Abstract:
An emergency lighting fixture combining the functions of an illuminated sign such as an exit sign and an emergency lighting unit integrated into one housing onto which one or more emergency lights can be mounted at predetermined locations of the housing, the combined emergency lighting structure providing both exit location information and ambient emergency lighting in a single cooperatively operating device. The present device replaces bulky prior combinations of discrete exit signs and emergency lighting units which have been assembled together essentially as individual devices without integration into a single housing or without substantial integration of operational features, the housing of the present device being only slightly larger than standard exit signage. The present fixture is preferably formed from light weight materials such as polycarbonate/ABS or sheet metal configured to mount in tension internal weight such as weight due to enlarged battery mass and the like as well as externally mounted emergency lights. Manufacture of the present fixture is improved by the ability to mold major portions of the fixture from suitable polymeric materials, thereby allowing formation of substantial portions of the fixture located internally of the housing integrally with the housing to substantially reduce the number of parts necessary to be assembled together in an assembly situation. Assembly, installation and maintenance of a molded fixture according to the invention is further improved by the ability to snap-fit together all structural elements of the fixture both internally and externally of the housing.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of application Ser. No 09/132,814, filed Aug. 12, 1998, now U.S. Pat. No. 6,142,648 which is a continuation of application Ser. No. 08/561,956, filed Nov. 22, 1998, now U.S. Pat. No. 5,797,673, issued Aug. 25, 1998, by the same inventors and assigned to the same assignee, said prior applications being incorporated hereinto by reference. 
    
    
     DESCRIPTION OF THE PRIOR ART 
     1. Field of the Invention 
     The invention relates generally to emergency lighting fixtures including illuminated signs and emergency lighting units and particularly relates to combinations of illuminated exit signs and the like with emergency lighting units to form fixtures having multiple emergency lighting functions in a single device. 
     2. Background of the Invention 
     Emergency lighting capability is mandated by building codes throughout most of the world for commercial buildings in particular. The most common type of emergency lighting is the exit sign which is also the most noticed due not only to its ubiquity but also due to the fact that most exit signs are constantly illuminated and are therefore readily seen. Exit signs are typically placed above doorways or in egress paths to indicate in a time of emergency the most efficient manner of exiting a building. Another common form of emergency lighting is generally referred to as an emergency lighting unit and typically operates two spaced lamps which are often referred to as “frog eyes”. Emergency lighting units operate only in the event of emergency and are intended to supply an acceptable degree of ambient illumination under emergency conditions, these conditions usually including loss of normal power. Since emergency conditions requiring the most immediate and effective use of both exit signs and emergency lighting units are normally associated with mains power loss, backup power is necessary for the continued operation of an exit sign and for start-up and continuing operation of an emergency lighting unit. This back-up power is provided by batteries, a typical exit sign having a battery and circuitry capable of switching to DC battery power from AC mains power on loss of AC power to the exit sign. An emergency lighting unit includes a battery and sensing circuitry which initiates operation of the battery on loss of normal building power, the lamps of the emergency lighting unit being then activated to provide emergency lighting. These two forms of emergency lighting, the exit sign and the emergency lighting unit, are placed in a building structure at locations requiring a particular function of each form. Certain situations require the use of both forms of emergency lighting in one location. Rather than USQ separate lighting fixtures in one particular location, common practice has been to use a “combination” exit sign and emergency lighting unit, this type of fixture being commonly referred to as an exit/unit combo. The “combo” has previously taken the form of an emergency lighting unit mounted to an exit sign, the emergency lighting unit most often being mounted along the top of the exit sign. In most instances, the exit sign and the emergency unit operate separately although certain functions can be shared between the exit sign and the unit by providing common circuitry such as would be useful to detect power line failure for switching the exit sign to DC battery power and for initiating operation of the emergency lighting unit. A particular exit/unit combo which has enjoyed substantial market acceptance is the QUANTUM Exit/Unit Combo manufactured by Lithonia Lighting, Inc. of Conyers, Ga., a wholly owned subsidiary of National Service Industries, Inc., of Atlanta, Ga., QUANTUM being a trademark of National Service Industries, Inc. The widespread use of the Lithonia Lighting combo has been brought about at least in part due to the reduced labor costs associated with installation of the Lithonia combo on site, the exit sign and the emergency lighting unit being factory assembled and prewired for shipment to a job site in a configuration allowing rapid and simultaneous final wiring of both the exit sign and the emergency lighting unit. Further, the Lithonia combo manufactured and marketed under the QUANTUM mark is comprised of a substantially all-plastic exit sign and a substantially all-plastic emergency lighting unit, thereby resulting in a combo product which is light in weight relative to previous combo products many of which included metal housings and parts which caused the products to be heavy and therefore more difficult to support especially in end mounted installations. The Lithonia QUANTUM combo could be rapidly and easily mounted at the top, back or ends with adequate support of the assembly being possible even when end mounted. Manufacture and maintenance of the Lithonia combo were facilitated by the virtual all-plastic structure of the Lithonia product which allows at least portions of the product to be positively and readily snap-fitted to each other. While the QUANTUM combo evidenced significant advantages in this art, the combination of two essentially different and distinct forms of emergency lighting into a single product with both the exit sign and the emergency lighting unit retaining its own housing inter alia such as would be employed in their separate use has caused combo products to continue being somewhat bulky in size and to be less attractive than most other forms of emergency lighting have become in recent years as the industry has devoted increased attention to the appearance of emergency lighting products generally. 
     Accordingly, the art has experienced a long-felt and continuing need for improvement of a combination exit sign and emergency lighting unit or combo product to the end that such products become a true integration of an exit sign and an emergency lighting unit capable of supporting the weights of batteries necessary for providing power to both sides of an exit sign as well as unit lamps including remote unit lamps. In addition to the need to support greater battery weights than previously necessary in exit signs alone, the need exists in a combo to support greater weight than is normally experienced with an exit sign per se so that a combo can be safely and positively mounted in wall or ceiling installations. The art has thus felt the need for the present combo invention which integrates the functions of an exit sign and an emergency lighting unit into a single housing with repositionable lamping elements mounted to exterior portions of the housing. The structure of the present exit/unit combo allows support of battery loads in tension rather than through the usual cantilevered support of loads disposed internally of a sign housing. The structure of the present combo housing provides support of such efficiency as to prevent warping or bowing of the housing over time, thereby providing substantially improved product quality along with substantially improved product appearance. The exit/unit combo of the invention is provided with significant structural features useful not only with the combo but also with exit signs per se and with emergency lighting units per se as well as remote emergency lighting units., The present invention thus provides substantial improvement over the prior art by the provision of an integral and integrated exit/unit combo characterized by ease of assembly, installation and maintenance as well as by extraordinarily acceptable appearance. 
