Abstract: A connector for use in connecting a push-on bell-type pipe joint together which comprises two legs positioned at right angles to each other, one of which may be welded to the surface of the male member and the other of which may be welded to the edge of the bell of the female member, the leg attached to the male member being rotated so that the other leg being attached to the female member will readily engage the female member.

Abstract: A fitting connection for joining plastic tubing to associated structure comprises a main fitting body having an axially inwardly extending cylindrical chamber with an inner end portion of a diameter d.sub.1 terminating at its innermost end in a radially inward extending wall. The outer end of the chamber opens to the exterior of the body and has an open diameter d.sub.2 which is larger than d.sub.1 with a shoulder at the juncture between the inner and outer end portions of the chamber. Plastic tubing having a circumferential corrugation adjacent an end portion thereof extends axially into the chamber with the innermost end of the tubing abutting the wall. A retaining ring acts to retain the tubing in the fitting body and includes a sleeve received in the outer portion of the chamber with the innermost end of the sleeve in engagement with the shoulder and a plurality of resilient tabs having free ends extending toward the shoulder.

Abstract: A device for tying an elastic balloon is disclosed. The nonmovable device defines a hole through which the neck of the balloon may be passed to form the knot in the neck. An opening at the edge of this hole facilitates removal once the knot has been formed. The device utilizes tabs and orthogonal retaining and restraining elements to simplify its utilization by either left- or right-handed people. No separate member remains with the balloon once the sealing through means of forming a knot has been affected. In addition, no parts of the device move and thus it greatly facilitates inexpensive and simple utilization in a repetitive fashion. Through the disclosure of several different embodiments, variations of the basic design are disclosed to enhance the possibility of inexpensive manufacture.

Abstract: A paddle handle latch includes a frame which defines a recess, and a peripheral handle which is mounted for pivotal movement in the recess. A retainer is mounted to the frame to define a channel having a latching axis and this retainer is shaped to receive a striker moving along the latching axis and to retain the striker against movement transverse to the latching axis. A catch is pivotably mounted in the retainer to move between an open position and a closed position. A linkage interconnects the paddle handle and the catch such that the paddle handle operates to move the catch between the open and closed positions.

Abstract: A latching device for sliding doors/windows which has a smooth, modern appearance and which enables a person to free himself. The device is used in combination with a push-bolt or bayonet style door lock mounted on a sliding door/window. Means for latching the bolt of the lock to the frame of the door/window includes a slotted, slideable frame member. The slideable frame member fits unobtrusively against the frame with no protruding parts. The bolt on the lock can be extended into a notch which is formed in the frame of the door/window and which includes a side opening. When the door/window is locked, the slideable frame member blocks this side opening, so that the bolt cannot escape. Alternately, by bringing a cutout in the frame member into alignment with the side opening, the frame member can be positioned so as not to block the side opening, thereby forming an opening through the bolt can move sideways.

Abstract: An apparatus for gripping tubular members about their outer diameter without causing surface damage or structural deformation to the tubular members, so that they may be axially rotated or secured against axial rotation. A generally cylindrical internal sleeve is contained within a molded flexible liner. One side of the internal sleeve is releasably attached to the flexible liner, forming an annular bladder-like structure within the flexible liner. Introduction of pressure into the bladder-like structure causes the flexible liner to inflate radially inward and thereby grip tubular workpieces within the friction grip. Axial splines on the releasable side of internal sleeve interfit mate with corresponding splines of the molded flexible liner, thereby evenly distribute torque forces throughout the flexible liner rather than such torque forces being concentrated at only the edges of the flexible liner.

Abstract: A visor system includes a visor panel which is concealed in a vehicle headliner and can be extended from the headliner and pivoted downwardly to an adjusted use position. The visor includes an auxiliary pivoted panel which as the visor is extended from its stored position, pivots outwardly to provide additional visor coverage to one side of the main visor panel.

Abstract: A snap-in visor rod mounting assembly includes a mounting plate which is adapted to receive a conventional visor rod mounting bracket. The plate is provided with a spring either integrally formed thereon or attached thereto. The visor rod mounting bracket is preassembled to the mounting plate in a conventional manner and subsequently the mounting plate is snap-fitted into an aperture formed in the vehicle roof during assembly of the visor into the vehicle.

