Abstract: A plunger 20 which moves in and out relative to an illuminated panel 10 to operate a switch 18 is assembled from the front of the panel by pushing a shaft 24 with radial extensions 28 through a socket. The extensions yield to allow the shaft to pass through the socket and spring out once the shaft has passed through. A compressible gasket 32 is positioned between a shoulder 34 on the knob and the front face of the panel 10, to prevent light leaking from behind the panel, and to provide a restoring force to return the plunger to its start position after operation.

Abstract: In an illumination lamp mounting structure for use in a measuring instrument, a lower case 21 includes a front surface opening portion 22 and a rear surface opening portion 23, a movement supporting intermediate wall 24 interposed between the front surface opening portion 22 and rear surface opening portion 23 of the lower case 21 is formed integrally with a light source supporting intermediate wall 25 which is situated nearer to the front surface opening portion 22 than is the movement supporting surface of the movement supporting intermediate wall 24. and on the light source supporting intermediate wall 25, there is supported an illumination lamp 32 which is used to illuminate the display plate 33 transmissively.

Abstract: An indicator assembly includes a dial assembly and a pointer assembly. The dial assembly includes an opaque outer member and a translucent inner member with tapered walls. The pointer assembly includes a translucent pointer and a opaque light collecting member. The translucent pointer is adapted to be mounted for rotation relative to the dial assembly about a pivot axis. The opaque light collecting member is attached to the end of the pointer and includes a light blocking wall radially extending around the end which defines a light collecting cavity that receives the end of the pointer.

Abstract: A backlighting system for a liquid crystal display (LCD) unit includes a first number of light emitting diodes (LEDs) configured to produce saturated radiation and a second number of LEDs configured to produce desaturated radiation, wherein the saturated and desaturated radiation is combined to form a resultant desaturated radiation of a target color. In a preferred embodiment, the colors and intensities of the first and second numbers of LEDs are chosen to produce a blue-green color of a typical vacuum fluorescent (VF) display unit, whereby the LCD unit may be used to simulated a typical VF display. By utilizing the concepts of the present invention, known dispersive effects associated with the LCD unit are minimized, and a substantially uniform light output from the LCD unit results regardless of a viewing angle relative to the normal of the viewing side of the LCD unit.

Abstract: Light emitting panel assemblies include in one form of the invention a light emitting panel member made of a transparent resiliently deformable elastomeric material that absorbs impact without breakage for use in automotive lighting applications of various types. In another form of the invention, a rigid light emitting panel member may be used with dome switches for switch area lighting or to backlight control buttons/key pads by providing holes or openings in the panel member for the control buttons/key pads. Also, a rigid light emitting panel member may be used as a structural member, and two or more such light emitting panel members may be stacked together and used to light an instrument panel or the like. One or more light sources may be mounted within one or more light transition areas adjacent one or more light input surfaces of the light emitting panel members.

Abstract: In a light illuminating type manipulation and display apparatus including a light source and rotary knobs having a plurality of stop positions and indicator sections which are illuminated and displayed with the light from the light source at each of the stop positions. In the apparatus, light reflecting bodies having a plurality of light reflecting surfaces corresponding to a plurality of the stop positions of the rotary knobs are disposed, and the light from the light source is reflected from each of the light reflecting surfaces of the light reflecting bodies and illuminates the indicator sections located at each of the stop positions. With this arrangement, the quality of the apparatus can be improved with reduced power consumption.

Abstract: A substrate coupling structure for a flat panel variable visual display monitor may be constructed with a guide rib, formed on the inside surface of a rear monitor cover, having a race for receiving two adjacent edges of a rectangular substrate (PCB); and a plurality of elastic snaps, formed on the rear cover opposite the guide rib, each having a catch for receiving the other two edges of the substrate, thereby enabling the substrate to be securely coupled to the rear cover.

Abstract: A demonstration display for light controls supports a number of lamps mounted behind translucent light transmitting panels each with a lighting control coupled thereto whereby the amount of light produced by the associated lamp is controlled by the setting of the controls. By operating the control, the user can vary the amount of light produced and appreciate the manner in which the control operates. The user can, by comparing various controls, select the one which meets his needs for installation.