     SUMMARY OF THE INVENTION 
     The invention provides an emergency lighting fixture which combines the functions of an illuminated sign, particularly an exit sign, with an emergency lighting unit, the structural combination being integrated into a single housing which internally contains those structural elements necessary to produce the functions of the feature and which carries emergency lamping externally of the housing at multiple locations thereby providing extraordinary flexibility in use. The present combination of an exit sign and an emergency lighting unit or “exit/unit combo” is preferably formed of a polymeric material such as polycarbonate/ABS, thereby allowing molding of a fixture housing with most of the structural elements necessary to produce the functions of the fixture being integrally formed with the housing, these molded structural elements and other structure contained within the housing being located in the housing in a manner whereby the elements combine to produce synergistic effects in addition to the primary functions of the structural elements, the fixture being totally integrated as to structure and function as well as being substantially integral in construction. Formation of the fixture essentially from moldable material further allows integral formation of snap-fitting structural elements which not only provide easy snap fitting of facing plates to the housing to form the primary structural portion of the combo per se but also the integral formation of snap-fitting structure with bulb holders, battery mounting elements and option board storage elements inter alia. Assembly of the fixture is therefore facilitated at least in part due to the reduced number of individual parts occasioned by the integral nature of the housing inter alia. 
     The housing of the present exit/unit combo fixture is configured to support battery weights inter alia which are typically greater than those battery weights encountered in conventional exit signs due to the need to operate exit lighting, unit lighting and even remote unit lighting with a single battery disposed within the housing. In order to accommodate greater battery weight and the weight of the fixture itself, the battery is centered with the housing disposed at a lower portion thereof, battery location couples with a central, vertical structural beam known as a “ladder” allows support of the battery inter alia in tension rather than in a cantilevered arrangement as has been previously employed in exit signs and the like. The structural features such as the ladder integrated with location of major weighting such as the weight of the battery actually allows use of a material such as plastic for formation of the fixture, the self-support provided by the structure itself preventing warping and bowing of the plastic exit/unit combo fixture over time such as would occur with a fixture having the weight of the exit/unit combo fixture if not provided with the integrated structural relationships of the invention. The dimensional stability of the present exit/unit combo fixture occurs due to the structural features of the fixture which maintain substantial portions of the fixture weight in tension. 
     The exit/unit combo fixture of the invention provides “unit” emergency lighting by the disposition of one or more emergency lamps mountable at different locations on the periphery of the fixture housing to accommodate differing lighting situations. The lamps are mounted by lamp holders fitted with swiveling concentric spherical structural elements which allow movement of the lamps with a degree of freedom not previously possible, the structure of the concentric spherical elements additionally yielding a compact profile which is not only attractive in appearance but functional due to the volumetric efficiency thus provided. The lamp holders of the invention are formed with torsion snap elements which fit into slots formed in peripheral edges of the housing, the slots receiving the snap elements of the lamp holders to positively mount the lamp holders in desired locations on the fixture. The particular snap element/slot arrangement of the invention allows rapid and ready mounting and dismounting of the lamp holders to and from the fixture housing with positive locking of the lamp holders to the housing once assembled. The lamp holders of the invention can be removed from the present fixture and mounted to remote slave mounting stations driven by the fixture with the snap elements of the lamp holder fitting into arranged slots of the slave station. Further, the lamp holder can be mounted to a station separate from the fixture with battery or other operation, the lamp holder being mounted to the station through use of the snap elements of the lamp holder in cooperation with slots formed in the station. 
     Various other features of the invention include structure for minimizing the “shadow” of the battery appearing through face plates of the exit/unit combo fixture; registration structure for mounting of a diffusion panel in a face plate of the fixtures; routing of wiring in association with the ladder support and in front of the battery with the use of slack in the wiring and structure for compartmentalization of electrical components within the interior of the fixture housing including snap-mounting of a capacitor inter alia. Many of the inventive features disclosed herein are useful in fixtures other than exit/unit combo fixtures and are disclosed for use in that variety of fixtures for which these features find utility. Use of these features is thus not limited to use in an exit/unit combo fixture. 
     Accordingly, it is an object of the invention to provide an integral exit/unit combo fixture having the capabilities of an exit sign and of an emergency lighting unit integrated into a fixture formed with a single housing for containing a substantial portion of the structures and for mounting emergency unit lamps on the housing externally thereof and at repositionally distinct locations of the housing. 
     It is another object of the invention to provide an integral exit/unit combo fixture substantially moldable of a polymeric material to allow formation of substantial structural portions of the fixture with a fixture housing, the housing and associated face plates being rapidly fitted together with snap features, components of the fixture internally of the housing being snap-fitted to the housing for rapid assembly thereof, structure holding emergency lighting lamping further being rapidly snap-fitted to the housing at predetermined locations on the exterior of the housing. 
     It is a further object of the invention to provide an integral exit/unit combo fixture substantially moldable of a polymeric material with structural support features providing dimensional stability to the fixture thereby minimizing warping and bowing of the fixture over time in spite of substantial weight occasioned by the use of heavy batteries as well as the weight of the fixture itself, the fixture including internal support elements which mount battery weight as well as the weight of the fixture per se substantially in tension. 
     It is a still further object of the invention to provide an integral exit/unit combo fixture having unit lighting provided by lamps mounted on exterior portions of the fixture by lamp holders mounted to the fixture by tension snap elements, each lamp being mounted by a swiveling double concentric structure which allows an extraordinary range of movement of the lamp and which allows formation of the unit lighting structure with a compact profile, the fixture requiring a reduced volume and vertical height for mounting of the fixture, the fixture being also mountable with the back of the fixture directly against a flat surface such as a wall. 
     Further objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first embodiment of the invention; 
     FIG. 2 is a side elevational view of the embodiment of the invention shown in FIG. 1; 
     FIG. 3 is a perspective view of a second embodiment of the invention; 
     FIG. 4 is a side elevational view of the embodiment of FIG. 3; 
     FIG. 5 is a front elevational view of a third embodiment of the invention; 
     FIG. 6 is a front elevational view of a fourth embodiment of the invention; 
     FIG. 7 is a front elevational view of a fifth embodiment of the invention; 
     FIG. 8 is a plan view of the embodiment of FIG. 3; 
     FIG. 9 is a view of the housing of the invention; 
     FIGS.10A and 10B are view of the back plate of the invention intended for wall mounting of the fixtures; 
     FIG. 11A is a front elevational view of the frame of the invention; 
     FIG. 11B is an elevational view taken from the rear of the frame of the invention; 
     FIG. 12 is a front elevational view of the invention partially in schematic illustrating an incandescent embodiment of the invention; 
     FIG. 13 is a front elevational view partially in schematic illustrating an LED/incandescent embodiment of the invention; 
     FIG. 14 is a perspective view of the invention illustrating remote location of a slave fixture according to the invention; 
     FIG. 15 is a perspective view of a fixture having a portion of the combination fixture forming a part thereof; 
     FIG. 16 is a perspective view illustrating the structure of FIG. 15 in an assembled relationship; 
     FIGS. 17A-E are elevational view of the frame of the invention; 
     FIG. 18 is a view of the ladder structure; 
     FIGS. 19A and 19B are detailed views of the battery compartment having a relatively small lead-acid battery mounted therein; 
     FIGS. 20A and 20B are detailed view of the battery compartment having a relatively larger lead-acid battery mounted therein; 
     FIGS. 21A and 21B are elevational views of a DC lamp mounting arrangement; 
     FIGS. 22A and 22B are detailed views of the electrical compartment of the housing. 
