Patent Publication Number: US-RE42218-E

Title: Underwater alert system

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to underwater alert systems for divers, and, more particularly, to an underwater alert system including a transmitter assembly, carried by one diver, and a receiver assembly, carried by another diver. 
     BACKGROUND OF THE INVENTION 
     A. Scuba Diving&#39;s Buddy System 
     Scuba (“Self-Contained Underwater Breathing Apparatus”) diving is a well-known activity practiced by people for applications such as sport, commercial, military, scientific, search and recovery, professional underwater photography and movie making. Because of the inherent risk and unfamiliarity associated with an underwater environment, people wishing to practice scuba diving are required to be trained and certified in diving safety, equipment, environment, communications, procedures, etc. 
     One of the fundamental safety practices of scuba diving is to never dive alone. A diver should always dive with another diver who remains nearby at all times. Preferably, the two divers should be separated under water by only a few feet. When divers dive in pairs, the divers are practicing what is conventionally called the “buddy system,” wherein each diver is a “buddy” to the other diver. Under the buddy system, the divers have a responsibility to each other. For the buddy system to work, both divers must want it to work and must learn to apply the practices that will maximize their safety and minimize their separation underwater. Further, each diver must constantly be aware of the other diver&#39;s situation. Hence, the buddy system increases the safety, as well as the enjoyment, of diving. 
     The buddy system increases diving safety because a diver&#39;s responsibility is primarily to prevent and overcome problems and emergency situations encountered by the other diver, and secondarily to generally assist the other diver, as needed. The problems and emergency situations that can occur underwater include being out of air, trapped, entangled, injured, etc. The general assistance that can be provided above the water includes putting on suits and equipment, checking equipment, removing an entanglement, etc. The general assistance that can be provided underwater includes reminding the other diver of time limits, depth limits, air supply limits, direction, temperature and assent rates, surveying the area for hazards, adjusting the other diver&#39;s equipment, assisting with navigation, keeping track of each other, etc. The buddy system also provides a psychological aid to divers because the divers feel more secure, less stress and less likely to panic when another diver is present. 
     The buddy system increases the diving enjoyment because two divers can share experiences and witness unusual occurrences or discoveries together rather than alone. Because two divers witness more than one diver, one diver can point out something of interest under water that the other diver might have missed. 
     B. Traditional Scuba Diving Communication 
     Under water, the buddy system requires that the two divers have some way of gaining each other&#39;s attention to initiate communications and then some form of communication with each other. Divers are trained to communicate with each other by using primitive techniques such as predetermined hand signals, an underwater writing slate, making noise by banging on the air tank with a hard object, or by tugging on a line held by each diver. However, a disadvantage of both the hand signals and writing slates is that they rely almost entirely upon the divers maintaining line of sight with each other. Various unavoidable circumstances related to diving break the line of sight between the divers to render the hand signals or messages on the writing slate inadequate to gain the attention of the other diver. Such circumstances include the orientation of the divers&#39; bodies or heads relative to each other, limited visibility through a mask or the water, separation beyond an arm&#39;s length distance, water currents, etc. A disadvantage of banging on the air tank is that a diver may not always have tools or devices for making sufficient noise under water that will attract the attention of the other diver. Further, since sound travels in all directions under water, a diver would not only gain the attention of their buddy diver, but also inadvertently gain the attention of other non-buddy divers in the vicinity of the tank. A disadvantage of tugging on a line is that the line limits the mobility between the divers and a diver&#39;s necessary mobility in the water can cause the line to be accidentally tugged. All of these circumstances can result in a breakdown of the buddy system to decrease the divers&#39; safety and enjoyment during the dive. Over the years people have proposed various devices to improve upon these traditional communication techniques. 
     C. Alert Systems 
     1. Single Diver Alert Systems 
     a. Single Diver Surface Alert Devices 
     Traditionally, scuba divers have relied on whistles to gain someone&#39;s attention on the water&#39;s surface. However, if a scuba diver is disabled and can&#39;t blow into the whistle, the whistle makes no sound at all. Further, if a scuba diver needs to attract the attention of someone who is too far away from to hear the whistle, then the whistle is of no help. 
     A Dive Alert™ device is a small, lightweight air horn that uses quick connect/disconnect hose fittings to become an integral part of a diver&#39;s power inflator used to inflate a scuba diver&#39;s buoyancy control device (BCD) using compressed air from the scuba diver&#39;s air tank. When the scuba diver presses a button on the Dive Alert™ device, the button engages a chrome-plated brass actuator valve stem causing a small amount of air to rush by a stainless steel diaphragm causing a piercingly loud sound to be emitted from an injection-molded thermoplastic body to gain someone&#39;s attention on the water&#39;s surface up to one mile away from the scuba diver. The Dive Alert™ device is better than the whistle when that a diver&#39;s air tank has enough air for the Dive Alert™ device to operate. However, both the Diver Alert™ device and the whistle share a disadvantage in that a diver would not only gain the attention of their buddy diver, but also inadvertently gain the attention of other non-buddy divers in the vicinity of the Dive Alert™ device. 
     b. Single Diver Underwater Alert Devices 
     A Sub Alert™ device is a small, lightweight air horn that includes a Sub Alert™ unit and a low-pressure hose to generate an underwater signal using compressed air from the diver&#39;s air tank. When the scuba diver presses a button on the Sub Alert™ device, the Sub Alert™ device generates an underwater signal that can be heard up to 25 feet away when the other diver is wearing a hood. 
     U.S. Pat. Nos. 4,635,242 and 5,010,529 disclose audible electronic signaling devices worn by a single diver and used to gain the attention of another diver in the vicinity. However, these patents do not teach or suggest a receiving device worn by another diver. 
     The Sub Alert™ device and the audible electronic signaling devices disclosed in U.S. Pat. Nos. 4,635,242 and 5,010,529 share the same disadvantage as the surface alert devices in that the alert not only gain the attention of their buddy diver, but also inadvertently gain the attention of other non-buddy divers in the vicinity. In some cases, a pair of divers or a small team of divers would like a discreet signal that will gain the attention of another diver without disturbing other divers in the vicinity. 
     2. Diver-to-Diver Alert Systems 
     U.S. Pat. Nos. 3,469,231 and 5,523,982 and publications WO 98-17526 and WO 98-45969 disclose diver-to-diver alert systems having a transmitter and a receiver, wherein each diver wears an alert system. These patent and publications disclose alerting a diver with an audible, a visual or a vibrating alert. These patent and publications also disclose that the alert system is carried on a diver&#39;s wrist, forearm, arm or waist. The patents and the publications do not teach or suggest that the transmitter, the receiver or the alert is carried on a diver&#39;s mask. The audible alert shares the same disadvantage as the surface and underwater single diver alert devices in that the audible alert not only gain the attention of their buddy diver, but also inadvertently gain the attention of other non-buddy divers in the vicinity. A disadvantage of the visual alert is that the visual alert would not immediately gain the attention of the diver if the diver does not constantly look at the visual alert on their wrist, forearm, arm or waist. Typically, divers dive with their head up to see where they are going and their arms at their sides to reduce water resistance. Hence, the diver&#39;s natural diving position is not conducive to monitoring a visual alert on their wrist, forearm, arm or waist. A disadvantage of the vibrating alert is that the vibrating alert conveys a very limited amount of information intended by the diver transmitting the alert signal, since the vibrating alert can only vibrate or not vibrate. 
     D. Underwater Wireless Voice Communication Systems 
     1. Single Diver Voice Communication Systems 
     Ocean Technology Systems (oceantechnologysystems.com) manufactures diver recall system called a DRS-100B Diver Recall/Hydrophone that is used on some charter dive boats. The diver recall system permits a diver on the boat to alert, to recall or to send voice communications to divers under water. The diver recall system generally includes an electronic package, a power supply, located on the boat, and a transducer, located in the water. All divers within range (e.g. 100 yards) of the transducer hear the communications with their naked ear and therefore have no need for an electronic listening device. Although the diver recall system is appropriate for general boat to diver communications, the diver recall system shares the same disadvantage as the surface and underwater single diver alert devices and the diver-to-diver audible alert devices in that the alert or voice communications gains the attention of all divers in the vicinity of the recall system. 
     2. Diver-to-Diver Voice Communication Systems 
     Various companies provide systems for underwater voice communication between two or more scuba divers. Ocean Technology Systems, Inc. (http://www.oceantechnologysystems.com) provides underwater communication systems including hard-wire, through-water, sonic, wireless, diver recall systems, Buddy Phone®, Aquacom®, Hot Mic®, and Buddy Line®. Another company, Ocean Reef (http://oceanreefgroup.com), provides an underwater communication system, called “Neptune”, having a mask, called a Neptune II, integrated with a regulator, called a NIRA (Neptune integrated regulator adapter), and a communication system, including a GSM (Global submarine messenger) ultrasound transceiver/receiver, a model M101A receiver unit, and a model M105 surface unit. Yet another company, Stone electronics ltd. of B.C. Canada using distributor, Scubapro (http://www.scubapro.com), provides an underwater communication system, called “Dive-Link®” (http://www.divelink.net), including a surface unit, a two way diver communicator, a diver listen only model and communication options for various full face masks provided by other companies. The Dive-Link® system includes a headpiece, having a transceiver, a battery, a switch, an audible signal generator and mask straps, and a mouth piece electrically coupled to the headpiece. The mask straps attached to a conventional mask. The switch has an on, off and emergency position. When the switch is in the emergency position, the audible signal generator produces a loud beep that can be heard by all divers in the vicinity of the audible signal generator. Although these voice communication systems provide improved underwater voice communications over those of the past, these systems remain relatively expensive due to relatively complicated voice communication circuitry. For example, for sport divers, the Buddy Phone® system model XT-100 is advertised at a price of $340.00 and the Dive-Link® system is advertised at a price of $649.00. 
     E. Underwater Wireless Data Communication Systems 
     1. Single Diver Wireless Data Communication Systems 
     U.S. Pat. Nos. 5,191,317, 5,899,204 and 6,054,929 disclose data communication system including a transmitter, carried by a diver&#39;s air tank, and receiver, carried by the same diver&#39;s wrist or mask, for communicating data from the diver&#39;s air tank to the same diver&#39;s wrist or mask. However, these patents do not teach or suggest a data communication system including a transmitter, carried by a first diver, and receiver, carried by a second diver. 
     2. Diver-to-Diver Wireless Message Communication Systems 
     U.S. Pat. No. 6,125,080 discloses diver-to-diver message communication device having a transmitter and a receiver, wherein each diver wears a message communication device. The message communication devices, carried by each diver, forms a communication network in which each diver can communicate preset data messages with any one of the other divers in the network or with a base station. The message communication device has belts (shown as straps with buckles) for attaching the device to a diver&#39;s hand, to another part of his body, his diving suit, or his own equipment. The message communication device also has a liquid crystal display (LCD) and a buzzer or vibrator for notifying a diver of an incoming message. However, this patent does not teach or suggest that the belts attach the data communication device to the receiving diver&#39;s mask in a manner that permits the receiving diver to view the LCD. 
     F. Dive Mask, Swimmer&#39;s Goggles or Eyeglasses Having a Visual Display or Indicator 
     U.S. Pat. No. 4,999,606 (dive mask), U.S. Pat. No. 5,191,317 (dive mask), U.S. Pat. No. 5,301,668 (dive mask), U.S. Pat. No. 5,685,722 (swimmer&#39;s goggles), U.S. Pat. No. 5,162,828 (eyeglasses), and publication WO 00/55676 (eyeglasses) disclose a display or indicator carried on a dive mask, swimmer&#39;s goggles or eyeglasses, respectively. However, these patents and the publication do not teach or suggest that the display or indicator is controlled or activated responsive to a signal transmitted by a transmitter carried by another diver. 
