US 3778803 A
A device for monitoring wave action on the surface of water in a swimming pool in a manner to sound an alarm when someone either accidentally falls into a swimming pool or uses the pool without authorization. A buoy floats on the surface of the swimming pool for detecting excessive wave action. At least one position-sensitive switch is attached to a pivotably mounted float within the buoy for detecting such wave action. A signal from the switch in the buoy is transmitted to a remote alarm unit either by a direct wire connection or by a low power radio transmitter located within the buoy.
Description (OCR text may contain errors)
[ SWIMMING POOL GUARD ALARM UNIT  Inventor: Darrel S. Jahn, M untain View.
 Assignee: Aquatic Systems, Inc., Sunnyvale,.
 Filed: Sept. 27, 1971  Appl. No.: 184,085
 Int. Cl. G08b 13/00  Field of Search 340/261, 258 R, 421, 340/244 B, 224; 200/612, 84 R, 230
 References Cited UNITED STATES PATENTS 2,816,973 12/1957 Beck et al 340/244 B 3,636,544 111972 Codina 340/224 3,329,935 Wiggins 340/261 11] 3,7?7S,803 1 Dec. 11, 1973 Primary Examiner.loh n W. Caldwell i Assista 'm Examiners-Glen R. Swann, III AttorneyGerald P. Parsons et al.
" ABSTRACT 7 or by a low power radio transmitter located within the buoy.
7 11 Claims, 8 Drawing Figures PATENTEB DEC 1 I I975 3L718'.803 sum 3 BF 4'' w INVENTOR,
BARREL .8. JAHN BY I WW .8
ATTORNEYS minimum 1 1 ms 3.778.803 sum w 4 INVENTOR. DARREL S. 'JAHN ATTORNEYS 1 SWIMMING POOL GUARD ALARM UNIT BACKGROUND OF THE INVENTION This invention relates generally to the art of sensing wave motion on the surface of a body of liquid, and more specifically relates to such devices designed for use on the surface of a swimming pool for detecting use of the pool.
is often desirable to be able to monitor an unattended pool to detect an unauthorizedperson using the pool. There. are several commercially available units for monitoring the use of a swimming pool, but these units suffer from certain disadvantages that are overcome by the monitoring device of the present invention.
In one such commercially available device, a sensor is held a few inches below the surface of the swimming pool water by anchoring an electrical controlcord to the pool bottom. The control wire is then connected to an alarm unit in an adjoining house or other structure. A difficulty with this type of device is that it has to be removed before the pool may be used for swimming. This device is battery operated and sounds an alarm continuously until shut off manually, thereby running down the batteries if someone does not immediately hear the alarm. The device is ineffective until the dead battery is discovered. Additionally, this type of device may be disabled by an unauthorized person by first cutting the wire between'the sensor in the pool and the alarm in the adjoining structure.
Another type of device that is commercially available is self-contained and floats on the surface of a pool. Gas
. under pressure is released when wave action reaches a threshold level. A horn on the device is then sounded.
The pressurized gas is contained in a removable cannister that may be replaced after the unit has once sounded. The primary difficulty with this type of pool monitoring unit is that once it sounds and uses all the pressurized gas of a cannist er installed therein, the unit is no longer effective. If the alarm is sounded while no one is within range of the pool to hear it, it will not be known that a new pressured gas cannister need be in stalled. Furthermore, such a device may be easily disabled and removed from the pool by someone desiring to use the pool without authorization.
Yet another type of pool monitoring unit utilizes a sound transducer installed along the bottom of a pool and is connected with a remote alarm unit by wires. The main difficulty with this type of monitoring device is that it may not always pick up surface noise such as that created by a child or an animal falling into the pool. The sound transducer is activated if a swimmer moves around but may not respond to a mere splash in the pool.
Therefore, it is an object of the present invention to provide a swimming pool monitoring device which can detect both a family pet or child falling into apool as well as detecting unauthorized use of the pool.
It is another object of the present invention to provide a pool monitoring device which looks like some other commonly used pool accessory in order to disprovide a pool mo nitofing device which is difficult to disable without sounding an alarm.