Abstract: According to the present invention, apertures are stamped in the outer flange of the vehicle body and a plurality of depressions are stamped into the inner panel of the vehicle body at a spacing corresponding with the spacing of the apertures of the outer panel. The panels are welded together with the outer panel flange overlying the inner panel flange and the plurality of apertures communicating with the plurality of depressions. The adhesive is applied and flows through the aperture and into the depressions. When the adhesive cures, the bead of adhesive has both an adhesive connection to the outer flange and also a mechanical connection with the inner and outer panels by virtue of having flowed into the depressions.

Abstract: A barrier to the passage of sound, vibration, and moisture through a hollow channel in a motor vehicle body and a method for producing same are provided. The barrier is comprised of a resilient body such as flexible foam and a heat-deformable member such as a tube which defines a passageway between the ends of the resilient body when the resilient body and the member are mounted in the hollow channel. The barrier may be coated with hot melt adhesive. The barrier is mounted in the hollow channel and the motor vehicle body is dipped in a paint bath and drained. Paint flows in and out through the passageway in the barrier, thus coating the interior of the hollow channel. When the motor vehicle body is passed through the bake oven, the heat-deformable member collapses, the barrier is closed, and the hot melt adhesive bonds the barrier to the channel.

Abstract: A mechanism for a wall proximity-type of recliner chair, in which the chair-back reclining and erecting action is separate from the ottoman thrusting and retracting action, in which the forward-upward travel of the upholstered seat and arm frame unit as the chair back reclines feels as smooth as if it were produced by support wheels riding up an inclined ramp (although no wheels and ramp are used, thus avoiding the potential problem of a debris-obstructed ramp). The back end chair movement is synchronized by travel linkage to provide the desired upward and forward translation. Further, the locking linkage function and driving linkage function are provided by the same linkages. The mechanism can also be used in a modular sofa having a reclining unit, or in an armless chair, as the mechanism need not rise into a chair arm while the back is reclined and erected or the ottoman is thrust or retracted.

Abstract: A seating element adapted to be arranged in rows of like seating elements for seating in halls, stadiums, stands, etc., consists of a seat section, which may be mounted to a support structure by way of a joint row attachment device, and a back-rest section movably linked to the seat section such that it can be laid down on the seat section in a covering position. The back-rest section is attached to the seat section in such a way that it falls back automatically into the covering position in the absence of counter lifting forces and rests on the seat section. This arrangement is compact, prevents the seat back-rests from being obstructions which would hamper evacuation in a panic situation, and is readily cleanable.

Abstract: There is disclosed an upholstered article of furniture in the form of a pouffe (10) which comprises a base (11), a single scrap rubber tire, or a stack of rubber tires, mounted generally horizontally on the base, upholstery (13), and padding (14) arranged at predetermined locations between the tire and the upholstery.

Abstract: A method and apparatus for removing debris from a vehicular debris collection hopper and transferring it to a debris receptacle.

Abstract: A material handling vehicle is disclosed which includes a substantially rectangular material container with an open rear end. The container is pivotably mounted to the vehicle frame so that the front end of the container can be lifted to cause material in the container to be discharged through the open rear end. A tailgate is mounted to the open rear end of the container and can be selectively moved between a closed position where the tailgate overlies and closes the open rear end of the container, a partially raised position to permit metering of a material therethrough, and a fully raised position where the tailgate is free to swing outwardly about a pivotal axis. A pair of hydraulically actuated lifting members selectively move the tailgate between the three positions.

Abstract: A method and fixture (10) for assembling compliant seals (30) includes an aligning member (12) having a grooved surface (14) for receiving a plurality of loose bristle elements (16). The bristle elements (16) are received within the grooves (26) and aligned thereby. First and second backing rings (20, 22) sandwich the aligned bristles (16) and are clamped by first and second clamping members (18, 24). The clamped rings (20, 22) and bristle elements (16) are then removed from the aligning member (12) and permanently secured together, forming the finished seal (30).

Abstract: A caster wheel which enhances critical shimmy velocity so as to minimize shimmy effects in operation. Two tread surface for contact with a ground surface and a pivot assembly for pivoting the wheel about a first vertical axis displaced from a second vertical axis extending through the center point of the wheel are provided such that the separation between the two tread surfaces strategically relate via a mathematical equation to said displacement in a manner for achieving a desired critical shimmy velocity.