Abstract: A transparent display panel such as an electroluminescent panel is overlapped on a part of a conventional instrument panel for use in an automobile. The overlapped display panel displays additional information such as navigation maps when required and is turned off under a normal driving condition. When the overlapped transparent display panel is turned off, the conventional instrument panel displays information such as a vehicle speed, an engine speed so and so forth. In this situation, overall luminance on the combined display panel is made uniform throughout a whole surface including the area where the transparent display panel is overlapped. To realize the uniformity of luminance, brightness of back lamps for illuminating the instrument panel is adjusted or a filter having an adequate transparency is used. The combined display panel may be also made by combining a non-transparent display panel with a conventional instrument panel.

Abstract: A light source is positioned to direct light downward from the cover of a conventional analog or electro-optical watch, indicator gauge, a meter panel directional gauge or ornamentation display of an image, logo or design or other similar articles. These articles are illuminated by the source for viewing in low light or in the dark by an illumination switch to activate said element. The light source is preferably an LED and it is small enough so that when it is off, it is virtually invisible.

Abstract: A surface light source device, comprising a light source (2); a light conductor (1) which has a light incident face (11) on at least one side end surface thereof which confronts the light source (2), and a light emitting face (12) on one surface thereof which is substantially perpendicular to the light incident face (11); and a light angle varying sheet (3) which is disposed at a side of the light emitting face (12) of the light conductor (1), wherein at least one of the light emitting face (12) and a back surface (13) of the light conductor (1) comprises a minute structure having an average slant angle of 0.5 to 7.5 degrees. The light angle varying sheet (3) may comprise a prism sheet having a plurality of prisms (31) which are formed parallel to one another on at least one surface thereof.

Abstract: A lighted keyboard comprising numerous small grain of wheat type lamps embedded in translucent mounting blocks fixedly positioned between keypads wherein the keypads are constructed of translucent material with a reflective back coating so that when the keypads are in their upper most position the keypad translucent material contacts the fixedly secured translucent block thereby allowing light to be transmitted from the translucent block into the keypad however when the keypad is depressed lighting is blocked resulting in a darkened keypad. The intensity of the lighting system is also automatically controlled by ambient light conditions wherein increased ambient light results in lower voltage supply to the numerous small grain of wheat type lamps and wherein increased ambient light decreases voltage to the grain of wheat type lamps. The lighted keyboard is also equipped with a manual resistor switch allowing a user to manually adjust the intensity of the keyboard lighting if desired.

Abstract: The present invention relates to a control knurl for the rotary adjustment of a potentiometer in an automotive vehicle which minimizes light loss of the light guide in a control knurl. The light guide of the control knurl reflects the light from inside onto the peripheral surface of the control knurl. A bright protective coating encompasses the light guide and reflects the beams of light which emit from the boundary surface of the light guide. Light loss is also avoided by not applying protective coating on mirror surfaces which redirect the light.

Abstract: As regards a surface light source device for use with back-light or the like of a transmissive display panel, the efficiency of the cooling structure for the device will be improved and dust and dirt will be prevented from adhering. The surface-light source device has a housing, a diffuser panel, a reflective plate, lamps, and an electric circuit portion. The housing has a window portion located ahead, a base portion located behind and side portions forming a flat space by connecting the two. The diffuser panel is mounted to the window portion of the housing. The reflective plate is supported by the side portions and partitions the flat space into a closed space ahead and an open space behind to be interposed therebetween. The lamps are housed in the closed space, and are positioned right above the reflective plate and right under the diffuser panel to radiate light toward the diffuser panel. The electric circuit portion is housed in the open space, and is electrically connected to the lamps to light them up.

Abstract: Image display apparatus incorporating an enclosure having substantially opaque, substantially reflective interior surfaces. A light source emits light rays within the enclosure. An image-bearing surface is mounted in a front portion of the enclosure. The image-bearing surface bears a predefined image having transmissivity and reflectivity characteristics which vary as a function of position on the image-bearing surface, such that a substantial portion of the image is substantially non-transmissive and substantially reflective, and the remaining non-substantial portion of the image is substantially transmissive and substantially non-reflective.