I It is still a further object of the present invention to provide a pool monitoring device that does not quickly consume its self-contained source of power to render the device inoperative without the knowledge of those using the device.
SUM MARY'OF THE INVENTION These and additional objects are accomplished by the pool monitoring device of the present invention which includes a buoy that floats on the surface of the pool and is designed to look like an ordinary pool chlorinator. A ring of flotation material supports a cylindrical container mounted in an upright position. A float is mounted in the container and carries at least one positional sensitive electrical switch. When surface wave action from a person falling, jumping or diving into the pool disturbs the float, the electrical switch is activated which sets off an alarm in a remote unit. The float is preferably pivotably attached to the interior of the container. When there is excessive wave action in the pool, the float is rotated about its pivot into a position that is different from the normal position. The entire container is made adjustable with respect to the ring of flotation material (and thus with respect to the pool water surface) in order to adjust the sensitivity of the device so that normal waves generated by the wind will not tilt the float enough to change the state of the switch.
In order to also detect when the device is withdrawn from the swimming pool by an unauthorized person, a second positional-sensitive switch is carried by the pivotably mounted float. The second switch is in a different position on the float from the first switch. In a specific preferred embodiment, the float is normally held slightly below a horizontal position by the water level of the swimming poolwhen the container is properly adjusted on the ring of flotation material. The first switch is oriented to change its state when the float is caused to rise by wave action. The second switch is oriented on the float to change its state when the float falls to a substantially vertical position. Having two switches makes it extremely difficult for an intruder to withdraw the buoy from the swimming pool without changing the state of one of the switches which activates a remote alarm.
A change of state of either of the switches located in the bony is transmitted to a remote alarm unit either by wire or by the use of a radio frequency transmitter within the bouy. Use ofa radio frequency transmitter rather than a wire connection has an advantage of providing greater flexibility in remote positioning of the alarm unit. The alarm unit may even be moved to a neighbors house for monitoring of the pool when the pool owner is away for an extended period. In either of the radio transmitter or wire connection embodiments, the switches within the buoy are normally in an of state. When either of the switches is closed (turned to its on" state), an audio alarm begins to sound. The alarm continues to sound even though the buoy switch is only on for an instant. A time delay circuit within the alarm unit allows the audio alarm to sound only for an adjusted predetermined period of time.
sertion in the buoy of FIG. 1;
In the radio transmitter embodiment, a small battery operated transmitter is installed within the cylindrical container of the buoy. The transmitter is operative only during the period of time that either one of the two position sensitive switches is closed. The frequency of operation of the transmitter is chosen to be within a band permitted for unlicensed low power transmitters by existing F.C.C. regulations. As part of the transmit- 'ter, the radio requency signal is modulated by a constant frequency audio oscillator but just outside of the 17, ahdthus the elevation of the'container 19 with re spect to the water surface 13, may be adjusted by rotating the container 19 w ith respect to the float 17. A scale 23 formed onthesurface on the container 19 indicates its elevation with respect'to the float 17. An
' opening 25 is provided in thebottom of the container 19 for water to pass into the container. Additionally, an
: opening 27 is provided on the side of the container 19 in order to open the volume inside the container and normal audio frequency range. The remote alarm unit contains a receiver for receiving the radio frequency; signal and demodulating it. A highly selective filter uni-t is made as part of the receiver so that the alarm is activated only when buoy transmitter modulating frequency is received. In making the modulating frequency something outside the audio range, the chances that the alarm of the receiver will be set off by voice operation of a transceiver on the same radio frequency as the buoy transmitter is substantially eliminated.
