Abstract:
An exit sign comprising a housing and a plurality of red and green color LEDs having the capability of being selectively activated to produce either red light or green light. The plurality of LEDs are mounted in a mutual lighting association in the housing. A switch is manually operable to selectively activate the plurality of red color LEDs to produce the red light and in the alternative, to selectively activate of the plurality of the green color LEDs to produce the green light. Means for passing light from the selected red light or selected green light in the form of indicia symbolizing an exit enables viewing by an observer, such means include a stencil having four independent letters forming the word EXIT. DC circuitry is in operative electrical connection with the plurality of LEDs. A source of DC electrical power activates the DC circuitry. The plurality of LEDs can be monochrome red LEDs and monochrome green LEDs or in the alternative, the plurality of LEDs can be bicolor LEDs having the capability of producing red light or green light. Red light and green light can be simultaneously emitted so as to produce yellow light. An emergency power backup battery is connected to the plurality of color LEDS. Means for producing emergency light is optional.

Description:
RELATED U.S. APPLICATION DATA  
       [0001]    This patent application claims benefit of U.S. Provisional Application No. 60/465,822 filed on Apr. 25, 2003 entitled, “Tri-Color LED Lamp for Illuminated Signage”. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to color light emitting diode lamps used in illuminated signs, and more particularly to illuminate emergency exit signs.  
         BACKGROUND OF THE INVENTION  
         [0003]    Originally, an exit sign used standard incandescent lamps. The earliest alternatives to incandescent lamps were radioactive tritium gas and compact fluorescent lamps. In 1985, light-emitting diodes (LEDs) were introduced for use in exit signs.  
           [0004]    The most cost-effective alternative today over the exit signs that use incandescent lamps are LED exit signs. A standard LED exit sign generally uses only about 1 to 5 watts of power per surface and costs less than $5.00 per year to operate depending on the model and local utility costs. Because LEDs also last considerably longer than incandescent lamps, life cycle savings are dramatic. When an LED exit sign is used instead of an incandescent exit sign, the cost saving multiple over a ten-year period including initial costs, energy expenditures, and maintenance requirements will be in the range of five times.  
           [0005]    There are currently several different types of LED exit signs available in the marketplace using a variety of LEDs in different configurations. There are a great number of LED sign manufacturers competing in the market. As a result, there is a wide range in price, quality, and energy consumption. Some LED signs use as few as 6 LEDs, others use 18 to 35 LEDs, and some use up to 200 LEDs. The rated energy consumption can thus range from as little as 1 watt up to 8 watts.  
           [0006]    Under National Fire Protection Association (NFPA), National Electrical Code (NEC), Underwriters Laboratories (UL) and local fire and building codes for each state, buildings that provide public access are required by law to have signs therein identifying the exits. These emergency signs are required to exhibit a specific amount of illumination and often times are required to have an emergency backup power source to provide emergency illumination to the exit sign for a specified period of time when electrical power to the building is interrupted to allow sufficient time for persons in the building to vacate. LED exit signs are presently available primarily with red or green color LEDs, or other approved colors as required by local ordinances or municipalities and depending on state and city codes.  
           [0007]    No LED exit sign presently exists that is commercially manufactured to the best of my knowledge that provides a choice of either red or green color LEDs along with a switch to select the color of the exit sign indicia that is legally required by the particular jurisdiction. In the selective color LED lamp of the present invention, the switch can selectively turn on the red color LEDs to produce a red color exit sign indicia, or selectively turn on the green color LEDs to produce a green color exit sign indicia. In addition, the LED lamp of the present invention can selectively turn on both the red and green color LEDs simultaneously to produce a yellow color exit sign indicia. Exit signs usually include a stencil having perforations that define indicia through which the LED light passes and which is readable by an observer. Existing stencil signs have solid colored green or red diffuser panels behind opaque sections with the letters EXIT cut out. Other exit signs can include a stencil manufactured out of a clear lens with the indicia or background masked with a red, green, or other color ink. The word EXIT is usually white in this case against the color background. The indicia generally form the letters of the word EXIT and include removable or permanent chevron arrows located on opposite sides of the word EXIT. Other words, symbols, or idiogram indicia can indicate an exit. Among these are words or symbols in non-English speaking countries that have an analogous meaning to the word EXIT in English.  
