with initial reference to fig1 , a refrigerator 2 includes an outer shell or cabinet 4 within which is positioned a liner 6 that defines a fresh food compartment 8 . in a manner known in the art , fresh food compartment 8 can be accessed by the selective opening of a fresh food door 10 . in a similar manner , a freezer door 12 can be opened to access a freezer compartment 13 . in the embodiment shown , freezer door 12 includes a dispensing unit 14 that enables a consumer to retrieve a water product , such as ice and / or fresh water , without accessing fresh food or freezer compartments 8 and 13 . for the sake of completeness , fresh food door 10 is shown to include a dairy compartment 15 and various vertically adjustable shelving units , one of which is indicated at 16 . in a manner known in the art , fresh food compartment 8 is provided with a plurality of vertically adjustable shelves 20 - 22 supported by a pair of shelf support rails , one of which is indicated at 25 . at a lowermost portion of fresh food compartment 8 is illustrated a pair of temperature controlled bins 28 and 29 , as well as a conventional storage compartment 30 . at an upper region of fresh food compartment 8 is a temperature control housing including a user interface 40 . in the embodiment shown , interface 40 includes a display zone 42 and a plurality of control elements 45 - 49 . interface 40 also includes a light 63 which , in a manner known in the art , is controlled by a switch 65 operated by opening and closing fresh food door 10 . refrigerator 2 also includes a power system 70 for supplying power at various voltage levels to various components such as a compressor , fans and light 63 , as well as components of dispensing unit 14 in a manner that will be detailed more fully below . as best shown in fig2 , dispensing unit 14 includes a facade 94 mounted to freezer door 12 . facade 94 includes a recessed portion 98 for receiving a beverage container , such as a glass , for collecting any water and / or ice released from dispensing unit 14 . dispensing unit 14 also includes a base portion 105 which is designed to catch small amounts of water and / or ice which may drip or otherwise be released from dispenser unit 14 when a container is not in recessed portion 98 . dispensing unit 14 further includes a user interface or keypad 110 having a plurality of user selection members or keys 114 - 118 and a display 124 . keys 114 and 115 control a dispenser light ( not shown ) and menu options , e . g ., filter reset and dispenser lock out , respectively , while keys 116 - 118 enable a consumer to select between dispensing water , crushed ice or cubed ice . in addition , dispensing unit 14 is provided with actuation switches that trigger release of water and / or ice . in the embodiment shown , dispensing unit 14 includes a first or water / ice activation switch 128 positioned within recessed portion 98 that is designed to be acted upon by a beverage container , as well as a sport water activation switch 130 for releasing water either independent from or in conjunction with ice activation switch 128 . in any event , the above described structure is provided for the sake of completeness and to enable a better understanding of the figures . instead , the present invention is particularly directed to a control system 140 for dispensing unit 14 . as best shown in fig3 and 4 , control system 140 includes first and second control circuits 142 and 144 . first or main control circuit 142 controls operation of main dispensing components as will be discussed more fully below , while second or fountain control circuit 144 provides signals to main control circuit 142 enabling activation of the main dispensing components in a manner that will also be discussed more fully below . with particular reference to fig3 , main control circuit 142 is operatively connected to a first motor or drive unit 157 which , in accordance with the present invention , constitutes an activation solenoid of a water valve . main control circuit 142 is also operatively connected to a second motor or drive unit shown 159 which takes the form of an ice dispensing auger . main control circuit 142 also contains a crushed ice select line 161 that provides input to auger 159 causing ice to be directed through a crusher depending upon user preferences . in any event , water valve 157 and auger 159 are coupled to a power supply 163 which provides line voltage , preferably approximately 120 volts , from power system 70 . power supply 163 also feeds a power supply box 164 , which provides low voltage ( preferably approximately 12 volts ) to main control circuit 142 and , through line 165 , to fountain control circuit 144 . in accordance with the invention , main control circuit 142 includes a plurality of control switches 169 - 171 which control operation of water valve 157 , auger 159 and crushed ice select line 161 respectively . each control switch 169 - 171 includes a corresponding relay portion 178 - 180 that selectively engages a contact portion 184 - 186 coupling water valve 157 , auger 159 and crushed ice select line 161 to power supply 163 . in addition , each relay portion 178 - 180 includes a corresponding diode circuit 189 - 191 to prevent feedback voltage from a corresponding one of control switches 169 - 171 . as will be discussed more fully below , each relay portion 178 - 180 is activated by power supplied from a relay control line 194 through a respective drive switch 197 - 199 . more specifically , drive switches 197 - 199 include corresponding control input terminals 204 - 206 , as well as respective first and second main terminals 207 , 208 , 210 , 211 and 213 , 214 . input terminals 204 - 206 are activated by signals provided by a main processing unit 216 . a signal from main processor 216 at one or more of input terminals 204 - 206 allows current to pass from relay control line 194 to a