignment and relative displacements between the coils. When the primary and secondary circuits are operatively coupled, a portion of the energy coupled from the primary circuit to the secondary circuit is reflected back from the secondary circuit and appears in the primary circuit. The amount of energy reflected in the primary circuit is related to the impedance that appears across the secondary circuit. In the representative arrangement shown, the secondary circuit includes a resistance type sensor.

For example, the illustrated sensor may be comprised of two small diameter wires (eg, # 24 AWG), spaced approximately 1 cm apart, and located in the absorbent portion of the representatively shown diaper article. The electrical resistance through these wires will be high (open circuit or high resistance) when the controlled part of the diaper is dry, and much lower when the controlled part of the diaper is moistened with an electrically conductive material, such as urine. The separate ends of these wires are electrically connected in parallel with the tuned secondary circuit. As a result, the dry absorbent pad can provide a reflected signal, in the outer primary circuit, that is significantly different from the reflected signal provided by a wet absorbent pad.

To provide the desired input power, the power source can be a micro-power system using a quartz crystal oscillator as a reference, oscillating at the selected input frequency, and a power amplifier. The output of the amplifier is directly connected to the series tuned primary circuit, composed of the outer coil and an adjustable resonance capacitor. Located between the power amplifier and the primary circuit is a directional coupler (60) from which the reflected energy from the coupled secondary circuit can be sampled and controlled. The directional coupler can be any device that can operatively separate the direct signal (from the power amplifier) ​​from the reflected signal, which is returned to the primary circuit from the secondary circuit located in the article. The reflected output from the directional coupler is then sensed to provide a voltage (Vdet), the magnitude of which is related to the amplitude of the reflected energy, and therefore related to the magnitude of resistance across the sensor. This tension is significantly different for a dry absorbent pad compared to a wet absorbent pad.

Referring to Figures 4, 5A, 6A and 6B, the input frequency can be provided by any conventional generating device. For example, the representatively shown arrangement may utilize a quartz crystal controlled oscillator that generates the input power at a frequency of about 10 or 24 MHz. Radio frequency energy is amplified and damped appropriately, such as by using circuitry including the (IC2) shown (for example, the MAX 626A device, available from Maxim Semiconductor, a company located in Sunnyvale, California). RF energy is supplied to the interrogator circuit antenna (64) and the antenna may, for example, be provided by the interrogator coil (52).

A directional coupler (60) can be provided by various types of operating circuits that are well known in the art. For example, in the representatively shown configuration, the directional coupler may be provided by circuitry that includes the shown transformer (T1) and associated capacitors (C15) and (C9) together with resistor (R5). As illustrated, the capacitor (C15) may be adjusted to tune to the reception of the output energy received by the interrogator coil (52) from the

ES 2 283 451 T3 coil (50) of the repeater. A suitable sampling device can monitor a value provided or derived from the indicator data supplied by the directional coupler. In the representatively shown configuration, the sample can use a detector to supply a selected signal for further processing. For example, the representatively shown arrangement may include an envelope detector. The detected voltage signal (Vdet) can then be supplied to a conventional comparison device.

Various conventional detection schemes can be used. For example, the sensed tension can be high or low when the controlled portion (22) of the article (20) is in its first condition (eg, dry). Similarly, the detected voltage signal can be high or low when the controlled portion 22 of the article is in its second (eg, wet) condition. In the representatively shown arrangement, the detection scheme is configured such that the sensed tension is high when the controlled part is in its dry condition and, the sensed tension is low when the controlled portion of the article is in its wet condition. .

The detector (36) may include an envelope detector, such as that supplied by the circuitry shown representatively, which includes the capacitor (C2), the resistor (R1) and the diode (D2) (for example, the Schottky SD103-AWDI device, available from Diodes, Inc., a company with offices located in Westlake Village, California). The envelope detector can operatively detect the indicator data received from the directional coupler and can use the indicator data to generate the sensed voltage (Vdet).

As representatively shown, the method and apparatus of the invention may desirably include a voltage threshold detection system (40). The voltage threshold detection system may include a comparator and a switch (42) that can be opened and closed in accordance with the amplitude of a voltage placed at its input. As representatively shown, the comparator may be equipped with circuitry that includes IC1 (eg, the MAX 921 device, available from Maxim Semiconductor). The switching operation may be provided by the circuitry that includes (Q1).

