Portal monitoring and alarm system

A set of sensors or sensor pairs capable of detecting the presence of a person passing through a portal is used for monitoring the portal. In one embodiment the portal has spaced apart upright supports. On one of the upright supports is mounted the sensors and the other upright support is used as a surface for reflection of the wave energy transmitted. When a person is present in the portal the person reflects the wave energy. The receiver is capable of detecting the time duration between transmission and receipt of the wave energy signal. In a second embodiment, the sensors are mutually inductively coupled in pairs. When a person is present within the portal the mutual inductance is changed in one or more of the sensor pairs. This change in mutual inductance is sensed and used as a means for determining which person is present in the portal. For example, a family may comprise two adults, a teenager, a preteen and a small child. The use of four sensors enables the system to detect when an adult passes through the portal which causes all four sensors to react due to the superior height of the adult. When three sensor react the system knows that the teenager is present. When two sensors react the system knows that the preteen is present, and when only one sensor reacts, the young child is present. A different alarm reaction is programmed for each instance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to child safety control systems, and more 
particularly to such a control system capable of discriminating between 
the movements of an adult and a small child or baby through a monitored 
portal. 
2. Description of Related Art 
The following art defines the present state of this field: 
Feher, U.S. Pat. No. 4,910,498 describes an infrared light emitter forming 
a beam of infrared light directed onto a set of mirrors or reflecting 
surfaces arranged to form a closed path about a swimming pool and spaced 
above the pool deck a sufficient amount so as to be intercepted by anyone 
who might walk through it. After the reflected beam has traversed the 
closed path about the pool, it then impinges upon a light detector. An 
electric circuit provides a continuous alarm which can either be sound or 
visual upon beam interruption and which must be manually reset before it 
becomes inactive. The monitoring system may be actuated so the operative 
state by a hand-held radio frequency transmitter. Electrical poser for the 
system can be a rechargeable battery which is recharged by a solar array 
mounted directly onto a part of the system obviating the need for 
interconnecting cable wiring. 
Sackett, U.S. Pat. No. 4,701,751 describes an alarm system for a swimming 
pool or the like whereby small inexperienced children or animals are 
detected prior to entering the pool or after an unauthorized entry into 
the water of the pool. The invention comprises the use of a height sensing 
apparatus employing fiber optics and a logic circuit whereby an 
interruption of the lowest light path only sounds an alarm. The invention 
further comprises the use of fiber optics and a movement sensor connected 
to the optics. Any impact on the water surface of he pool causes the 
sensor to change the state of the light transmission therethrough by 
transmitting or interrupting light transmission. This change of normal 
state activates the alarm. The invention still further comprises a 
wireless means for detecting a person in the pool water or a man overboard 
from a ship or the like and sounding an alarm. 
U.S. Pat. No. 5,757,274 describes an apparatus for providing an automatic 
crib gate position indication of a crib having a gate that can be 
positioned in an open or a closed condition, said apparatus comprising a 
gate sensor means, having a transmitter, coupled to the crib that 
wirelessly transmits a first signal indicative of the open condition to a 
baby monitoring system, the baby monitoring system including a baby unit 
adjacent the crib and a parent unit remotely-located from the crib and 
whereby the baby unit wirelessly transmits a second signal indicative of 
the baby sounds that is received by said parent unit, said first signal 
being received by said parent unit and controlling a crib gate indication 
means therein. 
Gustavsson, U.S. Pat. No. 5,625,340 describes a device for supervising an 
area in particular the crossing area between railway gates, in order to 
detect objects occurring in the area comprises a detector adapted to 
transmit detection signals and receive their reflection caused by objects. 
The detector is pivotably arranged in a reciprocal manner so as to 
transmit the detection signals in an angular area. The detector may be a 
laser, the light of which forms the detection signals. 
Byrne, U.S. Pat. No. 5,554,972 describes an apparatus and method to provide 
an electronic perimeter warning system to prove the ingress or egress of 
persons or machines from a selected area such as in an area along the 
perimeter of a roof under construction. Battery powered signal 
transmitters and receivers establish a signal beam between two locations. 
When the continuity of the signal beam is broken, an alarm is sounded to 
warn the person who is crossing the signal beam of imminent danger. 
Nakamura et al., U.S. Pat. No. 5,255,301 describes an apparatus for 
counting the number of passing persons by stature, wherein a projector is 
positioned for radiating light toward the head of a passing person, a 
light receiving lens for receiving light reflected from the person's head 
and alight position detector are arranged as one set at an upper portion 
of a gateway or a passageway. The light receiving lens converges reflected 
light to different light-received positions of the light position detector 
according to the height of the reflective position. The light position 
detector outputs electric signals which differ according to the reflected 
light received at the light-received positions and a counting operation 
performed discriminately for every output of the signals. 