Abstract: There is provided a surface light source device of side light type, which is not reduced in efficiency of illumination light utilization, even if the surface light source device is subjected to fringing such as to trim a luminant portion. For instance, a light shielding layer formed by coating black ink 21A, which absorbs illumination light, by means of printing is provided on a protection sheet 21 arranged as the outermost emission-side additional sheet. The light shielding layer absorbs and shields illumination light L1 tending to be transmitted through a peripheral edge portion of the protection sheet 12, and as a result, provides fringing. A reflective surface is formed by applying a silver tape 21B or the like to a surface facing the light guide plate 6. Since illumination light reflected by the silver tape 21B is used again inside the light guide plate 6, it is possible to avoid a reduction in efficiency of light utilization.

Abstract: A control panel that includes printed information cards used in conjunction with status indicators to give the user detailed information about printer operations. The invented control panel includes a series of status indicators, such as the indicator lights used on low cost printers, and a corresponding series of card holders. Each card holder is linked to one of the status indicators by, for example, positioning each card holder immediately adjacent to the corresponding status indicator. One or more information cards are attached to each card holder. Where more than one information card is used with a single card holder, each card is, preferably, swing mounted to the card holder so that the user can flip through the cards to view pertinent information.

Abstract: A liquid crystal display (LCD) device including an LCD panel having liquid crystal cells, a color filter, and fluorescent lamps for back lighting located at a rear side of the LCD panel. The light generated by respective fluorescent lamps has different wavelength distributions. Thus, the color of the display can be easily and accurately adjusted by a user. Particularly, the color can be adjusted according to user's choice or circumstances, improving an image.

Abstract: Disclosed are a backlight and avionics display using the same to provide light to a liquid crystal display (LCD) device. In the backlight, a day mode light source positioned on a first side of the LCD device and adapted to provide a first source of light for use by the LCD device during day mode operations. A night mode light source positioned on the first side of the LCD device is adapted to provide a second source of light for use by the LCD device during night mode operations. A sculptured transflector positioned between the day mode light source and the night mode light source has, at a first side adjacent the day mode light source, a transflective material and a plurality of arcuate or parabolic surfaces in order to maximize a percentage of light from the day mode light source which is reflected toward the LCD device.

Abstract: A light emitting grip comprising, a manually operable rotatable knob mounted on a fastening shank projecting from a first side thereof and having a selectively switchable light source carried by the knob.

Abstract: A wristwatch dial illumination system with a light guide beneath a light transmissive dial receiving light from an LED mounted on a PC board below the light guide. A pattern of white reflective dots on the bottom surface,of the light guide selectively ejects internally reflected light toward the dial and an absorption pattern of light absorbing material selectively absorbs ejected light, including the bright spot from the LED.

Abstract: A backlighted button or knob made by multi-shot molding has a translucent part and an opaque part. At the front of the button the translucent part contains a ridge shaped in the form of a symbol which is illuminated. The opaque part surrounds the ridge to mask light to surrounding areas. Where the symbol is a closed figure defining an island, a passage behind the ridge coupled the island to the surrounding areas to allow opaque material to flow to the island during molding, and results in an opaque bridge in the passage. To minimize a shadow of the bridge on the illuminated symbol the bridge is spaced far behind the ridge to allow light to be conducted through the translucent material to the ridge portion just in front of the bridge.

Abstract: An illuminative display device for use in an electronic apparatus including a cabinet with a metallic color surface and having at least a main function and a subsidiary function. The display device comprises a light source and a transparent sheet spaced apart therefrom by a predetermined distance, wherein a colored layer composed of a thin film and being the same or substantially the same in color as the metallic color of the cabinet is formed on one side of the transparent sheet opposed to the light source, and a backing layer with cutout characters is formed on one side of the colored layer opposed to the light source, so as to display the characters relative to the subsidiary function. And other display characters relative to the main function are shown on the surface of the transparent sheet at positions not overlapping with the display characters relative to the subsidiary function.

Abstract: A backlight unit for a display device includes a mold frame and a light guide panel. The mold frame includes a groove having at least one rounded corner. The light guide panel is on the mold frame and includes a light guide projection in the groove, having at least one rounded corner corresponding to the at least one rounded corner of the mold frame groove.

Abstract: An instrument panel having a light source and a transparent cover in front of the light source. The transparent cover has a first surface at the front side of the cover and a second surface at the back side of the cover, and is formed of a polymeric wall and a polymeric film. The polymeric film has a reflection-reduction layer thereon and is bonded by intermolecular forces to the wall so that the polymeric film is on at least one of the first and second surfaces of the cover and the reflection-reduction layer is sandwiched between the film and the wall. The reflection-reduction layer is formed of a material selected from the group consisting of (a) oxides of magnesium, zinc, or aluminum, or alloys thereof, (b) hydroxides of magnesium, zinc, or aluminum, or alloys thereof, and (c) semi-metals and metals which are non-alkali metals and non-alkaline earth metals, alloys thereof, and combinations thereof.

