Child monitor

A monitor system comprises first and second watches for wear by first and second users of the system. Each watch includes a battery therein for powering a transmitter and receiver. A signal limiter provides a base signal to a comparator so that the comparator can compare the base signal to a transmitted signal from one watch as received by the receiver of the other watch. Upon the received signal being less than the base signal, the comparator closes a relay which in turn energizes an alarm. The alarm indicates that an undesired amount of separation has occurred between the two watches. The strength of the signal produced by the signal limiter can be varied such that the desired degree of separation between the watches, which energizes the alarm, can be varied. A panic button is provided so that an alarm in one watch can be energized by the user of another watch irrespective of the distance between watches. The use of the monitor system in a watch-type configuration allows for its unobtrusive use.

BACKGROUND OF THE INVENTION 
This invention relates to a monitor system and, more particularly, to a 
two-way watch system which consistently monitors the distance between two 
wearers of watches of the system. 
Various types of monitor devices have been proposed which measure the 
distance between a base station and another monitor, an alarm being 
sounded at the base station upon the person exceeding a preselected 
distance. One monitor system is shown in U.S. Pat. No. 5,311,185 to 
Hochstein et al. Another system is shown in the Schlager patent U.S. Pat. 
No. 5,461,321 which shows a base station and one or more sensing units for 
wear by a child, a signal being sounded at the base station upon the child 
exceeding a certain distance. 
Although assumably effective in operation, such devices have been rather 
cumbersome to wear and may embarrass the child. Moreover, the base station 
is at a fixed location which constrains the movement of the monitor, such 
as a parent, to the base station area. Otherwise, any warnings of a 
wandering child exceeding a certain distance would not be heard. 
SUMMARY OF THE INVENTION 
In response thereto I have invented a two-way monitoring system in the form 
of first and second watches, each watch having a transceiver assembly 
therein in communication with a transceiver assembly in the other watch. 
Each watch assembly consistently monitors the distance between the other 
watch assembly. Upon separation of the watch wearers beyond a 
predetermined distance, an alarm will sound on the watches to indicate 
that the users have exceeded such distance. Accordingly, a dual alarm is 
given of such separation while allowing both users to move about. The 
predetermined distance of separation can be adjusted according to the 
situation at hand, i.e., a shorter distance may be set in a crowded 
environment as opposed to a longer distance when in a country environment. 
Each watch can sound an alarm in the other watch irrespective of the 
preselected distance being exceeded. 
It is therefore a general object of this invention to provide a monitor 
system which continuously monitors the distance of separation between two 
mobile users. 
Another object of this invention is to provide a system, as aforesaid, 
which provides transceivers for both users in the form of watches. 
A still further object of this invention is to provide a monitor system, as 
aforesaid, which sounds an alarm at each transceiver upon a preselected 
distance between the two users being exceeded. 
A further object of this invention is to provide a system, as aforesaid, 
wherein the preselected distance is adjustable. 
A still further object of this invention is to provide a system, as 
aforesaid, which enables one user to provide a signal to the other user 
irrespective of the preselected distance being exceeded.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning more particularly to the drawings, FIG. 1 shows a block diagram of 
one transceiver assembly 100 located in one of the watches 1000 of the 
user, it being understood that the other watch 1000' will have a similar 
assembly. This other assembly is referenced herein with identical but 
primed numbers. 
The system includes a battery power source 102 for the transmitter 110, it 
being understood that the delivery of the battery power to the transmitter 
140 may be regulated by depression of the mode button 1200 and start/stop 
button 1250 on the watch. Battery 102 may also be the battery used to 
energize the watch. Upon such power delivery the transmitter 110 will 
transmit signals that will be periodically sent to the receiver 130' of 
the other transceiver assembly 100' as received by the antenna 150' within 
watch 1000' proper. An interval timer 112 is provided so as to provide a 
periodic transmission of such signals. 
Upon reception of the signal by the receiver 130' in the other assembly 
100', the receiver 130' sends out a signal to a comparator 140'. The 
comparator 140' compares the received signal to a basic limit signal which 
has been provided by a signal limiter 160'. The base signal has a strength 
which corresponds to a strength of a received signal as transmitted at the 
preselected distance. Thus, the base signal strength decreases as the 
preselected distance increases. If the actual received signal strength is 
greater than the base signal, the watches are deemed to be within the 
preselected distance. If the received signal strength is less than the 
base signal strength, the watches are deemed to be without the preselected 
distance. Accordingly, the comparator 140' will deliver a control signal 
to relay 190 which in turn will sound the alarm 200' on the receiving 
watch 1000'. This alarm 200' may either be an alarm normally found in the 
watch or a separate alarm. 
As an option, upon setting the mode of the watch to the transmission mode 
by depression of mode button 1200, the preselected distance may be 
changed. Upon pressing the send/receive button 1400 a digital display will 
appear on the watch face as in FIG. 3. Subsequent depression of the button 
1400 will change the preselected distance displayed as well as the 
strength of the base signal provided by limiter 160 to comparator 140'. It 
is understood that as the preselected distance increases the strength of 
the base signal must decrease. Thus, at 225 feet the strength of the 
limiting signal will be at a minimum such that the reduced signal received 
by the receiver 130' from transmitter 110 at distances greater than 225 
feet will be less than this base signal so as to produce a control signal 
which will trigger the alarm 200. It is understood that the means for 
varying the signal strength of the signal limiter 160 is known in the art. 
Once set the start/stop button 1250 is depressed to start 
transmission/reception. 
The watch may also employ an alternative panic button 1500 which, upon 
depression, will cause the transmitter 110 to cease transmission. Thus, as 
receiver 160' will sense no signal the alarm 200' in the other watch 1000' 
will sound. 
Accordingly, it can be seen that as both watches 1000, 1000' are 
transmitting signals to each other a constant monitoring of the distance 
between the two individuals can be maintained without the need for one 
individual to remain immobile at a stationary base station. It is also 
understood that by adjustment of the preselected distance the monitor 
system can be used in various environments. For example, a preselected 
minimum distance may be used for a situation where monitoring is required 
in a crowded area as opposed to the maximum distance when monitoring is in 
an open environment such as in the park or the like is desired. 
Moreover, the use of the watch-like monitor provides for a system which is 
readily worn by the child and monitored and is not embarrassing, annoying 
or otherwise difficult to wear. 
It is to be understood that while a certain form of this invention has been 
illustrated and described, it is not limited thereto except insofar as 
such limitations are included in the following claims and allowable 
functional equivalents thereof.