above the water level to atomspheric air pressure. A flattened space, not shown, on the side of the container 19 extending'beneath the scale 23 provides an air passage to the opening 27 from the region above the float 17. A disturbance on the surface 13 of the swimming pool'is reflected into the container 19 in the form of a surface disturbance of the water therein. It is the distur- Further objects and advantages of the present inven- 7 tion will become apparent from the description which follows when taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG; 1 is a side view of a buoy containing a radio frequency transmitter according to one aspect of the present invention;
FIG. 2 is a partially cut away view of a container portion ofthe buoy of FIG. 1;
FIG. 3 is a sectional view of the container of FIG. 2 taken across section 3-3;
. FIG. 4 is a partial view of the broken away container of FIG. 2 under different conditions;
FIG. 5 is a circuit diagram of radio transmitter for in- FIGS. 6A and 6B show a radio receiver and alarm circuit diagram for the remote alarm unit; and
' FIG. 7 shows a circuit diagram for an alarm unit that Y is connected by wire to a buoy, according to another aspect of the present invention. 7
,- I DESCRIPTION OF THE PREFERRED EMBODIMENTS buoy 11 floating on a FIG. 1 shows a surface 13 of swimming pool water 15. The buoy 11 includes'two principal components. A volume of flotation material 1 17 is formed in the shape of a ring with a circular opening in its center for receiving a cylindrical container 19. These two components may be essentially the same as corresponding components of existing floating swimming pool chlorinators which are designed and sold for floating on the surface of swimming pools to dispense chlorine at a constant slow rate. The buoy ll, of I course, does not serve a function of chlorinating a swimming pool but its overall appearance as a pool I chlorinator conceals its true function to an intruder who may attempt to disable an obvious alarm unit before using the pool.
The float 17 is preferably made ofa light plastic foam material. The container 19 is in the shape of an elongated cylinder and isxpreferably made of a thin watertight plastic material. A single thread extending outward from the inner surface of the center hold of the float ring 17, not shown, supports the container 19 somewhere along its external surface threads 21. The
elevation of the container 19 with respect to the float bance of the water level within the container 19 that is detected by the 'buoy 11. When this disturbance is greater than a threshold amount, a radio transmitter within the container 19 is operated to emit a radio fre- V quency signal from a wire antenna 29 attached to the inner surface of a cap 31. The cap 31 is affixed tothe container 19 in a water-tight manner.
, A rigid plastic disc 33 forms a water-tight compartment flected within the container 19.
Referring to FIG. 2, an enlarged partially broken away view of the cylindrical container 19 is illustrated.
at the upper end of the container 19 for housing a transmitter and its battery in cavities 35 and 37, respectively. The cavities 35 and 37 are formed'by'heat and shock-absorbing plastic foam pieces 39 and 41.
Below the rigid disc 33 is the region of thecontainer 19 which receives swimming pool water. A block of lightweight plastic material is formed into the shape of a float 43. A rigid plastic rod 45 is attached to the float 43 and is pivotably mounted in rigid plastic blocks 47 and 49 at either end of the rod 45. The blocks 47 and 49 are firmly attached to the underside of thedisc 33.
Position sensitive switches 51 and 53 are, embedded within the float 43 by cutting holes in the float, inserting the switches therein andthen sealing the switches with a silicon rubber fluid which forms a water-tight seal. The pivotable position of the float 43 is controlled by the height of the liquid surface within the container 19. The electrical switches 51 and 53 thereby sense the level of the swimming pool surface as re- The switches 51 and 53 are preferablyof the type wherein an elongated generally cylindrically shaped glass tube is filled with a small amount of electrically conducting liquid such as mercury. A pair of conductors within each tube are normally spaced apart and insulated until the switch is oriented in a position to cause the mercury to flow and join the two electrodes in a complete electrical circuit. In the position of the float 43 shown in FIG. 2, a pool of mercury 54 restsat an end a within the glass tube of the switch 51. Since the pair of electrodes are at the end b of the switch 51, no electrical connection is made and the switch is in an off" state. As wave action on the swimming pool surface increases above some threshold level, the level of the liquid surface 55 within the container 19 will raise the float 43 into a horizontal position or above, thus causing the mercury pool 54 to flow toward the end b within the switch 51' and thus made an electrical connection between its bare pair of electrodes. The switch 51 is then in its on state. The sensitivity of the switch 51' is adjusted by raising or lowering the container 19 The internal electrodes ,of the switch 51 are connected by a flexible wire pair 57 to the transmitter, in
a manner discussed hereinafter, to transmit an alarm signal to a remote. alarm unit. The switch 51 need be changed from its normal of state to its on" state only for an instant to cause a pulse of radio frequency to be emitted by the antenna 29 and cause an alarm to be sounded in a remote location. Therefore, a single wave of a sufficient amplitude will operate a remote alarm. i
I The second switch 53 is connected electrically in parallel with the switch 51 and to the pair of conductors 57 so that the transmitter emits a signal when either of the switches are caused to be thrown into their on state. The switch 53 has a pool of mercury 59 at its end when the float 43 is in the position shown in FIG. 2.
