Abstract:
A pulse position modulated radio remote control system using distributed solid state data processing that includes a remote-control unit and a master-control unit, each unit having an associated transceiver so that information in the form of radio signals can be exchanged bidirectionally between the two units. The master-control unit controls operating functions of a pool or spa on command from the remote-control unit. The master-control unit also monitors operating conditions of the pool or spa and sends information about those conditions of the pool or spa and sends information about those conditions to the remote-control unit on command from the remote-control unit. A display on the remote-control unit allows a user to determine the status of various operating parameters of the pool or spa, such as water temperature. The remote-control unit also has a keypad that allows the user to input signals to be sent to the master-control unit.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention pertains to the field of remote-control devices, and more particularly to hand-held radio remote control units for pools and spas.  
           [0003]    2. Background  
           [0004]    A spa generally includes the following components: (1) a time clock; (2) a circulation pump; (3) a heater; (4) a thermostat; (5) a high- temperature limit device for safety; (6) an air blower or bubbler; (7) a light; and (8) an additional pump for jets used for hydro-massage. Spa owners typically do not keep their spas heated twenty-four hours per day, choosing instead to heat the spa only for use so as to minimize energy costs. Hence, the heater is equipped with an on/off switch and an accompanying thermostat. The time clock serves to operate the circulation pump for a few hours each day to keep the spa clean.  
           [0005]    A conventional method by which an owner can prepare the spa for use requires the steps of going to the equipment area and throwing a toggle switch to the “on” position to bypass the timeclock, which turns on the pump. The owner must then switch the heater to the “on” position and adjust the thermostat to the desired temperature. There follows a waiting period for an unspecified amount of time for the spa to reach the desired temperature. If the water is unheated at the start of the process and the ambient temperature is low, the time required to heat the water can be quite long.  
           [0006]    Periodically, the owner must either go to the heater to determine whether the heater is still on, i.e., that the water in the spa is not yet heated to the thermost at setting, or go to a fixed thermometer to check the temperature. To avoid having to go outside to the spa and the heater, the owner typically installs a hard-wired digital thermometer and thermostat control in a display box that is mounted to a wall inside the home. Such an instrument, however, is immobile, so that it cannot be carried around to check the temperature or give the status of any of the spa components. This type of unit is also relatively expensive. The owner would generally not have the option of installing several such devices throughout the home for more convenient monitoring. Additionally, such units are difficult to secure to prevent access by children. Moreover, a hard-wired device mandates that a conduit be run underground from an interior wall of the home to the outdoor spa. If added after the home is constructed, this may involve trenching and cutting through concrete walls of the home, requiring extensive and costly materials and labor in addition to inspections for compliance with building codes.  
           [0007]    For the foregoing reasons it would be desirable for spa owners to use a remote-control unit to turn the spa on or off and to receive information on water temperature and working status of spa components. However, conventional remote-control devices for pools or spas do not monitor operating status. Thus, there is a need for a relatively inexpensive, hand-held device that enables a user to communicate bidirectionally with the spa from anywhere in the home so as to both control necessary operating functions and obtain status information regarding operating parameters.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention is a unique and major advancement in the field of wireless remote control units for pools and spas. It utilizes Pulse Position Modulation (“PPM”) and distributed solid state data processing to permit the half duplex, simultaneous transmission of multiple sensing and control signals on a single frequency. This permits bi-directional transmission of multiple control signals and data through a single transceiver at each site. By using PPM the allowable regulatory power levels are 17 dB higher, permitting a longer range and a reduction in interference susceptibility. PPM and distributed data processing permit using identical multiple data groups to assure accurate data transmission through the most severe interference. The data processing system includes address switches, in both the hand held remote unit and the master control unit, that prevent the system from responding to signals that do not have the proper address code. This permits the use of multiple systems in close proximity without interfering with each other. The system is therefore more reliable and lower in cost than existing devices.  