respective control switches 169 - 171 . the particular drive switch 197 - 199 activated depends upon signals received based on the pressing of a key 116 - 118 from keypad 110 through a signal line 218 in a manner that will be discussed more fully below . main processor 216 receives power from power supply box 164 which is coupled to power system 70 and includes a voltage regulator circuit 220 that outputs very low voltage , preferably approximately 5 volts . with reference to fig4 , fountain control circuit 144 includes a second or fountain processor 240 coupled to a voltage regulator circuit 242 that supplies approximately 5 volts and , as described above , is coupled to power supply box 164 through line 165 . processor 240 is also coupled to dispensing switches 128 and 130 . more specifically , each dispensing switch 128 , 130 preferably takes the form of a membrane switch having corresponding first and second terminals 244 , 245 and 247 , 248 , with first terminals 244 , 247 receiving power from processor 240 through a supply line 254 and second terminals 245 , 248 providing a switch status signal to processor 240 through a corresponding return line 257 , 258 . preferably , processor 240 pulses supply line 254 until sensing that a dispensing switch 128 , 130 has been closed through a corresponding return line 257 , 258 . once processor 240 senses that one of dispensing switches 128 , 130 has been closed , power is provided to supply line 254 continuously until switch 128 or 130 is released . in any event , from the above description , it should be understood that main control circuit 142 and fountain control circuit 144 are linked by four lines , i . e ., lines 165 , 194 , 218 and a common or ground line 293 . in addition to providing an input signal to processor 240 , switches 128 and 130 enable current to pass along relay control line 194 to first control circuit 142 . as each switch 128 , 130 provides current to relay control line 194 in a similar manner , a detailed description will be made with respect to the closing of dispensing switch 128 with an understanding that the closing of dispensing switch 130 operates in a similar manner . once switch 128 is closed , a signal is sent through return line 257 into a branch circuit 280 , through a diode d 1 and resistor r 1 , and into an input terminal 283 of a first switching unit 284 . once power is provided at input terminal 283 , switching unit 284 enables low voltage power , preferably approximately 12 volts , to pass from power supply box 164 through a resistor r 2 , resistor r 3 , and first and second main terminals 291 , 292 of switching unit 284 before passing to ground line 293 . after passing through resistor r 2 , current is also received at a second input terminal 295 of a second switching unit 297 . at this point , low voltage from power supply box 164 can pass through first and second main terminals 305 , 306 of second switching unit 297 into relay control line 194 and pass to first control circuit 142 . in this manner , switching unit 284 and switching unit 297 , as well as resistors r 1 - r 4 , form an overall switching device of second control circuit 144 . once relay control line 194 is powered , current is received at first main terminals 207 , 210 and 213 of drive switches 197 - 199 respectively . having received a signal from a switch 116 - 118 on keypad 110 , main processor 216 selectively activates one or more of input terminals 204 , 205 and 206 of drive switches 197 - 199 in order to allow current to pass to one or more of control switches 169 - 171 . thus , for example , if a consumer simply wants to dispense water from dispensing unit 14 , activating switch 128 and key 116 sends power along relay control line 194 , while main processor 216 provides a signal to input terminal 204 , thereby allowing control switch 169 to activate water valve 157 , releasing water from dispensing unit 14 . in a similar manner , the operation of control switch 170 , with or without control switch 171 , can be controlled . at this point , it should be understood that the present invention provides a control system that ensures that single or multiple electronic component failures will not result in unintended dispensing of a water product from dispensing unit 14 . that is , by ensuring that current passes through dispensing switches 128 and / or 130 , and by providing multiple levels of redundancy , such as switching units 284 , 297 and drive switches 197 - 199 , dispensing unit 14 will not release a water product without being activated by a consumer . in this way , second control circuit 144 actually regulates the ability of main processor 216 to operate drive units 157 and 159 . therefore , a short in main processor 216 , which could potentially provide a signal to one or more of input terminals 204 - 206 , would still not enable an unintended dispensing operation to occur . similarly , a short in fountain processor 240 would not enable power to flow through relay control line 194 . moreover , the use of three different voltage levels provides a further control degree against an unintentional dispensing operation , while also enabling membrane switches to be readily used in dispensing unit 14 given the minimal voltage levels maintained at dispensing unit 14 at all times . although described with reference to a preferred embodiment of the invention , it should be readily understood that various changes and / or modifications can be made to the invention without departing from the spirit thereof . for instance , the number and types of switching units , drive units , and the like can be varied without departing from the spirit of the present invention . in addition , the control system could also be employed to dispense other substances , such as juice and other water - based products . in general , the invention is only intended to be limited by the scope of the following claims .