Abstract: An illuminating instrument panel gauge has a movable indicator, a front side for positioning toward a viewer and a back side for positioning away from the viewer. The gauge includes a light source, a subdial surface in front of the light source, a transparent gauge cover in front of and spaced apart from the subdial surface, and graphics corresponding to the movable indicator. The gauge cover has a first surface at the front side of the gauge cover and a second surface at the back side of the gauge cover. Either or both of the first and second surfaces of the gauge cover may be randomly textured. The movable indicator is positioned between the subdial surface and the gauge cover and is preferably closer to the gauge cover than it is to the subdial surface. The graphics are on either the first or second surface of the gauge cover.

Abstract: A cube corner article and method of manufacturing the article from a series of directly machinable unitary substrates. The method of manufacture comprises the first step of providing an initial unitary directly machinable substrate of material suitable for forming retroreflective surfaces. Then, a first cube corner element array zone is formed having a plurality of geometric structures including cube corner elements. The zone is created by directly machining at least two sets of parallel grooves in the substrate. A replica of the cube corner element array zone is formed as an additional unitary substrate suitable for forming retroreflective surfaces. Portions of the replica substrate material are removed. The removal of these portions forms at least two intersecting cavities bounded by side walls in the replica at a depth at least that of the cube corner elements formed by the groove sets.

Abstract: A surface mounting type light emitting display device is provided which includes a base plate and a case member. The base plate is formed with terminal electrodes at least along one edge thereof and carries light emitting elements thereon. The case member is provided for covering and accommodating the light emitting elements. The display device further includes a mounting device for attaching the case member to the base plate while allowing the case member and the base member to expand and contract independently of each other at least in one direction.

Abstract: A display apparatus is constituted by a planar display device and a planar illumination device therefor. A lowering in light quantity at a periphery of the planar illumination device is prevented by inserting a reflection member, such as a reflection frame, having an inside reflection surface along the periphery of the illumination device, or a combination of a scattering means and a transparent sheet member between the display device and the illumination device. A plurality of the display apparatus may be combined to allow an associate movement thereof so as to constitute a composite display apparatus, such as a head-mount display.

Abstract: A transmitted illumination type meter comprises a transparent light transmitting board having both a light entering bore and a shaft passing bore formed therethrough; a translucent dial plate placed on a front surface of the board, the dial plate having a shaft passing opening mated with the shaft passing bore of the board; a movement positioned behind the board; a light source positioned within the light entering bore; a drive shaft extending from the movement to the outside of the dial plate through the shaft passing bore and the shaft passing opening; a transparent pointer connected to the drive shaft to move over a front surface of the dial plate; and an annular convex peripheral wall defining the light entering bore. The annular convex peripheral wall allows light beams from the light source to enter the board and travel in parallel in the same. A plurality of stepped annular light reflecting surfaces are formed on a rear surface of the board and arranged to be concentric with the light entering bore.

Abstract: An apparatus (10) comprises a manually rotatable knob (14) and a source (18) of light. The knob (14) has an axis (15) of rotation, and has a discrete light-transmitting portion (40) which is spaced from the axis (15). A hollow part (36) of the knob (14) defines a chamber (39) extending from the axis (15) to the light-transmitting portion (40). A rotor (22) extends along the axis (15) from the chamber (39) to the source (18) of light. The rotor (22) is formed of material which is translucent sufficiently to transmit light from the source (18) to the chamber (39) to flood the chamber (39) with light, and thereby to illuminate the light-transmitting portion (40) of the knob (14).

Abstract: A transparent pointer has a rear surface coated with white paint and the remainder is covered by a highly reflective metal layer except for a light emitting indicator strip and a light receiving surface. Stationary high flux LEDs mounted behind the pointer illuminate the light receiving surface. Received light is efficiently reflected to the indicator strip to produce a bright line suitable for viewing through a dark face plate to achieve a dark dead front appearance. To avoid reflections from the pointer the reflective layer is covered with a black film.