           [0008]    The present invention provides an LED lamp that enables a user to selectively, or optionally, produce distinct color outputs. The selective color LED lamp is designed for use in illuminated signs generally including emergency exit signs, but also other types of illuminated signs that can be used in different locations. The use of the selective color LED lamp will allow the emergency signage to comply with all local fire and building code requirements. An LED exit sign manufacturer, wholesaler, and retailer can stock only one basic version of the selective color LED lamp exit sign thereby reducing manufacturing, inventory, and shipping costs. The selective color LED lamp is designed to replace existing incandescent and single color LED lamps. It can be used directly in sockets of existing emergency exit signs as retrofit LED lamps, or as the main light source in new emergency exit signs and other illuminated signs. Besides using the selective color LED lamp of the present invention in emergency exit signs, the selective color LED lamp can be used in illuminated advisory, directional, instructional, warning, and safety demarcation signs. In the latter uses, other selective colors can be used other than the red, green, and yellow colors of the selective color LED lamp. Another area where the selective color LED lamp of the present invention can be used is in warning and instructional lighting markers used in many truck-loading docks around the country.  
           [0009]    It is an object of the present invention to provide a selective color LED lamp wherein one of the color red or the color green can be selected for general signage lighting applications incorporating light emitting diodes as the main light source for use in existing and newly manufactured signage lighting fixtures.  
           [0010]    Another object of the present invention is to provide such a selective color LED lamp that can readily replace the incandescent and compact fluorescent lighting units offering energy efficiency, longer life with zero mercury, zero disposal costs, and zero hazardous waste. The present invention can be used with all types of illuminated signage.  
           [0011]    Yet another object of the present invention is to provide a selective color LED lamp that will easily produce a red color or green color while substantially using a low number of color LEDs wherein such use is in the field of emergency exit signs.  
           [0012]    Yet another object of the present invention is to provide a selective color LED lamp that will easily produce a red color or green color or a mixed red and green color to produce the color yellow while using a relatively low number of colored LEDs wherein such use is in the field of emergency exit signs.  
           [0013]    A further object of the present invention is to provide a selective color LED retrofit lamp containing integral electronic circuitry that can be readily and economically fabricated from simple electronic components for easy adaptation for use with existing illuminated signage.  
           [0014]    And yet a further object of the present invention is to provide a selective color LED lamp combined with surge suppression, uniform illumination, battery backup, and low power consumption to be readily and economically fabricated from simple components, for use in newly manufactured and multipurpose illuminated emergency signage that is readily adaptable to comply with fire and building code.  
           [0015]    A final object of the present invention is to provide a selective color LED lamp for use in newly manufactured illuminated signage with optional emergency lights integrally and operationally mounted with the main lamp unit.  
         BRIEF SUMMARY OF THE INVENTION  
         [0016]    The selective color retrofit LED lamp comprises an array of red color LEDs and an array of green color LEDs, each LED in each array is connected in a series and parallel relationship with similar color LEDs. Alternating current (AC) voltage is converted to direct current (DC) voltage by bridge rectifiers to power the LEDs. Switches will be provided to turn on or to select for operation only the array of red color LEDs or only the array of green color LEDs. Optionally, both arrays of red and green color LEDs can be turned on to emit light at the same time, the latter selection resulting in the production of the color yellow. The LEDs are mounted onto a rigid circuit board with or without an external housing. The AC power to the selective color retrofit LED lamp can terminate in any standard lamp configuration including, but not limited to bi-pin, medium screw base, candelabra base, etc. This selective color retrofit LED lamp can be used in single and double panel mount exit signs, edge mount exit signs, stencil exit signs, panel mount exit signs fitted with emergency lights, and other illuminated signage.  
           [0017]    The selective color LED lamp of the present invention can be used in newly manufactured illuminating signage as well. This selective color LED lamp in combination with a number of other components including a step-down transformer to convert 120/220/277 VAC to a lower voltage to power the LEDs and to serve as a voltage suppresser; a battery backup system with testing capability that is charged by the AC power input; a fixture housing or body; a fixture mount; background stencil and lettering or symbol indicia; at least one optical diffuser; and optional integral emergency lights, all combine to form a selective color LED illuminating sign of the present invention.  
