Abstract: A foot positioning training device with a mat having a transmitter and receiver to establish an electric eye. The electric eye is tied to an alarm that indicates when a batter has taken an improper stride while swinging the bat.

Abstract: A robot apparatus which may be turned to a sound source direction by a spontaneous whole-body concerted operation. With the possible range of rotation of the neck unit of a robot apparatus 1 of ±Y° and with the relative angle of the direction of a sound source S to the front side of the robot apparatus 1 of X°, the entire body trunk unit of the robot apparatus 1 is rotated through (X?Y)°, using the leg units, while the neck joint yaw axis of the robot apparatus is rotated through Y° to the direction of the sound source S, so that the robot apparatus is turned to the direction of the sound source S.

Abstract: A multiple mode pre-loadable fiber optic pressure and temperature sensor includes a generally cylindrical structure having at least one compression element, a fiber optic having a Bragg grating in contact with one side of the compression element, a diaphragm in contact with the other side of the compression element, and a fluid port in fluid communication with the diaphragm. According to preferred aspects of the, a groove is provided in at least one compression element for receiving the fiber optic. The sensor is pre-loaded by straining the diaphragm over the adjacent compression element when the cover is attached. The compression element in contact with the diaphragm preferably has a contoured surface contacting the diaphragm and the diaphragm is stretched to match that contour. By varying the contour of the compression element and the thickness of the diaphragm, the dynamic range of the sensor can be changed. The preferred diaphragm has a variable thickness and is made as an integral part of the structure.

Abstract: A multifunctional photoelectric switch comprises a display section for displaying a first display information and a second display information. The first display information includes a plurality of items concerning a threshold value and the second display information includes a plurality of items concerning functions of the photoelectric switch. A switch is provided for switching information to be displayed on the display section between each type of display information. A selection menu for the user to select either “Easy” or “Pro” is displayed in the progress of making a transition from a “light reception amount and/or threshold value display” mode of the basic display information to an “operation function setting” mode of the second display information. The user selects and sets either “Easy” or “Pro” on the selection screen. In the “Pro” mode, the set items concerning all functions are displayed; in the “Easy” mode, only the basic items are displayed.

Abstract: A self-aligning sensor assembly that is useful for mounting safety sensors that require precise alignment such as electric eyes and electric garage door opener sensors that include an aligned emitter and detector wherein the self-aligning mechanism allows the sensors to be realigned manually or automatically. This invention is also a method for deactivating a sensor mechanism such as a garage door opener sensor using the self-aligning mechanism of this invention.

Abstract: The invention relates to a light grid (1), comprising a predetermined number of pairs of transmitters (7) emitting light rays (6) and receivers (9), which form beam axes, wherein the light rays (6) emitted by the respective transmitter (7) impinge on the receiver (9) if the path of a beam axis is clear. Also provided is a control unit for controlling the transmitters (7) and for evaluating the signals received at the receiver (9) output, wherein an object detection signal can be generated in dependence on the signal received when an object interferes with at least one of the beam axes. A separate bit word is assigned to each beam axis via the control unit, wherein the beam axes can be divided into predetermined regions via at least one bit BLK of the bit words and wherein the object detection mode within this region can be preset by presetting the bit value of at least one additional bit of the bit words for the beam axes within one region.

Abstract: A home control system for automatic detection and warning of abnormal behavior includes a unit for observing behavior in a predetermined area under surveillance, a unit for processing an output of observed behavior from the unit for observing, and a pattern recognition module for recognizing whether the observed behavior is associated with predefined normal behaviors. The detection of predetermined normal behavior in progress leads to a provision of an anticipatory action. Upon recognition that the observed behavior is abnormal, an alarm signal is triggered to remind the user.

Abstract: A method and apparatus for guiding a vehicle into an optimal position within a parking space. A first linear ray of light is projected along the centerline of a parking space. A second linear ray of light is projected at an angle to and intersecting the first linear ray within the parking space. The first linear ray of light guides the driver while moving into and through the space when the driver aligns an indicator on the vehicle with the first linear ray of light. As the driver nears the optimal position, the second linear ray of light will move towards the indicator. When the indicator coincides with the intersection of the first and second linear rays of light, the vehicle is in the optimal position.