Abstract: A backlight display system having a display screen illuminated directly by high intensity daylight lamps and illuminated indirectly by lower intensity nightlight lamps positioned to reflect their light off the daylight lamps and onto the display screen. The backlight display system includes intensity gradient filters and/or distribution lenses to enhance the uniformity of reflected nightlight, a brightness enhancement filter/diffuser disposed before the display screen, and optical filtering positioned between the illumination sources and the display screen. Photosensor controlled intensity feedback is used to provide smooth continuous dimming transition from a wide range of maximum to minimum intensity. The system also provides a third monochromatic nightlight lamp array for "class A" Night Vision Imaging System (NVIS) compatibility and an override switch to assure that lighting restrictions needed for night-vision are maintained.

Abstract: An illuminated controller having a membrane potentiometer for use as a light dimmer or other voltage controlling device. The controller has a backplate that acts as a sturdy base, and a cover, having sidewalls and a top wall with a central opening. The cover is mounted on the backplate and a layered structure is interposed between the cover and backplate. The layered structure includes a membrane potentiometer for varying voltage, and an electroluminescent panel, for generating light to illuminate the controller.

Abstract: An indicator for use in a vehicle instrument panel has a light conductive pointer illuminated by a light emitting diode or LED. In order to provide an increased illuminating surface of the pointer, a slit is formed on a cap to extend from the outer periphery of the cap to a portion above a center of rotation of the pointer driven by a driving shaft. A fixture is connected to the driving shaft and holds a light receiving portion of the pointer at the portion above the center of rotation and the LED in the optical alignment with the pointer at a portion off an axis of the center of rotation. A balancing weight is disposed at a portion opposite the LED with respect to the driving shaft in order to keep balance of the indicator.

Abstract: A meter assembly for motor vehicle comprises a meter case including rear and front housings which are coupled. The front housing has an opening formed therethrough. A meter unit is installed in the meter case. The meter unit includes a dial board facing toward the opening of the front housing, a transparent pointer movable over the dial board and a light emitting unit located in front of the pointer to emit light to illuminate the transparent pointer from within. A semitransparent dark cover covers the opening of the front housing.

Abstract: A display gauge in which an electroluminescent display is arranged between a dial face and a support plate, the electroluminescent display being connected to electrical components arranged on the back side of the support plate.

Abstract: An instrument panel has a front side for facing toward a driver and a back side for facing away from the driver, a light source, a subdial surface in front of the light source, and a transparent cover in front of and spaced away from the subdial surface. The transparent cover is substantially (preferably, at least 50%) rounded outwardly toward the driver. The instrument panel may include graphics on or in the cover. Due to the curvature of the cover, the graphics may have an outermost portion which is closest to the driver and an innermost portion which is further from the driver. Preferably, the outermost portion of the graphics is narrower relative to the innermost portion so that the graphics appear to be in a plane parallel with the driver.

Abstract: An improved display system includes a plurality of light sources which are electroluminescent devices, such as light emitting diodes. The light emitting diodes have an intensity of 0.5 with a light dispersion angle of 24.degree. or less. An optical device creates a plurality of dispersion patterns from the light emitted by each of the light emitting diodes. The dispersion patterns have a viewing angle of 50.degree. or more. The optical device includes a plurality of linear grooves having side surfaces which cooperate to create a plurality of separate dispersion patterns from the light emitted by each light emitting diode. The dispersion patterns from the light emitted by one light emitting diode are disposed along a line which extends perpendicular to the longitudinal axes of the grooves.

Abstract: A transreflective instrument display has a generally planar reverse image light emitting display panel, a transflector surface positioned at a predetermined angle with respect to the display panel. The transflector has a P-plane reflectance and S-plane reflectance. A illuminated pointer is positioned behind the transflector. The display is formed of light transmitted from the pointer and reflecting light from said display panel simultaneously to form an image. The transflector is preferably coated with a coating that increases the reflectivity of the P-plane polarization of the transflector.

Abstract: A surface light source apparatus is constituted such that an overhang portion overhanging a light source is provided on part of an end surface where the light source of an optical guide plate is arranged in such a manner that it is flush with the front surface of the optical guide plate and that an incident light control unit formed from a resin for diffusing and attenuating light is provided integratedly on at least an overhang portion side out of the overhang portion and the end surface of the optical guide plate, and accordingly light from the light source is transmitted through the overhang portion, radiated in an illumination direction, and diffused and attenuated by the incident light control unit to equalize the amount of light so that it can be used as illumination light. Thereby, the total area of the light emitting portions is increased.