           [0018]    U.S. Pat. No. 6,567,010 issued to Lin and Zhu on May 20, 2003, discloses a traffic signal head with individual activation of 1) red light LED generating elements and green light LED generating elements, and 2) red light LED generating elements and green light LED generating elements with simultaneous activation of the red and green light LED generating elements producing yellow light. The two main claims in Lin set forth the combination of the individual activations of red, green, and yellow light, a housing, activation circuitry, and the inventive feature of circuitry for enabling adjustment of the relative intensity of the yellow light produced by the activation of the red and green light.  
           [0019]    However, Lin does not disclose, as does the present invention a combination of elements that includes means for passing selected red light or selected green light from an array of red LEDs and an array of green LEDs in the form of indicia symbolizing an exit and enabling viewing by an observer. Nor does Lin disclose means for optically diffusing the selected red light or selected green light positioned in the housing between the array of red LEDs and the array of green LEDs positioned in the housing, and the means for passing light in the form of indicia. The present invention includes yellow light produced by the simultaneous production of red and green light that also passes through the indicia symbolizing an exit. There is no adjustment of the relative intensity of the yellow light. The selected red light or green light is full on or full off resulting in a yellow light that is either full on or completely off only.  
           [0020]    The present invention will be better understood and the objects and important features, other than those specifically set forth above, will become apparent when consideration is given to the following details and description, which when taken in conjunction with the annexed drawings, describes, illustrates, and shows preferred embodiments or modifications of the present invention, and what is presently considered and believed to be the best mode of practice in the principles thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 shows a front view of an assembled selective color LED exit sign in accordance with the present invention;  
         [0022]    [0022]FIG. 1A shows the basic mount structure for the selective color LED exit shown in FIG. 1 along with two attached emergency lights along with LED lamps mounted thereto;  
         [0023]    [0023]FIG. 1B shows an optical diffuser of the selective color LED exit sign shown in FIG. 1 before being mounted to the mount structure shown in FIG. 1A;  
         [0024]    [0024]FIG. 1C shows the front face of a stencil defining indicia indicating an exit that is mounted to the mount structure shown in FIG. 1 over the optical diffuser of the selective color LED exit sign shown in FIG. 1B;  
         [0025]    [0025]FIG. 1D shows the front face of an alternative stencil;  
         [0026]    [0026]FIG. 2 shows the selective color LED exit sign as shown in FIG. 1 in a simplified form showing one each of a red and green light beam and one mixed yellow light beam from the combination of the one red with the one green light beam;  
         [0027]    [0027]FIG. 2A shows a chart of the typical dipswitch selections as related to FIG. 2;  
         [0028]    [0028]FIG. 3 shows an isolated schematic block diagram of the isolated selective color LED lamp of the selective color LED exit sign shown in FIGS. 1 and 2;  
         [0029]    [0029]FIG. 4 shows a schematic block diagram of the selective color LED exit sign shown in FIGS. 1 and 2 including the selective color LED lamp shown in FIG. 3;  
         [0030]    [0030]FIG. 5 shows the electrical circuit used for the selective color LED exit sign; and  
         [0031]    [0031]FIG. 6 is a schematic block diagram analogous to FIG. 3 that shows an alternative selective color LED lamp with bicolor red and green LEDs. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    Reference is now made to the drawings and in particular to FIGS. 1-6 in which identical or similar parts are designated by the same or similar reference numerals throughout.  
         [0033]    A selective color light emitting diode (LED) sign  10  is shown in FIG. 1-6 and in particular in assembled front view in FIG. 1. Sign  10  includes disassembled elements shown in FIGS. 1A, 1B,  1 C, and  1 D.  
         [0034]    In particular, FIG. 1A shows a disassembled front view  12  of sign  10  comprising a housing  14  and a flat rear panel  16  mounted thereto. A canopy  18  attached to the top edge  20  of housing  14  provides support for hanging the entire sign  10  to a ceiling structure (not shown). A step-down transformer  22  is mounted at top edge  20  at one side edge  24  of housing  14  opposite bottom edge  21  and a rechargeable backup battery  26  is mounted at top edge  20  at the opposed side edge  28  of housing  14 . Optional emergency lights  30 A and  30 B are attached to housing side edges  24  and  28  respectively. An array of thirty-six monochrome color LEDs  32  are horizontally mounted in a manner known in the art at equal intervals across the area of top edge  20  of flat rear panel  16  between side edges  24  and  28 .  
