Abstract: An illumination system can be configured for use with a liquid level gauge. A mounting bracket can be configured to secure a LED assembly to a frost-proof extension of the liquid level gauge, with the LED assembly disposed adjacent to a second edge face of the frost-proof extension that is opposite a liquid tube. The LED assembly can be thereby configured to illuminate the liquid tube via the second edge face of the frost-proof extension.

Abstract: Disclosed herein are a system and method for determining a liquid level in a container based on data extracted from a digital image of the container. An image capture apparatus captures an image of a container used to store liquid reagents used by analytical instruments to test patient samples. A controller receives the captured image and extracts an analysis region based on a container type and applies a gradient filter to the analysis region. A location of a minimum gradient value (i.e., a row index) is determined based on the air-to-liquid boundary of the liquid in the extracted analysis region. A volume module calculates the liquid level in the analysis region by dividing the row index by a length of a gradient column vector and compares the determined liquid level to a threshold analysis region fraction for the container type to determine whether to output an alert.

Abstract: An optical probe that measures the level of a liquid in a tank includes a transparent and refracting optical waveguide for receiving an injection of a collimated light beam. The optical waveguide internally reflects the collimated light beam according to a total reflection regime in any part of the optical waveguide located in a gaseous medium and refracts the collimated light beam according to a refraction regime in any part of the optical waveguide immersed in a liquid medium. The optical waveguide switches from the total reflection regime to the refraction regime at the interface between the gaseous medium and the liquid medium, and mirrors are arranged around said optical waveguide and reverse the path of a light beam collimated and refracted by the optical waveguide, the optical path covered by the collimated light beam representing the level of the liquid in the tank.

Abstract: A machine vision system that uses an imager to capture an optical image of a target object that may contain a liquid. The target object is illuminated by an illumination source positioned oppositely from the imager and a predetermined pattern is positioned between the illumination source and the target object so that the imager will capture optical images of the background pattern through any liquid positioned in the target object. A processor is programmed to analyze captured images to detect any distortions of the pattern that are attributable to the presence of a liquid in the target object.

Abstract: An apparatus for determining the volume of a liquid in a container. A digital camera is provided to view the container. A processor can optically detect certain characteristics of the container as viewed by the camera and accesses a computer memory having stored characteristics of a plurality of known containers, and the compare the detected certain characteristics with the stored characteristics to identify the container from the plurality of known containers. The processor can calculate the volume of the container as a function of the distance between the first and second ends of the container as viewed by the camera. The processor can receive at least one image from the camera and determine whether the liquid in the container contains any air pockets based on the at least one image. Methods are provided, including a method for use by an apparatus having a camera and a processor electrically coupled to the camera to confirm the dosage of a medicament in a container.

Abstract: A liquid observation device having a clear body structure 1C which is a disc-like shape which on the top surface has a thumb support member 1A that includes symbol indicator marks 1B thereon, on the opposite side of the clear body structure 1C a mechanical seal surface 2B having a mechanical seal 2A thereto, which has threads 3A extending from the mechanical seal surface 2B to the bottom of the said clear body structure 1C which located on the bottom surface at the center a phosphorescent tube. member 5 having a vent hole 4 at the top, which extends vertically down from the clear body structure 1C, toward the end has tube indicator section 6 that extends in a downwardly-inclined outwardly spiral.

Abstract: Devices, systems, and methods for measuring the blood loss of a subject during a medical procedure. Blood and other fluids are received within a container, and a blood measurement device determines the hemoglobin concentration of the fluid within the container. The blood measurement device can also calculate the estimated blood loss of the subject based upon the determined hemoglobin concentration and the volume of the fluid within the container and the patient's hemoglobin.

Abstract: An information processing apparatus includes a communication interface and a controller. The communication interface receives, from a sensor container, information indicating an orientation of the sensor container. The controller, based on the information indicating the orientation of the sensor container, calculates a calculated value indicating a remaining amount of contents of the sensor container. The controller determines an estimated value of the remaining amount on the basis of the calculated value. The communication interface transmits the estimated value indicating the remaining amount to an external device. When the calculated value indicating the remaining amount decreases by a first predetermined value or more within a predetermined time period, the controller does not perform the determination of the estimated value on the basis of the calculated value.