No electrical connection is made in this position between a pair of conductors within the switch 53. However if the buoy 11 is removed from the water by someone attempting to disable the device, the float 43 falls to a position shown in FIG. 4. The switch 51 remains in its of state but theswitch 53 is oriented in FIG. 4 so that its mercury pool has travelled to the end d of the switch, thus making contact between the two electrodes of the switch 53. The pair of wires 57 are then connected together. The radio frequency transmitter thusemits a signal which sounds an alarm in a remote alarm unit. I v
The float 43 is shaped to have a point 61 extending from itsbottom side for contacting a side wall of the container 19 as shown in FIG. 4 when the buoy is withdrawn from the swimming pool water. The reason for the extension 61 is to hold the center of gravity of the float 43 at a position that is to the left of the pivot rod 45 when the float isin the position shown in FIG. 4.
When buoy 11 is put back into the water, therefore,
water rushing in through the opening 25 at the bottom of the container 19 will not hold the float 43 in the position shown in FIG. 4 but rather will cause it to pivot clockwise with its position determined by the resulting level of the water within the container 19.
The swimming pool owner probably desires to remove the buoy 11 while the pool is being used with his authority or when being cleaned in order to prevent repetitive pulses from being emitted from the radio transmitter. Continued operation of the transmitter can run down itsbattery. In order to prevent the float 43 from i falling to the position shown in FIG. 4, where the switch 53 will keep the transmitter on, a volume of deformable plastic (not shown) is provided for insertion through the opening 25. Such a volume of plastic is designed to hold the float 43 at less than horizontal to prevent operation of the switch 51. This technique does not avoid operation of the remote alarm since it is difficult to insert a plastic block without setting off at least one transmitter pulse.
A detailed circuit diagram of the radio frequency transmitter for installation in the container 19 is shown in FIG. 5. An electrical representation of the switches emit a radio frequency signal from the antenna 29. A crystal 67 controls the frequency of oscillation of radio frequency oscillator circuit which includes the transis tor 0,. The transmitter of FIG. 5 operatesin the 27 megacycle range so the crystal 67 is chosen for a partic ular frequency in this range.
. the 27 megacycle range. The exact frequency of the oscillator 69 can be varied by changing both of the capacitors C, and C from the values shown in FIG. 5 to some other specific value. C and C are kept at substantially the same value. 1
Te particular circuit diagram of FIG. 5 is a modified commercially available super-regenerative transceiver. The commercially availablev transciver may be wired permanently to operate in the transmit mode and it voice circuitsare replaced by the single frequency oscillator circuit 69. Of course, there is a wide variety of different types of miniature low power transmitters that may be utilized as part of the present invention.
A preferred receiver for receiving the signal transmitted by the transmitter of FIG. Sat a location remote from the buoy is illustrated in the form of a detailed electronic circuit. diagram in FIG. 6A and 68. Such a receiver and alarm circuit can be mounted in a small box within a home adjacent the pool in which the buoy is floating for monitoring its use while unattended. The radio frequency signal is received at the receiver antenna 71 of FIG. 6A and an audio signal is demodulated therefrom by a receiver section enclosed by the dotted lines and indicated by the reference number 73. The audio signal being demodulated from the radio frequency signal received is presented at terminals 75 and 77. The receiver section 73 of the FIG. 6A circuit is again one that is commercially available, as part of a superheterodyne transceiver circuit. The commercially available transceiver is modified to operate permanently in its receiving mode, and additional components of the transceiver dealing with other functions than merely demodulating a radio frequency signal to obtain an audio signal therefrom are not used.