     FIG. 23 is a detailed view of an option storage compartment formed in the housing; 
     FIG. 24 is an assembly view of components comprising the repositionable emergency lighting unit lamp assembly; 
     FIGS. 25A-25C are views of the apparatus of FIG. 24; 
     FIGS. 26A-26C are views of the apparatus of FIG. 24; 
     FIGS. 27A-27F are views illustrating operation of the torsion snaps of the invention; 
     FIG. 28 is a simplified diagram of the circuitry of the invention; and, 
     FIG. 29 is a view of a front plate and diffusion panel arrangement of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and particularly to FIGS. 1 and 2, a combination exit sign/emergency unit fixture is seen at  10  to be comprised of a housing  12  and two emergency lighting unit lamp assemblies  13 . The fixture  10  will generally be referred to herein as the combo fixture  10  or merely as the fixture  10 . The housing  12  is essentially formed from frame  14  and face plate  16  as well as back plate  18 . In certain embodiments of the invention, the back plate  18  can be essentially identical to the face plate  16 , such a combo fixture  10  within constituting a double-faced fixture having indicia  20  on both faces thereof such as can occur in top and end mounted installations. In a direct wall-mounted installation, the back plate  18  is necessary in order for the combo fixture  10  to be mounted directly to a wall as will be described hereinafter. 
     The combo fixture  10  is typically provided with one or more directional indicators  22  which are often referred to as “chevrons”, the indicators  22  preferably comprising snap-fitting chevron structures which can be rapidly and positively mounted into openings  23  formed on the face plate  16  without the requirement for gaining access into the interior of the housing  12 . While various chevron structures can be utilized, a particularly suitable structure is disclosed in United States patent application Ser. No. 08/327,487, filed Oct. 21, 1994, now U.S. Pat. No. 5,611,163 by Stephen T. Smith with the title “Direction Indicator Covers for Emergency Lighting System”, the patent application being assigned to the assignee of the present patent application, the disclosure of Ser. No. 08/327,487, now U.S. Pat. No. 5,611,163 being incorporated hereinto by reference. Depending upon the exigencies of a particular installation, at least one of the indicators  22  is mated into the corresponding opening  23  to prevent light generated interiorly of the housing  12  from passing through the opening  23 . In certain installations wherein the combo fixture  10  may be placed directly over a doorway or the like, it is possible that both of the indicators  22  will be placed in the corresponding openings  23 . Certain other installations may require that neither of the directional indicators  22  be mounted in the corresponding openings  23 , such an installation signalling that a path of egress may exist to both sides of the combo fixture  10 . 
     As will be described in more detail hereinafter, and with additional reference to FIG. 9, a pair of incandescent lamps  24  are disposed within the interior of the housing  12  and operate on AC line voltage to illuminate the combo fixture  10  during normal, non-emergency situations during which the location of emergency egress paths is to be recognized by those persons using the environmental spaces within which the fixture  10  is mounted. A pair of emergency lamps  26  such as are seen in FIG. 9 are located internally of the housing  12  and powered only during loss of AC line voltage by means of a battery  30  (as seen in FIG. 9 inter alia), appropriate circuitry (not shown in FIGS. 1 and 2) causing DC voltage from the battery  30  to operate the emergency lamps  26  during a power failure such as would occur during emergency situations. The non-emergency lamps  24  thus illuminate the indicia  20  in normal situations with the emergency lamps  26  illuminating the indicia  20  during emergency situations. While the combo fixture  10  intends the indicia  20  to take the form of the word “EXIT” formed in the face plate  16 , it is to be understood that other indicia could be formed in the face plate  16  such as is conventional in the art. The use of non-emergency lamps such as the lamps  24  and driven by alternating current from building mains as well as the use of emergency lamps such as the lamps  26  operated on DC battery current in the event of power loss and/or emergency conditions is known in the art and need not be described in greater detail herein. As will be described hereinafter relative to FIG. 13, it is to be seen that a light emitting diode array  28  can be utilized in non-emergency situations as replacement for the lamps  24 . 
     Continuing to refer to FIGS. 1 and 2 as well as to FIGS. 3 through 5 and  8 , a canopy  32  is employed to mount the combo fixture  10  to a J-box (not shown) so that the fixture  10  is positively mounted either to the ceiling or to a wall of an environmental space within which the fixture  10  operates. As is seen in FIGS. 17B, C and D, openings  34  are provided in the frame  14  at least centrally of an upper edge of-the housing  12 . Openings  34  can similarly be provided on side edges of the housing  12  for end mounting of the fixture  10  such as can occur with the structure of FIGS. 6 and 7, that is, when one of the ends of the fixture  10  is available for end mounting. It is preferred that the combo fixture  10  be mounted either from the top or from the back as will be described in detail hereinafter and as is particularly shown relative to a top mount in FIGS. 1 and 2 inter alia. While various canopy structures can be utilized including a number of canopies which are conventional in the art, it is preferred to use the canopy described in co-pending United States patent application Ser. No. 08/343,775, filed Nov. 22, 1994, now U.S. Pat. No. 5,526,251 by Gary S. Andre, Andrew E. Masters and Stephen P. Smith. and entitled “Emergency Lighting Connections”, Ser. No. 08/343,775 now U.S. Pat. No. 5,526,251 being assigned to the assignee of the present application. While the canopy  32  and corresponding structure such as the openings  34  in the frame  14  inter alia which are present in the combo fixture  10  can be identical to that corresponding structure disclosed in co-pending patent application Ser. No. 08/327,487, now U.S. Pat. No. 5,611,163 it is to be understood that the canopy of the co-pending application for patent is only one of a number of canopy structures usable to fasten the combo fixture  10  to a J-box (not shown). In essence, mounting of the canopy  32  or any other canopy to such a J-box (not shown) is conventional in the art and further discussion of same is not believed necessary to an understanding of the present disclosure. 
     While the structural features of the combo fixture  10  which have been generally referred to hereinabove will be described in greater detail hereinafter, it is necessary at this point to describe certain general concepts which underlie the defined structure as seen in the drawings. Prior art combination exit sign/emergency lighting unit fixtures have usually been formed at least partially of metal especially in situations where the weight of the entire fixture is supported essentially by a housing such as the housing  12  which contains within the interior thereof essentially all structure except for the unit lamp assemblies such as the assemblies  13 . In such prior situations, batteries of substantial size have been necessary in order to provide power for the exit sign function as well as for the emergency unit function. Due to the substantial weight of the batteries and of the fixtures themselves, it has not been previously possible to support the weight of a combo fixture  10  when the fixture  10  has been effectively formed of “plastics” that is, polymeric materials, since a structurally all-plastic unit, until the present invention, would warp and bow over time even when formed of the strongest polymeric materials. If formed of plastic materials of lesser strength, a combination fixture usually deforms and is likely to break rather than merely deform. Therefore, the present invention provides a dimensionally stable combo unit  10  which does not warp or bow over time even though effectively formed completely of “plastic”, the combo fixture  10  being the first and only combo fixture formed of plastic wherein all batteries and other structural features are effectively contained and/or supported by a single housing such as the housing  12 . While the combo fixture  10  could be formed of a material such as sheet metal, it is to be understood that a number of the advantages of the invention would be lost if the combo fixture  10  is so formed. In particular, the combo fixture  10  can be assembled from a relatively small number of individual parts especially since the frame  14  as will be more fully described hereinafter can be molded from a plastic material to produce a single part having a very large number of structural features integrally formed therewith. All structural features of the combo fixture  10  are formed of plastic and are molded. Certain parts such as the lamps  24  and  26  and the battery  30 , for example, are not formed of plastic but are items which must be otherwise formed. However, these parts are not structural and have no function in support of the overall weight coupled with maintenance of the integrity of the combo fixture  10  per se. The function of the housing  12  as a single containing unit is further improved by the ability to snap-fit together virtually every combination of parts comprising the combo fixture  10 . Formation of the combo fixture  10  substantially from plastic materials facilitates not only the essentially integral nature of the fixture  10  with fewer parts but also facilitates the snap-fitting together of the relatively few parts comprising the fixture  10 . The essentially all-plastic single housing  12  is constructed as will be described hereinafter such that fixture weight can be supported without resort to metal structural features such as would be occasioned by battery weight inter alia in a combination exit sign/emergency unit fixture. 