         [0035]    [0035]FIG. 1B shows in isolation the front view of an optical diffuser  34  known in the art that is secured to housing  14  and positioned over LEDs  32 . FIG. 1C shows a rectangular stencil  36  in front view taken in isolation that is secured to housing  14  in assembled mode and positioned over optical diffuser  34 , LEDs  32 , and rear panel  16 . Stencil  36  is also shown in FIG. 1. Stencil  36  is generally non-transparent and includes four light passageway openings  38 A,  38 B,  38 C and  38 D that define the four letters, or four indicia, in capitalized mode of the word EXIT, respectively, that extend horizontally in the midarea of stencil  36  through which light beams projected by LEDs  32  pass through each light passageway opening  38 A,  38 B,  38 C and  38 D after passing through optical diffuser  34  for eventual viewing by an observer. Stencil  36  optionally defines two directional symbols, namely, opposed chevron arrow openings  39 A and  39 B through which light beams projected by LEDs  32  pass for eventual viewing by an observer.  
         [0036]    [0036]FIG. 1D shows an alternative embodiment of the rectangular stencil  36 , namely stencil  36 A in front view taken in isolation that is secured to housing  14  in assembled mode and positioned over optical diffuser  34 , LEDs  32 , and rear panel  16 . Stencil  36 A is clear and translucent, but is made non-translucent by a manner known in the art such as by the application of paint or other masking medium. Stencil  36 A provides four transparent areas  38 E,  38 F,  38 G, and  38 H that define the four letters or four indicia, in capitalized text mode of the word EXIT, respectively, and that extend horizontally in the general midarea of stencil  36 A through which light beams projected by LEDs  32  pass through each transparent area  38 E,  38 F,  38 G, and  38 H after passing through optical diffuser  34  for eventual viewing by an observer. Stencil  36 A optionally includes other transparent areas such as two directional symbols, namely, opposed chevron arrows  39 A and  39 B through which light beams projected by LEDs  32  pass for eventual viewing by an observer. Other variations of stencils  36  and  36 A are possible within the parameters of the present invention. It should be noted that the alternative stencil  36 A itself could be manufactured out of a diffusion material thereby further reducing parts by eliminating the need for a separate optical diffuser  34 .  
         [0037]    [0037]FIG. 2 shows a more detailed view  40  of the disassembled front view  12  shown in FIG. 1A and wherein thirty-six monochrome color LEDs  32  include for purposes of exposition twelve red LEDs  32 A and twenty-four green LEDs  32 B each individually mounted to and electrically connected to a circuit board  35  that is attached to housing  14 . The relative numbers of LEDs  32 A and  32 B can vary. For example, equal numbers of red LEDs  32 A and green LEDs  32 B can be used. As shown in FIG. 2, the arrangement of thirty-six LEDs  32  are such that there are two green LEDs  36 B located between every red LED  36 A with a green LED  36 B positioned at each end of the total array of thirty-six LEDS  32 . The actual number of red color LEDs  32 A and green color LEDs  36 B can vary depending on the make and type of LED  32  used as determined by the output beam angle and the output lumen generated by each LED  32 . For purposes of exposition a single red color beam  42  is produced from a single red LED  32 A and a single green color beam  46  is produced from a single green LED  32 B. A single yellow color beam  44  is produced from a combination of the red color beam  42  emitted from red LED  32 A with the green color beam  46  emitted from single green LED  32 B. Red color beam  42  represents all red color beams and green color beam  46  represents all green color beams, and yellow color beam  44  represents all yellow color beams.  