Abstract: Photoelectric proximity switch for detecting the presence of an object in a monitored area. A light pulse transmitter emits transmitting light pulses into the monitored area. The pulses are triggered by an output signal of a random signal generator or a pseudo-random signal generator and are emitted with a time interval between them. A light receiver is arranged in relation to the light pulse transmitter and to the monitored area such that in the absence of an object to be detected in the monitored area, the receiver receives essentially no light from the light pulse transmitter, but in the presence of an object to be detected in the monitored area, it receives such light from the light pulse transmitter due to reflection that a receiving signal evaluating device connected to the light receiver and to random signal generator or the pseudo-random signal generator delivers an object detection signal.

Abstract: A dispersion light smoke detector has a structure for providing a definite measuring volume, the structure being formed as two light receivers or an imaging optical system for one light receiver.

Abstract: The invention provides a method and apparatus for monitoring a moving object, the method comprising: emitting electromagnetic radiation so that the object passes through the electromagnetic radiation; detecting a plurality of reflection events, each comprising a reflection of the electromagnetic radiation from the object; determining a direction of each of the reflection events from the direction of emission of the electromagnetic radiation or from the direction of detection of the respective reflection event; and determining the relative timing of the reflection events; wherein information pertaining to the object can be determined, the information comprising any one or more of a speed, a location and a direction of the object.

Abstract: A perimeter monitoring system is arranged to detect passage across a perimeter of an area. The system primarily includes an emitter, a retroreflector, a detector and an alarm. The emitter provides a modulated visible laser beam. The retroreflector is arranged to direct the beam along a segment of the perimeter and return the beam along the segment. The detector includes a device that blocks reception of light outside an angle of less than 5 degrees. One or more local or remote alarms are activated in response to the signal. For example, a remote alarm is located on the inside of a residence window where it is activated by another visible laser beam. Alignment of the peripheral monitoring system is less costly and false alarms are less likely than with known systems.

Abstract: An automatically testable obscuration detector incorporates one of an electrically controllable filter or a mechanically selected filter. Filtered outputs can be compared to expected outputs by control circuitry to automatically assess detector operation.

Abstract: To provide an anti-thief security sensor assembly wherein an optical axis of a beam projecting unit can be accurately aligned with that of a beam receiving unit, the anti-thief security sensor assembly includes a beam projecting unit 1 for projecting an infrared beam IR and a beam receiving unit 8 for receiving the infrared beam IR. The beam projecting unit 1 includes a projector cover 21A detachably mounted on a mounting base 20A for enclosing and protecting a sensor circuit on the mounting base 20A, an opening detecting switch 7 for detecting a physical opening of the projector cover 21A, and a projected beam suppressing circuit 4 operable in response to detection by the opening detecting switch 7 to reduce a quantity of the infrared beam emitted from the beam projecting unit 1 to thereby reproduce the infrared beam of a quantity substantially equal to that having passed through the projector cover 21A.

Abstract: The invention relates to an optoelectronic monitoring device for the detection of objects intruding into a monitored zone comprising at least one transmitter, in particular a light grid, arranged at an end of the monitored zone and having a group of transmission elements spaced apart from one another and each transmitting electromagnetic radiation into the monitored zone, at least one reflector arranged at an end of the monitored zone opposite the transmitter for radiation transmitted by the transmission elements, at least one receiver which has at least one spatially resolving reception element for radiation reflected by the reflector, and an evaluation device coupled with the reception element, wherein the transmitter, the reflector and the receiver are made and arranged such that, during the monitoring operation, at least a part of the group of transmission elements comprising a plurality of transmission elements is imaged on the reception element by means of the reflector and a check is made by means of t

Abstract: An infrared detector includes a light emitter and a light receiver. The light emitter has plural light emitting units with a circuit connecting the light emitter with a CPU programmed decoder and a power amplifying controller, and then a special coded signal amplified and emitting out with infrared light beam by the light emitting units to the light receiver. The light receiver has plural infrared light receiving units and a circuit connecting the receiving units with a signal amplifier, a CPU programmed calculating and comparing decoder, and an output controller. The special coded signal with infrared light beam received by each separate infrared light receiving unit is sent at once to the signal amplifier for amplifying, and then fed to the CPU programmed calculating and comparing decoder for processing, and the controlled by the output controller, so as to prevent the infrared detector from disabled by unauthorized code or different code by illegally intending person.