In the example of the configuration shown, the voltage (Vdet) corresponding to a wet absorbent can be configured to turn the switch ON and the voltage (Vdet) corresponding to a dry absorbent can be configured to turn the switch OFF. The switching threshold may desirably be adjustable to account for different applications or situations, such as for different strengths of the controlled non-metallic substrate material, and for different thicknesses of the non-metallic substrate material.

When the comparator or other component of an operational threshold detector 40 appreciates that the indicator data, such as that represented by the sensed voltage (Vdet), has reached a selected threshold value, the comparator can generate an output signal. default. In the configuration shown, the comparator output signal is generated when the detected voltage (Vdet) falls below a predetermined reference voltage (Vref).

A desired reference voltage (Vref) can be provided by using any conventional circuitry. For example, the arrangement shown can provide the reference voltage by using a circuitry (THRESHOLD) that includes the adjustable potentiometer (POT1).

The comparator output signal can be configured to operate with any conventional switching device or with a switching circuit. For example, the switching circuit configuration shown may use a Q1 provided by a MOSFET (metal oxide semiconductor field effect transistor) device, (for example, the VN0605 device available from Vishay Siliconix, a division of Vishay Intertechnology Inc., a company with offices located in Malvern, Pennsylvania). In the arrangement shown, the switch is normally open and the switch closes when the comparator output signal is received. The switch closure can be used to activate a suitable annunciator system, and the annunciator can include any operational indicating device. For example, the output supplied from the switching circuits may be configured to activate an audible buzzer or other type of alarm that is contained on the outside of the system, such as that provided by the module assembly (68).

In a desired aspect, the annunciator may include a rebroadcasting or calling system, or a unit that can operably deliver a rebroadcasting signal to a more distant location. More particularly, the re-emitting device can be used to announce the presence of the threshold value of the indicator data at the most distant position.

In the example of the representatively shown configuration, the rebroadcast device may include a supplemental transmitter (70) that may have an RF transmitter, and a cooperating signal generator. The transmitter may be provided with a conventional circuit, such as a circuit that includes an RF module that is configured to transmit at a frequency of 418 MHz. As representatively shown, the RF transmitter may be provided with circuitry that includes the TX1 circuit module (for example, the HX1003 device, available from RF Monolithics, Inc., a company having offices located in Dallas, Texas). The signal generator can use any conventional circuitry, such as a circuit that includes the IC3 representatively shown (for example, the LS555 device available from National Semiconductor Inc., a company having offices located in Santa Clara, California). . In the representative example of the arrangement shown, the signal generator produces a square wave at a frequency of approximately 1 KHz. The signal

ES 2 283 451 T3 of 1 KHz is used to modulate the transmitted RF frequency and the energy directed and emitted by an operating antenna (104). In the arrangement shown, the radio frequency transmission is modulated through the use of a connect-disconnect key. Alternatively, other types of modulation can be used. Said modulation may include phase shift keys, frequency shift keys, digital code modulation, or the like, as well as combinations thereof. The various circuits of the input frequency generator, directional coupler, detector, comparator, and annunciator system can be operated by a suitable power supply module. In the configuration shown, the power supply may include a conventional battery, such as a 1.5 volt battery. The power supply may also utilize a voltage swing boost converter, such as a voltage swing converter that includes the circuit device (U1) shown representatively (for example, the MAX756 device, available from Maxim Semiconductor, Inc.).

With reference to Figures 4, 7, 8A and 8B, the relay system may include a separately arranged call unit 74, located remotely. The call unit may include a suitable supplemental receiver (72) which, in the arrangement shown, may be a cooperating RF receiver. The call unit may further include a signal detector (76), a comparator (78) or other threshold detector, and a suitable display system, such as that provided by a remote annunciator (44), along with a supply associated energy. The receiver part of the call unit is configured to receive the transmission generated by the relay device in the system module (68). Any compatible receive circuitry can be used.