         [0038]    Also seen in FIG. 2 are twenty-eight monochrome LEDs  48 A positioned in a concentric circular arrangement in optional emergency light  30 A mounted to side edge  24  of housing  14 , and twenty-eight monochrome LEDs  48 B positioned in a concentric circular arrangement in optional emergency light  30 B mounted to side edge  28  of housing  14 . A normally closed DC disconnect test switch  50  is positioned on circuit board  35  proximate to LEDs  32  to test the battery backup system, and a DC power status LED  52  is also positioned on circuit board  35 . A normally open DC connect test switch  50 A is also positioned on circuit board  35 , which when closed will connect power to LEDs  48 A and  48 B in emergency lights  30 A and  30 B respectively.  
         [0039]    A dipswitch  54  containing two separate switches is positioned on circuit board  35  proximate to and in electrical connection to LEDs  32 . Dipswitch  54  is in electrical connection to circuitry connected to the circuit board (not shown) and LEDs  32 , and is manually operable to select any one of the following options as shown in dipswitch settings table 2A as follows:  
         [0040]    1. Deactivation of any color to selective color LED sign  10 ;  
         [0041]    2. Activation of red LEDs  32 A so as to produce red color as represented by red beam  42 ;  
         [0042]    3. Activation of green LEDs  32 B so as to produce green color as represented by green beam  46 ;  
         [0043]    4. Activation of both red LEDs  32 A and green LEDs  32 B resulting in the emission of red and green colors that mix to produce yellow light as represented by yellow beam  44 .  
         [0044]    [0044]FIG. 3 shows a schematic block diagram  56  of a selective color LED lamp  58  taken in isolation. Selective color LED lamp  58  can be used in retrofit applications for existing illuminated signs or as the main selective color LED lamp in new fixtures. LED lamp  58  basically comprises an alternating current voltage (VAC) power input  60  that is readily converted into a DC voltage output to power red and green color LEDs  32 A and  32 B, respectively, by an AC to DC converter  62 .  
         [0045]    A single main or individual current limiter, or resistor  64 , is used to limit the current going into red LEDs  32 A and green LEDs  32 B. Red LEDs  32 A and green LEDs  32 B comprise of LEDs  32  connected in both a series and a parallel configuration for redundancy. This is done so that the majority of red LEDs  32 A and green LEDs  32 B will remain energized in the event that one or more LEDs  32  in each array should fail.  
         [0046]    Each of the red LEDs  32 A and green LEDs  32 B are in direct communication with a two-position dipswitch  54  previously discussed that is manually operable to close the power supply circuit and thereby energize all the red LEDs  32 A and green LEDs  32 B. Red LEDs  32 A can be energized independent of green LEDs  32 B, and vice versa. In the event that both red LEDs  32 A and green LEDs  32 B are switched on and energized, a third color, namely, the color yellow, will appear resulting from the combination of the mixing of the output color beams from red LEDs  32 A with green LEDs  32 B. Activated LEDs  32  are connected to ground  66  thereby completing the current path through red LEDs  32 A and green LEDs  32 B respectively.  
         [0047]    [0047]FIG. 4 shows a schematic block diagram  68  of exit sign  10 . The usual source of power to an emergency exit sign is alternating current voltage or VAC  60 . This voltage can be 120V, 240V, or 277V. Since the input AC voltage is high, a step-down transformer typified by step-down transformer  22  also shown in FIG. 2 is used to bring the input voltage down to a lower operating AC voltage, for example 8VAC. The 8VAC is then passed through AC/DC converter  62  typically a bridge rectifier.  
         [0048]    The direct current voltage or VDC is then connected to a momentary DC power disconnect test switch  50  that is normally closed. The function of DC power disconnect test switch  50  is to test the electronic circuitry of the backup system to battery  26  by simulating the interruption of DC voltage power. DC power indicator LED  52  signals the presence of AC voltage power.  
         [0049]    The DC voltage also goes through a charging circuit  70  connected to rechargeable battery  26  and then to a switching circuit  72 . The output of switching circuit  72  then goes through a main or individual current limiter  74 , and lastly to red LEDs  32 A and green LEDs  32 B. The function of switching circuit  72  is to provide power to red LEDs  32 A and green LEDs  32 B when normal input DC voltage is present, but will automatically switch over to battery backup  26  DC power in the event of input AC power failure. As described before two-position dipswitch  54  is operable to turn either or both red LEDs  32 A and green LEDs  32 B on and off.  