Abstract: A water amount measurement device includes a light emitting element to emit light, a light receiving element to receive the light reflected by a liquid surface and by a liquid bottom at a bottom surface within a pipeline, a storage to store a distance from the light emitting element to the liquid bottom, and a processor. The processor computes a water level of the liquid flowing through the pipeline according to different formulas depending on whether a comparison result of distance data obtained based on an output signal of the light receiving element, and the distance at a time of measurement, includes a component corresponding to a distance exceeding the distance generated by the reflection from the liquid bottom, or the comparison result includes a component corresponding to a distance less than the distance generated by the reflection from the liquid surface.

Abstract: The topology of a filling material surface is first determined by sampling the surface of the filling material in order to determine the fill level. When calculating the surface topology of the filling material, the measurement signal, which has been reflected at the filling material surface and has been picked up by the antenna unit of the fill level measurement device, is evaluated, taking into account the distance between the source of the measurement signal and a center of rotation of the main emission axis of the antenna. This makes it possible to accurately determine the fill level of bulk materials, even if the source of the measurement signal and the center of rotation of the main emission axis do not coincide.

Abstract: A method for controlling fuel switching of a fuel switching system in a vehicle via a controller configured to receive one or more measured signals in order to issue a fuel shortage warning or in order to control fuel switching is disclosed. The system includes an LPG rail pressure sensor for measuring a pressure in an LPG rail, and a bombe pressure sensor for measuring a pressure in the bombe. The method includes a first LPG rail pressure determining step of determining whether the pressure in the LPG rail is lower than a second reference value or not and a first bombe pressure determining step of determining whether the pressure in the bombe is lower than a third reference value or not. If at least one of the first pressure determining steps is positive, the method further includes switching the fuel to gasoline.

Abstract: The embodiments disclosed herein is a system for optical coherence tomographic imaging of turbid (i.e., scattering) materials utilizing multiple channels of information. The multiple channels of information may encompass spatial, angle, spectral and polarization domains. More specifically, the embodiments disclosed herein is related to methods and apparatus for utilizing optical sources, systems or receivers capable of providing (source), processing (system) or recording (receiver) a multiplicity of channels of spectral information for optical coherence tomographic imaging of turbid materials. In these methods and apparatus the multiplicity of channels of spectral information that can be provided by the source, processed by the system, or recorded by the receiver are used to convey simultaneously spatial, spectral or polarimetric information relating to the turbid material being imaged tomographically.

Abstract: A system for separating a sample and collecting the separated sample. The system includes an ultracentrifuge having a cylindrical rotor. The system includes a gradient delivery assembly for delivering a gradient solution to the ultracentrifuge rotor, and a sample delivery assembly for delivering the solution containing the sample to the ultracentrifuge rotor. The system includes a fraction collection assembly for collecting discrete volumes of the separated sample. The system includes a processor for controlling operation of the ultracentrifuge, as well as the gradient delivery assembly, the sample delivery assembly, and/or the fraction collection assembly.

Abstract: Method of determining a laundry load size in a laundry treating appliance comprising a rotatable drum at least partially defining a treating chamber for receiving laundry for treatment in accordance with a treating cycle of operation, an imaging device, and a controller having a processor, the method includes generating an images, detecting, marking in the generated image, and determining, by the controller, a load size based on the image.

Abstract: An approach is provided for smart order management. Smart utensils measure consumption of a meal by a customer. The smart utensils include at least one processor to perform the measuring and a transmitter that transmits data corresponding to the measured consumption. The smart utensils transmit the measurement to a restaurant data collection device. The approach predicts, based on the measuring, a completion time of the meal by the customer and notifies restaurant staff members of the predicted completion time.

Abstract: An optical sensor for a conventional tank gauge designed to allow a user to remotely check the liquid level of a tank without the need for a visual inspection. Using an emitter circuit board with a plurality of photoemitters and a detector circuit board with a plurality of photodetectors, the optical sensor can fit over a conventional tank gauge without disturbing the gauge. The circuit boards can be attached to an optical sensor frame, which can be adjusted on the conventional tank gauge by a height adjustment screw and a series of set screws. Alternatively, one or more sliders can be used to maintain proper alignment. Analog data generated from the photodetectors can be digitized using a microcontroller and can be made available for viewing on a stationary or mobile device via an integrated network connection.