     G. Conclusion 
     Accordingly, scuba divers, practicing the buddy system, have a long-felt but unsolved need for an underwater alert system that increases the safety, as well as the enjoyment, of diving. The underwater alert system would be a practical, safe, inexpensive, simple, easy to use and reliable system. The underwater alert system would provide a substantial improvement over the traditional scuba diving communication techniques and yet cost much less than the underwater wireless voice communication systems. The underwater alert system would permit one scuba diver to discreetly and immediately gain the attention of another scuba diver, unlike many of the conventional underwater alert systems, and yet not be as complicated as the underwater wireless data communication systems. Alternatively, the underwater alert system would be a two-way system to permit each scuba diver to discreetly and immediately gain the attention of the other scuba diver. Further, alternatively, the underwater alert system would interface with a scuba diver&#39;s dive computer to permit dive computer data to be communicated from one scuba diver to another scuba diver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an underwater alert system including a first transmitter assembly, carried by a first diver, and a first receiver assembly, carried by a first mask worn by a second diver, in accordance with a first preferred embodiment of the present invention. 
         FIG. 2  illustrates a front, top and right side perspective mechanical view of the first transmitter assembly, shown being carried by the first diver in  FIG. 1 , in accordance with the first preferred embodiment of the present invention. 
         FIG. 3  illustrates a front, top and left side perspective mechanical view of the first receiver assembly; shown being carried by the second diver in  FIG. 1 , in accordance with the first preferred embodiment of the present invention. 
         FIG. 4  illustrates a schematic diagram of the first transmitter assembly, shown in  FIGS. 1 and 2 , in accordance with the first preferred embodiment of the present invention. 
         FIG. 5  illustrates a schematic diagram of the first receiver assembly, shown in  FIGS. 1 and 3 , in accordance with the first preferred embodiment of the present invention. 
         FIG. 6  illustrates a flowchart describing steps of a method of operation performed by the first transmitter assembly, shown in  FIGS. 1 ,  2  and  4 , in accordance with the first preferred embodiment of the present invention. 
         FIG. 7  illustrates a flowchart describing steps of a method of operation performed by the first receiver assembly, shown in  FIGS. 1 ,  3  and  5 , in accordance with the first preferred embodiment of the present invention. 
         FIG. 8  illustrates a front, left and top side perspective view of the first receiver assembly, shown in  FIGS. 1 ,  3  and  5 , attached to a frame of the first mask, in accordance with the first preferred embodiment of the present invention. 
         FIG. 9  illustrates a front, top and left side perspective view of the first receiver assembly, shown in  FIGS. 1 ,  3  and  5 , attached to a strap of the first mask, in accordance with the first preferred embodiment of the present invention. 
         FIG. 10  illustrates a front, top and left side perspective view of the first receiver assembly, shown in  FIGS. 1 ,  3  and  5 , integrally formed with the first mask, in accordance with the first preferred embodiment of the present invention. 
         FIG. 11  illustrates a schematic diagram of a first transceiver assembly, in accordance with a second preferred embodiment of the present invention. 
         FIG. 12  illustrates a front, top and left side perspective view of the first transceiver assembly, as shown in  FIG. 11 , attached to a frame of a mask, in accordance with the second preferred embodiment of the present invention. 
         FIG. 13  illustrates a schematic diagram of an underwater alert system including the first transceiver assembly, electrically coupled to a first dive computer carried by the first diver, and a second transceiver assembly, electrically coupled to a second dive computer carried by the second diver, in accordance with a third preferred embodiment of the present invention. 
         FIG. 14  illustrates the underwater alert system, shown in  FIG. 13 , carried by the first diver and the second diver, in accordance with the third preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A. Overview of the Underwater Alert System of the Preferred Embodiments 
     1. General Overview 
       FIGS. 1 through 10  illustrate an underwater alert system in accordance with a first preferred embodiment of the present invention. In the first preferred embodiment of the present invention, the underwater alert system  10  includes a first transmitter assembly  12 , carried by a first diver  14 , and a first receiver assembly  16 , carried by a first mask  18  worn by a second diver  20 . The underwater alert system  10 , according to the first preferred embodiment of the present invention, permits the first diver  14  to discreetly and immediately gain the attention of the second diver  20 .  FIGS. 11-12  illustrate an underwater alert system  10  in accordance with a second preferred embodiment of the present invention. In the second preferred embodiment of the present invention, the underwater alert system  10  includes a first transceiver assembly  232 , carried by a second mask worn by the first diver  14 , and a second transceiver assembly  254 , carried by the first mask  18  worn by the second diver  20 . The underwater alert system  10 , of the second preferred embodiment of the present invention, provides a two-way system to permit each diver to discreetly and immediately gain the attention of the other diver.  FIGS. 13 and 14  illustrate an underwater alert system  10  in accordance with a third preferred embodiment of the present invention. In the third preferred embodiment of the present invention, the underwater alert system  10  includes the first transceiver assembly  232 , electrically coupled to a first dive computer  252  carried by the first diver  14 , and a second transceiver assembly  254 , electrically coupled to a second dive computer  256  carried by the second diver  20 . The underwater alert system  10 , of the third preferred embodiment of the present invention, provides a two-way system to permit dive computer data to be discreetly and periodically shared between two or more divers. Each of the first, second and third preferred embodiments of the present invention advantageously provides scuba divers, practicing the buddy system, with an underwater alert system  10  that increases the safety and the enjoyment of diving. 
     2. Particular Overview 
     More particularly, in the first preferred embodiment of the present invention, the underwater alert system  10  comprises the first transmitter assembly  12 , the first receiver assembly  16  and the first mask  18 . The first transmitter assembly, carried by the first diver, has a waterproof transmitter housing  38  for carrying an alert switch  68 , a transmitter  66  and a transmitting element  80 . The alert switch  68  generates an electrical alert actuation signal  86  responsive to the alert switch  68  being actuated, either manually by the first diver  14  or automatically by the first diver&#39;s equipment. The transmitter  66  generates a predetermined electrical transmit signal  98  responsive to receiving the electrical alert actuation signal  86 . The transmitting element  80  generates a predetermined wireless signal  36  responsive to receiving the predetermined electrical transmit signal  98 . The first receiver assembly  16 , carried by the second diver  20 , has a waterproof receiver housing  48  for carrying a receiving element  126 , a receiver  128  and an alert device  110 . The receiving element  126  generates an electrical receive signal  152  responsive to receiving the predetermined wireless signal  36 . The receiver  128  generates a predetermined electrical alert attention signal  135  responsive to receiving the electrical receive signal  152 . The alert device  110 , such as a visual  112 , an audible  114  or a tactile  116  alert device, generates a predetermined alert  161 , such as light  162 , sound  164  or vibration  166 , respectively, responsive to receiving the predetermined electrical alert attention signal  135 . The first mask  18  carries the first receiver assembly  16 , either separate from or integral with the first mask  18 , in a way that permits the predetermined alert  161  to gain the attention of the second diver  20  when the first mask  18  is worn on the second diver&#39;s head. The first transmitter assembly  12  and the first receiver assembly  18  each have a power switch  70  and  120 , such as a water-activated switch, and a power supply  82  and  132  for providing power to the electrical circuits carried therewith. Preferably, the first transmitter assembly  12  and the first receiver assembly  14  share a common electrical identity  77  and  125 , such as a frequency channel or a signal address, to provide discreet communications between the divers. 
     In the second preferred embodiment of the present invention, the underwater alert system  10  includes all of the preferred and alternative features described with reference to the first preferred embodiment of the present invention. In the second preferred embodiment of the present invention, a second transmitter assembly, a second receiver assembly and a second mask, adapted to be worn on the first diver&#39;s head, permits the second diver  20  to gain the attention of the first diver  14  in an analogous, reverse manner. In this case, the first transmitter assembly  12  and the second receiver assembly, each carried by the first diver  14 , may be combined into a first transceiver assembly  232  to be carried, either separate from or integral with, the second mask. Likewise, the second transmitter assembly and the first receiver assembly  16 , each carried by the second diver  20 , may be combined into a second transceiver assembly to be carried, either separate from or integral with, the first mask  18 . Hence, the underwater alert system of the second preferred embodiment of the present invention advantageously permits two-way communications between the first diver  14  and the second diver  20 . 
     In the third preferred embodiment of the present invention, the underwater alert system  10  includes all of the preferred and alternative features described with reference to the first and/or the second preferred embodiments of the present invention. In the third preferred embodiment of the present invention, the first transmitter assembly  12  is electrically coupled to the first diver&#39;s dive computer to permit dive computer data, associated with the first diver  14 , to be transmitted to the receiver assembly  16 , carried by the seconds, diver  20 . Likewise, the second transmitter assembly is electrically coupled to the second diver&#39;s dive computer to permit dive computer data, associated with the second diver  20 , to be transmitted to the receiver assembly, carried by the first diver  14 . Hence, the underwater alert system of the third preferred embodiment of the present invention advantageously permits dive computer data to be transmitted from the first diver  14  to the second diver  20  or to be exchanged between the first diver  14  and the second diver  20 . 
     B. Underwater Alert System of the First Preferred Embodiment 
     1. Practical Example 
       FIG. 1  illustrates an underwater alert system  10  including a first transmitter assembly  12 , carried by a first diver  14 , and a first receiver assembly  16 , carried by a first mask  18  worn by a second diver  20 , in accordance with a first preferred embodiment of the present invention. The first diver  14  and the second diver  20  are shown as scuba divers practicing the buddy system during an underwater dive to increase the safety and enjoyment of their dive. Although the first diver  14  and the second diver  20  are separated from each other by only a short distance, such as one or two meters, the orientation of their bodies in the water causes the line of sight  22  of the first diver to be in one direction and the line of sight  24  of the second diver  20  to be in another, different, direction. Because each diver has a line of sight extending in a different direction, the divers do not have eye contact with each other. While diving, the first diver  14  discovers an octopus  26 . The second diver  20  does not see the octopus  26  and observes ordinary underwater fish  28  and plant life  30 . The first diver  14  is excited about the discovery of the octopus  26  and wants to share the discovery of the octopus  26  discreetly, without disturbing the octopus  26  and other wildlife or other divers in the vicinity, and immediately, before the octopus  26  swims away or hides. 
     The first diver  14  preferably carries the first transmitter assembly  12  on his right wrist using a wristband  32 . The first diver  14  alerts the second diver  20  of the discovery of the octopus  26  by pressing a pushbutton  34  on the first transmitter assembly  12  using his left hand. The first transmitter assembly  12  transmits a predetermined wireless signal  36  through the water. 
     The second diver  20  carries the first receiver assembly  16  on the first mask  18 . The first receiver assembly  16  receives the predetermined wireless signal  36  and causes an alert to be generated to alert the second diver that the predetermined wireless signal  36  was received. The alert is preferably visual, such as light, but may also be vibration or sound. The generation of the alert gains the attention of the second diver  20 . 
     After the first diver  14  gains the attention of the second diver  20 , various conventional forms of underwater communication may be used to further convey a message or an intention. The second diver  20  knows that the first diver  14  caused the alert to be generated, so the second diver  20  responds by looking at the first diver to see why the first diver  14  gained his attention. The first diver  14  may or may not make eye contact with the second diver  20  depending on the particular situation. In this example, the first diver  14  may keep the octopus  26  within his line of sight and merely point to the octopus  26  with his hand to indicate to the second diver  20  the reason for the alert. Alternatively, the first diver  14  may make eye contact with the second diver  20  and motion with his hand for the second diver  20  to come closer to his area. The second diver  20  enjoys the opportunity to view the octopus before the octopus swims away or hides and both divers were able to share their discovery in further detail after the dive. Hence, the underwater alert system  10  advantageously permits the first diver  14  to discreetly and to immediately gain the attention of the second diver  20 . 