         [0050]    Two separate monochrome LED lights  30 A and  30 B, respectively, act as optional emergency lights. The LEDs  48 A and  48 B for use in emergency LED lights  30 A and  30 B are monochrome comprising either white and/or yellow color LEDs. They are optional and serve as emergency lighting for the egress and evacuation of buildings or other establishments in the event of power failure and general lighting is not available. A separate DC power connect test switch  50 A energizes the optional emergency monochrome LEDs  48 A and  48 B. The output of switching circuit  72  also goes through current limiter  74 A and then to monochrome LEDs  48 A and  48 B.  
         [0051]    Momentary DC power status connect switch  50 A is normally open and when depressed will connect the DC voltage power directly to test optional emergency lights  30 A and  30 B. In the absence of AC voltage power or when the DC power disconnect test switch  50  is depressed, backup battery  26  voltage power will kick in to power both red LEDs  32 A and green LEDs  32 B as well as providing power for LEDs  48 A and  48 B in optional emergency lights  30 A and  30 B. The storage capacity of backup battery  26  should provide enough reserve voltage to power all the LEDs in exit sign  10 , including optional emergency lights  30 A and  30 B for a duration of 1.5 to 3.0 hours when there is no AC voltage input. Red LEDs  32 A and green LEDs  32 B and LEDs  48 A and  48 B in emergency LED lights  30 A and  30 B are connected to ground  66  thereby completing the current paths through red LEDs  32 A and green LEDs  32 B and LEDs  48 A and  48 B in emergency LED lights  30 A and  30 B.  
         [0052]    [0052]FIG. 5 depicts the electrical circuit used for selective color LED exit sign  10 . Step-down transformer  22  shown here as TI has multiple primary input voltage taps depending on the voltage available. As mentioned before, these may be 120 volts, 240 volts, or 277 volts AC. The secondary output voltage of transformer  22  is the same at about 8 volts AC, also as mentioned before. The 8 volts AC are attached to the AC inputs of AC/DC converter  62  shown here as a bridge rectifier BR 1 . The negative output of bridge rectifier BR 1  becomes the DC ground  66 , while the positive output of bridge rectifier BR 1  serves to deliver power to four main circuits by way of the normally closed momentary test switch  50  shown here as SW 1 .  
         [0053]    A first circuit  78  passes DC voltage through current limiter  64 , shown here as resistor R 1 , that limits current to DC power indicator LED  52 , also indicated as LED 1 . One end of resistor R 1  is connected to the anode of power indicator LED  52 , and the cathode of power indicator LED  52  (LED 1 ) is connected to DC ground  66 . DC power indicator LED  52  lights up when AC input voltage is present and test switch  50  (SW 1 ) is not depressed. Due to the fact that power indicator LED  52  (LED 1 ) is by nature a diode itself, it prevents reverse current flow from DC ground  66  back to the positive DC output of bridge rectifier BR 1 . Therefore current flows only in one direction from the anode of DC power indicator LED  52  (LED 1 ) to the cathode of DC power indicator LED  52  (LED 1 ).  
         [0054]    A second circuit  80  represents the charging circuitry  70  for delivering power to rechargeable battery  26  (BATTERY) for backup power in case of AC input voltage failure. DC voltage passes through diode D 2  into resistor R 2  and directly into the positive terminal of battery  26  (BATTERY). The negative terminal of battery  26  (BATTERY) is connected to DC ground  66 . Diode D 2  prevents the reverse current flow from battery  26  (BATTERY) back to the positive DC output of bridge rectifier BR 1 , and therefore allows current to flow only in one direction from the anode of diode D 2  to the cathode of diode D 2 .  
         [0055]    Third circuit  82  includes a complete array of red LEDS  32 A as shown in FIG. 5 comprising individual red LEDs, namely, LED 2  to LED 2 X,Y connected in an electrical series and parallel configuration for redundancy. Third circuit  82  also includes a complete array of green LEDs  32 B as shown in FIG. 5 comprising individual green LEDS, namely, LED 3  to LED 3 X,Y also connected in an electrical series and parallel configuration. This identification of red and green LEDs sets forth that red LEDs  32 A and green LEDs  32 B can each comprise of at least one red LED and at least one green LED connected in an electrical serial and parallel configuration.  
