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1. (WO1993019437) APPAREIL DE SURVEILLANCE D'ENFANT
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DESCRIPTION
Child Monitoring Apparatus
Technical Field
This invention relates to improvements in child
monitoring apparatus .
Children often accompany parents to various places in which a child can be lost or abducted if the child becomes separated from the parent. For this reason, parents must always be vigilant in monitoring the location of their children. However, parents often become distracted from monitoring children and this momentary distraction may be long enough for a child to become lost or abducted.
Accordingly, there is a great need for devices that
automatically monitor the location of children so that a parent will be alerted if a child becomes separated.
However, even if a parent is alerted that a child has become separated, there is a need for the parent to be able to locate the child if the child is out of sight. Of course, any child locating device also must be compact and portable.
Background Art
Many patents have been issued for devices to monitor the location of children, other people or objects.
U.S. Patent 4,598,272 to Cox discloses an electronic monitoring apparatus including a first unit that broadcasts an alarm if a second unit becomes separated from the first unit. Further, the user of the first unit can cause the second unit to transmit an alarm to assist in locating the second unit.
U.S. Patent 4,549,169 to Moura discloses a system for monitoring the security of persons in a waterside
environment, including a portable transmitter that
transmits a signal to a base unit. The base unit activates an alarm if it does not receive a transmitted signal from the portable unit. The portable .unit may transmit either on a time sharing basis with other portable units or in response to an interrogation from the base station.

1 U.S. Patent 4,260,982 to DeBenedictis discloses a
system for producing an alarm whenever the distance between a transmitter and a receiver exceeds a predetermined
distance.
5 U.S. Patent 4,785,291 to Hawthorne discloses a distance monitor including an unmodulated transmitter of constant low power and a normally fixed indoor monitor.
U.S. Patent 4,888,580 to Distel includes a device that sounds an alarm when a child is separated from a stuffed 10 animal.
U.S. Patent 4,899,135 to Ghahariiran discloses a child monitoring device employing ultrasonic transceivers .
International Patent Application No. PCT/FR86/00407 by Royoux discloses a device for remote surveillance of a •j_5 human being including an RF oscillator and a separate
receiver which is orientable in all directions .
International Patent Application No. PCT/US87/00996 by Corwin discloses a remote monitoring and alarm system using digitally encoded FM signals transmitted at minimum time 20 intervals.
U.K. Patent Application No. 8526445 (GB 2 182 183 A) by Andow, et al. discloses a child vicinity radio alarm
system.
U.K. Patent Application No. 8905121.3 (GB 2 217 084 A) 25 discloses personal security devices comprising a
transmitter attached to a person to be protected and a
portable receiver.
Because any child monitoring device must be compact and portable, it would be desirable to be able to use a minimum 30 number of components to perform transmitting and'receiving functions. During the 1930's, superregenerative
transceivers were known, which used one tube for both
transmitting and receiving radio signals . These
transceivers suffered a number of limitations and fell into 35 disuse. One of the main problems with these transceivers was that they did not transmit and receive on the same
frequency. The reason for this was understood to be the fact that the "effective" capacity between the grid and plate of the triode tube is changed slightly by changes in" the operating point and signal level between transmit and receive. "Operating point" is the voltage across and the current through the tube or other active device.
"Effective capacity" is the actual measured capacity multiplied by the amplification factor of the tube or other active device. Since this capacity is effective across the frequency determining tuned circuit, a change of capacity causes the frequency shift between transmit and receive.

Thus, when two of these units were in use, each operator in turn would retune his unit when receiving to best hear the other unit's signal. As a result, the frequencies would gradually move until they were outside the assigned
frequency band. At that time there seemed to be no
practical remedy for this problem. The same problem occurs with semiconductors such as transistors and the device physics suggests that transistors will have an even greater frequency shift than vacuum tubes .