A power supply circuit 79 is provided for developing v the required positive DC voltage at a terminal 81 with respect to a neutral terminal 83. Also, the power supply circuit 79.develops a negative direct current voltage at a terminal 85, with respect to the neutral terminal 83. Although the circuit of FIGS. 6A and 68 could be operated by batteries, it is felt preferable to use ordinary house'current. Since current is consumed by the circuit of FIGS. 6A and 63 throughout the period that the pool 'is being monitored, the use of batteries and the inconvenience of having to replace them at periodic intervals is avoided.
The demodulated audio signal at terminals and 77 is operated upon by an electronic filter section of the circuit of FIG. 68 indicated at 87. The filter unit 87 includes the use of four operational amplifiers 89, 91, 93, and 95, all connected in series. The filter unit 87 is a highly selective filter which presents a voltage at its output terminal 97 only when the input signal is very close to the center frequency to which the filter unit 87 is tuned.
' The first three operational amplifiers 89, 91, and 93' of the filter section 87 of the FIG. 6B circuit comprise the actual filter while the last operational amplifier 95 serves to provide voltage amplification. To adjust the filter circuit 87, a modulated signal is transmitted'to the receiver of the circuit of FIG. 6A. The potentiometers 99 and 101 are then adjusted for a peak voltage output ,at theterminal 97. The receiver is then adjusted for its" mating buoytransmitter. The filter 97 is narrowly received at the antenna 71 which has been modulatedby the audio range frequency to which the filter section has been tuned. When such a signal is received, the
voltage at the terminal 97 jumps to a maximum value.
However, the current available atthe output terminal 97 is not sufficient for driving a relay and time delay t ube. Therefore, a current driving circuit 103 is connected to the output of the filter circuit 87 and includes a transistor which acts as a power amplifier. An output terminal 105 of the current driving circuit 103 is connected with a signal circuit 107.
A relay coil 109 is connected between the output terminal 105 of the driving circuit 103 and to the positive 'DC supply developed at power supply output terminal 81 in series with a normally closed circuit breaker 111.
t The circuit breaker 111 is part of a delay tube to be described below. The relay includes switches 113, 115, and 117 which are normally held in positions shown in FIG. 6B absent a current being applied to the relay coil 109 of sufficient magnitude to move the switches to their alternate positions. I
When in the rest position shown in FIG. 6B the power supply circuit 79 is connected with the filter circuit 87 through the relay switches. The relay switch 113 normally connects the positive direct current voltage from the power supply 79 to the filter circuit 87.
The relay switch 117 normally connects thenegative. direct current voltage to the filter circuit. When a signal is received that moves these relay switches to their second positions, however, both the positive and negative direct current voltage are disconnected from the filter circuit in order to prevent any spurious signals 'from being generated At the same time, the relay switch 115 connects to ground the terminal of the relay coil 109 that is continually connected with the driver output terminal 105. This keeps the relay coil 109 energized and even though after the first instant there may no longer be a signal at the terminal 105 that will drive the relay coil 109. This keeps the relay switches 113,
that is ihdependent of the length of this radio frequency pulse.
When the relay coil l09 is energized, the switches f 113 and 11 5 connect-the positive direct current and ground, respectively, across an audio horn 119. Connected parallel with the horn 119, and thus also across the positive direct current source, is a heating element of ta commercially available delay tube, indicated by the resistance 121. When the heating element 121 has been connected across the positive direct current source for a time sufficient to reach a predetermined level, the circuit breaker 111- is thrown, which disconnects the entire circuit from the positive direct current output terminal 81. At this point, the relay coil 109 is also disenergized and the switches 113, 115 and 117 are returned to their rest position shown in FIG. 6B. The sounding of the horn is. then discontinuedand the resistance element 121 of the delay tub is disenergized. When the resistance element 121 cools sufficiently, the
-circuit breaker 111 automatically returns to complete the positive direct current circuit to supply the remaining portion of the receiver and alarm circuit. Thereceiver is then ready to detect the next radio frequency signal from the buoy.