           [0009]    The present invention is therefore directed to a relatively inexpensive, hand-held device that enables a user to communicate bidirectionally with the spa from anywhere in or near the home so as to both control necessary operating functions and obtain status information regarding operating parameters. To this end a PPM radio remote control has a remote-control unit and a master-control unit; and each unit has an associated transceiver. Preferably, the remote-control unit and the master-control unit can exchange information with each other bidirectionally via the transceivers. Advantageously, the remote-control unit includes a display from which a user can obtain status information received from the master-control unit on the working components of a pool or spa. Most desirably, the remote-control unit has a keypad with which the user can input control information for the master-control unit.  
           [0010]    Accordingly, it is an object of the present invention to provide a remote-control device that can be used to turn spa equipment on or off reliably from a distance as well as to determine the water temperature in the spa. These and other objects, features, aspects, and advantages of the present invention will become better understood with reference to the following description and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a block diagram of a remote-operated control system for a pool or spa.  
         [0012]    [0012]FIG. 2A is a schematic circuit diagram of the pulse position modulated transceiver.  
         [0013]    [0013]FIG. 2B is a schematic circuit diagram of encoder, keypad, and power circuitry in a remote-control unit in the system of FIG. 1. FIG. 2B is a schematic circuit diagram of decoder, address-switch, and display circuitry in a remote-control unit in the system of FIG. 1.  
         [0014]    [0014]FIG. 3A is a schematic circuit diagram of decoder, encoder, address-switch, and processor circuitry in a master-control unit in the system of FIG. 1. FIG. 3B is a schematic circuit diagram of control logic and relays in a master-control unit in the system of FIG. 1.  
         [0015]    [0015]FIG. 4 is a perspective view of a remote-control unit in the system of FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Turning in detail to the drawings, FIG. 1 illustrates a remote-operated control system  10  for a pool or spa. In a preferred embodiment, the system  10  comprises two units: a remote-control unit  12  and a master-control unit  14 .  
         [0017]    The remote-control unit  12  of FIG. 1 includes an associated transceiver  16 , which is preferably mounted on a printed circuit board of the remote-control unit  12 . In a preferred embodiment, the remote-control unit  12  also includes a processor which includes an encoder and a decoder associated with the transceiver  16 . The remote control also includes address switches  22 , a keypad  24 , and LCD display  26 , and a battery  28 .  
         [0018]    In the remote-control unit  12  of FIG. 1, which in a preferred embodiment is hand-held, the battery  28  serves as a power source. The keypad  24  is connected to send electrical signals to the processor  18 , which receives addressing in the form of electrical signals from the address switches  22 . The encoder is connected to encode the encoded signal from the keypad and send the encoded signal to the transceiver  16 . The processor&#39;s decoder, which likewise receives addressing in the form of electrical signals from the address switches  22 , is connected to decode electrical signals received from the transceiver  16  and to send the decoded signals to the LCD display  26 .  
         [0019]    The master-control unit  14  of FIG. 1 likewise includes an associated PPM transceiver  30 . In a preferred embodiment, the transceiver  30  is identical to the transceiver  16  that is associated with the remote-control unit  12 . Preferably, the transceiver  30  is mounted externally to a wall of the master-control unit  14 . The preferred master-control unit  14  also contains a processor  36  which includes an encoder  32  and a decoder  34  associated the transceiver  30 , and a processing unit. The master control unit also includes address switches  38 , a temperature sensor  40 , a safety hi-limit circuit  42 , relay control logic  44  and an associated fireman&#39;s switch  46 , a power supply  48 , and eight relays  50 ,  52 ,  54 ,  56 ,  58 ,  60 ,  62 ,  64 .  
         [0020]    In the master-control unit of FIG. 1, the encoder and the decoder are addressed with electrical signals sent from the address switches  38 . The decoder is connected to receive and decode electrical command signals from the transceiver  30  and to send the decoded signals to the processing unit. The processor  36  is connected to send the command signals to the relay control logic  44 . The encoder is connected to encode status signals received from the processing unit and send the encoded signals to the transceiver  30 . The status signals that the processor sends to the encoder carry temperature information that the processor  36  receives from the temperature sensor  40 . In a preferred embodiment, the temperature sensor  40  comprises two thermistors, one used to sense water temperature and the other serving to sense when water temperature has exceeded a preset ceiling level, or hi-limit. Preferably, the hi-limit is 112 degrees Fahrenheit, but alternatively it can be set to 116 degrees Fahrenheit. The relay control logic  44  controls the safety hi-limit circuit  42 , which senses when water temperature has reached a predetermined ceiling level and shuts off the water heater by sending an electrical signal to the on/off heater relay  50 . The on/off jets relay  52 , on/off pump relay  54 , on/off light relay  56 , on/off aux  1  relay  58 , on/off aux  2  relay  60 , on/off aux  3  relay  62 , and on/off ozonator relay  64  are individually connected to receive electrical control signals from the relay control logic  44 .  
         [0021]    With reference to FIG. 2B, a schematic diagram of circuitry in a preferred remote-control unit  12  is shown. FIG. 2B represents a preferred design for the remote-control unit  12  of FIG. 1 and would be readily understood by one of ordinary skill in the art. Moreover, one of skill in the art would also understand that many different designs for the remote-control unit  12  of FIG. 1, are possible.  
         [0022]    [0022]FIG. 2B depicts an encoder and related electronics. Command signals manually input to the keypad  24  of FIG. 1 are sent to a buffer that stores the data. From the buffer  66  the data signals are sent to the encoder. The encoder is addressed by a switch  22 . A battery  28  supplies power to the remote control unit  12 . A pair of transistors within the processor serves as a sleep-mode circuit to cut off the Vcc power supply in the absence of user activity for a sustained time period. A third transistor ensures that no erroneous transmissions are generated during sleep mode. Also included is a timer, which sends a continuing message while the user depresses a keypad switch to switch back and forth between transmit and receive modes. A regulator  78  supplies Vcc (voltage) to the remote-control unit  12 . A transceiver information element  80  transmits data from a TXD output of the encoder to the transceiver  16  of FIG. 1 and receives data from the transceiver  16  of FIG. 1. Data received from the transceiver  16  of FIG. 1 is sent to a decoder.  
         [0023]    In FIG. 2B, a decoder and display electronics are also shown. The decoder receives the data at an RXD input. An address switch  22  provides addresses for the decoder (as well as for the encoder). The decoded data bits are sent to the processing unit.  
         [0024]    Referring now to FIGS.  3 A- 3 B, a schematic diagram of circuitry in a preferred master-control unit  14  is depicted. FIGS.  3 A- 3 B represent a preferred design for the master-control unit  14  of FIG. 1 and would be readily understood by one of ordinary skill in the art. Moreover, one of skill in the art would also understand that many different designs for the master-control unit  14  of FIG. 1 are possible.  
         [0025]    [0025]FIG. 3A illustrates a processor  36 , an address switch  38 , and related electronics. In FIG. 3A a transceiver information element  102  receives command data from the transceiver  30  of FIG. 1 or sends status data from a TXD output of the processor&#39;s encoder to the transceiver  30  of FIG. 1. The transceiver information element  102  is also connected to send command data from the transceiver  30  to an RXD input of the processors decoder. In a preferred embodiment, a second transceiver information element  104  can be included with the transceiver information element  102 . Outputs form the elements  102 ,  104  are OR&#39;d such that a single RXD signal represents the OR result of the two outputs form the elements  102 ,  104 . The decoder and encoder are connected to address switches  38 , which in a preferred embodiment must address the decoder and encoder with the same eight-bit address used by the address switch  22  of FIG. 2B.  
         [0026]    The decoder sends parallel bits of decoded command data through a parallel resistor block  106  to a data bus. The data bus is connected to carry the command data signals to the processor  36  and then transport the resultant command signals generated by the processor  36  to a storage buffer, which holds the command signals before sending them to the relay control logic  44  of FIG. 1. The processor  36  received at an A/D input a water-temperature status signal from two thermistors (i.e., the temperature sensor  40 , of FIG. 1). The processor  36  sends status data signals (including the status signals received at the A/D input) to the encoder  32 , which as stated above sends a resultant status signal from the TXD output to the transceiver information elements  102 ,  104 . Additionally, the processor  36  outputs a heat-enabled command signal. The processor  36  is powered by a regulator  110  (FIG. 3B).  
         [0027]    [0027]FIG. 3B shows control logic for nine relays  50 ,  52 ,  54 ,  58 ,  64 ,  112 ,  114 ,  116 ,  118 . The control logic is a configuration of digital gates that forces one or more conditions to be satisfied in order for each relay  50 ,  52 ,  54 ,  58 ,  64 ,  112 ,  114 ,  116 ,  118  to turn on. Also, an over-temp (i.e., emergency shutdown) signal from the safety hi-limit circuit  42  prevents any of the relays  50 ,  52 ,  54 ,  58 ,  64 ,  112 ,  114  from being on.  
         [0028]    Thus, for the low pump (i.e., filter pump) relay  54  to turn on, a heating command from the processor  36  must be present and there must be neither a jets command not an over-temp signal present. Alternatively, and also only if neither a jets command nor an over-temp signal is present, a pump-delay signal from the fireman&#39;s switch  46  of FIG. 3E will activate the filter pump relay  54 . Finally, and again in the absence of both a jets command and an over-temp signal, the filter pump relay  54  can also be turned on manually from the remote time clock.  
         [0029]    The high pump (i.e., jets) relay  52  turns on in the absence of an over-temp signal when a jets command is received from the processor  36 . Likewise, the blower (i.e., aux  1 ) relay  58  turns on in the absence of an over-temp signal when an aux-1 command is received from the processor  36 . The ozonator relay  64  turns on only if either the pump filter relay  54  or the jets relay  52  is on. The heater relay  50  turns on when the heating command is present and the over-temp signal is not present. In a preferred embodiment, an alternate heater relay  112 , is provided for larger spas or pools. The heater relay  112  has the same control logic as the heater relay  50 . A hi-limit relay  114  is also provided in a preferred embodiment. The hi-limit relay  114  is always on unless the over-temp signal is present. Preferably, a pool-valve relay  116  is provided, turning on in the presence of a heat-enable command signal. Advantageously, a spa-valve relay  118  is also provided to turn on if a heat-enable command is present. Neither the pool-valve relay  116  nor the spa-valve relay  118  require absence of the over-temp signal in order to be activated.  
         [0030]    Control logic is also depicted for three other relays  56 ,  60 ,  62 . As in FIG. 3B, the control logic is a configuration of digital gates that forces one or more conditions to be satisfied in order for each relay  56 ,  60 ,  62  to turn on. However, all of the relays  56 ,  60 ,  62  remain enabled regardless of whether an over-temp signal is present. Thus, the light relay  56  requires only the presence of a light command signal from the processor  36  in order for the light to be turned on. Similarly, the aux  2  relay is activated with the presence of an aux  2  command, and the aux  3  relay is activated with the presence of an aux  3  command.  
         [0031]    A custom keyboard  32  to permit localized control may or may not be connected to the processor  36  depending upon desired configuration.  
         [0032]    With reference to FIG. 4, a perspective view of the remote-control unit  12  according to a preferred embodiment is shown. The remote-control unit  12  includes an LCD display  26  and a keypad depicted generally as  24 . The keypad  24  includes an up switch  130 , a down switch  132 , a status switch  134 , a heat switch  136 , a jets switch  138 , a light switch  140 , an aux  1  switch  142 , an aux  2  switch  144 , and an aux  3  switch  146 . Preferably, the LCD display  26  displays two and one-half or more digits of temperature set point followed by actual water temperature and status icons. Also, the LCD display  26  can be connected to display temperature in either degrees Fahrenheit or degrees Centigrade. In a -preferred embodiment, the following status icons are displayed: READY; HEATING; JETS; LIGHT; AUX  1 ; AUX  2 ; AUX  3 ; and degrees F. or degrees C.  
         [0033]    In operation of the remote-operated control system  10 , the remote-control unit  12  is used to operate the master-control unit  14  and to receive and display temperature and status data. In a preferred embodiment, the master-control unit  14  operates portable-spa or spa/pool functions upon command from the remote-control unit  12 . The master-control unit  14  interprets data from the remote-control unit  12  via the transceiver  30 , and based on the data, either turns on or turns off the spa/pool functions. Preferably, an external time clock is attached to the master control unit  14  to operate the filter pump of the spa or pool automatically. The master-control unit  14  also sends temperature and status data back to the remote-control unit  12  upon request from the remote-control unit  12 . The transceivers  16  and  30  operate at a preferred frequency of 915 megahertz. A keypad  24  on the master control unit  14  permits local control of the same functions as the remote control&#39;s  12  keypad.  
         [0034]    With reference to FIG. 4, function of the switches  130 ,  132 ,  134 ,  136 ,  138 ,  140 ,  142 ,  144 ,  146  on the remote-control unit  12  is described according to a preferred embodiment. The up switch  130  raises water temperature in the spa to a set point. The up switch  130  also serves to reset the safety hi-limit circuit  42  of FIG. 1 in the event that the safety hi-limit circuit  42  has been tripped, i.e., if water temperature exceeded 112 degrees Fahrenheit. To accomplish the reset, the user depresses the up switch  130  and the down switch  132  together after the water temperature has cooled down to below 108 degrees Fahrenheit. When the up switch  130  is held in a depressed position, the transceiver  16  continues transmitting the up command and receives the updated temperature set point on the display  26 , which updates at two-to-three seconds intervals. When the desired temperature set point is observed, the up switch  130  should be released. The set point increments in five-degree steps as the water temperature rises from thirty-five to eighty degrees Fahrenheit. Thereafter, until the temperature reaches 104 degrees Fahrenheit, the set point increments in one-degree steps.  
         [0035]    The down switch  132  operates similarly to the up switch  130 , except that the down switch  132  lowers the temperature set point instead of raising it. As discussed above, if the down switch  132  and the up switch  130  are depressed together, a preset safety hi-limit command is initiated to clear the safety hi-limit emergency shutdown provided the water temperature is below 108 degrees Fahrenheit.  
         [0036]    The status switch  134  provides several functions. First, the status switch  134  activates the Vcc power supply if the remote-control unit  12  is in sleep mode. Second, the status switch  134  serves to request temperature and status information from the master-control unit  14 . Third, the status switch  134  can be used to clear the reset to the safety hi-limit circuit  42 .  
         [0037]    The heat switch  136  is used to send a heat command to the master-control unit  14 . The heat command toggles the heat mode between on and off. When the heat mode is on, one of two status icons is shown on the display  26 . A HEATING icon is shown if the water temperature is below the temperature set point. Otherwise, i.e., if the water temperature is equal to or above the temperature set point, a READY icon is displayed. In similar fashion the jets switch  138  sends a jets command to the master-control unit  14  that toggles the jets function between on and off. When the jets function is on, the JETS icon is shown on the display  26 . Likewise, the light switch  140  sends a light command to the master-control unit  14  that toggles the light function between on and off. When the light function is on, the LIGHT icon is shown on the display  26 . The aux  1  switch  142 , the aux  2  switch  144 , and the aux  3  switch  146  are used in the same manner as the jets switch  138  and the light switch  140 . The aux  1  function is generally used to control blower motor.  
         [0038]    In a preferred embodiment, the remote-control unit  12  also includes a sleep circuit designed to turn off the Vcc power supply if there has been no action from the keypad  24  for fifteen seconds. As discussed above, the status switch  134  must be depressed to reactivate the Vcc power supply. The two address words from the address switches  22 ,  38  must match in order to have verified transmission from the decoder  20 .  
         [0039]    In operation of the master-control unit  14 , the processor  36  controls all of the master-control functions in a preferred embodiment, except for the time clock and the safety hi-limit shutdown. The tasks of the processor  36  include monitoring water temperature; storing temperature set point; reacting to received commands such as heat commands, status commands, jets commands, light commands, aux  1  commands, aux  2  commands, or aux  3  commands; resetting the safety hi-limit; and conditioning temperature set point when power is applied to the processor  36 .  
         [0040]    The processor  36  monitors the water temperature via a thermistor connected to the A/D input of the processor  36 . The processor  36  converts the analog input into degrees Fahrenheit, accounting for the thermistor curve. Also, if the water temperature exceeds 112 degrees Fahrenheit (as monitored via a second thermistor), the processor  36  shuts down all functions and sends a character back to the remote-control unit  12 . The character appears on the display  26  as a HI icon in lieu of the temperature display when the status switch  134  of the remote-control unit  12  is depressed.  
         [0041]    The processor  36  stores a temperature set point that increments in five-degree steps from thirty-five to eighty degrees Fahrenheit, and in one-degree steps from eighty to 104 and from thirty-two to thirty-five degrees Fahrenheit. The temperature set point can be incremented up by sending an up command or down by sending a down command from the remote-control unit  12 . Upon receipt of either an up or a down command, the processor  36  sends the temperature set point to the remote-control unit  12 . In addition, when a status command is received the processor  36  sends the temperature set point- to the remote-control unit  12  with the actual temperature data following in approximately two seconds.  
         [0042]    When a heat command is received from the remote-control unit  12 , the processor  36  sends a heat-enable command to the relay control logic  44 . Then the processor  36  compares the water temperature with the temperature set point. If the water temperature is lower than the temperature set point, the processor  36  sends a heating command signal to the relay control logic  44  and sends back to the remote-control unit  12  a status message including data to display the HEATING icon. If instead the water temperature is equal to or higher than the temperature set point, the processor  36  sends back to the remote-control unit  12  a status message including data-to display the READY icon. In a preferred embodiment, the HEATING and READY icons are never shown simultaneously on the display  26 . When in the heat mode, the processor  36  periodically compares the water temperature with the temperature set point and turns the heating command signal to the relay control logic  44  on or off accordingly as required to maintain correct water temperature (with hysteresis of one degree Fahrenheit). If a heat command is received while the processor  36  is in the heat mode, the processor  36  exits the heat mode and, if necessary, turns off the heat-enable command signal and the heating command signal to the relay control logic  44 . The processor  36  then sends back to the remote-control unit  12  a status message that clears the HEATING icon or READY icon from the display  26 .  
         [0043]    When a status command is received from the remotecontrol unit  12 , the processor  36  sends a status message back to the remote-control unit  12 . This status message always contains information to turn on or turn off the status icons as required and then display the temperature set point followed in roughly two seconds by the actual water temperature. The status command also clears the reset command signal to the safety hi-limit circuit  42  as discussed above.  
         [0044]    When a jets command is received from the remote-control unit  12 , the processor  36  turns on the jets command signal to the relay control logic  44  and returns a status message to the remote-control unit  12 . Another jets command from the remote-control unit  12  causes the processor  36  to turn off the jets command signal to the relay control logic  44 . In a preferred embodiment, if the processor  36  receives no jets command from the remote-control unit  12  after spending a specified time in the jets mode, the processor  36  automatically turns off the jets command signal to the relay control logic  44 .  
         [0045]    The aux  1  command is used in a preferred embodiment to operate the blower motor of the spa. The processor  36  handles a received aux  1  command in the same fashion as a jets command. The light command also is handled like the jets command, except that no similar time limit is provided to turn the light off after a specified time without a received light-on command. The aux  2  and aux  3  commands are handled like the light command.  
         [0046]    As discussed above, a safety hi-limit command can be generated by simultaneously depressing the up switch  130  and the down switch  132  of the remote-control unit. If the water temperature is below 108 degrees Fahrenheit, the processor  36  sends a reset command signal to the safety hi-limit circuit  42 . A status command from the remote-control unit  12  clears the reset command.  
         [0047]    A preferred embodiment includes a safety hi-limit circuit  42  that is completely independent from the processor  36 , except that a reset command signal from the processor  36  is necessary to clear the emergency shutdown. The safety hi-limit circuit  42  detects both water temperature and the condition of the discrete thermistors, such as an open thermistor or a cut thermistor cable. The emergency shutdown command is sent directly from the safety hi-limit circuit  42  to the on/off heater relay  50 .  
         [0048]    In a preferred embodiment, the relay Control logic  44  controls the built-in relays  50 ,  52 ,  54 ,  56 ,  58 ,  60 ,  62 ,  64 . The on/off pump relay  54  is operated from three sources. First, provided the safety hi-limit shutdown signal and the jets command signal from the processor  36  are off, the on/off pump relay  54  turns on when the heating command signal is sent from the processor  36  to the relay control logic  44 . Second, the on/off pump relay  54  can be turned on by the remote time clock if the jets command signal is not present. Third, the on/off pump relay  54  can be activated by the pump delay, or fireman&#39;s switch, circuit  46  in the absence of the jets command signal. In a preferred embodiment, the fireman&#39;s switch  46  turns on approximately two minutes after the processor  36  generates the heating command signal, and remains on until approximately fifteen minutes after the heating command signal is turned off. This allows the heater to go through a cool-down period before the water flowing through the heater is turned off. Whenever the jets command is turned on, the on/off pump relay  54  turns off. However, provided any of the above-discussed three conditions is met, the on/off pump relay  54  turns back on as soon as the jets command is turned off.  
         [0049]    The on/off jets relay  52  turns on whenever the jets command is received from the processor  36  by the- relay control logic  44 , provided the safety hi-limit shutdown signal is off. The on/off light relay  56  turns on when the light command is received from the processor  36  by the relay control logic  44 . However, the safety hi-limit shutdown signal need not be off because the water temperature is unrelated to whether the light is on or off. In a preferred embodiment, alternate light-function applications are provided. In the portable-spa setting twelve volts AC is wired to the spa light. In contrast, the spa/pool setting provides 115 volts AC for the pool or spa lights.  
         [0050]    The on/off aux  1  relay  58 , normally used for the spa blower in a preferred embodiment, is turned on when the aux  1  command is present and the safety hi-limit shutdown signal is absent. The on/off aux  2  and on/off aux  3  relays  60 ,  62  are activated when the aux  2  or aux  3  commands are present. The on/off ozonator relay  64 , which is used only in the portable-spa application of a preferred embodiment, is turned on if either the on/off pump relay  54  or the on/off jets relay  52  is on. In a preferred embodiment, a hi-limit relay  114  is provided for use only with the portable-spa application. The hi-limit relay  114  is always on unless the safety hi-limit shutdown signal is present.  
         [0051]    Like most of the other relays, the on/off heater relay  50  turns on when the heating command is present unless the safety hi-limit shutdown is present. The on/off heater relay  50  is preferably used only for portable-spa applications. Advantageously, an option can be provided via a jumper or a switch to inhibit the heater from coming on if either the on/off pump relay  54  or the on/off aux  1  (blower) relay  58  is on. Preferably, this option is only provided for low-power systems that also use 1.5 kilowatt or lower AC heaters. Most desirably, the on/off heater relay  50  is wired in series with an external pressure switch and does not operate unless the pump motor is running. In a preferred embodiment, an additional on/off heater relay  112  can be provided, operable under the same conditions but for use in pool/spa applications with gas-heater thermostats. it may also be advantageous in spa/pool applications to provide an on/off pool-valve relay  116  that turns on when the heat-enable command signal is present. An external twenty-four-volt AC transformer can be used to operate the pool valve. In similar fashion an on/off spa-valve relay  118  can be provided.  
         [0052]    As stated above, a preferred frequency for the transceivers  16 ,  30  is 915 megahertz. This frequency is acceptable in both the United States and Canada, and allows the transceivers to communicate with each other through free air over a distance of greater than 1000 feet.  
         [0053]    While preferred embodiments have been shown and described, it will be apparent to one of ordinary skill in the art that numerous alterations may be made without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited except in accordance with the following claims.