Abstract: An optical switch having a housing, and two optical fibers, that can be connected to a light source and a light detector. The optical switch includes a moveable member that moves from a first position to a second position. In the first position, an optical path is present through the two fibers guide using a reflection or emission of light from the glowable member. In the second position, there is no optical path present through the switch.

Abstract: A self-alignment filling level detecting device has a reflector and a sensor detachable from each other. The sensor has a light emitter, a light sensor, and a controller. The light sensor receives different light intensities when the reflector is assembled to the sensor and when the reflector is not assembled to the sensor. Thus, the controller determines whether the reflector has been accurately engaged and aligned with the sensor or not based on sensing results of the light sensor. Since the reflector and the sensor are detachable from each other, either the reflector or the sensor can be replaced individually if any one of them malfunctions.

Abstract: A system for measuring fluid level is provided. The system includes a dipstick configured to be received in a fluid reservoir and having a photoluminescent portion. The system also includes a light source operable to emit a first light to excite the photoluminescent portion. A fluid level is determined based on a degree of illumination of the photoluminescent portion when the dipstick is removed from the reservoir and the photoluminescent portion is exposed to the first light.

Abstract: A detector for detecting a change in a fluid level and generating a digital signal uses a light source and a photodetector mounted diametrically on a tube in a predetermined location where a change in fluid level is to be detected. The circuit provides two stable output states or levels, one which corresponds to fluid not being in the tube between the light source such as an LED light and the photodetector and the other level when fluid is in the tube. In a particular application, the invention is utilized to monitor fluid level in a predetermined location of a manometer to shut off a radon remedial system and provide audio/and or visual alarms when there is a fluid level change which indicates that the radon remedial system is not operating effectively.

Abstract: The invention relates to a test arrangement comprising a waveguide, a first signal reflecting device and a second signal reflecting device. The first signal reflecting device is configured to reflect an electromagnetic signal traveling along the waveguide from the second signal reflecting device back towards the second reflecting device and to allow, at least during a time period, an electromagnetic signal traveling along the waveguide from the second signal reflecting device towards the first signal reflecting device to pass the first signal reflecting device. Hereby, a selected number of passages through a waveguide can be used to simulate passage through a much longer waveguide, and that this allows for use of a high-quality waveguide which would otherwise be too bulky, too heavy or too expensive to use depending on field of application.

Abstract: A dielectric antenna (1) having at least one supply element (2) and at least one lens (3) formed of a dielectric material. The dielectric antenna makes it possible to measure the surface of a medium with an essentially consistent measuring accuracy in that the lens (3) has an outer component (4) and an inner component (5). The outer component (4) has a radiating surface (6) that is spherical and an inner surface (7) that is spherical, and the inner component (5) has a contact surface (8) that spherical. Furthermore, the antenna is usable as part of a fill level sensor operating on the radar principle.

Abstract: The method comprises the steps of generating a transmission signal; propagating the transmission signal towards the product; receiving a reflected signal; providing a reference signal exhibiting a time-varying phase difference in relation to the transmission signal; forming a measurement signal; and determining the filling level based on the measurement signal. The method further comprises the steps of: determining a reduced time period comprising a time when the time-varying phase difference corresponds to an anticipated filling level, the reduced time period being shorter than the measurement sweep time period; controlling the level gauge system to change from a low-power state to a high-power state at a start of the reduced time period; and controlling the level gauge system to change back from the high-power state to the low-power state at an end of the reduced time period.

Abstract: Its object is to allow measurement of the volume of fuel (2) using optic fiber cables (3); it is characterized in that, adhered to one or more of the inner faces of the tank (1) there is at least one sheet (4) in which a plurality of optic fiber cables (3) with different lengths are included, located between the inner face of the tank and the sheet (4). One set of the ends (10) of the optic fiber cables (3) are disposed so that they are in contact with the fuel (2) when it reaches their level, thereby allowing measurement of the fuel level at all times. The preferred embodiment distributes the optic fiber cables (3) on two opposing lateral faces of the tank (1) so that they cross over one another and in opposite directions to measure any fuel level. It is applied in aeronautics.

Abstract: A fluid overfill detection and control system for controlling the transfer of fluid into a transport vehicle having multiple fluid compartments includes a plurality of overfill sensors that are connected in series with one another and that each produces an output pulse when the fluid level in its associated compartment is below a threshold level. A diagnostic line connected to each of the overfill sensors provides a diagnostic signal indicative of the number of overfill sensors that generate an output pulse, while a module on the vehicle provides an indication of the total number of overfill sensors located in the vehicle. To prevent a hazard due to the possible bypass of a overfill sensor, the controller compares the overfill sensor count signal to the diagnostic signal and inhibits the transfer of fluid into the vehicle if the values do not match.