The background art focuses primarily on the technical aspects of child monitoring devices. However, the
background art does not disclose solutions to several common problems. For example, it is normally desirable to have a child monitoring device that is easily attachable to the child. It is also desirable to have such a child monitoring device that cannot be accidentally deactivated by the child. It is further desirable to have a child monitoring device that can be easily and conveniently recharged without requiring disassembly or other
manipulation. It is also desirable to provide a child monitoring device that is extremely compact, so that the use of one device for both transmitting and receiving is desirable.
It is therefore an object of this invention to provide a child monitoring apparatus that is easily and safely attachable to a child or the child's clothing.

It is a further object of this invention to provide such an apparatus that is compact and portable .
It is a further object of this invention to provide an apparatus that cannot be accidentally deactivated by the child.
It is a still further object of this invention to provide such a device that is easily and conveniently recharged for use.
Disclosure of the Invention
The electronic monitoring apparatus of this invention comprises a first housing having a pin recess and a pin hole, a first transceiver mounted in the first housing, a pin having a point retractably mounted on the first
housing, spanning the pin recess and extending into the pin hole, whereby the point extends into the pin hole.
Retracting the pin withdraws the point from the pin hole and exposes the point. This allows the housing to be attached to the clothing of the child . Preferably an urging means is connected to the pin, such as a spring, to urge the point of the pin into the pin hole.
The apparatus also includes cooperating switches in the parent device and the child device so that they are
deactivated when they are attached to each other and become activated when they are detached. This is preferably accomplished by an apparatus comprising a first housing, a first transceiver housed in the first housing, a second housing configured to be attached to the first housing, a second transceiver housed in the second housing, a first switch housed in the first housing operably connected to the first transceiver and configured to be activated when the first housing is attached to the second housing, and a second switch housed in the second housing operably
connected to the second transceiver and configured to be deactivated when the first housing is attached to the second housing. Thus, the first switch deactivates the first transceiver and the second switch deactivates the second transceiver when the first housing is attached to the second housing, and the first switch activates the first transceiver and the second switch activates the second transceiver when the first housing and the second housing are detached.
The apparatus also preferably is powered by
rechargeable batteries and is preferably recharged by a recharger having portions configured to receive the child device and the parent device when they are attached to eac other and to recharge the batteries when the attached devices are received in the aperture.
The apparatus preferably uses superregenerative
transceivers in order to allow the devices to be compact. These receivers allow one device to function as both a receiver and transmitter, which is useful for reducing siz and increasing battery life. This is preferably
accomplished with apparatus comprising a self quenched superregenerative detector comprising an active device tha oscillates at both a receiving frequency and a quench frequency, a first semiconductor switch operatively
connected to the device to switch off the quench frequency, and a second semiconductor switch operatively connected to the device to increase power of the oscillation. The apparatus also uses a reactive circuit element (capacitor or coil) to address the problem of frequency shift in a superregenerative receiver. This is accomplished by employing an apparatus comprising a frequency determining circuit for reception and a reactive circuit element that changes its value in accordance with applied bias
operatively connected to the frequency determining circuit. Brief Description of Drawings
Fig. 1 is a perspective view of the best mode of the parent device and the best mode of the child device
attached to each other and received by the best mode of th recharger.