The particular type of delaytube of which the resistance element 121 and the circuit breaker 111 are a part is chosen for the length: of time the horn 119 is desired to sound when a large wave on the surface of the swimming pool strikes the buoy. If a short time is required, a commercially available 6C5 delay tube may be used for about a S-second horn blast. If about a 30- second sounding of the horn is desired, a 6C30 delay tube may be used. I
The transmitter andreceiver circuits of FIGS. Sand 6A and 68, respectively, have the advantage that several buoys may be employedv in several swimming pools and monitored by a single receiver/alarm unit. The audio oscillator 69 (FIG. 5) of each buoy is tuned to a unique frequency by having the capacitors C, and C, fixed at a unique value for each buoy. The receiver circuit of FIG. 6B is then modified to include a plurality of filters 87 in parallel, one filter tuned to the audio oscillator frequency of each buoy.
'For reasons primarily of economy, some users may prefer a direct wire connection between the positional sensitive switches of the buoy and an alarm unit rather 7 than the radio frequency connection described above.
In such a case, of course, the transmitter and battery FIG. 1, and one end ofa long wire is connected with the switches 51 and 53. The alarm unit installed in an adjoining structure is connected to the other end of the long wire and is greatly simplified from the receiver/a- Iarm unit of FIGS. 6A and 68. FIG. 7 shows a preferred circuit for the alarm unit which is connected by wire to the switches 51 and 53 of the buoy. A double-pole, double-throw relay is used having a coil 123 and switches 125 and 127. The switches 125 and 127 are shown in FIG. '7 in their rest position when the relay coil 123 is not energized, and it-will be noted that in this state no electrical connection is made by the relay switches.
A circuit breaker 129 is part of the delay tube which also includes a heating element denoted by the resistance 131, similar to the signal circuit 107 of FIG. 6B. A low direct current voitage source, preferably from a battery, may be connected across terminals 133 and 135. A master on-off switch 137 is connected to the oneeIectrical state when liquid is below a predeterpositive voltage source terminal 133. A battery may bemined level within the container and a second elecused in this case since the circuit is operative only for trical state when liquid is above said predetermined a short time after either of the buoy switches 51 and 53 legel, a f; is momentarily closed. A horn 139 sounds an alarm means electricallyv connected with said switch for when one of the switches of the buoy is instantaneously communicating its state to a remote location, closed. whereby waves on the surface of the liquid cause ,2 The principle of operation of the circuit of FIG. 7 is said pivotably mounted float to change its angular 5 similar to that of the signal circuit 107 of the more position relative to said container and signals said i complicated receiver/alarm unit of FIGS. 6A and 6B. 10 positional change to said remote location, and
When the on-off switch 137 is closed, the relay coil 123 a second two-state position sensitive switch carried 1 i is connected across the voltage terminals 133 and 135 a by said pivotably mounted float and oriented genwhen either of the switches 51 and 53 in the buoy are erally to be in one of its states when liquid is near closed for an instant. When this occurs, the switches said predetermined level within said container and 125 and 127 of the relay are moved to the alternate poin another of its states when the float is not sup sition from that shown in H6. 7. The switch 125 then ported against gravity within the container. connects the relay coil 133 across the power input terj 2. A swimming pool alarm unit, comprising: minals 133 and 135 to lock the relay after the switches a volume of material for floating on the surface of the 51 and 53 both become open again. After the relay is swimming pool, said volume of material formed in so thrpwn, the horn 133 sounds and the heating eler the shape ofa ring having a circular opening in its ment 131 of the delay tube is connected across the voltcenter, 1 g age input terminals 133 and 135. a tubular container positioned within the opening of This circuit state occurs until the heating element said ring and threadedly engaged therewith in a 131 of the delay tube gets hot enough to throw the cirmanner that the container may be moved up and cuit breaker 129 of the delay tube. When the circuit down relative to the ring by twisting's'aid container breaker 129 is thrown, the input voltage across termiwith respect to thering, nals 133 and 135 is disconnected from all of the circuit 3 said container including a water inlet opening in the elements, including the relay coil 123, the horn 139 v H vacinity of its bottom and an air opening in the and the heating element 131 of the delay tube. The vacinity of its top, thereby allowing water to rise horn then stops blowing, the relay switches 125 and within the coritainer to a level porportiorial to the 127 return to their rest position shown in FIG. 7, and water surface level surrounding said ring of flotathe heating element 131 of the delay tube begins to tion material, cool. When the heating element 131 is cooled suffiat least one position sensitive electrical switch within ciently, the circuit breaker 129 returns to its position said container positioned to detect the water level shown in FIG. 7 to connect all of the elements to the within said container, and voltage input supply. The circuit is now ready for anmeans electrically connected with said switch for other pulse by momentary closing of either. of the communicating its state to a remote location. switches 51 and 53. lt will be noted that the direct wire 3. Apparatus for monitoring surface waves on a body connected embodiment of the alarm system of the presof liquid, comprising: ent invention as shown in P16. 