Abstract: Systems and methods for determining liquid depth information in a condensate pan of a climate control unit are provided. The systems and methods radiate a light beam into a liquid contained in a condensate pan associated with a climate control unit. The light beam is detected at a point of the condensate pan that is below a surface of the liquid. Information related to the depth of the liquid is determined based at least in part on the detected light beam. The systems and methods disclosed herein can determine if liquid depth in a condensate pan is greater than a threshold depth and can control evacuation of the liquid from the condensate pan.

Abstract: A liquid level sensing system includes waveguides disposed in a liquid and distributed along a path with a gap between adjacent waveguides. A source introduces electromagnetic energy into the waveguides at a first end of the path. A portion of the electromagnetic energy exits the waveguides at a second end of the path. A detector measures the portion of the electromagnetic energy exiting the second end of the path.

Abstract: An ink cartridge includes a case, an ink supply opening, and a light transmissive member positioned in the case and facing the ink supply opening. The light transmissive member is configured to allow light entering via the ink supply opening to pass therethrough. The light transmissive member includes a reflective surface having a first reflectance for light entering via the ink supply opening and passing through the light transmissive member when the reflective surface contacts ink stored in the ink chamber. The reflective surface has a second reflectance for light entering via the ink supply opening and passing through the light transmissive member when the reflective surface does not contact ink stored in the ink chamber. The first reflectance is different from the second reflectance.

Abstract: A method of measuring a liquid level of a cell culture solution stored in a cell vessel, includes: irradiating the cell culture solution with at least two kinds of light beams including a first light beam having a first wavelength and a second light beam having a second wavelength; measuring a first absorbance of the cell culture solution with respect to the first light beam, and a second absorbance of the cell culture solution with respect to the second light beam; and determining a liquid level of the cell culture solution based on the first absorbance and the second absorbance.

Abstract: The present invention relates to a coverslipping machine (1) including: a hollow needle (2) for applying mounting medium onto a specimen slide (5); a transparent container (103) to be filled with a liquid; a light source (101) for radiating measurement light in a principal radiating direction (A) into the container (103); and a light sensor (102, 102?) for detecting the measurement light, the light source (101) being arranged with respect to the container (103) in such a way that the radiated measurement light is refracted by a liquid in the container whose fill level exceeds a fill level limit, the light sensor (102, 102?) being arranged with respect to the container (103) in such a way that only measurement light refracted by the liquid or only measurement light not refracted by the liquid is detected.

Abstract: A system for monitoring a liquid level in an aircraft shock strut includes a cylinder having an internal chamber sealed by a piston telescopically movable within the cylinder. The chamber contains a gas and a liquid, and a sensor assembly is provided for monitoring a condition of a level of the liquid in the chamber. The sensor assembly includes at least one probe within the chamber, and a fitting assembly allows one or more leads from the probe to pass through the wall of the strut while maintaining pressure in the chamber. The fitting assembly includes a plug molded to the one or more leads extending from the probe. The fitting assembly also includes a retainer for holding the plug in sealed relationship with a through passage in the strut.

Abstract: The invention relates to an apparatus on which a drinking vessel may be placed, in particular an apparatus which provides information, wherein the information is connected with the drinking vessel. An apparatus for indicating the filling level of a drinking vessel comprises a placement device on which the drinking vessel is placed, a detection device for detecting the filling level of the drinking vessel (200), and a display element which displays the detected filling level.

Abstract: Device for monitoring the level of the condensate collected in the measurement cylinder of a standardized distillation apparatus for automatically distilling liquid specimens, characterized in that it comprises: on the one hand, a double optical barrier emitting a central beam centered on the measurement cylinder (1), so as to allow detection of the part below the meniscus, and an eccentric beam offset with respect to the central beam and located close to the wall of the measurement cylinder (1), so as to allow the part above the meniscus to be detected; and, on the other hand, a fixed optical barrier intended for counting the drops of condensate falling into the measurement cylinder (1) during distillation.