Britt, U.S. Pat. No. 5,844,487 describes an alert alarm responsive to the 
passage of child unaccompanied by an adult. An adult sensor is placed at 
an adult height higher than any anticipated child. A child sensor is 
placed at a height lower than the height of the shortest anticipated 
child. Actuator circuitry is actuated if a child passes the child sensor 
within a limited time either before or after the adult passes. 
Jones, II et al., U.S. Pat. No. 5,831,527 describes a system to prevent 
cheating at a casino gaming table, where sensors are strategically 
positioned about a casino gaming table to monitor the movement about 
certain established area on the gaming table during certain established 
times during the play of the game. The tripping of a sensor in response to 
the detection of unauthorized movement about a certain area of the table 
sends a signal to a monitoring system which in turn alerts the casino so 
that the casino may respond to the unauthorized movement accordingly. The 
system of sensors can be used with a wide variety of card-based or 
chip-based casino gaming tables. 
Thornton, U.S. Pat. No. 5,793,291 describes an alarm system for detection 
the presence of a person locked in a parked automobile. The alarm system 
includes a motion detector and a temperature detecting element coupled to 
a NOR gate. The motion detector transmits a low signal to the NOR gate 
once it detects motion within the interior of the automobile. The 
temperature detecting element transmits a low signal to the NOR gate if 
the temperature in the automobile exceeds a pre-determined extreme 
temperature. The NOR gate, upon receiving low signals from both the 
temperature detecting element and the motion detector, transmits an alarm 
signal. 
Slomowitz et al., U.S. Pat. No. 5,757,274 describes a crib gate position 
indicator for use with a baby crib to automatically alert the parent or 
infant-caretaker, who is at a location outside of the room or location of 
the baby crib, when the crib gate has been left in an open condition. 
Other variations of this crib gate position indicator are used in 
conjunction with a baby monitoring system, thus supplementing a baby 
monitoring system with the ability to provide a crib gate position 
indication, in addition to permitting the parent or infant-caretaker to 
listen to the sounds being made by the baby. 
The prior art teaches clearly teaches a number of distinct techniques for 
the detection of hazards related to small children and babies. However, 
the prior art does not teach that a movement alarm may be adapted to 
sensing the movement of a small child or baby in a manner similar to that 
of Britt, but with greater security and fail safe control. The present 
invention fulfills these needs and provides further related advantages as 
described in the following summary. 
SUMMARY OF THE INVENTION 
The present invention teaches certain benefits in construction and use 
which give rise to the objectives described below. 
The present invention provides a set of sensors and, or sensor pairs 
capable of detecting the presence of a person passing through a portal. In 
one embodiment the portal has spaced apart upright supports. On one of the 
upright supports is mounted the sensors and the other upright support is 
used as a surface for reflection of the wave energy transmitted. When a 
person is present in the portal the person reflects the wave energy. The 
receiver is capable of detecting the time duration between transmission 
and receipt of the wave energy signal. In a second embodiment, the sensors 
are mutually inductively coupled in pairs. When a person is present within 
the portal the mutual inductance is changed in one or more of the sensor 
pairs. This change in mutual inductance is sensed and used as a means for 
determining which person is present in the portal. For example, a family 
may comprise two adults, a teenager, a preteen and a small child. The use 
of four sensors enables the system to detect when an adult passes through 
the portal which causes all four sensors to react due to the superior 
height of the adult. When three sensor react the system knows that the 
teenager is present. When two sensors react the system knows that the 
preteen is present, and when only one sensor reacts, the young child is 
present. 
A primary objective of the present invention is to provide a portal monitor 
having advantages not taught by the prior art. 
Another objective is to provide such a monitor capable of discriminating 
between individuals of different height and, or mass. 
A further objective is to provide such a monitor capable of record and 
playback of a voice message. 
A still further objective is to provide such a monitor using mutual 
inductance as a means for detecting the passage of an individual through a 
portal. 
An important objective is to provide such a monitor using both wave energy 
as well as inductance for detecting the passage of an individual through 
the portal and for determining the identity of said person. 
Other features and advantages of the present invention will become apparent 
from the following more detailed description, taken in conjunction with 
the accompanying drawings, which illustrate, by way of example, the 
principles of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
The prior art teaches, as shown in FIG. 1, that portal may be monitored by 
two sensors. One of the sensors is placed too high to sense a child, but 
will sense a taller person in the portal. The other sensor is place low 
enough for a small child to be detected. A logic circuit is set to call 
for an alarm condition whenever the lower sensor is activated without the 
upper sensor being activated either just before, during or after the lower 
sensor is activated. If an adult passes through the portal both sensors 
are activated so that no alarm condition is sensed. 
The above described drawings in FIGS. 2 and 3 illustrate the present 
invention, an apparatus capable of monitoring the movements of persons and 
discriminating between such persons by physical size and, or mass in order 
to safeguard small children and babies when a portal may hold a danger for 
such children. The apparatus, as shown in FIG. 2, comprises a portal 10 
providing a walkway surface 20 and a pair of spaced apart upright sensor 
supports 30, 40 the sensor supports being positioned such that passage of 
a person through the portal 10 requires moving between the upright sensor 
supports 30, 40. In a first embodiment, a set of four sensors 50, 60, 70, 
and 80 are mounted on one of the upright sensor supports 30 in a 
vertically spaced apart manner as shown, the four sensors are further 
defined as top 50, upper 60, lower 70 and bottom 80 sensors. The four 
sensors are positioned for discriminating between persons of varying 
height so as to determine the identity of a person passing through the 
portal 10. An electrical circuit 90, shown schematically in FIG. 3, is 
adapted for receiving signals from the four sensors 50-80 and for 
processing the signals for identification of the person, and is further 
adapted for enabling an alarm action, said alarm action being dependent 
upon the identified person. 
In a first embodiment, the four sensors 50-80 are wave energy transceivers 
each adapted for transmitting a wave energy signal directed laterally 
between the two upright sensor supports. They are further adapted for 
receiving a reflected signal from a reflecting surface of the other of the 
two sensor supports when the wave energy signal is not intercepted by a 
person present in the portal. When a person is present in the portal the 
reflected signal from that person is received and the person is identified 
because of the shorter time between signal transmission and receipt. 
Alternately, the sensors could use infrared light transmission and 
reflection. 
In an alternate embodiment two sets of four vertically oriented inductive 
sensors 50', 60', 70', 80' each, are mounted on the upright sensor 
supports in fixed positions with matched pairs taken from the two sets 
being placed in physical opposition for establishing an electromagnetic 
field between them, the field being dependent for its intensity on the 
mutual inductance of each of the pairs of inductive sensors. The sensors 
are adapted for discriminating between persons by mass when such persons 
are positioned between the inductive sensors so as to determine the 
identity of a person passing through the portal. The electrical circuit, 
in this embodiment, is adapted for receiving signals from the inductive 
sensors and for processing these signals for identification of the person 
and further adapted for enabling an alarm action, said alarm action being 
dependent upon the identified person. 
The inductive sensors are coupled by electromagnetic mutual inductance such 
that the value of said mutual inductance is different when a person is not 
present in the portal relative to the value of said mutual inductance when 
a person is present in the portal, the value of mutual inductance being 
related to the mass of the person within the portal. It should be noted 
that a single inductive pair might well be used instead of four sets. When 
one extended length pair of inductors is used, the mass of the person 
within the portal is used to determine the nature of the person. But it 
has been found that a set of four pairs provide an advantage in 
determining the size as well as the mass of the person. With these two 
pieces of information, it has been discovered that a relatively high level 
of discrimination is possible between persons. For instance, the two 
adults in a family may be about the same height. Or the mother and her 
teenage child may be about the same height. But with the ability to 
measure mass, the system is able to determine the mother from the more 
massive father, or the son from the more massive mother. 
The inductive sensors are inductors, i.e., wire wound ferrite cores. When 
current flows in these two opposing inductors an electromagnetic field is 
produced and interlocked between the spaced apart inductors such that 
current flow in one inductor is affected by the field produced by the 
other inductor. The opposite is true as well. When a person is in the 
portal, the energy field is disturbed because some energy is absorbed by 
the person. When this occurs the value of mutual inductance changes and it 
is this change that may be detected by the circuit in a manner that is 
well known in the art. 
From FIG. 3 it is seen that the sensor or sensor set is interconnected with 
a sensor interface 100. This interface provides noise filtering, signal 
strength boosting and analog to digital signal conversion. The digital 
representation of the original signal is then fed to a microcontroller 110 
where data processing is completed. The processor 110 is able to output an 
alarm signal through a transmitter 120 to a remote receiver 130 so that an 
alarm signal may be received remotely. For example, the backyard pool gate 
may be monitored and an alarm signal sent to the kitchen area at the front 
of the house when an emergency occurs. The processor 110 may alternately 
simply provide an alarm signal output to a buzzer 140 or other audible 
alarm, to achieve a local alarm indication. Another possibility is the use 
of a record and playback machine 150, such as a tape recorder, where the 
processor 110 enables a prerecorded announcement as a warning. Such an 
announcement might be, "Warning, a child has entered the pool area." 
Clearly, when both types of sensors are used together, the relative height 
as well as the mass of a person in the portal is determined. This 
information is useful for determining the identity of a person especially 
if the height and mass (weight) of each member of a family is provided in 
a look-up table in the processor 110. 
While the invention has been described with reference to at least one 
preferred embodiment, it is to be clearly understood by those skilled in 
the art that the invention is not limited thereto. Rather, the scope of 
the invention is to be interpreted only in conjunction with the appended 
claims.