     The structural strength of the present combo fixture  10  is provided even though the housing  12  is only slightly larger than the housings of most conventional exit signs. 
     A further general feature of the combo fixture  10  is occasioned by the cooperative relationship between the emergency lighting unit lamp assemblies  13  and the frame  14  of the housing  12 . The assemblies  13  can be positioned on each end of the housing  12  as is seen in FIGS. 1 and 2. However, the assemblies  13  can be otherwise mounted to the housing  12  such as is seen in FIGS. 5 and 7 by the simple provision of a pattern of slots (not shown in these figures) so that the assemblies  13  can be mounted to one side and to the top as seen in FIG. 5 or with two assemblies on top as seen in FIG.  7 . Although not shown in the drawings, slots can be formed in lower surfaces of the housing  12  so that one or more of the assemblies  13  could be mounted along the lower edge of the housing  12 . As is seen in FIG. 6, a dual unit lamp assembly  36  is mounted along the top edge of the housing  12  utilizing the same slot pattern as would be used with the structure shown in FIG.  7 . The structure preferred for mounting of the assemblies  13  and the assembly  36  will be described in detail hereinafter. Appreciation of the structure of the assemblies  13  and of the assembly  36  is necessary in order to understand the importance of the fact that said assemblies  13  and  36  can be repositioned on the housing  12  or removed entirely to constitute slave and/or remote units for producing lighting at locations distant from the combo fixture  10 . 
     Reference to FIGS. 3,  4  and  8  in particular illustrates a further capability of the invention, double-sided dual unit lamp assemblies  38  being substituted for the assemblies  13  so that the unit emergency lighting function can be provided relative to both faces of the housing  12 . Due to the low-profile space-saving nature of the structure of the assemblies  13 , it is a simple matter to form the double-sided dual unit lamp assembly  38  without substantial modification, this structure being best understood by subsequent description of the assemblies  13  inter alia. 
     As is best seen in FIGS. 14,  15  and  16 , either of the assemblies  13  and  38  can be removed from the housing  12  and attached to a mounting base  40  and driven as a remote slave unit from power provided by the battery  30  within the housing  12 . optionally, a battery (not shown) within the mounting base  40  (or made a part of the assembly  13  or the assembly  38 ) could provide power for a totally separate fixture as shown in FIGS. 14,  15  and  16 . The dual unit lamp assembly  36  of FIG. 6 as previously described could also be removed from the housing  12  of FIG.  6  and provided with a mounting base (not shown) of a greater lengthwise dimension than said base  40  and provided with a slot pattern capable of mounting said assembly  36  for use as a remote slave unit or as a remote, self-contained unit. FIG. 15 illustrates the pattern of slots  42  useful for mounting of the assemblies  13  and  38  to the mounting base  40  in a manner such as will be described in detail hereinafter. 
     Due to the complexity of the structural details of the combo fixture  10  and further in view of the independent nature of at least certain of the sub-systems comprising the fixture  10 , the remaining disclosure is organized by sub-headings which will allow for more ready access to information concerning the various structural features and sub-systems of said fixture  10 . 
     Housing Frame Construction 
     As previously described, the housing  12  essentially comprises a container formed by the frame  14 , the face plate  16  and the back plate  18 . In those installations wherein both faces of the housing are visible and are intended to provide egress information, the back plate  18  is replaced by a plate which would be essentially identical to the face plate  16 . The back plate  18  is used to enclose the housing  12  in those situations wherein the visible indicia  20  is only required on the “front” of the housing  12  and is provided by the face plate  16 . The back plate  18  is particularly used in situations wherein the combo fixture  10  is installed directly against a J-box (not shown) mounted flushly in a vertical wall (not shown), the back plate  18  being then mounted directly to such a J-box (not shown) through use of conventional connections with the back plate  18  connecting to the frame  14  as will be described hereinafter. 
     Referring now to FIGS. 17A through 17E, inter alia, the face plate  16  and the back plate  18  each connect to the frame  14  by means of four snap-fitting connections  44  which comprise two spaced slots  46  formed along top and bottom edges of each of the plates  16 ,  18 , each plate  16 ,  18  thus having a total of four slots  46  intended to facilitate connection of the plates  16 ,  18  to the frame  14 . The frame  14  is provided with a total of eight rounting tabs  48  with two each of said tabs  48  being disposed along each side of both of the top and bottom edges of the frame  14 , the tabs  48  being positioned to be received one each within each of the slots  46  formed in the plate  16 ,  18  so that the plate  16 ,  18  can be readily and rapidly assembled to the frame  14  to enclose the housing  12  as is best seen in FIGS. 17D and 17E. 
     Essentially all of the features of the combo fixture  10 , with the exception of the lamp assemblies  13  or similar structure, are contained within the housing  12  and are supported by the frame  14 . The lamp assemblies  13  are in essence also carried by the housing  12  but on exterior portions thereof. The weight of the combo fixture  10  due both to that structure located interiorly and exteriorly of said housing  12  is effectively supported in tension rather than by cantilever as is conventional in the prior art. The housing  12  and particularly the frame  14  is thus engineered in a manner particularly intended to support the weight of the fixture  10  in tension, thereby allowing the formation of the fixture  10  and particularly of the frame  14  essentially entirely of a “plastic” material such as polycarbonate/ABS. This ability to form the fixture  10  and particularly the frame  14  from plastic material then further allows the frame  14  to be molded integrally to thereby reduce the number of parts which must be formed and then assembled to produce the combo fixture  10 . The construction and structure of the frame  14  as a single molded piece still further allows the carriage of heavy parts such as the battery  30  inter alia internally of the housing  12  and within the single housing  12 . Formation of the combo fixture  10  and especially the integral frame  14  from a plastic material further facilitates the snap-together construction of the combo fixture  10 , virtually all parts of the fixture  10  being snap-fitted together thereby yielding a total structure which can be readily and rapidly assembled. 
     The advantages thus enumerated which accrue from the structure of the frame  14  inter alia can be best appreciated by consideration of the frame  14  shown in FIGS. 17A inter alia. FIG. 17A illustrates the one-piece frame  14  without mounting of other portions of the fixture  10  thereto. FIGS. 17B through 17E illustrate the frame  14  with the plates  16 ,  18  mounted thereto as illustration of the enclosed housing  12 . Prior to a discussion of the interior structure of the frame  14 , those features best seen exteriorly. of the fixture  10  will be described. 
     The frame  14  is seen to be provided on each end with a pattern of four slots  50  which are of a size and which are spaced apart in a rectangular form in the manner of the slots  42  discussed above relative to the mounting of one of the lamp assemblies  13  to the mounting base  40  to form a remote fixture. The top of the frame  14  is provided with two of the patterns of four slots  50 . The slots  50  are formed in the frame  14 ; however, portions of the periphery of the plates  16 ,  18  face the slots  50  on assembly of said plates  16 ,  18  to the frame  14  and to render less conspicuous the slots  50  into which torsion snaps  52  are inserted to mount the lamp assemblies  13  (as well as the lamp assembly  36  to the top of the housing  12 ) to the housing  12 . While not shown in FIG. 17E, a pattern of the slots  50  could be formed along the bottom of the housing  12  if mounting of one or more of the lamp assemblies  13  to the bottom of the housing  12  is desired. Mounting of one or more of the lamp assemblies  13  to the bottom of the housing  12  would be advantageous in situations where flexibility of operation is desirable within the space within which the combo fixture  10  is utilized. The frame  14  is also seen in FIG. 17E to be provided with fixed louver vent openings  54  to facilitate ventilation of the housing  12 . A flapper switch  56  is provided in the bottom of frame  14  in association with test circuitry (not shown in FIG. 17E) to allow testing of the electrical systems of the combo fixture  10  as will be described in detail hereinafter. 
     The canopy  13  referred to hereinabove can be used to mount the combo fixture  10  as will be described hereinafter and as is described in co-pending U.S. patent application Ser. No. 08/343,775, filed Nov. 22, 1994 as aforesaid, the disclosure of this application for patent being incorporated hereinto by reference. 
     Considering now the construction of the frame  14 , reference is particularly made to FIG. 17A wherein upper and lower walls  58  and  60  are integrally formed with side walls  62  and  64 , said walls defining the periphery of the frame  14  and thus of the housing  12 . An upper interior wall  66  extends parallel to the upper wall  58  and terminates at respective ends in corner plates  68  and  70 , the plates  68  and  70  each having side-mounted upper and lower angled elements  72  and  74  which have open-ended slots  76  which are capable of receiving wiring (not shown in FIG. 17A) for holding said wiring in place within the interior of the housing  12 . The plates  68  and  70  respectively define spaces  78 ,  80  within which wiring, wire nuts, plugs and the like (not shown) can be disposed. The plates  68 ,  70  along with the angled elements  72  and  74  provide strengthening of the frame  14  even in the absence of the interior wall  66 . Coupling of the interior wall  66  with the plates  68 ,  70  and angled elements  72 ,  74 , respectively, and further with interior side walls  82  and  84  provides a high degree of stiffness and rigidity to the frame  14 . The side walls  82  and  84  connect at respective ends to a lateral platform  86  comprised of horizontally disposed side tables  88  and  90  which connect to a central mounting angle  92  which is surmounted by central support webs  94  and  96  which further connect to side webs  96  and  98  respectively through upper vertical walls  100  and  102 . The side webs  96  and  98  respectively connect to end webs  104  and  106  through triangular normally related supports  108  and  110 , the end webs  104  and  106  respectively connecting to lowermost ends of the side walls  82  and  84 , thereby providing a continual interior structural web which is centrally bisected by a vertical ladder  112  formed of spaced vertical stiles  114  having horizontal rungs  116  regularly disposed along the stiles  114 . Openings between the rungs can be utilized for management of wiring within the interior of the housing  12  and particularly relative to options available with the combo fixture  10 . At the lower end of the ladder  112 , the support webs  94  bend 90° to form ladder connection walls  118  which join to respective ends of the stiles  114 . A bottom ladder plate  120  completes connection of the stiles  114 , the plate  120 , the lower ends of the stiles  114 , the walls  118 , and the support webs  94  by connecting to and being integrally formed with top portions of the angle  92 . The top end of the ladder  112  joins integrally with the upper interior wall  66  and the upper wall  58 , thereby providing a tensioned support structure internally of the housing  12  which acts to support the weight of the combo fixture  10  substantially in tension rather than cantilevered as in prior exit signs and sign-like fixtures. The weight of the battery  30  located within battery compartment  122  is particularly seen to be mounted in tension by the ladder  112  inter alia due also in part to the placement of the battery  30  (and any other battery) centrally of the interior of the housing  12  and along the lower portion thereof. 
     Interior canopy mounting housing  124  are respectively disposed centrally between the upper wall  58  and the interior wall  66  and between the side walls  62 ,  64  and the interior side walls  82 ,  84 . wiring guide clips  126  are disposed on either side of the uppermost mounting housing  124  to facilitate a desired location of wiring (not shown in FIG. 17A) along upper portions of the housing  12 . Substantially conventional mounting elements  128  each releasably hold lamp bases  130  and associated non-emergency AC bulbs  132 , the mounting elements  128  also being integrally formed with the frame  14 . Mounting bases  134  capable of holding lampsockets  136  and associated DC emergency bulbs  138  are integrally formed on respective portions of the support webs  94 , the location of the bulbs  138  acting to produce light at locations above the battery compartment  122  so that light can be directed about the upper portions of the battery  30  (or other battery) to reduce the shadowing effect of the battery  30  within the indicia  20  as will be described in greater detail hereinafter. 
     An electronics compartment  140  is located below the side table  88  and laterally of the battery compartment  122  while an options compartment  142  is located below the side table  90  and to the other side of the battery compartment  122 . The respective compartments  140  and  142  are separated from the battery compartment  122  by means of respective vertical walls  144  and  146 . The various structures integrally formed with the frame  14  and contained within the compartments  122 ,  140  and  142  will be described in detail hereinafter. Clips  148  disposed on opposite sides of the interior of the housing  12  extend respectively from the corner plates  68 ,  70  and are adapted to hold respective LED arrays  28  (see FIG. 13) within the interior of the housing  12 . The structures described above and which can be seen in FIG. 17A are integrally formed with the frame  14  by molding of a plastic material. In essence, the entire structure seen in FIG. 17A is a single unitary structure comprising the frame  14  and molded with said frame  14  are openings provided as a means for reducing the amount of plastic necessary for molding thereof. 