7 also has the advantage a piece of flotation material for supporting the appa- W that the length of time that the horn 139 is sounded is ratus on the liquid surface, li independent of the length of time that one of the a float pivotably mounted with respect to said flotaxii switches of the buoy is closed. The length of the horn tion material in a manner to be supported against I blast may be set by choice of the delay tube. gravity by the liquid surface, said float including a The present invention has been described in its 'pre- 5 block of plastic material with a pivot rod extending ferred specific embodiments and it will be understood through one end thereof for supporting the float that the full scope of the invention is defined by the apwith respect to said flotation material in a manner pended claims. v to be rotatable with respect thereto,
What is claimed is: at least one position sensitive electrical switch em- 1. Apparatus for monitoring surface waves on a body 7 bedded in said pivotably mounted float in a manner of liquid, comprising 1 to have one electrical state when the liquid surface a piece of flotation material for supporting the appais calm and a second electrical state when a liquid ratus on the liquid surface, 7 surface wave of sufficient magnitude strikes the floa container supported by said flotation material in a -tation material, and
manner to be partially submersed below the liquid meanselectrically connected with said at least one surface, said container having an opening in the switch for communicating its state to a remote lovacinity of its bottom for liquid to pass therecation, whereby waves on the surface of the liquid through into said container and an air opening in cause said pivotably mounted float to change its the vacinity of its top, thereby allowing liquid to 1 angular position relative to said container and sigrise within the container to a level proportional to nals said positional change to said remote location.
the height of the liquid surface surrounding said 4. An alarm system according to claim 3 wherein the flotation material, single frequency of the transmitter audio oscillator is a float pivotably mounted within said container, the outside of the normal voice frequency range range.
angular position of said float being controlled by 5. An alarm system according to claim 3 wherein said the level of liquid within the container, means for sounding an audio alarm includes a switch a first position sensitive electrical switch carried by means operable in response to a momentary signal outsaid pivotably mounted float in a manner to have put from said filter to connect an audio sounding device and a delay tube to a power source for a predetermined period, said delay tube being connected in a manner to disconnect said power source from the audio sounding device and the delay tube after a period of signal, and further wherein said receiver includes a fil-' ter circuit tuned to the single frequency of the audio oscillator to enable said indication means when the received signal includes the modulating single frequency.
7. Apparatus according to claim 3 wherein said means for communicating the state of said at least one switch to remote location includes:
a radio frequency transmitter carried by said flotation material and connected with said at least one position sensitive switch in order to transmit a signal when said at least one switch isin its said second state, and I a radio frequency receiver located in a position remote from said flotation device and tuned to receive said radio frequency signal, said receiver includes means for giving an indication upon receipt of said signal.
8. Apparatus according to claim 4 wherein said indication means contains an alarm means for sounding an audio alarm for a predetermined time after first receiving the radio frequency signaL'whereby' a mere pulse of radio frequency energywill sound an alarmof said receiver for said predetermined time.
9. Apparatus according to claim 6 whereinsaid means for communicatingthe state of said at least one switch to a remote location includes:
a length of wire electrically connected with said switch and extending from said flotation material to said remote location, and
a signaling device lo'cated at said remote location and connected with said switch by said length of wire,
said signaling device being operated when said at least one switch is in its second state.
10. Apparatus according to claim 9 wherein said signaling device includes an audio alarm that sounds for a predetermined time independent of the length of time a that said at least one switch'is in its second state.
apparatus is replaced in the liquid. 7 I v e a: