This invention relates generally to fire protection systems and, more particularly, to such a system for use in protecting rural residential building located in high fire risk areas.
 in the western third of the United States, arid conditions create extreme fire danger during certain periods every year. Residential building have become more vulnerable in recent years due to the fact that many homes are left unattended for long periods of time because they are occupied as vacation homes or by families in which both parents work. Compounding this problem is the proliferication of homes in scenic forested or mountainous areas where the quality of life is superb, but the fire danger is high.
 While some of these areas are served by rural fire protection districts, the response times of these entities are generally very long. Moreover, many mountain homes are simply without public fire protection of any kind. Home owners in these high risks areas face significantly higher insurance premiums than city homeowners, and some are not able to obtain fire coverage at any cost.
 Several systems are known for protecting buildings from the risk of fire. Such systems are described in U.S. Pat. No. 4428434 to GELAUDE, U.S. Pat. No. 5165482 to SMAGAC et. al, U.S. Pat. No. 5263543 to NIGRO, U.S. Pat. No. 5692571 to JACKSON and U.S. Pat. No. 5732511 to SCOTT.
 While these devices fulfill their objectives, they do not describe a fire protection system with a single large gun nozzle that is comparatively inexpensive to install and maintain and that is effective in protecting single rural properties and multiple homes on smaller city lots.
 The present invention is therefore directed to a fire protection system that is inexpensive to install and maintain and that is simple yet effective in protecting a building from approaching fire.
 The present invention employs, in accordance with the illustrated preferred embodiment, a plurality of radio frequency temperature sensors remotely located around a building to be protected, one or more sprinkler heads coupled to a water supply line and mounted on the roof of the building to provide sprinkler coverage of the building and/or a perimeter area surrounding the building, and control circuitry responsive to a radio frequency signal transmitted by one or more of the remotely located temperature sensors when a temperature exceeding a threshold temperature of the sensors is sensed thereby to initiate the flow of water to the one or more sprinkler heads for a predetermined period.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 is a front elevation pictorial diagram of an exterior of the fire protection system of the present invention, illustrating the spiral relationship between a building to be protected by an approaching fire, heat sensors positioned to detect the approaching fire at a distance from the building, and the sprinkler pattern required to adequetely protect the building.
 FIG. 2 is atop plan pictorial diagram of the exterior portion of the fire protection system of FIG. 1 illustrating the areas of water coverage provided by a combination of a gun sprinkler and/or two, supplemental smaller sprinklers.
 FIG. 3 is a top plan pictorial diagram illustrating the areas of water coverage for for multiple houses on smaller city lots.
 FIG. 4 is a block diagram of the interior control portion of the fire protection system of the fire protection system of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
 Referring now to FIGS. 1,2 and 3 there shown pictorial diagrams of the exterior Portion of the fire protection system of the present invention that is designed to protect a building 100 from an approaching fire. A plurality of heat sensors 10 is typically placed 300-500 feet from building 100, depending on topography and foliage. Up tp 16 heat sensors 10 may be employed in the system described herein. Heat sensors 10 preferable comprise commercially available radio frequency transmitter temperature sensors of the type having a treshold temperature of 135 degrees F. and that transmit a 900 MHz radio signal when the sensed temperature exceeds the threshold temperature. One or more water sprinklers are preferably positioned at the highest point on the roof of building 100 to provide a water spray pattern that extends approximately 112 feet around the building 100. The sprinklers may comprise a single gun sprinkler 20 that is centrally mounted on the roof, such as the Rainbird SR103 EM sprinkler that sprinkler that dispenses 57 gallons/minute over a full circle 222 feet in diameter. This type of sprinkler facilities the wetting of foliage at the highest point possible. A pair of supplimental sprinklers 22 may be positioned at each end of the roos, if desired. Sprinklers may comprise, for example a pair of Rainbird 35A-TNT sprinklers, which operate with 30-60PSI water pressure and provide circular coverage extending approximately 42 feet. The water lines which feed sprinklers 20, 22 may be conventionally fabricated using copper or PVC materials. All water lines are slpoped to provide drainage after the fire protection systems is used or tested. Damage to the water lines caused by freezing in cold climates is thereby prevented.
 Referring now to FIG. 4, there is shown a water line 40 that conveys water from the existing main water line in the building to the roof-mounted sprinklers 20, 22 of FIGS. 1 and 2. IN situations in which storage tank is needed to increase the volume of water available to the fire protection system, the existing building water line is divided, with one branch supplying the storage tank as a fill line. It is controlled by a float in the tank which maintains a desired water level in the tank at all times. A conventinal amnual valve 42 serves as a system shut off valve when it is desired to repair of drain the fire prtection system. A conventional drain valve 44 is similarily conventionally employed to drain water from the fire protection system. A manual bypass valve 46 is provided in a bypass water line section 48 around an electric water valve 50 to permit manual operation of the fire protection system. Electric water valve may comprise a commercially available RainBird 075—DV valve, whose operation is controled by controll circuitry 52 that is mounted inside the building, preferably adjacent water line 40. Control circuitry 52 comprises a power switch 54, a conventional 24-volt transformer 56, a timing relay 58, a pair of general purpose relays 60 and 62 a 12-volt AC adapter and a reciever 66. Timing relay 58 , may comprise, for example, a commercially available solid relay having and adjustable time delay of 1.2 to 120 minutes.
 Relay 60 may comprise a KP12V14 general purpose relay, and relay 62 may comprise a Zetler individual relay. Reciever 66 may comprise a commercially available Inevonics FA416R reciever.
 In operation, one ore more of the remotely located heat sensors 10 transmits a radio frequency signal whenever a temperature exceding the threshold temperature of the sensor is sensed. The transmitted signal is recieved by reciever 66, which in turn supplies a control signal that is applied, through relay 62, to timing relay 58. Timing relay 58 then signals relay 60 to actuate electric water valve 50 for a predetermined period of time to which timing relay 58 is set. The result is that water is permitted to flow from the building water supply line through water line 40 to the roof sprinklers 20, 22 thereby wet the building and a perimeter area defined by the coverage of sprinklers 20, 22.