     Tension Support and Weight Management Arrangements 
     As described above, the ladder  112  is provided as an integral portion of the frame  14  to provide support in tension for the entirety of the combo fixture  10  and particularly for the battery  30  held within the battery compartment  122  (or for any other battery held within the battery compartment  122 ). The ladder  112  is advantageously located within the interior of the housing  12  to provide tension support for the weight of the fixture  10  as well as for battery weight. It should be understood, however, that the ladder  112  could take other forms, such as a solid vertical member whether or not connected permanently to the angle  92  at the lower end thereof or to the interior wall  66  and the wall  58 . The ladder  112  is formed of the stiles  114  and of the rungs  116  in order to provide openings  115  between the rungs through which wiring can be strung for management of the location of wiring within the interior of the housing  12 . The openings  115  are also provided for reduction of material and for facilitating light movement within the interior of the housing  12 . When the fixture  10  is back mounted, the openings  115  also serve to provide access for routing wiring (not shown) within the interior of the housing  12  as will be better appreciated hereinafter. The battery  30  is located centrally of the lower portion of the housing  12  so as to advantageously allow the ladder  112  to act in tension to support the weight of the battery  30 . While the battery  30  is intended to be a conventional rechargeable lead-acid battery, it is possible to utilize lead-acid batteries of greater capacity with weights up to approximately 4 pounds when a greater amount of power is necessary for providing for a greater period of time and for that additional power necessary to operate slave units remote from the fixture  10  such as has been described above. It is also possible to utilize nickel-cadmium batteries of smaller size, the smaller Ni—Cd battery (not shown) being mounted within the interior of the battery compartment  122 , the details of mounting of the Ni—Cd battery within the compartment  122  not being described herein. As aforesaid, the ladder  112  is provided with horizontal elongated tab elements  154  and  156 , the elements  154  and  156  being preferably used for management of wiring (not shown) associated with the fire alarm interface  150 . The ladder  112  is further provided with peg elements  152  disposed one each on either side of the ladder  112  and extending from each of the stiles  114  near the uppermost end of the ladder  112 , the peg elements  152  acting to receive snap elements  158  and  160  located on the interior wall of the back plate  18  as will be described hereinafter, the snap elements  158  and  160  cooperating respectively with the peg elements  152  to facilitate mounting of the frame  14  to the back plate  18  when the back plate  18  is mounted directly to a J-box (not shown) mounted flushly in a wall surface. 
     Battery Mounting Arrangements 
     As aforesaid, the battery compartment  122  is configured to house the battery  30  as well as a larger battery  162 . It is to be understood, however, that only one of the batteries  30  and  162  would be utilized at any one given time. As can be seen in FIGS. 17A inter alia, the battery compartment  122  is formed centrally of the lower portion of the combo fixture  10  and is provided with snap fingers  164  on inner surfaces of the walls  144  and  146 , the snap fingers  164  extending from said wall surfaces at a lesser height forwardly of the compartment  122  and terminating at a greater height interiorly of the compartment  122  such that the battery  30  can slide over the snap fingers  164  and into a position of essentially against a back wall  166  of the battery compartment  122 . It is to be seen that the battery compartment  122  is provided with a top wall  168  having tabs  170  extending downwardly therefrom at the outermost end of said top wall  168  so that the larger battery  162  can be slipped into place under the tabs  170  and into a position abutting the back wall  166  and held by the tabs  170  in order to hold the larger battery  162  in place. Accordingly, the battery compartment  122  is provided with structure capable of holding batteries of at least two different sizes within said compartment  122  by snap-fitting arrangements. 
     When placed within the battery compartment  122  as is necessary for operation, the batteries  30  and  162  are of a sufficient height as to extend into the lower part of the indicia formed in the face plate  16 . Due to this extension of the battery  30  and the battery  162  into the legend, it is possible that a shadowing effect is caused such that lower portions of the indicia are darker than upper portions of the indicia. The location of the lamps  24  within the interior of the housing  12  during normal operation and the location of the lamps  26  within the interior of the housing  12  during emergency operation provides light within the interior of the housing  12  which is reflected within said housing interior. This light is controlled in part by means of a reflective cover  172  attached to the top of the battery  30  (or the battery  162 ) with the lower edge of the reflective cover  172  extending downwardly to at least the level of the side tables  88  and  90  such that light is reflected outwardly of the lower portions of the indicia  20  on the face plate  16  to locally increase the amount of light passing through said indicia  20  at lower portions thereof. Provision of the reflective cover  172  thus acts to reduce the effect of the otherwise dark form of the battery  30  or the battery  162  so that the shadowing effect does not detract from the appearance and function of the indicia  20 . Optionally, at least the upper portion of the batteries  30 ,  162  could be painted with a white paint or coated with a reflective material in order to provide a function similar to the function of the reflective cover  172 . The reflective cover  172  can also be utilized as a pull tab for removal of the battery  30 ,  162  from the battery compartment  122 . The ability to allow the upper portion of the battery  30 ,  162  to extend into the “legend” or indicia  20 , allows the height of the housing  12  to be reduced so that the combo fixture  10  is more compact and exhibits a relatively lower profile. 
     It is to be seen that wiring extends from the electronics compartment  140  to the options compartment  142  as is seen in FIG. 9 , this wiring  174  is caused to be slack in front of the battery compartment  122  so that insertion of one of the batteries  30 ,  162  into the battery compartment  122  does not engage the wiring  174  and pull said wiring into the battery compartment  122 . 
     Emergency DC Lamp Mounting 
     Referring now to FIGS. 21A and 21B, as well as to FIGS. 17A inter alia, one of the mounting bases  134  intended for mounting one of the DC bulbs  138  is now described, a description of one of the DC emergency lamps  26  sufficing for a description of both. The bulb  138  is snapped into the lamp socket  136  to be structurally held thereby and to electrically connect with the lamp socket  136  to power provided in an emergency situation by the battery  30 ,  162  inter alia. The lamp socket  136  is formed of a rectangular collar  176  open at one end to receive the bulb  138 , electrical contacts (not shown) being located within the interior of the collar  176 . The collar  176  terminates at the end opposite the bulb  138  in a reduced lower base portion, the lamp socket  136  snap-fitting into one of the mounting bases  134 . The lamp base  134  is formed of two basic upper elements  180  each having walls  182  which are perpendicular to each other, rear walls  182  extending toward each other but not contacting at the rear of the base  134 . Snap tabs  184  extend from the facing walls  182  toward each other at the upper end of the base  134 , the heights of the walls  182  being essentially equal to the height of the collar  176 . A pair of lateral snaps  186  extend from the rear of the base  134  below the walls  182  and receive the lower base portion  178  therebetween when the lamp socket  136  is snap-fitted into the mounting base  134 . The collar  176  of the lamp socket  136  is partially enclosed by the walls  182  with the sanp tabs  184  abutting against upper edges of the collar  176  to prevent dislodgement of said socket  136  in an upward direction. The discontinuity provided by the lack of contact between the rear walls  182  thereby allows upper portions of the mounting base  134  to expand on insertion of the lamp socket  136  thereinto. Snap mounting of the lamp socket  136  to the mounting base  134  therefore occurs. The lateral snaps  186  prevent dislodgement of the lamp socket  136  forwardly of the mounting base  134 , the snaps  186  fitting against the reduced lower base portion  178  so that the lamp socket  136  is positively retained within the mounting base  134 . 
     The mounting of the DC emergency lamps  26  can thus be accomplished both rapidly and easily and within a minimum of parts not integrally formed with the frame  14 . 
     Housing Details 
     As seen particularly in FIG. 23, the options compartment  142  is further defined by back wall  188  which has a plurality of openings  190  formed therein to reduce the quantity of plastic material necessary for formation of the frame  14  and to facilitate ventilation of the housing  12 . A variable printed circuit board capturing assembly is seen to be disposed centrally of the compartment  142  at  192  to comprise spaced apart upper and lower plates  194  and  196  with each plate having an inwardly extending lip  198  formed along respective outer edges of the plates  194 ,  196 . The plates  194 ,  196  are attached along inner edges thereof to the back wall  168  and have the capability of springing together when separated from each other by pressure. A printed circuit board bearing an option such as a fire alarm interface option can be mounted between the plates  194 ,  196  and held by the spring function existing between said plates  194 ,  196 . The lips  198  further act to hold the printed circuit option board between the plates  194 ,  196 . The printed circuit board is thus mounted in a manner to prevent damage thereto. 
     Pairs of horizontal surfaces  200  and  202  mount respectively at lower portions of the compartment  142  and at upper portions thereof to form small interior spaces within the compartment  142  for placement of other options such as buzzers and the like. A pair of vertical stem walls  204  mounted in spaced relation to each other and under the lower plate  196  also act to form a space capable of storing an option board or a shrink-wrap option or the like. 
     Referring now to FIG. 22, inter alia, the electronics compartment  140  is seen to be provided with a space for snap-mounting of a capacitor  206  therewithin, upper and lower housing walls  208  and  210  extending interiorly of the compartment  140  to form a housing space for the capacitor  206 . A flexible snap element  212  mounted to back wall  214  and formed in a slot between side walls  216  and  218  which are also mounted to the back wall  214 . The snap element  212  is provided with fingers  220  which abut the capacitor  206  and in combination with fixed snap tabs  222  formed on interior wall surfaces of the frame  14  act to positively hold the capacitor  206  within the compartment  140 . A charger board  224  is snap-fitted within the compartment  140  by tabs  226 , the board  224  having an LED indicator  228  extending therefrom through an aperture  230  formed in the frame  14 , the aperture  230  being best seen in FIG.  17 E. The flapper switch  56  seen in FIG. 17A is seen in FIG. 22 to engage a test circuit seen as a block diagram in FIG.  28 . The electronics compartment  140  is covered by means of a shaped cover  234  formed preferably of a fiberboard material known as fish paper. The cover  234  form fits over the opening in the compartment  140  to prevent accidental intrusion into the compartment  140 . 
     Diffusion Panel Mounting Arrangement 
     Referring now to FIG. 29, the face plate  16  is seen with diffusion panel  236  in an assembly view illustrating the manner by which the panel  236  is mounted to inner walls of the face plate  16 . As is seen in FIG. 1 inter alia, portions of the diffusion panel  236  are seen through the indicia  20  formed in the face plate  16 . The diffusion panel  236  is formed as a filter or from colored material so that a desired color such as red or green is seen through the indicia  20 . The diffusion panel  236  is held to the face plate  16  by means of spaced pairs of snaps  238  located on opposite sides of the indicia  20 , the pairs of snaps  238  being spaced apart a distance equal to the width of the panel  236  at the locations of the snaps  238 . The panel  236  is formed with a tab  258  located on lower edge  244 , the tab  258  allowing the panel to only fit within rectangular recess  240  in one orientation such that the appropriate face of the panel  236  faces outwardly and is disposed immediately behind the indicia  20 . The panel  236  also has an upper edge  242  with angled side edges  246  and  248  which terminate in opposing flat edges  250  and  252 , the flat edges  250  and  252  respectively fitting between raised tabs  254  and  256 . The tabs  254  and  256  prevent lateral motion of the panel. The tab  258  abuts the upper edge of the recess  240  to prevent mallocation of the panel. Further, the tab  258  will not fit under one of the snaps  238  when the panel  236  is inappropriately inverted. 
     The face plate  16  is also provided at its upper edge with a structural wall  260  which joins to corner elements  262  and  264  each having angled elements  266  and  268  respectively formed thereon, this structure cooperating with opposed structure on the frame  14  as described above to further strengthen the housing  12 . 
     Back Panel Mounting Arrangement 
     Referring to FIGS. 10A and 10B, the back panel  18  is seen to be formed with knock outs  270 ,  272  and  274  as well as with a center channel knock out  276 . The knock out  276  is removed when the back panel  18  is to be used to directly mount the combo fixture  10  to a wall (not shown). A J-box (not shown) in a wall is fitted with a bracket (not shown) as is conventional and the appropriate knock out  270 ,  272  or  274  corresponding to the size of the J-box is knocked out by removing the plastic flashing within ovals  278  associated with a particular ring of the knock outs. The back plate  18  is then mounted to the J-box and bracket (not shown). The frame  14  is then mounted to the back plate  18  with peg elements  152  being received within apertures  155  formed in the snap elements  158  and  160  extending from the inner face of the back plate  18 . Housing  12  is thus snap-fitted to the back plate  18  to mount substantial portions of the weight of the combo fixture  10  in tension. Angled ramps  161  and  163  provide lead-ins to engage the peg elements  152  in the apertures  155 . 
     The back plate  18  is formed at upper corners thereof with structural corner plates  280  and  282  each having angled elements  284  and  286  respectively formed thereon, the structure cooperating with opposed structure of the frame  14  as described above to further strengthen the housing  12 . 
     Unit Lamp Mounting Arrangement 
     Referring now to FIGS. 24 and 25 , one of the emergency lighting unit lamp assemblies  13  is seen to comprise a lamp holder  284  having an opening  286  formed in at least one major face thereof, an arcuate swivel plate  288  having the general shape of a spherical segment and being receivable within the opening  286  and snap-fitted thereinto for swiveling motion in said opening  286 , a lamp housing  290  which snap-fits onto the swivel plate  288  for movement relative to said plate  288 , a parabolic reflector  292  and a lens  294 . A bulb  296  preferably comprising a T5 wedge base incandescent lamp manufactured by the General Electric Corporation is mounted to the lamp housing  290  and is activated on failure of AC line voltage and driven by DC power supplied by the battery  30 , the battery  162  or a Ni—Cd battery as aforesaid. The structure of one of the assemblies  13  sufficies for description of any other one of the assemblies  13  since the assemblies are essentially identical. 
     The lamp holder  284  comprises a stationary platform mounted to the frame  14  by insertion of the four torsion snaps  52  into any one of the patterns of four of the slots  50 . The lamp holder  284  is thus quickly mountable to the frame  14  and readily removed from the frame. The lamp holder  284  preferably takes the form of front and rear angled surfaces which outwardly terminate at  298 . Triangular lateral surfaces of the lamp holder  284  complete the shape of the lamp holder  284 . It is to be understood that the lamp holder  284  can be otherwise shaped as long as at least one major surface is available for formation of the opening  286  therein. It is also to be understood that an opening such as the opening  286  could be formed in the other major surface of the lamp holder  284  so that additional lamping could be carried by the lamp holder  284  as seen generally in FIGS. 3 and 4 inter alia. Four of the torsion snaps  52  are formed on base edges of the lamp holder  284  and are positioned thereon to mate with the slots  50  as aforesaid. 
     The swivel plate  288  is provided with pairs of lands  300  placed about the periphery of said plate  288 , three pairs of the lands  300  being adequate for support of the plate  288  within the opening  286  of the lamp holder  284 . The lands  300  prevent the plate  288  from falling into the interior of the holder  284  and facilitate swiveling motion of the plate  288  within the opening  286 . Cut-outs  302  are formed between two pair of the lands  300 . Each of the cut-outs  302  has a U-shaped snap  304  located within the cut-out  302 , the snaps  304  facilitating the snap-fitting of the plate  288  into the opening  286  of the lamp holder  284 , movement of the plate  288  within the opening  286  being also thus facilitated. The third pair of the lands  300  is spaced equidistantly from the two pair of lands  300  having the cut-outs  302  formed therein, a T-shaped cut-out  306  being formed between the lands  300  of this third pair of lands. A prong  308  is formed immediately behind the cut-out  306 , the prong  308  acting to hold the plate  288  within the opening  286  and to provide a stop function in concert with detent  309  located interiorly of the lamp holder  384 . A guide track assembly  310  is formed centrally of the spherical swivel plate  288  and comprises a base  312  having spaced pairs of spaced track tangs  314  which surmount one each of a slot  316  in a pattern of the slots  316 , the slot pattern being rectangular in conformation. An oval slot  318  is formed in the plate  288  centrally thereof and within the assembly  310 , one each of a pair of apertures  320  being formed in the plate  288  on opposite sides of the oval slot  318  and between vertically related slots  316  of the pairs of slots  316 . At least certain of the openings thus formed in the swivel plate  288  facilitate passage of wiring (not shown) from a bulb socket  297  into the interior of the lamp holder  284 . 
     The lamp housing  290  is formed as a spherical segment which is concentric with the spherical shape of the swivel plate  288 , the spherically shaped rear walls of the lamp housing  290  being received into the concentrically formed spherical concavity of the swivel plate  288  to cause the assembled unit to exhibit a low profile. Flats  322  are formed parallel to each other at spaced edges of the lamp housing  290  with a perpendicularly disposed flat  324  being also formed at the edge of the lamp housing  290 . An arcuate slot  326  formed centrally of the lamp housing  290  and extending from the flat  324  to the edge of the lamp housing  290  opposite the flat  324 . An arcuate bridge  328  extends immediately below the slot  326  and is formed with a snap detent  330  therein immediately interiorly of the flat  324 , the detent  330  having a spring capability such that the detent  330  snaps back to its original position after being biased inwardly of the housing  290  on fitting of the swivel plate  288  to the lamp housing  290 . The bridge  328  is further formed with a bulb base mount  332  near the end thereof opposite the detent  330 . The mount  332  is formed of spaced track elements  334  with a depressable tongue  336  being disposed between the track elements  334 . The bulb  296  is mounted by a socket base  338  having a plate  340  extending from the base  338  to fit under the track elements  334  and being held therebetween by the tongue  336  which is depressed downwardly on insertion of the plate  340  between the track elements  334  and which rebounds to bias against the plate  340  to maintain the base mount  332  and thus the bulb  296  in place. Track following edges  342  of the lamp housing  290  which define the slot  326  are received under the tangs  314  of the guide track assembly  310  on the swivel plate  288  to allow the lamp housing  290  to move in an are relative to the swivel plate  288  essentially along a detent of that circle-like geometric shape defined by the periphery of the swivel plate  288 . When the lamp housing  290  is fully received by the guide track assembly  310 , the detent  330 , which detent  330  is depressed as the lamp housing  290  is received by said guide track assembly  310 , is released and springs back to engage a wall  344  of the assembly  310  to prevent disengagement of the lamp housing  290  from the swivel plate  288  without first depressing the detent  330 . 
     A reflector  292  is received within the lamp housing  290 , the reflector  292  comprising a plastic structure which is coated with a reflective layer  346 . The reflector  292  is formed as a parabola of rotation which fits within the lamp housing  290  and is received within the housing  290 . An opening  348  formed in the reflector  292  allows the bulb base mount  332  of the lamp housing  290  to extend therethrough to be exposed for its intended purpose. The periphery of the reflector  292  is shaped to fit the shape of the lamp housing with a flange  350  having a cut-out  352  being formed at the periphery of the reflector  292  adjacent the opening  348 , the cut-out  352  receiving an end of the bridge  328  of the lamp housing  290 . Portions of the flange  350  are received under a peripheral segment  354  formed on the lamp housing  290 , the segment  354  being connected to that end of the bridge  328  received by the cut-out  352 . 
     The lens  294  snap-fits onto the lamp housing  290 , the periphery of the lens being shaped to fit the shape of the lamp housing. A flange  356  having a cut-out  358  is formed on one edge of the lens  294 , the cut-out  358  receiving an end of the bridge  328  of the lamp housing  290 . Portions of the flange  356  are received under the peripheral segment  354  of the lamp housing  290  to facilitate holding of the lens  294  to the lamp housing  290 . A snap  360  formed in the lens  294  opposite the flange  356  snaps the lens  294  onto the lamp holder  290  in cooperation with a cut-out  362  formed in the reflector  292  and snap fingers  364  formed on the lamp holder  290  and received into the cut-out  362 . The lens  294  can be “frosted” if desired to provide a more diffuse light. 
     The lamp assembly  13  is seen to mount to the frame  14  of the housing  12  by means of the torsion snap  52  fitting into the slots  50 . Each of the torsion snaps  52  are essentially plow-shaped with a rounded shank  366  extending directly from the lamp holder  284 , distal end  368  of the snap  52  tapering to a point and being outwardly angled medially of the shank  366 . The torsion snaps  52  on insertion into the slots  50  actually act to pull the lamp holder  284  to the housing  12 . When the snaps  52  are inserted into the slots  50 , the snaps  52  are bent straight in order to fit into said slots  50 . While the snaps  52  are formed of a plastic material, the snaps  52  are resistant to creeping. Even if the snaps  52  creep, the degree of creep will not be sufficient to cause the snaps  52  to creep to clearance, that is, the snaps  52  will not deform over time to allow the snaps  52  to straighten sufficiently to fall from the slots  50 . 
     The concentrically spherical arrangement of the swivel plate  288  and the lamp housing  290  allow an optimized degree of freedom while allowing a low profile of the assembly  13 . The assembly  13  is therefore compact volumetrically while being adjustable in position over a wide angular range. The degree of angular freedom is constrained by stop structure as described above which prevents wire breakage. 
     Electrical Systems 
     Referring now to FIGS. 12 and 28, the circuitry employed in the incandescent embodiment of the invention is shown. The circuit is disclosed in co-pending U.S. patent application Ser. No. 08/519,804, filed Aug. 28, 1995, by James C. Johnson, and entitled Emergency Lighting Battery Charging Circuit, the pending application for patent being assigned to the assignee of the present application for patent. The disclosure of Ser. No. 08/519,804 now U.S. Pat. No. 5,646,502, is incorporated hereinto by reference. FIG. 28 comprises a wiring diagram which particularly shows the use of a single pole battery connector  370  used with a lead-acid battery such as the battery  30 . When the Ni—Cd battery is used as seen in FIG. 28, a polarized battery connector  372  is utilized. FIG. 13 illustrates mounting of the LED arrays  28  on opposite sides of the housing  12 . The arrays  28  provide non-emergency lighting of the indicia  20  on AC mains power. When the arrays  28  are used, the AC lamps  24  are eliminated. 
     Particular embodiments of the invention have been described above in relation to illustrations of a preferred combo fixture  10  as provided in the drawings. However, it is to be understood that the invention can be embodied other than as is described and shown herein. The invention can particularly be used in the construction of emergency lighting fixtures other than combination exit sign/emergency unit fixtures. Accordingly, the scope of the invention is defined by the recitations of the appended claims.