     2. Transmitter Assembly—Mechanical 
     a. Overview 
       FIG. 2  illustrates a front, top and right side perspective mechanical view of the first transmitter assembly  12 , shown being carried by the first diver  14  in  FIG. 1 , in accordance with a first preferred embodiment of the present invention. The first transmitter assembly  12  of  FIG. 2  generally includes a transmitter housing  38 , the pushbutton  34 , the wristband  32  and a power switch  33 . The transmitter housing  38  has sufficient volume and dimensions to carry the electronic components and circuitry illustrated in FIG.  4 . The transmitter housing  38  is preferably waterproof or otherwise suitable for being submerged underwater at depths of up to 50 to 100 meters, without causing damage to the electronic components and circuits contained inside the transmitter housing  38 . The transmitter housing  38  is made using conventional molding techniques and using conventional plastic molding materials. Preferably, the transmitter housing  38  is made so that the bottom side of the transmitter housing  38 , facing the first diver&#39;s wrist or forearm, is slightly convex to permit a more comfortable fit around and against the first diver&#39;s wrist or forearm. 
     b. Attachment Mechanism 
     The wristband  32  preferably comprises two straps, one strap attached to and extending from each opposite end of the transmitter housing  38 . One strap  40  preferably has hook fasteners  44  attached thereto and the other strap  42  preferably has loop fasteners  46  attached thereto. The hook and loop fasteners, otherwise known as a Velcro™ fastener, provide a convenient mechanism to secure the straps to each other. The straps each have a length sufficient to secure the transmitter housing  38  to the first diver&#39;s wrist or forearm. Alternatively, any other mechanism may be used to secure the transmitter housing  38  to any body part of the first diver  14  or to the first diver&#39;s equipment. Body parts of the first diver for locating the transmitter housing  38  include, without limitation, the first diver&#39;s hand, wrist, forearm, upper arm, foot, ankle, lower leg, upper leg, waist, torso, neck and head. The first diver&#39;s equipment that may carry the transmitter housing  38  include, without limitation, a mask, a snorkel, a wet suit including a body suit, a hood and gloves, a bathing suit, a buoyancy compensation device including a vest, a compressed air tank, a regulator, air hoses, and a weight belt. For example, the wristband  32  may be one continuous elastic strap for securing the transmitter housing to the first diver&#39;s wrist or forearm. Further, the transmitter housing  38  may be attached to a cord or strap to permit the transmitter housing  38  to hang around the first diver&#39;s neck, like a pendant, or may be attached to a band or belt to permit the transmitter housing  38  to be located on the first diver&#39;s waist. Further, the transmitter housing  38  may be attached to a spring-loaded clip or clamp to permit the transmitter housing  38  to be clipped to the first diver&#39;s equipment. 
     c. Pushbutton 
     The pushbutton  34  is located on the top side of the transmitter housing  38  and has sufficient dimensions to permit the first diver to easily find and press the pushbutton  38 . The pushbutton  34  is preferably waterproof or otherwise suitable for being submerged underwater without causing damage to the electronic components and circuits contained inside the transmitter housing  38 . The pushbutton  34  is made using conventional molding techniques and using conventional plastic molding materials. The pushbutton may be illuminated by a light source, such as a light emitting diode (LED) or an incandescent bulb, which is also carried by the transmitter housing  38 . Preferably, the light source would be disposed underneath the pushbutton  38 . In this case, the pushbutton  38  would be made from a transparent or translucent material to permit the light from the light source to illuminate the pushbutton  38 . Alternatively, the light source may illuminate a perimeter of the pushbutton  38  made from an opaque, or otherwise light blocking, material. Preferably, the pushbutton  38  bears an inscription or other suitable logo or design conveying the purpose of the pushbutton  38 . In  FIG. 2 , the pushbutton  38  bears the inscription “Alert.” Alternative inscriptions may include, without limitation, “Emergency,” “Attention,” “Buddy.” 
     d. Power Switch 
     The power switch  33  of the first transmitter assembly  12  turns the electronic components and circuitry that are located inside the transmitter housing  38  on and off. Preferably, the power switch  33  is implemented as a water-activated or wet switch, as is well known in the art, that turns the power on when the transmitter housing  38  is under the water and that turns the power off when the transmitter housing  38  is above the water. 
     3. Receiver Assembly—Mechanical 
     a. Overview 
       FIG. 3  illustrates a front, top and left side perspective mechanical view of the first receiver assembly  16 , shown being carried by the second diver  20  in  FIG. 1 , in accordance with a first preferred embodiment of the present invention. The first receiver assembly  16  of  FIG. 3  generally includes a receiver housing  48  having a power switch  49 . The receiver housing  48  has sufficient volume and dimensions to carry the electronic components and circuitry illustrated in FIG.  5 . The receiver housing  48  is preferably waterproof or otherwise suitable for being submerged underwater at depths of up to 50 to 100 meters without causing damage to the electronic components and circuits contained inside the receiver housing  48 . The receiver housing  48  is made using conventional molding techniques and using conventional plastic molding materials. 
     b. Attachment Mechanism 
       FIG. 3  also illustrates an attachment mechanism for securing the receiver housing  48  to any body part of the second diver  20  or to the second diver&#39;s equipment. The second diver&#39;s body parts and equipment are the same as mentioned with reference to  FIG. 2  for the first diver  14 . In the first embodiment of the present invention, the receiver housing  48  is carried by the second diver&#39;s mask, as shown and described with reference to  FIGS. 8 ,  9 ,  10  and  11 . 
     Preferably, the attachment mechanism comprises a thin, planar carrier  50 , made from a material such as tape or a foam pad, and having an adhesive  62  disposed on opposite sides of the carrier having the majority of the surface area. In this case, the adhesive  62  disposed on a top side of the carrier  50  is attached to a bottom side of the receiver housing  48  and the adhesive (not shown) disposed on a bottom side of the carrier  50  is attached to the second diver&#39;s equipment, such as the second diver&#39;s mask. Using the carrier  50 &lt;with adhesive  62  results in a semi-permanent attachment of the receiver housing  48  to the second diver&#39;s equipment because the receiver housing  48  is not meant to be removed but may be removed by tearing the receiver housing  48  away from the second diver&#39;s equipment and thereby damaging the carrier and/or the adhesive  62 . 
     Alternatively, the attachment mechanism comprises a bracket  52  having spring-loaded clips  54  and  56  disposed at opposite ends of the bracket  52 . A bottom side of the bracket is attached to the second diver&#39;s equipment, such as the second diver&#39;s mask, using the carrier  50  with adhesive  62  as described above with reference to  FIG. 3. A  top side of the bracket  52  is attached to the bottom side of the receiver housing  48  using the spring-loaded clips  54  and  56 . In this case, the spring-loaded clip  54  is adapted to fit into recess  58  on one side of the receiver housing  48  and the spring-loaded clip  56  is adapted to fit into recess  60  on another opposite side of the receiver housing  48 . The second diver  20  attaches the receiver housing  48  to the bracket  52  by aligning the recesses  58  and  60  on the receiver housing  48  with the spring-loaded clips  54  and  56 , respectively, on the bracket  52  and pressing the receiver housing  48  against the bracket  52 . The force of the receiver housing  48  against the bracket  52  produces a bias force on the spring-loaded clips  54  and  56  thereby causing the spring-loaded clips  54  and  56  to deflect away from each other. Preferably, the spring-loaded clips  54  and  56  on the bracket  52  each have a beveled or otherwise contoured top edge to facilitate receiving the receiver housing  48  with minimum interference. When the recesses  58  and  60  on the receiver housing  48  are disposed opposite to the spring-loaded clips  54  and  56 , respectively, on the bracket  52  the spring-loaded clips  54  and  56  return to their original unbiased position inside the recesses  58  and  60  of the receiver housing  48  thereby securing the receiver housing  48  to the bracket  52 . Using the bracket  52  and the carrier  50  with the adhesive  62  permits the receiver housing  48  to be attached to and removed from the second diver&#39;s equipment. The bracket  52  and the carrier  50  with the adhesive  62  remain attached to the second diver&#39;s equipment as a semi-permanent attachment. Alternatively, any other type of attachment mechanism may be used to permit the receiver housing  48  to be attached to and removed from the second diver&#39;s equipment. Such other attachment mechanisms include, without limitation, hook and loop fasteners, such as a Velcro™ fastener, straps and bands, and clips or clamps, as described herein with reference to  FIG. 3. A  removable attachment mechanism advantageously permits the receiver assembly  16  to be used on different masks, separate from the second diver&#39;s mask, and on land-based eyewear or other land-based applications, such as, without limitation, a belt, wristband, neck strap, a pocket, and the like. 
     c. Power Switch 
     The power switch  49  of the first receiver assembly  16  turns the electronic components and circuitry that are located inside the receiver housing  48  on and off. Preferably, the power switch  49  is implemented as a water-activated or wet switch, as is well known in the art, that turns the power on when the receiver housing  48  is under the water and that turns the power off when the receiver housing  48  is above the water. 
     4. Transmitter Assembly—Electrical 
     a. Overview 
       FIG. 4  illustrates a schematic diagram of the first transmitter assembly  12 , shown in  FIGS. 1 and 2 , in accordance with the first preferred embodiment of the present invention. The first transmitter assembly  12  generally includes the transmitter housing  38 , a transmitter controller  64 , a transmitter  66 , an alert switch  68 , a transmitter power on/off switch  70 , a transmitter dive computer interface  72 , a transmitter identity selection device  74 , a transmitter memory device  76 , a transmitter amplifier  78 , a transmitting element  80 , an alert device  81 , a transmitter power supply  82 , and a transmitter charging circuit interface  84 . The transmitter memory device  76  further includes a transmitter identity  77 . 
     b. Transmitter Controller 
     Generally, the transmitter controller  64  receives various input signals from and generates various output signals to the various electrical circuitry and components shown and described responsive to a predetermined set of commands or instructions forming a computer program stored in the transmitter memory device  76 . 
     c. Transmitter Power Switch 
     The transmitter power switch  33  of the first transmitter assembly  12  turns on and off power to the various shown and described electronic components and circuitry. Preferably, the transmitter power switch  33  is electrically coupled to the transmitter controller  64  via power signal  88 , as shown in  FIG. 4 , but may alternatively be electrically coupled directly to the transmitter power supply  82 , each construction being well known in the art. Preferably, the power switch  33  is actuated automatically. Types of automatically activated power switches include, without limitation, the water-activated or wet switch, as described hereinabove, a motion sensitive switch responsive to the diver&#39;s physical motion, or a location sensitive switch responsive to a location of the transmitter assembly  12 , such as being secured to a bracket. Alternatively, the power switch  33  may be actuated manually. Types of manually activated power switches include, without limitation, a push-type, lever-type, twist-type or slide-type switch, as are well known in the art. 
     d. Transmitter Power Supply 
     The transmitter power supply  82  provides electrical power  102  to the various shown and described electronic components and circuitry. Generally, the transmitter power supply  82  is a storage device that stores electrical power or the potential for electrical power for later or concurrent use by the electronic components and circuitry. Preferably, the power supply  82  is a conventional battery. The battery is preferably a conventional nine volt battery, but may have a lower voltage if it is sufficient to power the circuitry for a reasonable period of time. Preferably, the battery is non-rechargeable, but may be rechargeable by a charger  65  via the transmitter charging circuit interface  84 . The transmitter charging circuit interface  84  provides a charging signal  104  to the transmitter power supply  82  implemented as a rechargeable battery, as is well known in the art. The transmitter charging circuit interface  84  also communicates with the transmitter controller  64  via a bi-directional charge control signal  105  to permit the transmitter controller  64  to monitor and/or control the charging and discharging process of the transmitter power supply  82 , as is well known in the art. Preferably, the transmitter controller  64  monitors the transmitter power supply  82  for a low voltage condition and provides the first diver  14  with an appropriate alert, such as visual, audible or tactile, when the transmitter power supply  82  reaches a predetermined voltage. The predetermined voltage preferably corresponds to a level when the first transmitter assembly  12  could not transmit a signal  36  strong enough to reach the first receiver assembly  16  over a predetermined distance for a predetermined amount of time. These various factors may be determined during the engineering process of the first transmitter assembly  12  and the first receiver assembly  16 , as are well known in the art. Moreover, the first diver  14  may actually test the first transmitter assembly  12  and the first receiver assembly  16  together to verify proper operation, either under the water or above the water. 
     e. Alert Switch 
     The alert switch  68  generally is a device for making, breaking or changing the connections in an electrical circuit and, more particularly, is a device adapted to generate an electrical alert actuation signal  86  responsive to the alert switch  68  being actuated. Actuation of the alert switch preferably causes a closed circuit condition to generate the electrical alert actuation signal  86 , but may also cause an open circuit condition to generate the electrical alert actuation signal  86 , as is well known in the art. 