As representatively shown, the remote receiving system may include a single chip hybrid AM (amplitude modulation) radio receiver having a receiving antenna (106), a low frequency detector (76), a voltage level comparator, an alarm annunciator (such as an audible buzzer), and a voltage regulated power supply (eg, Figures 7, 8A and 8B). The RF signal (eg at 418 MHz) can be received using the amplitude modulation hybrid chip receiver. The output from the receiver (72) can be a square wave of constant amplitude at the selected modulation frequency (eg, 1 KHz). This low frequency square wave signal can be subsequently detected to provide a voltage whose amplitude is related to the strength of the received RF signal, thus providing a method and apparatus for activating the remote reception system by a situation outside the operating range. This voltage is compared to an adjustable reference voltage with the comparison circuit below. Thus, a wet absorbent (or an out-of-range situation) will result in the activation of the selected annunciator or alarm device (eg, an audible buzzer).

The receiving circuitry may use, for example, an integrated circuit module IC20. An example of a suitable HRX1 integrated circuit is a RX1300 device available from RF Monolithics, Inc. The received RF modulated signal is operationally detected. The detector can use any suitable conventional circuitry. In the arrangement shown, the detector is provided with a circuitry that includes the resistor (R21), the capacitor (C4) and a diode system (D21) (for example, Dual Schottky device BAS70-062X, available from Diodes , Inc.). The sensed signal can be used to generate a sensed voltage (Vin) and the sensed voltage can be supplied to a suitable comparator circuit. The comparator circuit may include, for example, the IC21 representatively shown (for example, the MAX921 micro-energy comparator). The sensed voltage (Vin) is compared with a reference voltage (Vref) when the sensed voltage (Vin) reaches a selected value, the comparator can generate an output signal that drives a unit with a suitable indicating device. In the example of the arrangement shown, the indicating device unit includes an audible buzzer (BP1).

The call unit includes a suitable power supply unit such as a power supply including a battery. In the arrangement shown, the power supply uses a nine volt battery that is connected to a voltage regulator (VR1) (eg, the 78L06SM device, available from National Semiconductor, Inc.) that provides the desired regulated voltage. In the arrangement shown, the voltage is regulated to about 6 volts.

The passive repeater (28), when ready for use, may be positioned at any convenient position on the selected article (20). The repeater, or an operating part thereof, may be located in a front, rear, or side position of the article, as desired. For example, the repeater coil 50 may be located at a predetermined position along a portion of the waistband of a diaper, as representatively shown in Figures 1-3A. In a desired embodiment, the repeater coil may be located in a generally centered position at the front waist section of the diaper. Insulated electrically conductive cables can operatively connect the repeater (eg, the portion provided by the repeater coil (50)) to the sensor (26). In a desired configuration, the sensor may be provided with bare-ended patch cords (with the insulation removed) that may be spaced an operating distance from each other. For example, the bare ends of the cable may be spaced about 1 cm apart. The sensor (eg, the bare ends of the cable) can be located in any operative position on the article. In an example of a desired configuration, the sensor may be located in an intended front section of the diaper, proximate to an intermediate crotch portion of the absorbent pad.

An operating part of the repeater (for example, the repeater coil (50)) can be located proximate to any operating surface of the article, which can be a top surface, a bottom surface, a side surface, an interior surface, or a surface. exterior, as desired. For example, the repeater coil may be

ES 2 283 451 T3 located in an operative position that is proximally adjacent to a planned outer surface of the diaper. Additionally, the plane of the coil may desirably be aligned generally parallel to the outer surface of the diaper.

During ordinary use, the interrogator may be located in operational proximity to the passive repeater (28). For example, the interrogator coil (52) may be located adjacent an outer surface of the module assembly (68), with the plane of the interrogator coil disposed generally parallel to the outer surface. The module assembly may be attached to the diaper by a suitable fastener to operatively align the interrogator coil (52) with the repeater coil (50). Desirably, the fastener can be selectively disassembled and reassembled (eg, a hook and loop fastener). In a desired configuration, the repeater coil and the interrogator coil may be arranged approximately concentrically. Even though there are intermediate layers of the article (eg, the outer shell of the diaper), operative wireless communication can exist between the repeater coil and the interrogator coil. In the example of the representative configuration shown, the selected annunciator (eg, call unit -74-) may be configured to activate the associated indicating device (eg, a "buzzer") until a positioning is established. operational between the interrogator and the repeater (eg, an operational alignment between coil 52 of the interrogator and coil 50 of the repeater).

Having preferably described the invention in full detail, it will be clearly apparent that various changes and modifications can be made without departing from the scope of the invention. All such changes and modifications are considered to be within the scope of the invention as defined in the dependent claims.