Fig. 2 is a top view thereof;
Fig. 3 is a front view thereof;

Fig. 4 is a rear view thereof;
Fig. 5 is a bottom view thereof;
Fig. 6 is a left side view thereof, the right side view being a mirror image;
Fig. 7 is a left side view of the best mode of the child device and the best mode of the parent device showing how they are attached to each other;
Fig. 8 is a top view of the child device;
Fig. 9 is a front view thereof;
Fig. 10 is a side view thereof, the other side view being a mirror image;
Fig. 11 is a rear view thereof;
Fig. 12 is a bottom view thereof;
Fig. 13 is a top view of the best mode of the parent device;
Fig. 14 is a front view thereof;
Fig. 15 is a left side view thereof, the right side view being a mirror image;
Fig. 16 is a rear view thereof;
Fig. 17 is a bottom view thereof;
Fig. 18 is a top view of the best mode of the
recharger;
Fig. 19 is a front view thereof;
Fig. 20 is a rear view thereof;
Fig. 21 is a bottom view thereof;
Fig. 22 is a left side view thereof, the right side view being identical;
Fig. 23 is a flow chart of the functions of the best mode of the parent device and the best mode of the child device;
Fig. 24 is a block diagram of the best mode of the child device;
Fig. 25 is a block diagram of the best mode of the parent device;
Fig. 26 is a block diagram of the best mode of the recharger;

Fig. 27 is a circuit diagram of the best mode of the child device;
Fig. 28 is a circuit diagram of the best mode of the parent device; and
Fig. 29 is a circuit diagram of the best mode of the recharger.
Best Mode for Carrying Out Invention
The best mode contemplated for carrying out the present invention is the preferred embodiment illustrated by way of example in Figs. 1-29. First, the external configuration of the apparatus will be described, and then the functional aspects of the best mode will be described, concluding with detailed information about the use of superregenerative transceivers .
Referring to Figs. 1 to 7, the general external
configuration of the preferred embodiment comprises a child device 100 configured to be attached to a parent device 400, and a battery recharger 700 configured to receive the child device 100 and parent device 400 when they are attached together.
Referring to Fig. 11, the child device 100 is provided with a recessed pin aperture 120 which is spanned by a retractable pin 140. The pin 140 is retracted by pulling back on a grip 160, which will allow a portion of the child's clothing to be placed in the pin aperture 120 and allow the clothing to be pierced by pin 140 and thereby attach the child device 100 to the child. The child device 100 is preferably provided with an urging means, such as a spring 145, to bias the pin 140 in the extended position so that the point of the pin 140 is normally received in a pin hole 150. If the child device 100 will not be pinned to the child, the pin 140 can still be used to attach the device to the child by passing a string, wire or other elongated member through the pin recess 120 and behind the extended pin 140. If a string is used, the child device 100 then can be -tied to the child or hung like a pendant, bracelet or other item of jewelry. Preferably, the child device is attached to the back of the child so that the child cannot reach it to take it off.
Referring to Fig. 9, the front of the child device 100 is provided with speaker holes 180 and a light emitting diode (LED) 190. The speaker holes 180 are for an audible alarm of conventional design and the LED 190 is to indicate whether the child device 100 is activated.
Referring to Fig. 12, the bottom of the child device 100 is provided with child device recharging contacts 220 and 222 for recharging the child device 100.
Referring to Figs. 16 and 17, the parent device 400 is provided with a belt clip 410 that has an inwardly
extending dimple 420 to help retain the belt clip 410 on a belt. The middle of the back of the parent device 400 is provided with an auxiliary dimple 425 to help retain the parent device 400 on a belt. The belt clip 410 is also configured to slidably engage with a raised portion 170 of the child device 100, as shown by Fig. 7. A recharger locking recess 430 is provided that matches a recharger protrusion 770 on the recharger 700 to lock the parent device 400 in position on the recharger 700.
Referring to Fig. 13, the top of the parent device 400 is provided with an alarm button 600 (sometimes referred to as a "panic switch" or "location switch") which activates the audible alarm behind the speaker holes 180 on the child device 100 when pushed.
Referring to Fig. 14, the front of the parent device 400 is provided with speaker holes 480 and a light emitting diode (LED) 490. The speaker holes 480 are for a threshold alarm (referred to as an alarm on Fig. 23 and a -buzzer on Fig. 25)
Referring to Fig. 12, the bottom of the parent device is provided with parent device recharging contacts 520 and 522.
Referring to Fig. 19, the recharger 700 is preferably provided with a light emitting diode (LED) 710 that
indicates whether the child device 100 and the parent device 400 are recharging, and is provided with four large feet 720, 722, 724 and 726 for stability, because the recharger 700 can become top heavy when the child device 100 and the parent device 400 are positioned for recharging.
Referring to Fig. 18, the recharger 700 also is
provided with a parent device cavity 740 configured to receive the bottom of the parent device 400. The front of the recharger 700 is configured to form a child device cradle 750 which is configured to receive the bottom of the child device 100. The child device cradle 750 is provided with child device cradle contacts 752 and 754 that are positioned to be in recharging contact with child device recharging contacts 220 and 222 when the child device 100 is placed in the child device cradle 750. Similarly, the parent device cavity 740 is provided with parent device cavity contacts 742 and 744 that are positioned to be in recharging contact with parent device recharging contacts 520 and 522 when the parent device 400 is placed in the parent device cavity 740.
Turning now to the functional aspects of the present invention, it is preferred that the child device 100 and the parent device 400 serve as radio transceivers as disclosed in U.S. Patent 4,598,272 to Cox, which is
incorporated herein by reference, with the use of
superregenerative transceivers as described below. For ease of reference, the function flow of the best mode is set forth in Fig. 23. In the Cox apparatus, the child device includes an audible alarm, a first radio receiver for receiving an activating signal ("panic signal" in Fig. 23) to activate the audible alarm and a first radio
transmitter for transmitting a normal signal to the parent device. The parent device includes a second radio receiver that monitors the transmissions from the first radio transmitter and sets off a threshold alarm on the parent device if the transmissions indicate a threshold condition has been met ( such as a threshold distance between the child device and the parent device has been exceeded) . The parent device further includes a second radio transmitter for transmitting an activating signal to the first radio receiver to activate the audible alarm on the child device.
In use, the child device would be secured to the child and the parent device would be secured to the parent. If the threshold condition is met, namely the child device (and therefore the child) becoming separated from the parent device by a threshold distance, then the threshold alarm on the parent device will be set off . The user of the parent device then can activate the audible alarm on the child device to assist in locating the child device or perhaps alarming a person who might have seized the child. Although the apparatus disclosed in the Cox patent is preferred as to the functional aspects of this invention, this invention can be practiced using other forms of child monitoring apparatus . For example , other forms of
transmission and reception between the child device and the parent device are acceptable, such as ultrasonic or
infrared transmission and reception. Accordingly, the terms "transceiver", "transmission", "reception" and similar words shall be given their broadest meanings and shall not be limited to radio frequency or electromagnetic radiation.
Because the child monitoring apparatus must be
convenient to use, the activating and recharging of the parent and child devices must be extremely easy and
convenient. Also, it should be difficult for a child or other person to* accidentally or deliberately disable the apparatus .
To this end, the child unit 100 and the parent unit 400 are preferably designed so that they are deactivated when they are slidably attached together as shown in Fig. 7, preferably through a first normally closed push button switch 200 on the back of the child device which becomes depressed when the child device is slidably attached to the parent device. Similarly, the parent device is provided with a second normally closed push button switch 500 which opens when the parent device is slidably attached to the child device 100 as shown in Fig. 7. Thus, when the child device and the parent device are slidably attached
together, they are both deactivated.
Turning to the use of superregenerative transceivers and referring to Figs. 27 and 28, the best mode employs a transistor Ql which is the superregenerative detector and when switched becomes the transmitting device. In the receiving condition this transistor oscillates at the signal or received frequency at a very low signal level and this oscillates is switched off and on at a high frequency rate which is lower than the received frequency and this frequency is called the "quench frequency" . The principle is low power oscillation and switching the oscillation off and on by a quench frequency is the original invention of Armstrong and is what is called superregenerative. The quench frequency may be generated by an additional external superregenerative detector. The quench frequency may also be generated by the simultaneous oscillation of a single active device oat both the receiving frequency and the quench frequency. In this case the detector is called a self quenched superregenerative detector. Only the self quenched superregenerative detector is of concern here. The quench frequency is generated by the same transistor simultaneously oscillating at a frequency above the highest modulation frequency. This frequency is determined by the tuned circuit consisting of the 1000 Pf . capacitor C13 and 10 uh. choke L2 connected between the base and emitter of transistor Ql. The transistor is biased by the 47 K.
resistor R19, the 3.9 K. resistor R3, and the 1N4148 diode Dl which in conjunction with the 820 ohm emitter resistor R16 establish the "operating point" of the transistor and stabilize it against changes in temperature. The audio signal is recovered from the changes in voltage occurring across the 8.2 K. resistor R23 connected to the signal tuned circuit connected to the collector of Ql . All of the above is well known to those, skilled in this art. The present invention consists of the addition of transistor U5 across the 820 ohm emitter resistor R16. This transistor when turned on effectively grounds the emitter "of Ql and stops the quench frequency oscillation and biases the transistor on so that it may oscillate with greater
amplitude for transmitting. In addition, a second
transistor U6 connected across the 8.2 K. ohm resistor R23 increases the power of the oscillations in transistor Ql so that an adequate transmitting signal may be obtained. If desired, a resistor R20 may be connected between the collector of U6 and the tuned circuit so that the
transmitted signal level may be limited to comply with government regulations . The base of U6 and the base of U5 are connected by inverter U4 so that one positive going signal will turn on both transistors and switch Ql from receive to transmit. If desired, Ql may be either
amplitude or frequency modulated in the transmit condition. Means for doing this will be apparent to persons skilled in this art. In alarm systems, merely keying Ql on and off in the proper pattern is sufficient to provide the desired transmitting signal which may be detected by another receiver tuned to the transmitted frequency. The devices shown in the diagram merely show one means for achieving the desired result. Other means will be obvious to those skilled in the art.
Turning to the problem of frequency shift in
superregenerative receivers and referring to Figs . 27 and 28, in the present device, the frequency of transmission or reception is determined by the coil Loop-Ant. in series with the collector of Ql and the capacitors C15, C8 and VC1 across that coil along with the capacity of the transistor Ql and stray circuit capacities . These are well known to persons skilled in the art. In this invention, a
semiconductor diode D4 which changes capacity with changes in voltage (commonly known as a varicap diode) is connected in series with another capacitor C14 across the tuned circuit and a resistor R18 is connected from the common point of the diode and capacitor to ground. The varicap diode has a high capacity when a low voltage is applied to it and a low capacity when a high voltage is applied to it. In the receiving condition the voltage from the collector of Ql to ground is approximately one-half of the supply voltage. This then is the bias voltage across the varicap diode D4 in the receiving condition and determines the capacity while receiving. That capacity in series with the other capacitor becomes part of the tuned circuit and establishes the operating frequency of reception. When Ql is switched to the transmitting condition, the voltage from the collector of Ql to ground is almost equal to the supply voltage. Therefore the bias voltage across the varicap diode D4 is almost doubled. This decreases the capacity and causes the total circuit capacity to be decreased by an amount determined by the values of the various components in the circuit. Since the calculation of the various circuit values is obvious to persons skilled in the art, it will not be described here. By properly selecting these component values, it is possible to make the frequency remain the same or change in any desired direction when the circuit is switched from transmit to receive. Other ways of achieving the same results include using a switching diode which is a low capacity diode which presents a low impedance path when biased on but a high impedance low capacity path when biased off. This could be connected to a network so that it would be switched off and on as the collector voltage change from receive to transmit. Other means include the use of an inductor which changes it's inductance by changes in saturation of its magnetic core with changes in current. None of these will be further described as their use will be obvious to persons skilled in this art.
While the present invention has been disclosed in connection with the particular preferred embodiment
described herein, it should be understood that there may be other embodiments which fall within the spirit and scope of the invention, as defined by the claims. Accordingly, no limitations are to be inferred or implied except as
specifically and explicitly set forth in the attached claims .
Industrial Applicability
This invention can be used to monitor children or other persons and portable objects.