     Preferably, the alert switch  68  is a pushbutton switch adapted to generate the electrical alert actuation signal  86  responsive to the pushbutton switch being manually actuated by the first diver  14 . In this case the pushbutton  34 , such as a small button or knob, as shown in  FIG. 2 , overlays the pushbutton switch to permit the pushbutton  34  to actuate the underlying pushbutton switch responsive to the first diver  14  manually pressing the pushbutton  34 . As an alternative to a push-type switch, any other type of switch may be used including, without limitation, a lever-type, twist-type or slide-type switch, as is well known in the art. 
     Preferably, the first transmitter assembly  12  has one alert switch  68  that generates one electrical alert actuation signal  86  responsive to the one alert switch  68  being actuated. For example, one “Discovery” alert switch preferably generates a first electrical alert actuation signal, indicative of a discovery by the first diver  14  that the first diver  14  obtained sight or knowledge of for the first time or found out what he did not previously know, as related to his exploration, investigation or a chance encounter during the dive. 
     Alternatively, the first transmitter assembly  12  may have multiple alert switches that generate multiple electrical alert actuation signals, respectively, responsive to the multiple alert switches, respectively, being actuated. In this case, each alert switch generates a different electrical alert actuation signal. For example, a “Discovery” alert switch may generate a first electrical alert actuation signal, as described hereinabove. Then, an “Emergency” alert switch may generate a second electrical alert actuation signal, different from first the electrical alert actuation signal, indicative of an emergency situation, associated with the first diver  14 , caused by an unforeseen combination of circumstances or the resulting state that calls for immediate action or an urgent need for assistance or relief. Hence, this first alternative advantageously permits the first diver  14  to easily recognize and remember that one switch generates one electrical alert actuation signal and another switch generates another electrical alert actuation signal. 
     Still alternatively, the first transmitter assembly  12  may have one alert switch that generates multiple electrical alert: actuation signals responsive to the one alert switch being actuated in different ways. For example, one alert switch may generate a first electrical alert actuation signal, indicative of a discovery by the first diver  14 , responsive to the alert switch being actuated once within a predetermined period of time, such as five seconds. Then, the alert switch may generate a second electrical alert actuation signal, different from first the electrical alert actuation signal, indicative of an emergency situation associated with the first diver  14 , responsive to the alert switch being actuated more than once within the predetermined period of time, such as the five seconds. Hence, this second alternative advantageously reduces the number of switches required to generate the multiple electrical alert actuation signals. 
     Preferably, the first diver  14  manually actuates the alert switch  68 . Alternatively, the alert switch  68  may be automatically actuated. In this case, the first diver  14  conditions associated with the first diver&#39;s body, equipment or environment automatically actuates the alert switch  68 . Conditions associated with the first diver&#39;s body include, without limitation, the first diver&#39;s heart rate and breathing rate. Conditions associated with the first diver&#39;s equipment include, without limitation, information and data associated with the first diver&#39;s dive computer or gauges, such as dive table time limits, depth limits, air supply limits, direction, distance, and assent rates. Conditions associated with the first diver&#39;s environment include, without limitation, any parameter of the water, such as temperature, density, opacity, etc. 
     f. Dive Computer Interface 
     The dive computer interface  72  permits the information and data associated with the first diver&#39;s dive computer or gauges to be received by the transmitter controller  64 . The dive computer interface  72  generates a dive computer signal  90  representative of the information and data associated with the first diver&#39;s dive computer or gauges. The dive computer interface  72  may be a wired interface or a wireless interface, such as radio frequency, infrared, acoustic, ultra-acoustic, sonic, or ultrasonic. 
     g. Transmitter Memory Device 
     The transmitter memory device  76  stores the predetermined set of commands or instructions forming the computer program for first transmitter assembly  12 . The transmitter controller  64  and the transmitter memory device  76  exchange memory control signals  94 . The memory control signals  94  from the transmitter memory device  76  to the transmitter controller  64  are representative of the instructions of the computer program instructing the transmitter controller  64  of what to do next. The memory control signals  94  from the transmitter controller  64  to the transmitter memory device  76  are representative of the state or condition of the circuitry of the first transmitter assembly  12  being reported back to the computer program. The transmitter memory device  76  is preferably read only memory (ROM), but may alternatively be random access memory (RAM), electrically erasable programmable read only memory (EEPROM), firmware, and the like, as are well known in the art. 
     h. Transmitter Identity Selection Device and Transmitter Identity 
     The transmitter identity selection device  74  provides a mechanism for providing first transmitter assembly  12  with the transmitter identity  77  stored in the transmitter memory device  76 . As will be described in further detail herein below with reference to  FIG. 5 , the first receiver assembly  16  includes a receiver identity selection device  122  adapted to provide the first receiver assembly  16  with a receiver identity  125  that matches the transmitter identity  77  to permit the first receiver assembly  16  to receive the predetermined wireless signal  36  from the first transmitter assembly  12 . Practically, the first transmitter assembly  12  and the first receiver assembly  16  are electronically matched or mated so that only those two assemblies will work together. This matching advantageously provides discreet electronic communications between the first diver  14  and the second diver  20  without alerting other divers in the vicinity having the same transmitter and receiver assemblies. 
     Any type of electronic identity scheme may be used for the transmitter identity  77  and the receiver identity  125 . Preferably, the electronic identity is a frequency channel. The frequency channel is the frequency at which the first transmitter assembly  12  communicates with the first receiver assembly  16 . The first transmitter assembly  12  is designed to generate the predetermined wireless communication signal  36  at the designated frequency. The first receiver assembly  16  is designed to receive the predetermined wireless communication signal  36  at the same designated frequency. 
     Alternatively, the electronic identity may be an address assigned to the first transmitter assembly  12  and the first receiver assembly  16 . The address is a label that precedes the predetermined wireless communication signal  36  transmitted from the first transmitter assembly  12  to the first receiver assembly  16 . The first transmitter assembly  12  is designed to generate the predetermined wireless communication signal  36  with a designated address. The first receiver assembly  16  is designed to receive the predetermined wireless communication signal  36  having the same designated address. 
     Still alternatively, the electronic identity may be a code for encoding the predetermined wireless communication signal  36  transmitted by the first transmitter assembly  12 . The first receiver assembly  16  uses the same code to decode the predetermined wireless communication signal  36  received by the first receiver assembly  16 . The first transmitter assembly  12  is designed to generate the predetermined wireless communication signal  36  encoded with a designated code. The first receiver assembly  16  is designed to receive the predetermined wireless communication signal  36  decoded with the same designated code. 
     For any electronic identity scheme, including the frequency channel, the address, and the code, preferably multiple electronic identities are provided for the first transmitter assembly  12  and the first receiver assembly  16 . The multiple electronic identities advantageously permit pairs of the first transmitter assembly  12  and the first receiver assembly  16  to be matched and at the same time distinguished from other pairs of the same first transmitter assembly  12  and the first receiver assembly  16 . For example, four divers include two sets of buddy divers. One set of buddy divers set their first transmitter assembly  12  and first receiver assembly  16  to be matched to a first electronic identity, and the other set of buddy divers set their first transmitter assembly  12  and first receiver assembly  16  to be matched to a second electronic identity, different from the first electronic identity. In this example, one set of buddy divers may discreetly and immediately gain attention without disturbing the other set of buddy divers. 
     The electronic identity scheme, including the frequency channel, the address and the code, having multiple electronic identities preferably requires a method or mechanism for changing the electronic identity associated with the first transmitter assembly  12  and the second transmitter assembly  16 . Preferably, the transmitter identity selection device  74  provides the method or mechanism to do this by generating an electronic identity signal  92  for the transmitter controller  64 . The method or mechanism may be embodied in hardware or software. Hardware embodiments include, without limitation, switches, such as dip or micro switches, carried by each of the first transmitter assembly  12  and the first receiver assembly  16 . For example, two switches provide for up to four electronic identities (i.e., binary 0-3) and a set of three switches provides for up to eight electronic identities (i.e., binary 0-7). In the preferred embodiment of the present invention, hardware switches are used to set the electronic identity. Software embodiments include, without limitation, commands or instructions transmitted from the first transmitter assembly  12  to the first receiver assembly  16  over a communication link, such as physical wire or wirelessly, such as radio frequency, infrared frequency, acoustic frequency or ultrasonic frequency. The wireless communication link is preferably an infrared communication link, as specified by the Infrared Data Association (IRDA), having a communication distance of one meter. 
     Transmitter and receiver assemblies, having multiple electronic identities, and a way to select one of the multiple electronic identities may be used in a variety of beneficial ways to increase the safety and enjoyment of diving. For example, one transmitter assembly may be electronically matched with one receiver assembly, as described hereinabove with reference to the two pairs of buddy divers. In a second example, one transmitter assembly may be electronically matched to multiple receiver assemblies. In this second example, a dive instructor, carrying the transmitter assembly, may be teaching or leading a group of students, each carrying a receiver assembly, on a dive. In yet a third example, multiple transmitters may be electronically matched to one receiver. In this third example, a group of students, each carrying a transmitter assembly, may need to gain the attention of one dive instructor, carrying a receiver assembly. In a fourth example, multiple transmitter assemblies may be electronically matched to multiple receiver assemblies. In this fourth example, a small group of six divers go diving as three sets of buddy divers. However, all six divers dive relatively close to each other and they desire to be alerted to any discovery or emergency actuated by one of the divers. 
     i. Transmitter 
     The transmitter controller  64  generates a predetermined electrical information signal responsive to receiving the electrical alert actuation signal  86 , in a manner that is well known in the art. The transmitter  66  generates a predetermined electrical transmit signal  98  responsive to receiving the predetermined electrical information signal  96 . The transmitter  66  generally causes a signal to be conveyed through space or a medium, such as water, from one location, such as from the first diver  14 , to another location, such as to the second diver  20 . 
     j. Transmitter Amplifier 
     The transmitter amplifier  78  generates a transmit amplified signal  100  responsive to receiving the predetermined electrical transmit signal  98  from the transmitter  66 . The transmitter amplifier  78  advantageously increases the power or the amplitude level of the predetermined electrical transmit signal  98  so that the predetermined electrical transmit signal  98  will have enough energy to be carried through the space or the medium, such as water, to reach the first receiver assembly  16 . 
     k. Transmitting Element 
     The transmitting element  80  generates the predetermined wireless signal  36  responsive to receiving the transmitter amplified signal. The transmitting element  80  is conventionally called a source or a transducer. The transmitting element  80  is preferably implemented as a hydrophone, as is well known in the art. 
     The predetermined wireless signal  36  is wireless in the sense that it is generally an electromagnetic wave defined as being one of the waves that are propagated by simultaneous periodic variations of electric and magnetic field intensity. The frequency of the predetermined wireless signal  36  is preferably one of a sonic, ultrasonic, acoustic, ultra-acoustic frequency, and the like. In this case, “sonic” means operated by or using sound waves. “Acoustic” means operated by or using sound waves. Further, “ultra” means beyond the range or limits of, on the other side of, or beyond what is ordinary, proper or moderate. The frequency ranges of each of these types of sound waves are well known in the art. The predetermined wireless communication signal  36  having any one of these frequency ranges can be efficiently sent through a medium, such as water. Thus, sound transmission is very good under water, since water is a non-compressible medium. Sound waves are longitudinal pressure waves in any material medium, such as water, regardless of whether they constitute audible sound. The predetermined wireless signal  36  is radiated from the transmitting element  80  as sound vibrations in an omni-directional pattern, otherwise described as a spherical pattern. By contrast, the transmission of radio frequency waves through water is limited to relatively short distances, since water effectively “shorts out” radio waves. Hence, although sound frequency waves are preferred, radio frequency waves may alternatively be used in the present invention. 
     The word “predetermined” in the phrase predetermined wireless signal  36  generally means to impose a direction or tendency on beforehand. In the preferred embodiment of the present invention, the predetermined wireless signal  36  is determined before the alert switch  68  is actuated. The word “predetermined” may otherwise be called preset, preselected, and the like. Characteristics of the predetermined wireless signal  36  that may be predetermined include amplitude, frequency and modulated information. When the predetermined wireless signal  36  is an alert signal or a data signal, each of the amplitude, frequency and modulated information is predetermined. By contrast, underwater voice communication systems transmit wireless signals that are not predetermined because the modulated information changes with the diver&#39;s voice. 
     Various factors detrimentally affect the propagation of the predetermined wireless signal  36  in water. The predetermined wireless signal  36  can bounce off the bottom of the dive zone, the surface of the water, a thermocline (i.e., an abrupt change in the temperature of the water at a particular depth), and large natural or man-made objects. Further, the sound intensity of the predetermined wireless signal  36  from the transmitting element  80  varies inversely with the square of the distance from the transmitting element  80  (i.e. sound intensity is proportional to 1/(distance) 2 ). Still further, as the predetermined wireless signal  36  passes through water, some of the energy associated with the signal is absorbed and converted into heat to cause attenuation of the signal, and some of the energy of the signal is scattered by objects, such as seaweed and bubbles, to cause diffraction of the signal. Still further, the temperature of the water may cause the predetermined wireless signal  36  to bend and the density of the water also affects the predetermined wireless signal  36 . All of these various factors are taken into account during the design of the transmitter assembly  12  and receiver assembly  16  to produce a reliable system. Practically, since buddy divers preferably use the underwater alert system  10 , several meters typically separate the buddy divers. Commercially, the underwater alert system  10  would be designed so that the transmitter assembly  12  and the receiver assembly  16  would operate at a separation distance of fifty meters, but may be designed to operate at other separation distances. The factors related to bounce, attenuation, diffraction and bending do not significantly affect the design of the underwater alert system  10 . The factor related to the sound intensity is considered when determining the power output requirement of the transmitter assembly  12 . 
     1. Transmitter Alert Device 
     The transmitter alert device  81  generates an alert to the first diver  14  carrying the transmitter assembly  12  related to any function of the transmitter assembly  12 . Various alerts that may be generated by the transmitter alert device  81  include, without limitation, low voltage warning, verification of operation, confirmation of transmitter identity selection, confirmation of activation of the alert switch  68  or the transmitter power on/off switch  33 , conditions of the charging circuit  84 , and the like. The transmitter alert device  81  may be implemented in an analogous manner as a visual, audible or tactile alert devices explained in more detail below with reference to the receiver assembly  16 . 
     5. Receiver Assembly—Electrical 
     a. Overview 
       FIG. 5  illustrates a schematic diagram of the first receiver assembly  16 , shown in  FIGS. 1 and 3 , in accordance with the first preferred embodiment of the present invention. The first receiver assembly  16  generally includes the receiver housing  48 , a receiver controller  106 , a receiver  128 , an alert device  110 , an alert selection device  118 , a receiver power on/off switch  49 , a receiver identity selection device  122 , a receiver memory device  124 , a receiving element  126 , a receiver amplifier  108 , a receiver dive computer interface  130 , a receiver power supply  132 , a receiver charging circuit  134 . The alert device  110  generally includes at least one of a visual alert device  112 , an audible alert device  114  and a tactile alert device  116 . The receiver memory device  124  further includes a receiver identity  125 . 
     The receiver controller  106 , the receiver power on/off switch  49 , the receiver identity selection device  122 , the receiver memory device  124 , the receiver power supply  132 , and the receiver charging circuit  134  are generally made and operate in an analogous manner as the transmitter controller  64 , the transmitter power on/off switch  33 , the transmitter identity selection device  74 , the transmitter memory device  76 , the transmitter power supply  82 , and the transmitter charging circuit  84 , respectively, as shown and described with reference to FIG.  4 . All of the features, construction, function, examples, alternatives, and the like that are described hereinabove for these transmitter elements shown in  FIG. 4  also apply to these receiver elements shown in FIG.  5 . Hence, a corresponding description for these receiver elements will not be duplicated with reference to FIG.  5 . However, the receiver  128 , the alert device  110 , the alert selection device  118 , the receiving element  126 , the receiver amplifier  108 , and the receiver dive computer interface  130  have characteristics that are unique to the first receiver assembly  16  and are described in further detail below. 
     b. Receiving Element 
     The receiving element  126  generates an electrical receive signal  152  responsive to receiving the predetermined wireless signal  36 . Practically, the receiving element  126  senses or detects the electromagnetic sound waves traveling through the water in the vicinity of the receiving element  126 . The receiving element  126  is conventionally called a receiver or a hydrophone. The receiving element  126  is preferably implemented as a hydrophone, as is well known in the art. 
     c. Receiver Amplifier 
     The receiver amplifier  108  generates a receive amplified signal  154  responsive to receiving the electrical receive signal  152  generated by the receiving element  126 . The receiver amplifier  108  advantageously increases the power or amplitude level of the electrical receive signal  152  so that the electrical receive signal  152  will have enough energy to be recognized, identified or detected by the receiver  128 . 
     d. Receiver 
     The receiver  128  generates a predetermined electrical alert attention signal  156  responsive to receiving the receive amplified signal  154  from the receiver amplifier  108 . The receiver  128  is generally a device that receives a signal and causes the signal to be converted from one form into another. 
     e. Receiver Controller 
     The receiver controller  106  generates a predetermined electrical alert attention signal  135  responsive to receiving the predetermined electrical alert attention signal  156  from the receiver  128 . 
     f. Alert Device 
     The alert device  110  generates a predetermined alert  161  responsive to receiving the predetermined electrical alert attention signal  135  from the receiver controller  106 . The alert device  110  is generally a device that alerts the second diver  20 . The word “alert” generally means to call to a state of readiness, to make aware of, or to warn. 
     The alert device  110  may be any type of alert and includes, without limitation, at least one of a visual alert device  112 , an audible alert device  114  and a tactile alert device  116 . Hence, with these three categories of alert devices, there is a potential for eight combinations of the three alert devices to be implemented in the receiver assembly (i.e., binary 000=no alert devices, binary 111=all three alert devices). The particular combination of alert devices implemented in the receiver assembly  16  depends on engineering factors including, without limitation, size, weight, power, complexity, functionality, and the like, as are well known in the art, as well as business or marketing factors including, without limitation, customer preferences, price, application, and the like, as are well known in the art. Preferably, each of the three types of alert devices are included in the receiver assembly  16  to permit a diver to mount the receiver assembly according to his preference and to be alerted according to his preference. 
     When multiple alert devices are implemented in the receiver assembly  16 , various combinations of the generated alerts may be configured. In the preferred case where each of the three types of alert devices are included in the receiver assembly  16 , there is a potential for eight combinations of the three alerts to be generated by the three alert devices (i.e., binary 000=no alert devices, binary 111=all three alert devices). For example, a vibrating alert and a visual alert may be generated at the same time. Further, the various alerts may be interspersed among each other. For example, the visual alert may be generated for a first predetermined period of time, such as 5 seconds, followed by the vibrating alert for a second period of time, such as 5 seconds. Hence, multiple variations of alerts may be generated depending on the particular application. The multiple variations of alerts may be preset by the manufacturer of the receiver assembly  16  or may be programmed by the user of the receiver assembly  16 . 
     The alert device  110  may be located outside, inside or integrated with the second diver&#39;s mask  18 , depending on the desired implementation. The location of the alert device  110  may be determined by the manufacturer of the receiver assembly  16  or by the user of the receiver assembly  16 , depending on the anticipated application of the receiver assembly  16  when the receiver assembly  16  was manufactured. 
     The alert device  110  may generate the predetermined alert  161  as a continuous or pulsed signal, depending on the particular application. For example, the predetermined alert  161  may be continuous within a predetermined period of time, such as five seconds, to represent a discovery by the first diver  14 , and may be pulsed within the predetermined period of time, such as the five seconds, to represent an emergency associated with the first diver  14 . 
     The alert device  110  may also provide an indication of the range or distance of the second diver  20  relative to the first diver  14 . 
     The visual alert device  112  generates a predetermined visual alert  162 , as the predetermined alert  161 , responsive to receiving a predetermined electrical visual alert attention signal  136 , as the predetermined electrical alert attention signal  135 . The receiver assembly  16  is mounted on the second diver&#39;s mask  18  in such a manner that the second diver  20  can see the predetermined visual alert  162  generated by the visual alert device  112  when the second diver  20  is wearing the mask  18 . 
     Preferably, the visual alert device  112  is a light source adapted to generate a predetermined visible light signal, as the predetermined visual alert  162 . The light source may include, without limitation, a light emitting diode (LED), an incandescent bulb, and the like, as is well known in the art. Preferably, the light source is a LED. The light source is the preferred visual implementation when the predetermined wireless signal  36  is representative of a discovery or an emergency by the first diver  14 . The light source may have one or more colors to indicate various conditions of the alert. For example, a light source emitting green light may be representative of a discovery by the first diver  14  and the same or different light source emitting a red light may be representative of an emergency associated with the first diver  14 . 
     A light guide may be used to guide the predetermined visual alert  162  in a manner that is pleasing or noticeable to the second diver  20  when the second diver is wearing the mask  18 . The light guide includes, without limitation, optical fibers, lens covers, and the lens on the mask itself, and the like. For example, one or more optical fibers may be disposed along at least a portion of the perimeter of the lens of the mask, either on the outside or the inside of the mask. In another example, the light source may enter a side edge of the lens of the mask to illuminate at least a portion of the lens. 
     Alternatively, the visual alert device  112  is a display device including, without limitation, a LED display, a liquid crystal display (LCD), and the like, as is well known in the art. Preferably, the display device would be a LCD display because of its low power requirements or an organic LED display because of its small size. The display device is the preferred implementation when dive computer data is received. The display device visually presents the dive computer data in format that the second diver can recognize and interpret, such as for example and without limitation, alpha characters, numeric characters and alphanumeric characters. 
     The audible alert device  114  generates a predetermined audible alert  164 , as the predetermined alert  161 , responsive to receiving a predetermined electrical audible alert attention signal  138 , as the predetermined electrical alert attention signal  135 . The receiver assembly  16  is mounted on the second diver&#39;s mask  18  in such a manner that the second diver  20  can hear the predetermined audible alert  164  generated by the audible alert device  114  when the second diver  20  is wearing the mask  18 . The audible alert device  114  may otherwise be called a buzzer or a beeper. 
     Preferably, the audible alert device  114  is an electroacoustic transducer adapted to generate a predetermined audible acoustic signal, as the predetermined audible alert  164 . The electro-acoustic transducer may otherwise be called a speaker. The electro-acoustic transducer is a preferred audible implementation when the predetermined wireless signal  36  is representative of a discovery or an emergency by the first diver  14 . 
     The tactile alert device  116  generates a predetermined tactile alert  166 , as the predetermined alert  161 , responsive to receiving a predetermined electrical tactile alert attention signal  140 , as the predetermined electrical alert attention signal  135 . The receiver assembly  16  is mounted on the second diver&#39;s mask  18  in such a manner that the second diver  20  can feel the predetermined tactile alert  166  generated by the tactile alert device  116  when the second diver  20  is wearing the mask  18 . 
     Preferably, the tactile alert device  116  is a vibrator adapted to generate a predetermined vibration signal, as the predetermined tactile alert  166 . The vibrator is preferably constructed of a small motor having a small weight asymmetrically attached to the motor&#39;s shaft. When the motor spins the shaft, the weight also spins, but because of its asymmetrical position, the spinning weight consequently causes the motor to move. When the motor is secured to the receiver housing  48 , the moving motor causes the receiver housing  48  to vibrate. Other types of vibrators, such as disc-type vibrators may also be used, as are known in the art. 
     g. Alert Selection Device 
     The alert selection device  118  is an input device that permits the second diver  20  to determine which alert device among multiple alert devices to activate or how a particular alert device is activated. The alert selection device  118  generates an alert selection signal  142  for receipt by the receiver controller  106  responsive to a selection being made. Any type of alert selection device  118  may be used including, without limitation, switches, keypads, voice recognition, and the like, as are well known in the art. For example, a set of three switches will permit the second diver  20  to select any one combination among the eight combinations of the three alert devices  110 . The alert selection device  118  may be respond to either manual or automatic selection. The second diver  20  preferably performs the manual selection. Automatic selection may be responsive to the location of the receiver assembly  16 . For example, the audible alert device  112  is automatically selected when the receiver assembly  16  is above the water (when the second diver  20  is not likely wearing the mask) and the tactile alert device  116  is automatically selected when the receiver assembly  16  is under the water (when the second diver  20  is likely to be wearing the mask). In another example, the visual alert device  112  is automatically selected when the receiver assembly  16  is attached to the mask  18 , and the audible alert device  114  is automatically selected when the receiver assembly  16  is removed from the mask  18 . The automatic selection is preferably performed with appropriate sensor, as are well known in the art. 
     h. Receiver Dive Computer Interface 
     The receiver dive computer interface  130  permits the information and data associated with the second diver&#39;s dive computer or gauges to be received by the receiver assembly  16 . The receiver dive computer interface  130  generates a dive computer signal  160  representative of the information and data associated with the second diver&#39;s dive computer or gauges. The receiver dive computer interface  130  may be a wired interface or a wireless interface, such as radio frequency, infrared, acoustic, ultra-acoustic, sonic or ultra-sonic. Hence, the receiver dive computer interface  130  advantageously permits the second diver  20  to perceive the information and data using an appropriate alert device  110  of the receiver assembly  16 . 
     6. Transmitter Assembly—Method 
       FIG. 6  illustrates a flowchart  170  describing steps of a method of operation performed by the first transmitter assembly  12 , shown in  FIGS. 1 ,  2  and  4 , in accordance with the first preferred embodiment of the present invention. Practically, the steps of the flowchart  170  are representative of instructions or commands embodied within the computer program stored in the transmitter memory device  76  upon which the transmitter controller  64  operates. 
     At step  172 , the transmitter controller  64  starts the method of operation. At step  172 , the transmitter assembly  12  is assumed to be powered on by the transmitter power on/off switch  33 , which is typically a hardware function. 
     At step  174 , the transmitter controller  64  reads the voltage level of the electrical power  102  provided by the transmitter power supply  82 . 
     At step  176 , the transmitter controller  64  determines whether the voltage level of the electrical power  102  is acceptable to operate the transmitter assembly  12 . If the determination at step  176  is negative, then the method continues to step  178 . Otherwise, if the determination at step  176  is positive, then the method continues to step  180 . 
     At step  178 , the transmitter controller  64  generates a transmitter alert signal  83  to activate the transmitter alert device  81  to indicate to the first diver  14  a low voltage condition of the transmitter power supply  82 . After step  178 , the method returns to step  174 . 
     At step  180 , the transmitter controller  64  reads the transmitter identity  77  from the transmitter memory device  76 . Step  180  assumes that the transmitter controller  64  has already read and stored the selected the transmitter identity  77  from the transmitter identity selection device  74 . 
     At step  182 , the transmitter controller  64  reads the dive computer data  90  from the dive computer interface  72 . 
     At step  184 , the transmitter controller  64  waits for the alert switch  68  to be activated. 
     At step  186 , the transmitter controller  64  causes the transmitter  66  to generate the predetermined electrical transmit signal  98  responsive to the alert switch  68  being actuated, which, in turn, causes the predetermined wireless signal  36  to be generated at step  188 . 
     At step  190 , the transmitter controller  64  places the transmitter assembly  12  into a sleep mode to conserve the electrical power  102  provided by the transmitter power supply  82 , until the transmitter controller  64  is interrupted from the sleep mode in a manner that is well known in the art. 
     The transmitter controller  64  performs other method steps not shown in the flowchart  170  but described herein such as, without limitation, functions associated with the transmitter charging circuit  84 , selecting the transmitter identity  77 , and the like. Further, the method steps shown in the flowchart  170  are not limited only to the combination of steps shown and described, but may be rearranged in another combination that remains suitable for operation of the transmitter assembly  12 . 
     7. Receiver Assembly—Method 
       FIG. 7  illustrates a flowchart  192  describing steps of a method of operation performed by the first receiver assembly  16 , shown in  FIGS. 1 ,  3  and  5 , in accordance with the first preferred embodiment of the present invention. Practically, the steps of the flowchart  192  are representative of instructions or commands embodied within the computer program stored in the receiver memory device  124  upon which the receiver controller  106  operates. 
     At step  194 , the receiver controller  106  starts the method of operation. At step  194 , the receiver assembly  16  is assumed to be powered on by the receiver power on/off switch  49 , which is typically a hardware function. 
     At step  196 , the receiver controller  106  reads the voltage level of the electrical power  158  provided by the receiver power supply  132 . 
     At step  198 , the receiver controller  106  determines whether the voltage level of the electrical power  158  is acceptable to operate the receiver assembly  16 . If the determination at step  198  is negative, then the method continues to step  200 . Otherwise, if the determination at step  198  is positive, then the method continues to step  202 . 
     At step  200 , the receiver controller  106  generates the predetermined electrical alert attention signal  135  to activate the alert device  110  to indicate to the second diver  20  a low voltage condition of the receiver power supply  132 . After step  200 , the method returns to step  196 . 
     At step  202 , the receiver controller  106  determines whether the predetermined wireless signal  36  has been received. If the determination at step  202  is negative, then the method continues to step  216 . Otherwise, if the determination at step  202  is positive, then the method continues to step  204 . 
     At step  204 , the receiver controller  106  the receiver  128  generates the predetermined electrical alert attention signal  156  responsive to receiving the predetermined wireless signal  36 . 
     At step  206 , the receiver controller  106  reads the receiver identity  125  from the receiver memory device  124 . Step  206  assumes that the receiver controller  106  has already read and stored the selected the receiver identity  125  from the receiver identity selection device  122 . 
     At step  208 , the receiver controller  106  determines whether the receiver identity  125  matches the transmitter identity  77 . If the determination at step  208  is negative, then the method continues to step  216 . Otherwise, if the determination at step  208  is positive, then the method continues to step  210 . 
     At step  210 , the receiver controller  106  reads the dive computer data  160  from the dive computer interface  130 . 
     At step  212 , the receiver controller  106  reads the alert selection signal  142  from the alert selection device  118 . 
     At step  214 , the receiver controller  106  causes the predetermined alert  161  to be generated. 
     At step  216 , the receiver controller  106  places the receiver assembly  16  into a sleep mode, responsive to method steps  202 ,  208  and  214 , to conserve the electrical power  158  provided by the receiver power supply  132 , until the receiver controller  106  is interrupted from the sleep mode in a manner that is well known in the art. 
     The receiver controller  106  performs other method steps not shown in the flowchart  192  but described herein such as, without limitation, functions associated with the receiver charging circuit  134 , selecting the receiver identity  125 , and the like. Further, the method steps shown in the flowchart  192  are not limited only to the combination of steps shown and described, but may be rearranged in another combination that remains suitable for operation of the receiver assembly  16 . 
     8. Receiver Assembly Carried by the Mask 
     a. Overview 
       FIGS. 8 ,  9  and  10  generally each illustrate a front, left and top side perspective view of the receiver assembly  16 , shown in  FIGS. 1 ,  3  and  5 , carried by the second diver&#39;s mask  18 , in accordance with the first preferred embodiment of the present invention.  FIG. 8  illustrates the receiver assembly  16  attached to the second diver&#39;s mask  18  and activating the tactile alert device  116 .  FIG. 9  illustrates the receiver assembly  16  attached to the strap of the second diver&#39;s mask  18  and activating the audible alert device  114 .  FIG. 10  illustrates the receiver assembly  16  integrated with the second diver&#39;s mask  18  and activating the visual alert device  112 .  FIGS. 8 ,  9  and  10  illustrate three implementation examples and do not limit the many ways that the receiver assembly  16  may be carried by the second diver&#39;s mask  18  in a manner that permits the alert device  110  of the receiver assembly  16  to discreetly and immediately gain the attention of the second diver  20  when the second diver  20  wears the mask  18 . 
     b. Mask Design 
     The mask  18  is a diver&#39;s window to the underwater environment. Divers must wear masks because of the physical characteristics between air and water. The human eye is designed to function in air. Water, being significantly denser, conducts light differently than air does. This difference in refraction distorts underwater vision. The mask  18  allows a diver to see clearly underwater by maintaining an air space in front of the divers eyes. Numerous styles and shapes of masks are available, and the type selected is a matter of diver preference after other selection factors have been considered. The most important factors in the selection of the mask are fit and comfort. 
     The mask  18  generally includes a faceplate or lens  220 , a skirt  222 , a frame  224 , a strap  226  and strap buckles or fastenings  230 . When equalization is necessary, a nose pocket  228  is incorporated into the skirt  222 . 
     The skirt  222  may be made of silicone or neoprene. Presently, the majority of masks on the market have a skirt  222  made of silicone. Neoprene is a synthetic material derived from natural gum latex. Carbon is generally added to neoprene as both a coloring agent and as a block against ultraviolet (UV) radiation. The carbon is what makes most neoprene black in color when color dyes are not used. Neoprene breaks down with sufficient exposure to UV or ozone. Silicone is not a rubber but a synthetic compound derived from silicone. Silicone is naturally translucent, virtually impervious to damage by ozone or ultraviolet (UV) rays, tends not to deteriorate over time, is hypoallergenic, is soft, and is aesthetically pleasing. Skirts made of silicone are more expensive than skirts made of neoprene, but the advantages of the silicone typically outweigh the differences in price. Preferably, the skirt will gradually thin as it approaches the edge of the skirt. This makes the edge of the skirt more flexible when it comes in contact with the diver&#39;s face, thus ensuring a better fit. 
     Nose or finger pockets are typically integrally formed with the skirt. The nose pocket  228  is a nose-shaped cavity located inside of the mask  18  and extending outside of the mask  18  to receive a diver&#39;s nose when the diver wears the mask  18 . Finger pockets (not shown) are two cavities located outside of the mask  18  and extending inside of the mask  18 , one on each side of the diver&#39;s nose position, to receiver a diver&#39;s finger or thumb. The finger pockets provide a convenient way for a diver to pinch off their nostrils through the skirt  222  while equalizing pressure in their ears. Typically, a diver pinches off his nostril using his thumb and index finger of one hand or the index fingers of both hands. 
     The strap  226  secures and positions the mask  18  against the diver&#39;s head. Typically, masks have quick release strap buckles or fastenings  230  one or both sides of the mask  18  to permit a diver to quickly change the length of the strap thereby ensuring a proper fit. 
     The lens  220 , typically made of tempered glass, resist scratches and, to a degree, breakage. If broken, however, tempered glass will generally crumble into a number of small, dull pieces that are less dangerous than large, sharp pieces. Diver&#39;s with impaired vision may be able to see properly by purchasing masks with lenses that are preground to the diver&#39;s approximate prescription, having an optician bond lenses with the diver&#39;s precise prescription to the inside of the lens  220 , or by simply wearing contact lenses in conjunction with an unaltered mask. 
     The frame  224  joins the lens  220  and the skirt  222  together and is typically made of a non-corrosive material. Preferably, the skirt  222  is integrally formed with a gasket as a unitary unit that provides a waterproof seal for the lens  220 . 
     A wraparound mask (not shown) has two additional panes of lens disposed on each side of the mask to improve a diver&#39;s peripheral vision. 
     c. Receiver Assembly Attached to the Frame of the Mask 
       FIG. 8  illustrates a front, left and top side perspective view of the first receiver assembly  16 , shown in  FIGS. 1 ,  3  and  5 , attached to a first mask  18 , in accordance with the first preferred embodiment of the present invention. In  FIG. 8 , the receiver assembly  16  is attached to the mask  18  as shown and described in FIG.  3 . 
     Generally, the receiver assembly  16  may be attached to the outside or the inside of the mask  18 , on the frame  224  or the lens  220 . Typically, the receiver assembly  16  is attached to the frame  224 , the lens  220  or the strap  226 . 
     The receiver assembly  16  may be further tethered to the mask  18 , such as the strap  226 , by a lanyard  227  to provide a redundant attachment mechanism in case the receiver assembly  16  separates from the adhesive or the bracket  52 . Hence, the lanyard  227  advantageously prevents the receiver assembly  16  from becoming lost. 
     The receiver assembly  16  in  FIG. 8  is implemented with the tactile alert device  116  that vibrates the mask  18 , as shown by the vibrating alert  166 , responsive to the receiver assembly  16  receiving the predetermined wireless signal  36 . The vibrating alert  166  is sufficiently strong enough to be noticeable to the diver but not so strong as to break the air seal of the skirt  222  against the diver&#39;s face. 
     d. Receiver Assembly Attached to the Strap of the Mask 
       FIG. 9  illustrates a front, top and left side perspective view of the first receiver assembly, shown in  FIGS. 1 ,  3  and  5 , attached to a strap of the first mask, in accordance with the first preferred embodiment of the present invention. In  FIG. 9 , the receiver assembly  16  is attached to the strap  226  of the mask  18  using one or more bands  229 . The receiver assembly  16  is attached to the outside of the strap  226  to provide a comfortable fit of the strap  226  against the diver&#39;s head. The receiver assembly  16  is positioned on the strap  226  so that the receiver assembly  16  is near the diver&#39;s ear. 
     The receiver assembly  16  in  FIG. 9  is implemented with the audible alert device  114  that generates an audible alert  164  that the diver can hear responsive to the receiver assembly  16  receiving the predetermined wireless signal  36 . The audible alert  164  is sufficiently strong enough to be noticeable to the diver but not so strong as to disturb other divers or underwater wildlife in the vicinity. The receiver assembly  16  may be positioned so that the audible alert device  114  directs the audible alert  164  towards the diver&#39;s ear or away from the diver&#39;s ear, as shown in FIG.  9 . 
     c. Receiver Assembly Integrally Formed with the Frame of the Mask 
       FIG. 10  illustrates a front, top and left side perspective view of the first receiver assembly  16 , shown in  FIGS. 1 ,  3  and  5 , integrally formed with the frame  224  of the mask  18 , in accordance with the first preferred embodiment of the present invention. The receiver assembly  16  is disposed on the center of the top surface of the frame  224  of the mask  18 . The frame  224  is formed to extend above the mask  18  to create a cavity of sufficient volume to hold the electrical components and circuitry associated with the receiver assembly  16 . By extending the frame  224  above the mask  18 , the diver&#39;s view through the lens  220  is not obstructed. 
     The receiver assembly  16  in  FIG. 10  is implemented with the visual alert device  112  that generates an visual alert  162 , via an optical fiber light guide  221 , disposed along a part of the perimeter of the inside of the lens  220 , that the diver can see responsive to the receiver assembly  16  receiving the predetermined wireless signal  36 . The visual alert  162  is sufficiently strong enough to be noticeable to the diver but not so strong as to disturb other divers or underwater wildlife in the vicinity. 
     C. Underwater Alert System of the Second Preferred Embodiment 
       FIG. 11  illustrates a schematic diagram of a transceiver assembly  232 , in accordance with a second preferred embodiment of the present invention. The transceiver assembly  232  generally includes a transceiver controller  234 , a transceiver power supply  236 , a transceiver charging circuit interface  238 , a transceiving element  240 , a transceiver identity selection device  242 , a transceiver memory device  244 , a transceiver dive computer interface  246 , a transceiver housing  248 , a transceiver power on/off switch  250 , the alert switch  68 , the alert device  110 , the transmitter  66 , the transmitter amplifier  78 , the receiver  128 , the receiver amplifier  108 , the alert selection device  118 . The alert device  110  further includes at least one of the visual alert device  112 , the audible alert device  114  and the tactile alert device  116 . The transceiver memory device  244  includes a transceiver identity  252 . 
     Generally, the transceiver assembly  232  is a combination of a transmitter assembly  12 , as shown in  FIG. 4 , and a receiver assembly  16 , as shown in FIG.  5 . Hence, the transceiver assembly  232  has the function of both the transmitter assembly  12  and the receiver assembly  16 . The alert switch  68 , the transmitter  66  and the transmitter amplifier  78 , are the same as shown and described for the transmitter assembly  12  of  FIGS. 4 and 6 . The receiver  128 , the receiver amplifier  108 , the alert selection device  118 , and the alert device  110  are the same as shown and described for the receiver assembly  16  of  FIGS. 5 and 7 . The transceiver controller  234 , the transceiver power supply  236 , the transceiver charging circuit  238 , the transceiving element  240 , the transceiver identity selection device  242 , the transceiver memory device  244 , the transceiver dive computer interface  246 , the transceiver housing  248 , and the transceiver power on/off switch  250  are unique to the transceiver assembly  232  but represent combinations or substitutes of analogous elements in the transmitter assembly  12  of  FIGS. 4 and 6  and in the receiver assembly  16  of  FIGS. 5 and 7 . For example, the transceiver controller  234  represents a combination of the functions of the transmitter controller  64  and the receiver controller  106 . The transceiver power supply  236  represents a combination or substitution of the functions of transmitter power supply  82  and the receiver power supply  132 . The transceiver charging circuit  238  represents a combination or substitution of the functions of transmitter charging circuit  84  and the receiver charging circuit  134 . The transceiving element  240  represents a combination or substitution of the functions of transmitting element  80  and the receiving element  126 . The transceiver identity selection device  242  represents a combination or substitution of the functions of transmitter identity selection device  74  and the receiver identity selection device  122 . The transceiver memory device  244  represents a combination of the functions of transmitter memory device  76  and the receiver memory device  124 . The transceiver dive computer interface  246  represents a combination of the functions of transmitter dive computer interface  72  and the receiver dive computer interface  130 . The transceiver housing  248  represents a combination of the functions of transmitter housing  38  and the receiver housing  48 . The transceiver power on/off switch  250  represents a combination or substitution of the functions of transmitter power on/off switch  33  and the receiver power on/off switch  49 . 
     The transceiver assembly  232  advantageously permits a diver to both send and receive the predetermined wireless communication signal  36 . In operation, the transceiver assembly  232  provides two-way communications, as distinguished from the separate combination of the transmitter assembly  12  and receiver assembly  16  that provides one-way communication. In application, the first diver  14  carries a first transceiver assembly  232 , preferably on the first diver&#39;s mask, and the second diver  20  carries a second transceiver assembly (not shown), preferably on the second diver&#39;s mask, to permit both divers to both send and receive alert signals. Of course, two divers may effectively obtain two-way communications using the separate combination of the transmitter assembly  12  and receiver assembly  16  when two sets of the combination are used. In this example, the first diver  14  carries both the first transmitter assembly  12  and a second receiver assembly (not shown), and the second diver carries both a second transmitter assembly (not shown) and the first receiver assembly  16 . The first transmitter assembly  12  and the second transmitter assembly are preferably carried on the first diver&#39;s wrist and the second diver&#39;s wrist, respectively. The first receiver assembly  16  and the second receiver assembly are preferably carried on the second diver&#39;s mask  18  and the first diver&#39;s mask, respectively. 
       FIG. 12  illustrates a front, top and left side perspective view of the transceiver assembly  232 , as shown in  FIG. 11 , attached to a frame  224  of a mask  18 , in accordance with the second preferred embodiment of the present invention. Although the transceiver assembly  232  is preferably attached to the top side of the frame  224  using the carrier  50  with adhesive, as shown and described with reference to  FIG. 3 , any attachment mechanism and any location on the mask, as shown or described herein may alternatively be used. 
     The pushbutton  68  has a location and size that permits the diver to easily find and press the pushbutton  68  with his finger or palm while wearing the mask  18 . Preferably, the pushbutton  68  is located on the left side of the transceiver assembly  232 , but may alternatively be located on the top side or front side of the transceiver assembly  232 . 
     An overhang or plenum  233  is attached to the transceiver housing  248  of the transceiver assembly  232 . The overhang  233  extends away from the front side of the mask  18  and then down along the front side of the mask  18  so that a portion of the overhand  233  is positioned in front of the lens  220  of the mask  18 . The visual alert device  112 , such as an LED, is positioned at a distal end of the overhang  233  in such a manner that a diver can view the visual alert device  112  through the lens  220  of the mask  18  when the diver is wearing the mask  18 . Hence,  FIG. 12  provides an example of the visual alert device  112  being used as the alert device  110  on the mask  18 . 
     Alternatively, the transceiver assembly  232  may be integrally formed with the mask  18  as a single unitary unit in an analogous manner as shown and described with reference to FIG.  10 . 
     D. Underwater Alert System of the Third Preferred Embodiment 
       FIG. 13  illustrates a schematic diagram of an dive computer system  251  including the first transceiver assembly  232 , electrically coupled to a first dive computer  252  carried by the first diver  14 , and a second transceiver assembly  254 , electrically coupled to a second dive computer  256  carried by the second diver  20 , in accordance with a third preferred embodiment of the present invention. The dive computer system  251  in  FIG. 13  generally includes the first transceiver assembly  232 , a first receiver  258 , the first dive computer  252 , a first display  253 , a first housing  260 , a second transceiver assembly  254 , a second receiver  262 , the second dive computer  256 , a second display  255 , and a second housing  264 . The first diver  14  carries the first transceiver assembly  232 , the first receiver  258 , the first dive computer  252 , the first display  253 , and the first housing  260 . The second diver  20  carries the second transceiver assembly  254 , the second receiver  262 , the second dive computer  256 , the second display  255 , and the second housing  264 . 
     The first transceiver assembly  232  is electrically coupled to the first dive computer  252  to permit dive computer data, associated with the first diver  14 , to be transmitted by the first transceiver assembly  232  as the predetermined wireless signal  36  to the second diver  20 , and to permit dive computer data, associated with the second diver  20 , to be received by the first transceiver assembly  232  as the predetermined wireless signal  36  from the second diver  20 . 
     The first display  253  and the second display each display dive computer data associated with the first diver  14  and the second diver  20 . In  FIG. 13 , the dive computer data for the first diver matches on each of the first display  253  and the second display  255 , and the dive computer data for the second diver matches on each of the first display  253  and the second display  255 . Hence, a point of reference for the dive computer data is from the point of view of one diver. Alternatively, the point of reference for the dive computer data may be from the point of view of each diver. In this alternative case, the dive computer data for the first diver on the first display  253  matches the dive computer data for the second diver on the second display  255 , and the dive computer data for the second diver on the first display  253  matches the dive computer data for the first diver on the second display  255 . 
     Each one of the first display  253  and the second display  255  may operate in a variety of ways depending on various engineering factors including, without limitation, the size of the display, the data to be displayed, etc. For example, the display may be large enough to display all of the dive computer data associated with both the first diver  14  and the second diver  20 , as shown in FIG.  13 . Alternatively, the display may be configured to display the dive computer data of only one diver at a time. Further, alternatively, the display may be configured to display portions of the dive computer data at a time. Various types, sizes, control, etc. of displays are well known in the art. The first display  253  may be a separate device or may be integrated with either the dive computer  252  or the first transceiver assembly  232 . 
     Hence, the first display  253  displays dive computer data related not only to the first diver  14 , but also related to the second diver  20 . The mutual sharing of dive computer data between buddy divers increases the safety and the enjoyment of the dive because the divers can electronically monitor various dive conditions related to the other diver. Therefore, the divers no longer need to rely on conventional communication techniques such as hand signals, or even alerts or under water voice communications to relay dive computer related information between each other. Further, with each diver monitoring the status of the other diver&#39;s dive computer data, one diver may become aware of a critical situation, such as a low air supply level for the other diver, which the other diver does not realize. 
     The dive computer data that is shared between divers may be related to the diver, the diver&#39;s equipment and the diver&#39;s environment. The dive computer data includes, without limitation, dive table time limits, dive time duration, depth limits, air supply limits, direction, distance, water temperature, assent rates, heart rate, breathing rate, and the like. Alternatively, an alarm, similar to the alert device  110 , carried with the dive computer, the transceiver, or the display may be activated if the dive computer data is an undesirable, predetermined value, such as being outside a predetermined range of permitted dive computer data. 
     The first transceiver  232  and the second transceiver  254  communicate over a long-range wireless communication link. The link has a long range in that is long enough to relay a signal between a transmitter and a receiver, both being located on different divers separated by a distance. Hence, the long-range wireless communication link may be described as being not personal to one diver, but as being personal between two divers. The long-range wireless communication link preferably has a range of 50 to 100 meters, but may be any distance. 
     The first receiver  258  receives a signal  270  from a first transmitter (shown in FIG.  14 ), worn on another part of the first diver  14 , and relays data carried by the signal  270  to the first dive computer  252 . The transmitter is preferably coupled to the first diver&#39;s air tank and transmits a signal representative of the air supply level in the air tank. The first receiver  258  and the first transmitter communicate over a short-range wireless communication link. The link has a short range in that is long enough to relay a signal between a transmitter and a receiver, both being located on the same diver. Hence, the short-range wireless communication link may be described as being personal to the diver. The short-range wireless communication link preferably has a range of 3 meters, but may be any distance. 
     The first transceiver  232 , the first dive computer  252 , the first display  253  and the first receiver  258  may be separate modules carried by separate housings and electrically coupled to each other, or may be integrated as a single unit carried within a single housing. Any combination of modules or integration may be implemented among the elements depending on various engineering and business factors. Further, when the modules are separate, they may be carried on different parts of the diver or the diver&#39;s equipment. For example, the first dive computer  252 , the first transceiver  232 , and the first receiver  258  may be carried on the first diver&#39;s wrist, but the first display  253  may be carried on the first diver&#39;s mask. 
     The second transceiver  234 , the second dive computer  256 , the second display  255  and the second receiver  262  are constructed and operate in an analogous manner as shown and described with reference to the first transceiver  232 , the first dive computer  252 , the first display  253  and the first receiver  258 . In other words, the first group of elements is a duplicate of the second group of elements, and together they comprise the dive computer system  251  of the third preferred embodiment of the present invention. 
       FIG. 14  illustrates the dive computer system  251 , shown in  FIG. 13 , carried by the first diver  14  and the second diver  20 , in accordance with the third preferred embodiment of the present invention. The first transceiver  232 , the first dive computer  252 , the first display  253  and the first receiver  258  are carried in the first housing  260  on the first diver&#39;s wrist or forearm. The second transceiver  254 , the second dive computer  256 , the second display  255  and the second receiver  262  are carried in the second housing  264  on the second  274 . A low pressure hose, carried by the second diver&#39;s air tank, carries the second transmitter  276 . 
     E. Users of the Underwater Alert System 
     The underwater alert system  10  of the first, second and third preferred embodiments of the present invention, as shown and described herein, are preferably used by scuba divers, as explained herein above. The underwater alert system  10  of the first and second preferred embodiments of the present invention, as shown and described herein, may also be used by skin divers and swimmers. Although skin divers and swimmers typically do not have a need for using the third preferred embodiment of the present invention because they typically do not carry or use dive computers, they may also use the third preferred embodiment of the present invention, if desired. 
     Skin divers, otherwise known as snorkel divers, typically use a mask, fins and a snorkel as they float on the surface of the water, such as in a pool, lake or ocean, or make shallow dives in the water, without using a compressed air supply. Skin divers preferably carry the receiver assembly  16  or the transceiver assembly  232  on the skin diver&#39;s mask. 
     Swimmers sometimes use a mask, otherwise called goggles, while swimming in water, such as in a pool, lake or ocean, to keep the water away from their eyes. Swimmers preferably carry the receiver assembly  16  or the transceiver assembly  232  on the swimmer&#39;s goggles. 
     F. Applications of the Underwater Alert System 
     The underwater alert system  10  of the first, second and third preferred embodiments of the present invention, as shown and described herein, are preferably used in water-based applications, such as scuba diving, snorkeling and swimming. Water-based applications include, without limitation, applications such as sport, training, commercial, military, scientific, search and recovery, professional underwater photography, and movie making. 
     However, the first, second and third preferred embodiments of the present invention, as shown and described herein, may also be applied in an analogous manner to applications above water, such as on land. In this case, other types of eyewear, rather than the underwater mask, carry the receiver assembly  16  or the transceiver assembly  232 . The other types of eyewear include, without limitation, sun glasses, prescription eye glasses, safety glasses, goggles, and the like. Applications on land include, without limitation, recreational activities such as motorcycling, bicycling, hiking, hunting, running, skiing, canoeing, kayaking, climbing, fishing and walking. 
     G. Commercial Sales of the Underwater Alert System 
     The underwater alert system  10  of the first, second and third preferred embodiments of the present invention, as shown and described herein, may be sold commercially in a variety of ways depending on factors related to engineering, business and customer preference. Several examples, without limitation, of how the underwater alert system  10  may be sold are described as follows. 
     In the first preferred embodiment of the present invention, the transmitter assembly  12  and the receiver assembly  16  are sold as a set in a single package, along with an appropriate attachment mechanism. If two divers desire two-way communication, then two sets are purchased. However, the transmitter assembly  12  and the receiver assembly  16  may also be sold separately, as well, to accommodate customer applications, such as the one transmitter assembly  12  to multiple receiver assemblies or the multiple transmitter assemblies to the one receiver assembly  16 , as described herein. Further, the attachment mechanism may also be sold separately, as well, or just with the associate receiver assembly in the same package. 
     In the second preferred embodiment of the present invention, the first transceiver  232  and the second transceiver  254  are preferably sold as a set in a single package, along with appropriate corresponding attachment mechanisms. Alternatively, the transceivers may be sold separately to accommodate various customer applications. 
     In both the first and the second preferred embodiments of the present invention, the receiver assembly  16  or the transceiver assembly  232  may be integrally formed with the mask, as shown and described herein. In this case, a mask integrally formed with the receiver assembly  16  or the first transceiver assembly  232  may be sold either separately or in combination with the transmitter assembly  12  or the second transceiver assembly  254 , respectively, in a single package. 
     In the third preferred embodiment of the present invention, the first transceiver  232  is integrated with the first dive computer  252 , the first display device  253  and the first receiver  258  in a single housing  260 . Alternatively, the first dive computer  252  and the first display device  253  may be integrated into a single housing and a second housing may carry the first transceiver  232 , with or without the first receiver  258 . 
     Further, a design of various components, systems or assemblies described herein may be duplicated among the various embodiments to achieve design and manufacturing economies of scale. For example, a transceiver designed for the second preferred embodiment of the present invention may also be used for the third preferred embodiment of the present invention. A single manufacturer having lines of diving equipment, including masks and dive computers, may achieve this economy of scale alone. Alternatively, different manufacturers having different lines of diving equipment, including one manufacturer making masks and another manufacturer making dive computers, may achieve this economy of scale together. 
     H. Electronic Integration of the Underwater Alert System 
     In the first, second and third preferred embodiments of the present invention, as shown and described herein, the various electrical elements may be made from discrete electrical components, in an integrated circuit or any combination thereof depending on such engineering design considerations such as cost, complexity, performance, reliability, size, weight, etc., as are well known in the art. 
     I. Summary of the Detailed Description of the Preferred Embodiments 
     In the first preferred embodiment, the underwater alert system  10  comprises the transmitter assembly  12 , the receiver assembly  16 , and the mask  18 . The transmitter assembly  12 , carried by the first diver  14 , has the waterproof transmitter housing  38  for carrying the alert switch  68 , the transmitter  66 , and the transmitting element  80 . The alert switch  68  generates the electrical alert actuation signal  86  responsive to the alert switch  68  being actuated, either manually by the first diver  14  or automatically by the first diver&#39;s equipment. The transmitter  66  generates the predetermined electrical transmit signal  98  responsive to receiving the electrical alert actuation signal  86 . The transmitting element  80  generates the predetermined wireless signal  36  responsive to receiving the predetermined electrical transmit signal  98 . The receiver assembly  16 , carried by the second diver  20 , has the waterproof receiver housing  48  for carrying the receiving element  126 , the receiver  108 , and the alert device  110 . The receiving element  126  generates the electrical receive signal  152  responsive to receiving the predetermined wireless signal  36 . The receiver  108  generates the predetermined electrical alert attention signal  154  responsive to receiving the electrical receive signal  152 . The alert device  110 , such as the visual  112 , the audible  114  or the tactile  116  alert device, generates the predetermined alert  161 , such as light  162 , sound  164  or vibration  166 , respectively, responsive to receiving the predetermined electrical alert attention signal  154 . The mask  18  carries the first receiver assembly  16 , either separate from or integral with the first mask  18 , in the way that permits the predetermined alert  161  to gain the attention of the second diver  20  when the mask  18  is worn on the second diver&#39;s head. Preferably, the transmitter assembly  12  and the receiver assembly  16  share the common electrical identity  77 ,  125 , such as the frequency channel, the address or the code, to provide discreet communications between divers. 
     In the second preferred embodiment, the underwater alert system  10  includes the first transceiver assembly  232 , carried by, integrally to or attached to, the first diver&#39;s mask, and the second transceiver assembly  254 , carried by, integrally to or attached to, the second diver&#39;s mask. 
     In the third preferred embodiment, the underwater alert system  10  includes, the transmitter assembly  12  or the first transceiver assembly  232  electrically coupled to the first diver&#39;s dive computer  252  to permit dive computer data, associated with the first diver  14 , or the alarm associated with the dive computer data to be transmitted to and received by the receiver assembly  16  or the second transceiver assembly  254 , respectively, carried by the second diver  20 . 
     J. Expanded Embodiments of the Underwater Alert System 
     Hence, while the present invention has been described with reference to various illustrative embodiments thereof, the present invention is not intended that the invention be limited to these specific embodiments. Those skilled in the art will recognize that variations; modifications and combinations of the disclosed subject matter can be made without departing from the spirit and scope of the invention as set forth in the appended claims.