         [0056]    In addition, third circuit  82  includes monochrome LEDs  48 A and  48 B. LEDs  48 A is shown in FIG. 5 as comprising of individual monochrome LEDs, namely, LED 4  to LED 4 X,Y, and LEDs  48 B is shown in FIG. 5 as comprising of individual monochrome LEDs, namely, LED 5  to LED 5 X,Y. This identification of individual monochrome LEDs sets forth that LEDs  48 A and  48 B can each comprise of at least one monochrome LED in an electrical serial and parallel configuration.  
         [0057]    The actual number of red LEDs  32 A and green LEDs  32 B and monochrome LEDs  48 A and  48 B in optional emergency lights  30 A and  30 B can be the same number or can differ in number.  
         [0058]    Third circuit  82  drives red LEDs  32 A, namely, LED 2  to LED 2 X,Y and green LEDs  32 B, namely, LED 3  to LED 3 X,Y during normal operation when input AC voltage is present and test switch  50  (SW 1 ) is not depressed. DC voltage passes through diode D 1  from the anode side to the cathode side. Diode D 1  prevents the reverse current flow from LEDs  32 A and  32 B back to the positive DC output of bridge rectifier BR 1 , and therefore allows current to flow only in one direction from the anode of diode D 1  to the cathode of diode D 1 . DC voltage passes to red LEDs LED 2  to LED 2 X,Y by way of resistor R 4 . Likewise DC voltage passes to green LEDs LED 3  to LED 3 X,Y by way of resistor R 5 . Resistors R 4  and R 5  provide current limiting to the individual red LEDs  32 A and green LEDs  32 B respectively. Red and green LEDs LED 2  to LED 2 X,Y and LED 3  to LED 3 X,Y each have at least one color LED connected in a series and parallel configuration for redundancy. The cathode of the last LED 2 X,Y of the red LEDs  32 A is connected to one side of the first switch of two-position dipswitch  54  (SW 3 ) with the other side of the first switch of two-position dipswitch  54  (SW 3 ) connected to DC ground  66 . Likewise, the cathode of the last LED 3 X,Y of green LEDs  32 B is connected to one side of the second switch of two-position dipswitch  54  (SW 4 ) with the other side of the second switch of two-position dipswitch  54  (SW 4 ) connected to DC ground  66 . When either switch on two-position dipswitch  54  (SW 3  or SW 4 ) is switched to the ON position, the cathode of the corresponding LED 2 X,Y or LED 3 X,Y relating to the first or second switch, respectively, will in effect be connected to DC ground  66 . This completes the respective circuit and will energize all the corresponding red LEDs  32 A and/or green LEDs  32 B LED arrays.  
         [0059]    Normally open momentary power connect test switch  50 A (SW 2 ) is provided to test and turn on optional emergency LED lights  30 A and  30 B by providing temporary DC voltage power from the positive output of bridge rectifier BR 1 . The DC voltage passes to LEDs  48 A, namely, LED 4  to LED 4 X,Y by way of resistor R 6 . Likewise DC voltage passes to LEDs  48 B, namely, LED 5  to LED 5 X,Y by way of resistor R 7 . Resistors R 6  and R 7  provide current limiting to the individual LEDs  48 A and  48 B in optional emergency LED lights  30 A and  30 B. LEDs LED 4  to LED 4 X,Y and LED 5  to LED 5 X,Y each comprise of at least one LED connected in a series and parallel configuration for redundancy. The cathodes of LED  4 X,Y and LED 5 X,Y are each connected to DC ground  66 .  