Abstract: There is described a hydraulic friction brake for controlling deceleration of a mine hoist which brake includes a pump continually circulating hydraulic braking fluid through a valve. The valve regulates the flow of hydraulic fluid to control braking pressure applied by the brake to brake the mine hoist. The hydraulic friction brake includes a controller for controlling operation of the valve. The controller a comparator for comparing a differentiated signal indicative of hoist speed with the reference signal indicative of a predetermined hoist deceleration to provide a switching output signal having a first output value when the differentiated signal is greater than the reference signal and having a second value when the differentiated signal is less than or equal to the reference signal. The control means also includes an integrator responsive to the output signal to provide a first valve signal that controls the operation of the valve.

Abstract: In an anti-lock brake system (ABS) for a motorcycle the driving stabilty is improved by measuring the position of lateral inclination of the motorcycle and adjusting at least one threshold value for the anti-skid control in response to the measurement. In another embodiment the transverse acceleration of the motor cycle is measured and an ABS threshold value adjusted accordingly.

Abstract: A method for determining an accurate vehicle speed, based upon the wheel speed data, for vehicle antilock systems in which the integrity of each individual wheel speed value is verified before including that wheel speed value in the reference speed calculation. Reference speed is then computed as a function of only those wheel speed values which have been successfully accepted into the calculation.

Abstract: A fluid pressure circuit is provided in which two independent systems are provided with a pressure generator for supplying pressure through each of the circuits so as to operate the brake system of a vehicle in an antiskid mode. The fluid pressure circuits have a phase difference of a half a period with respect to each other so as to provide for a continuous pressure to each of the brake systems of the independent fluid pressure systems. By providing such an arrangement, pulsation effects of each independent system are reduced without adversely influencing the pressure generator apparatus and while decreasing the noise associated with the operation of the fluid pressure system under such operating conditions.

Abstract: A brake pressure control device introduces pump pressure which is produced by a pump (16) into piping which connects a master cylinder (4) and wheel brakes (11, 11', 12, 12'). The increase, decrease and retention of the wheel brake pressure are effected by utilizing the pump pressure. Absorbers (19, 19') which consume hydraulic fluid are installed in branches from piping which connects the master cylinder (4) and the wheel brakes (11, 11', 12, 12'). 4-port 2-position control valves (5, 5') are installed in the hydraulic passages which connect the master cylinder (4) and the absorbers (19, 19') and at the inlet port for the pump pressure and at the outlet port to the absorbers (19, 19').

Abstract: The case-stand performs two functions; as a protective case in the fully closed position, and as a desk stand in the fully open position for hand-held calculators, computers, and data collectors; comprises a case bottom (1) which holds the instrument (17) securely by the insert holding feature (11) and a case top (2) which has a latch (7) feature that allows the case bottom (1) and case top (2) to securely latch together in the fully closed position. The case bottom (1) and case top (2) are hinged together with hinge (3) with two pins (4) which are pressed through case bottom (1) hole (13) into hinge (3) hole (15) in each of case to the proper depth and with two pins (4) which are pressed through case top (2) hole (14) into hinge (3) hole (15) in each side of case to the proper depth.

Abstract: A front cabinet door, attached to the first and second side panels for swinging movement therebetween, so that said front cabinet door can assume an open position with a substantially horizontal orientation parallel to the flippable board and a closed position vertically oriented perpendicular to the flippable board.

Abstract: The invention relates to an infrared optical system which is capable of providing an effective focal length of about 240 mm, but fitting into a spherical package whose diameter is approximately 150 mm. To achieve such a degree of compactness, the invention employs an optical path including three reflections, which in combination define a question-mark-shaped optical path. Between the first and second reflections, the transmitted beam is passed through a focal plane and then is recollimated, and the collimated beam is then passed through the succeeding two reflections, after which it is directed telecentrically onto a detector. The invention further relates to a specific combination of lenses.

Abstract: A process is disclosed for making an achromatic hologram which is adapted to be reconstructed with white light and which is recorded on a photographic record carrier by means of an object beam and a reference beam of coherent monochromatic light in an operation in which the object beam and a reference beam of coherent monochromatic light in an operation in which the object beam passes through an image-forming optical element between the object and the recording material. The image forming element has a large relative aperture. When the first hologram has been recorded on the record carrier a reference beam is projected in a direction which is opposite to the direction of the reference beam used to record the first hologram and is thus used to reconstruct the object wave from the first hologram.