Abstract: The present invention is a liquid crystal display with an improved backlighting system. A light source in the backlighting system radiates light in a first non-preferred direction. An optical apparatus coupled to the light source receives the light radiated by the light source in the first non-preferred direction and refracts it into a first preferred direction.

Abstract: A display (100) provides reversible contrasting indicia (112, 114) in order to accommodate an increased number of easily distinguishable indicia on the display. The display provides a first contrast mode (200) in which one set of indicia (112) become visually more prominent than another set (114) and a second contrast mode (300) in which the contrast of the first contrast mode is reversed. Selecting between the first and second contrast modes (200, 300) is controlled by backlighting of the display (100).

Abstract: A display device for use in a vehicle includes display lamps for displaying various states, and a centralized control substrate on which electronic parts for driving the display lamps are mounted. The centralized control substrate is extended backwardly of the display lamps in a direction to visually recognize the display lamps.

Abstract: Device for illuminating a set (1) of equipment items (3), such as indicators or dials of measurement apparatus (4), which are mounted on an outer face (2E) of a common support (2).According to the invention, this device includes:an electroluminescent plate (5), arranged in such a way that its illuminating face (5I) is opposite said outer face (2E) of said common support (2), spaced away from said outer face, and provided with a plurality of apertures (7);a facing (8) arranged on the non-illuminating face (5E) of said electroluminescent plate (5), and also provided with a plurality of apertures (9); andelectrical power supply means (6) for said electroluminescent plate (5).Illumination of instrument panels, particularly for aircraft.

Abstract: A rotary switch having a terminal base molded on a lead frame which includes internal contacts and external terminals, along with the connecting straps between them, all formed of a single metal part. Portions of the metal of the lead frame are selectively removed in order to create a variety of switch configurations. Different switch actuating rotors are provided which further allow creation of different switch modes (single throw, double throw, etc.). The rotor is also provided with detents in order to allow for retention and indexing of the switch positions. A ramp may be selectively installed into the rotor to eliminate unwanted detent positions without requiring a different rotor. One or more "floating" movable contact elements complete the circuits when the rotor allows a respective spring to force a floating movable element into contact with both of a corresponding pair of stationary contacts of the terminal base.

Abstract: An indicator for use in a vehicle instrument panel has a light conductive pointer illuminated by a light emitting diode or LED. In order to provide an increased illuminating surface of the pointer, a slit is formed on a cap to extend from the outer periphery of the cap to a portion above a center of rotation of the pointer driven by a driving shaft. A fixture is connected to the driving shaft and holds a light receiving portion of the pointer at the portion above the center of rotation and the LED in the optical alignment with the pointer at a portion off an axis of the center of rotation. A balancing weight is disposed at a portion opposite the LED with respect to the driving shaft in order to keep balance of the indicator.

Abstract: A combination display unit and a display method for a motor vehicle, with a primary display element and at least one secondary display element for indicating and displaying various regularly-detected operating parameters. The user is informed visually by a change in the optical display of the secondary display element in question that a critical operating parameter value has been reached. Only the primary display element, serving for speed display, or areas thereof is illuminated with an increased basic brightness. The secondary display elements or areas thereof are illuminated with the basic brightness during normal operation, while the secondary display element in question or areas thereof is/are likewise illuminated with increased basic brightness when a critical operating parameter value is reached.

Abstract: A lighting system utilizing an optical fiber is provided. In the preferred embodiment of the present invention, light rays from a light source are focused into an outer end of the optical fiber wound in a spiral shape. The light rays are focused in by a ball lens. In one embodiment, the spiral shape optical fiber is enclosed by a casing having a reflective inner surface along the periphery and the bottom; however, there is an aperture in the casing to permit light rays from the light source to reach the outer end of the spiral shape optical fiber.

Abstract: A device for backlighting a plastic panel associated with a control knob and carrying indicia thereon for illumination by an electroluminescent panel under the plastic panel containing the indicia with the electronic circuitry for illuminating the electroluminescent panel being contained within the hollow control knob. A light-responsive device may be used to maintain the circuit in the OFF position until the ambient light intensity fails below a predetermined level.