Abstract: The present invention is a well gauge used to indicate the relative depth of water inside a shallow well. Specifically, the present invention is water well gauge with a calibrated pipe, which visually displays various quantities of water within the well. The calibrated pipe or the floating shaft of the present invention is to be floated perpendicularly to water surface within the well. The shaft is supported by a group of buoys, which floats in line with the water in the well. The buoys are positioned radially around and perpendicularly to the shaft. The present invention further comprises a collar which helps position the shaft vertically and perpendicularly to the water level. The calibrated pipe of the present invention can be read in the absence of light due to an attachment of a solar light-emitting diode (LED). With the present invention installed, water user can regulate water more effectively.

Abstract: The present invention includes: plural common terminals; plural water level measurement terminals that are arranged at a certain interval along a longitudinal direction; a water level measurement control unit that measures the water level of a measurement subject by letting an electric current flow to the plural common terminals, then reading the state information of an electric current flowing to the plural water level measurement terminals; and an LED unit that reads and displays the water level measurement results through plural LEDs.

Abstract: A level detection device for detecting an upper surface of a liquid at a reference level. The device includes a reservoir having a bottom wall and one or more side walls that delimit a cavity for containing the liquid; a light emitter for emitting a light beam towards this cavity; at least one reflection surface for reflecting the light beam; and a light detector for detecting the emitted light beam upon reflection. The emitter and detector are so arranged that, when the surface of the liquid passes the reference level, a state of detection of the light beam by the detector is changed. The emitter, detector and reflection surface(s) are so located and oriented relative to the cavity that the emitted light beam is: detectable by the detector upon travelling through the liquid in the cavity; and refractable at the surface of the liquid towards or away from the detector so that the state of detection is a function of such refraction.

Abstract: A sight assembly may include a body portion configured to couple between a first fluid transport segment and a second fluid transport segment. The body portion may define an aperture configured for fluid flow through an interior of the body portion. The sight assembly may also include a light source disposed within the body portion. The light source may be configured to provide illumination of the interior of the sight assembly. The light source may be disposed within the body portion approximately between an outer edge of the body portion forming the aperture and an external surface of the body portion.

Abstract: The electro-optic liquid level sensing system detects a level of liquid in a container having an upper opening, such as for a server container of a beverage maker for a transport system, such as for aircraft, trains, trucks, buses and the like. A support housing mates with the upper opening of the container, and a primary liquid level sensor is mounted in the support housing for non-intrusively measuring the liquid level. A secondary liquid level sensor may be mounted in the support housing to sense a predetermined liquid level to prevent accidental overflows. Protective lenses may be placed in front of the primary liquid level sensor.

Abstract: A liquid container for use in an inclination detector includes a container body containing liquid forming a free surface and having a circumferential wall in a spherical form, in which the circumferential wall is formed so that a center of the circumferential wall and a center of the free surface coincide with each other.

Abstract: An apparatus and method are disclosed for detecting a combustible fuel leakage into the cabin of a bi-fuel or dual-fuel vehicle. The apparatus comprises a box affixed inside the cabin of a bi-fuel vehicle which alerts a driver to the presence of a combustible fuel inside the cabin using an audible alarm and flashing lights, and which then either disables the vehicle or switches the fuel powering the vehicle's engine to gasoline. Certain embodiments of the present invention include substitute means of generating and transmitting alerts to drivers, as well as of manipulating vehicle function.

Abstract: The present invention proposes an apparatus (100) and method for managing the liquid volume in a container. The apparatus (100) comprises a detector (101) for detecting liquid volume changes in said container during a first preset period, a first determiner (102) for determining whether said changes are lower than said first preset threshold value and a presenter (103) for presenting the first prompt information in the case of said changes being lower than said preset threshold value. The apparatus and method provided in the present invention can prompt people to drink drinkable liquids such as water in time, enable people to control their drinking intake and are beneficial to their health.

Abstract: To implement an ink tank and a printing apparatus that can detect a residual quantity of ink in an ink containing part optically with high accuracy by solving a problem of false detection of an ink residual quantity caused by irregular reflection light and scattered light generated by light from a light emitting part. For that purpose, the light source for emitting light of a first wavelength and the light receiving part for receiving light of a second wavelength are provided. Then the light of the first wavelength from the light source is configured to be irradiated on a luminescent material that is provided in the ink tank and emits the light of the second wavelength using an optical prism only when the ink does not exist in the ink tank.

Abstract: A gas measurement apparatus can comprise a sensor and a processor, in an example. The sensor can measure a pressure condition of a gas tank, in an example. The processor can select at least one light source, the light source can be positioned or be of a distinct color to indicate a corresponding level of gas remaining in the tank when illuminated. The level of gas can be based on the measured pressure. Banks of high intensity LEDs can allow visually discernable colors at a significant distance underwater. A visual beacon mode can be included. An alphanumeric pressure readout mode can be included. A depth sensor can be included.

Abstract: A gas measurement apparatus can comprise a sensor and a processor, in an example. The sensor can measure a pressure condition of a gas tank, in an example. The processor can select at least one light source, the light source can be positioned or of a distinct color to indicate a corresponding level of gas remaining in the tank when illuminated. The level of gas can be based on the measured pressure.

Abstract: A liquid level sensor probe for determining liquid level within a vessel, the liquid level sensor probe comprising at least one light source positioned for emitting radiant energy; at least one photosensor positioned for detecting an amount of radiant energy received from at least one light source wherein a change in the amount of radiant energy as detected by at least one photosensor is indicative of a change in liquid level within the vessel; at least one light shield positioned between at least one light source and at least one photosensor wherein at least one light shield prevents radiant energy from directly hitting at least one photosensor; and encapsulation material.

Abstract: Methods and systems are provided for monitoring a solid-liquid interface, including providing a vessel configured to contain an at least partially melted material; detecting radiation reflected from a surface of a liquid portion of the at least partially melted material; providing sound energy to the surface; measuring a disturbance on the surface; calculating at least one frequency associated with the disturbance; and determining a thickness of the liquid portion based on the at least one frequency, wherein the thickness is calculated based on L=(2m?1)vs/4f, where f is the frequency where the disturbance has an amplitude maximum, vs is the speed of sound in the material, and m is a positive integer (1, 2, 3, . . . ).

Abstract: A pressure vessel 12 with a CO2 liquid level indicator 14, for use with a paintball marker 10, includes a magnetic float assembly 42 disposed within the pressure vessel 12 and adapted to float on liquid phase CO2 39 contained within the pressure vessel 12, in combination with a magnetically sensitive indicator 44 on an outer surface 40 of the pressure vessel 12 and which is adapted to detect and to display the location of the magnetic float assembly 42 within the pressure vessel 12. When connected to a conventional paintball marker 10, the pressure vessel 12 magnetically shows the indicated location of the magnetic float assembly 42, thereby showing the amount of liquid phase CO2 39 remaining within the pressure vessel 12. This remaining amount of liquid phase CO2 39 can be correlated to an approximate number of additional paintball rounds that can be shot before the CO2 is depleted.

Abstract: A system and method for identifying the levels of one or more liquids in a vessel using an optical imager and one or more appropriately positioned light sources and an optical imager for capturing digital images of the illuminated vessel. A laser line generator is positioned oppositely from the imager and oriented to project a laser line through the vessel so that it may be imaged by the imager. A second light source, such as an LED, may be positioned above or below the vessel and oriented to project light downwardly or upwardly through the vessel and its contents. Captured images of the vessel are then processed by a programmable device, such as a microcontroller, to determine the levels of materials in the vessel based on the optical characteristics revealed in the captured image.

Abstract: An apparatus for monitoring a position of a semiconductor process fluid interface in a dispense nozzle includes an extended optical source adapted to provide an optical beam propagating along an optical path. The optical beam is characterized by a path width measured in a first direction aligned with a dispense direction. The apparatus also includes an optical detector coupled to the optical path and adapted to detect at least a portion of the optical beam and a dispense nozzle disposed along the optical path at a location between the extended optical source and the optical detector. The apparatus further includes a nozzle positioning member coupled to the dispense nozzle and adapted to translate the dispense nozzle in the first direction.

Abstract: An illuminated level has a housing containing a solid body pivotally mounted in the housing and forming a pendulum which can pivot to a first position in which the surface is accurately level. A light path is provided through the solid body having an exit opening at the pivot point and an entry opening the opposite end. A source of laser light on the housing is arranged to transmit light through an orifice on the housing so that the light through the orifice enters the entry opening to pass along the path when the solid body is in the first position and is prevented from entering the entry opening when the solid body is out of the level position. A light receiver in the housing at the outlet is responsive to the passage of light through the path for providing a sound indicating when the solid body is in the first position.