Abstract: A novel optoelectronics package includes an optical semiconductor, an electronic cooling element carrying the optical semiconductor and electrically connected to one of the terminals thereof, a pair of transmission lines having distributed constant characteristics and an airtight vessel housing the optical semiconductor, cooling element and transmission lines. A grounding line of the transmission lines is connected between the terminal of the optical semiconductor and an external ground terminal fixed at the vessel. A signal line of the transmission line is connected between the other terminal of the optical semiconductor and an external signal terminal, whereby the stray capacitance of the cooling element is shorted by the distributed constant grounding line.

Abstract: A solar-ray energy radiation device for medical application comprises a transparent or semi-transparent cylindrical member, a cover-member for closing off one end of the cylindrical member, and an optical conductor cable having a light-ray emitting end disposed at approximately the central portion of the cover-member. The solar-ray energy transmitted through the optical conductor cable is emitted from the light-ray emitting end into the cylindrical member. An open-ended side of the cylindrical member is placed in such a way as to emit solar-ray energy onto a place needing medical treatment. The cylindrical member has notches or holes causing the inner and outer portions of the cylindrical member to come in contact with each other at the open-ended side wall.

Abstract: The invention is a multiplexer which enables light to be sent to and received from samples for simultaneous analysis. A multiplexer is described which uses a transverse probe to reflect light at an angle into an optical rod. The transverse probe is selectively rotated to transmit light to a second optical rod. Various numbers of optical rods may be used in the linear mutliplexer. A multiplexer is also described in which a conjugate optical barrel is utilized to selectively reflect light to various probes.

Abstract: An apparatus is described for efficiently transforming light from concentrated sources into uniform diffse light. The apparatus comprises (1) a light guide resonator which comprises (A) a light guide and (B) mirrors for reflecting light back into the light guide; (2) means for injecting light from a light source into the light guide resonator; and (3) a light-diffusing element placed within the field distribution of the light in the resonator, the whole apparatus being designed to set up a regime of optical resonance. The light guide resonator is uniformly filled with light; within the resonator the uniformly lit light-diffusing element acts as an efficient light source of uniform brightness.

Abstract: An monolithic integrated transceiver formed on an Si substrate comprising: a III-V compound light source, a III-V compound light detector and a pyramidal groove formed in the substrate for aligning an optical fiber with said transmitter.

Abstract: An optoelectronic transmission and reception device includes an optical transmitter inserted into a silicon wafer as a laser chip composed of III/V compound semiconductor material, an optical receiver inserted into the silicon wafer as a reception diode chip composed of III/V compound semiconductor material or which is monolithically integrated into the silicon wafer as a metal-semiconductor diode. A coupling optics for connection to an optical fiber is monolithically integrated into the silicon wafer, as is a controller that includes a drive circuit for the transmitter and a pre-amplifier circuit for the receiver, a wavelength selective beam splitter and light wave guides for light guidance. The device is particularly useful as a bi-directional transmission and reception module.

Abstract: An excimer laser fabricates either an optical coupler opening or an optical mode scrambler by ablatively removing the cladding from the optical core of an optical fiber bus without damaging the optical core. Either coupler housing or a mode scrambler housing is attached to the optical fiber bus where the coupler or mode scrambler is to be fabricated. The coupler housing is used to position the laser, secure and align a coupler fiber, and provide cavities for junction and cladding repair materials. The mode scrambler housing serves a similar purpose.

Abstract: A method for forming a three gate optical coupler, operating on a beam splitting principle, or a five gate optical coupler characterized by providing a carrier block having a pair of marks to define a line of a parting plane, creating a continuous branching waveguide structure having a waveguide node located adjacent to the parting plane of the carrier block by a ion exchange method, parting the carrier block in the parting plane, polishing the parted surfaces and forming a light transmitting optical layer, such as a frequency selective filter layer on a polished surface, then rejoining the two parts with the waveguides aligned. The method is particularly useful in forming three gate and five gate frequency multiplexers/demultiplexers, which have a continuous light waveguide structure except in the location of the frequency selective filter layer.