         [0060]    A fourth circuit  84  provides the automatic switching of DC voltage power to LEDs  32 A,  32 B,  48 A, and  48 B in the event of AC power failure. The positive terminal of battery  26  is connected to the emitter of PNP transistor Q 1 . The collector of transistor Q 1  is connected to the inputs of red and green LED arrays  32 A and  32 B by way of diode D 3  and also to the inputs of monochrome LEDs  48 A and  48 B in optional emergency lights  30 A and  30 B by way of diode D 4 . Diodes D 3  and D 4  prevent the reverse current flow from the individual diode arrays back through transistor Q 1  into the positive terminal of battery  26 , and likewise back to the positive DC output of bridge rectifier BR 1 , thus allowing current to flow only in the directions from the anodes of diodes D 3  and D 4  to the cathodes of diodes D 3  and D 4  respectively. The base of transistor Q 1  is properly biased through resistor R 3  to DC ground  66  and the cathode of diode D 1  such that transistor Q 1  remains off and does not conduct when DC power is present at the positive DC output of bridge rectifier BR 1 . When there is an absence of DC power at the positive DC output of bridge rectifier BR 1  as a result of AC power failure or if power disconnect test switch  50  (SW 1 ) is depressed, the base of transistor Q 1  will cause transistor Q 1  to conduct and allow the DC voltage from battery  26  to flow from the positive terminal of backup battery  26  through transistor Q 1  from the emitter to the collector and through diode D 3  to power red LEDs  32 A and green LEDs  32 B, and also to flow through diode D 4  to power monochrome LEDs  48 A and  48 B in optional emergency light LED lights  30 A and  30 B.  
         [0061]    [0061]FIG. 6 shows a schematic block diagram  56 A of a selective bicolor LED lamp  58 A taken in isolation. Selective bicolor LED lamp  58 A is an alternative embodiment to selective color LED lamp  58  shown in FIG. 3. Selective bicolor LED lamp  58 A can be used in retrofit applications for existing illuminated signs or as the main selective color LED lamp in new fixtures. LED lamp  58 A includes alternating current voltage (VAC) power input  60 A that is converted by AC to DC converter  62 A, analogous to AC/DC converter  62  shown in FIG. 3, into a direct current DC voltage output. A single main or individual current limiter, or resistor  64 A, is used to limit the current going into the bicolor LED consisting of a red and a green LED die having separate anodes and sharing a common cathode. Bicolor red and green LED  86  is analogous to monochrome red LEDs  32 A and green LEDs  32 B of selective color sign  10 .  
         [0062]    A current limiter, or resistor,  64 A, which is analogous to current resistor  64  of LED lamp  58 , is in direct current communication with a two-position dipswitch  54 A, which is analogous in operation to dipswitch  54  discussed before and now relative to selective color LED lamp  58 A, is manually operable to close the power supply circuit. Dipswitch  54 A is in turn in direct current communication with bicolor red and green LED  86 . Current limiter  64 A thus limits the current to red and green bicolor LED  86 . Bicolor LED  86  may comprise a plurality of bicolor LEDs  86  connected in both a series and a parallel configuration for redundancy. This is done so that the majority of red and green bicolor LEDs  86  will remain energized in the event that one or more bicolor LEDs  86  in each array should fail. Red colors and green colors of bicolor LED  86  can be energized independently of one another by dipswitch  54 A. When both the red and green colors of bicolor LED  86  are switched on and energized, a third color, namely, the color yellow, will be produced from the color mixing of the output color emissions of the color red with the color green. Bicolor LED  86  is connected to DC ground  66 A. Dipswitch  54 A comprises two operational internal switches  54 AX and  54 BX. Internal switch  54 AX is capable of contact with the red color of bicolor LED  86 , specifically to the anode(s) of the LED die(s) for red colors while the cathode(s) of the color red of LED  86  is tied directly to DC ground  66 A. Internal switch  54 BX is capable of contact with the green color of bicolor LED  86 , specifically to the anode(s) of the LED die(s) for green colors while the cathode(s) of the color green of LED  86  is tied directly to DC ground  66 A.  
         [0063]    Selective color LED lamp  58 A allows the use of a single or multiple bicolor LEDs, that is, a single or multiple red and green bicolor LED(s) such that the entire package of an alternative to selective color LED sign  10  that includes separate anodes and a common cathode can be manufactured as an alternative to the individual and discrete red and green LEDs set forth and described herein for selective color LED lamp  58 . Thus the bicolor LED(s)  86  of FIG. 6 each contain red and green LED dies that can be selectively energized independent of each other so as to cause the emission of the color red or the color green, or can be energized simultaneously to emit red color and green color to produce the color yellow.  
         [0064]    Although the present invention has been described in some detail by way of illustration and example for purposes of clarity and understanding, it will, of course, be understood that various changes and modifications may be made in the form, details, and arrangements of the parts without departing from the scope of the invention set forth in the following claims.