Abstract: A continuously variable fiber optic attenuator which can be constructed in a size amenable to direct mounting on optical data application apparatus is presented. The attenuator utilizes a flexible filter of varying optical density which is oriented in an optical coupling region between two optical fibers. The filter can be displaced in a manner to vary the filter density in the optical coupling region and thereby vary the attenuation across the device. A resistor coupled to the attenuator provides means for calibration of the attenuator to provide a highly accurate and reproducible attenuation.

Abstract: A non-invasive optical coupling device comprises means to hold an optical fibre while bending it with a radius of curvature sufficiently small to cause light to leak through the cladding, and means to hold a tap fibre in a predetermined position to receive at least a portion of the light leaking from the main fibre. This device enables light sources, sensors and various other optical communications devices to be connected via tap fibres to ring main fibres and data buses, without degradation of the fibres to which the tap fibres are connected.

Abstract: The invention relates to a device and method of aligning an optical fibre (4) with respect to the lens (2) of a connector, the optical fibre (4) being positioned such that a beam issuing from the optical fibre (4) and passing through the lens (2) is directed concentrically at a four-quadrant measuring device (8). A very simple method is obtained in that the four-quadrant measuring device (8) is provided with a focussing lens (10) at a distance equal to the focal length, and in that the axial distance between the front face of the optical fibre (4) and the lens (2) of the connector is adjusted such that the sum of the light intensities measured by the four elements (9) of the four-quadrant measuring device (8) has a minimum value.

Abstract: This invention comprises a new group of fiber optic switching devices that use layers of surface-established ferroelectric liquid crystals (FLCs) as the switching media. In each of the devices light impinges upon the ferroelectric liquid crystal at an angle of 90.degree. (normal incidence) with the surface plane. Each FLC gives 0.degree. or .pi..degree. optical rotation, depending upon the polarity of the electric voltage applied. A series of polarizing beam splitters are used to separate unpolarized light into its s and p polarization components. After ferroelectric liquid crystal switching, other polarizing beam splitters are used to direct the s and p light to output optical paths. The switches discussed below are voltage controlled 2.times.2, 1.times.4, 1.times.6, 1.times.8, 4.times.4, or N.times.N devices that use one or more layers of surface stabilized ferroelectric liquid crystals.

Abstract: Light generated by an illumination source (26) travels through a fiber optic cable (40) to optrode (14) which is immersed in the process fluid (16) to be analyzed. The optrode collimates the light beam before it crosses the sampling gap (68) where the beam transects the process fluid to be analyzed. As it crosses the sampling gap 68, the light beam is absorbed in a specific wavelength band by the chemical species in solution. The collimated beam is then picked up by an opposing collimated lens in the optrode and transmitted to the protected analytical module (20) by a second optical fiber (42).

Abstract: An optical circuit device includes an optical fiber element, a lens and several holders. An inner holder which is elastic, holds the optical fiber element and a lens on the same optical axis. An intermediate holder fixes the inner holder therein. An outer holder, which is connected to an optical signal receiving device, holds the intermediate holder therein. An optical axis of the inner holder is adjusted by shifting the position of the intermediate holder in the outer holder parallel to the optical axis. Also, the optical axis is adjusted by moving the outer holder perpendicular to the optical axis.

Abstract: A spherical lens (5) is fixed to the front end of a tubular housing (1) and an end part of a lightconducting fibre (9) is fixed with its first end face (11) in the focal plane of the lens. The line through the center (13) of the lens (5) and the middle of the first end face (11) is the optical axis (17). The housing (1) with the lens (5) is placed against a seat (25), which is formed as a cavity with a rotationally symmetrical surface, on whose axis of rotation (27) a light detector (31) is mounted. The detector is designed to determine deviations between the direction of a light beam coming from the lens and the direction of the axis of rotation. Near the second end face (45) of the fibre (9) light is injected into the fibre, and the rear end of the housing is displaced in two directions (x, y) perpendicular to the optical axis, until the light beam emerging from the lens ( 5) coincides with the axis of rotation (27). The lens (5) with the seating (25) thereby functions as a ball hinge.

Abstract: In a branch device for multi-core optical fiber according to the present invention, a branch portion protector including a spindle-shaped protector and a perforated member which are integrally formed with each other is provided between the end portion of the multi-core optical fiber and the single-core optical fiber protection tubes so that no excessive force is exerted on the branching-out single-core optical fibers and the optical loss is stable.

Abstract: A fiber optic switch is formed using cylindrical or biconic fibers optic connector components for axially aligning pairs of fibers to be switched. The ferrules of the connector are rotatably mounted within an alignment sleeve, such that a pair of fibers in a first ferrule may be rotated relative to a pair of fibers mounted in a second ferrule to effect a bypass switch operation. Various forms of switch actuators, including rotary and linear actuators, are disclosed, along with fail-safe arrangements.

Abstract: A core-clad plastic optical fiber is described, comprising a polyglutarimide series polymer having a polymeric structural unit represented by formula (I) ##STR1## wherein R represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aromatic group and n represents a positive integer,having a thermal deformation temperture of at least 120.degree. C. as a core, and an organic polymer having a refractive index lower than the refractive index of the core as a clad layer, said plastic optical fiber having the characteristic that the light transmission loss measured at 655 nm is not more than 500 dB/km.

Abstract: The invention provides a reflective sheeting material having a structured reflective surface having a linear ray of isosceles prism reflecting elements, each element including a pair of reflective surfaces at an angle of about 120.degree. therebetween. The invention also provides a reflective sheeting material having a structured reflective surface comprising an array of reflecting elements, each comprising a polyhedron having three paralellogram faces. The invention also provides an apparatus such as a light pole for transporting light and reflecting the light in a broad, uniform pattern. The apparatus comprises (a) a columnar light conduit, for transporting light therealong, the conduit having a proximate end and a distal end; (b) a light source provided at the proximate end of the light conduit,and (c) a light distributing reflective member, such as the reflective sheeting material described above, comprising a multiplicity of repeating reflecting elements.

Abstract: An arrangement for discriminating whether a semiconductor laser employed in a light transmission system is functional or non-functional includes a circuit for generating a pulse pattern repeatedly with a unit of a plurality of bits and outputting the pulse pattern to the semiconductor laser and a medium for passing a light pulse signal output from the semiconductor laser. Receiving equipment includes a circuit for regenerating the pulse pattern from the light pulse signal and outputting a regenerative pulse pattern, and a discriminating circuit responding to the regenerative pulse pattern.The discriminating circuit discriminates whether or not a pseudo-pulse exceeding a predetermined threshold level appears at a specific position in the regenerative pulse pattern during a predetermined time interval, and indicates a result of the discrimination.

Abstract: A lens barrel having a movable barrel with a first cam channel, a fixed barrel with a second cam channel, a lens holding frame and a cam follower fitted in each of the first and second cam channels and fixed onto the lens holding member. The cam follower is made of elastic material and has a contact portion formed on the peripheral surface thereof so as to be in elastically pressing contact with one of the movable barrel, the fixed barrel and the lens holding member.

Abstract: A catadioptric lens system capable of an automatic focusing operation without the necessity of increasing the outer diameter of a lens barrel is provided. The catadioptric lens system comprises a focusing optical unit, a focusing optical unit holder capable of movement in a direction of an optical axis of the lens band for holding the focusing optical unit, and a driving means disposed between a mount and a reflecting mirror which is disposed to reflect light coming from an object toward an object side and connected directly or indirectly to the focusing optical unit holder for transmitting a driving force to the focusing optical unit holder at a reduced speed so as to move the focusing optical unit holder in the direction of the optical axis to effect focusing.

Abstract: A method for producing a transparent light deflecting panel comprising making a series of parallel cuts in a sheet of transparent solid material with a laser cutting tool. Said panel when positioned in an opening in the facade of a building deflects incident daylight towards the ceiling of said building thereby improving the natural lighting within the building.

Abstract: An optical filter for use with visual display devices such as cathode ray tubes (CRT's) used with video display terminals (VDT's), television sets and the like enhances the viewability of characters and graphics displayed by increasing the contrast ratio, i.e., relative brightness, between illuminated picture elements (pixels) and un-illuminated pixels. The filter comprises a thin, transparent flexible polyvinyl chloride (PVC) plastic film adherable to the faceplate of the CRT or other display device by surface adhesion alone. Dyes are incorporated into the plastic film which color the film subtractively complementarily to the emission color of the display, thereby causing reduced light transmittance for wavelengths close to wavelength of peak light emission of the display device.