Abstract: A very reliable alarm system is comprised of transceiver node devices interconnected via infrared links forming a secure perimeter, whereby each transceiver node in the perimeter receives an infrared transmission from a previous transceiver node, and itself transmits an infrared signal to the next transceiver node in the perimeter. If a break of an infrared link occurs, such as would happen if an intruder enters the perimeter area, an indication of the break is communicated around to a base unit device either by each subsequent node device inhibiting its infrared transmission, or changing its transmission to that of a special alarm signal. Upon receiving an indication of a perimeter break the base unit device alerts alarm signaling devices such as audible or visual alarm indicators.

Abstract: An intrusion detector and method of operation which include a light source having a certain correlation length, and first and second light paths, wherein at least the first path extends through a secured area. A modulator, which is advantageously either a phase rotation modulator or path length modulator, is provided in the second path. At least one optical detector is placed to detect light traveling along the two paths. A comparator is electrically coupled to the detector to compare the detected signal with a signal applied to the modulator.

Abstract: A security system employs a plurality of towers for detecting an intruder. A detection beam extends between adjacent towers, and a breach in the detection beam detects the presence of intruders. The solar tower includes a solar panel, a solar mounting bracket, a swivel clamp, a swivel solar bracket, a solar cap opening mechanism, a solar base cap, and a top plate. The solar tower further includes a base unit, frame support rods extending from the base unit, a frame unit having face shield slots, and opposing face shields mounted in the face shield slots. The top plate is secured to the frame support rods with suitable fasteners.

Abstract: A patient monitoring system is described including a monitoring beam generating device for generating a monitoring beam along a substantially straight-line path of a selected length and a detecting means that signals the system to generate an alert signal in response to the monitoring beam being broken at least in part at a position along the length of its path.

Abstract: A customer conversion system connects existing, conventional sensors to a point of sale computer or other computer. Entries by people into a retail space so equipped are counted and recorded on a continuous or on a periodic interval basis.

Abstract: A security system employs solar towers for detecting an intruder. The security system includes a receiver/processor and transmitter for communicating with electronic devices in the solar beam towers, the receiver/processor and transmitter having an antenna, a housing and an indicator. The indicator includes information on the location of an intrusion. A detection beam extending between adjacent towers is used to detect intruders. The detection beam can include infrared, laser, microwave, and visible light. The alarms sent out by the system can include devices such as visual alarms, audible alarms, telephone dialers, and printers. The central unit exchanges information between the remote units via two way half-duplex radio. The system is a radio data reporting system, which reports events and selectively transmits an alarm. The alarm is transmitted to the central unit when a new event is detected, and it is displayed there.

Abstract: A vehicle door stop safety system for preventing closure of a vehicle door when an object moves between an open door and body of the vehicle. The system includes field producing device for producing a field adjacent to a latch end of the door, when the door is open; and sensing device for sensing an interruption of the field and for producing a block or stop signal when the interruption is sensed. Blocking device is provided for blocking closure of the door upon an interruption of the field. Alternatively, braking device is provided for stopping the door's movement at a position when an interruption of the field is sensed. A controller is provided for actuating the blocking or braking device upon sensing by the sensing device of an interruption of the field.

Abstract: An apparatus is provided for detecting a shopping cart used to bring items to a checkout location, and inspecting its bottom tray for the presence of items. The apparatus includes a cart-detector to detect the presence of the cart at a pre-determined location; and an item-detector to detect the presence of items placed on the lower tray of the cart. The cart detector includes an arrangement of three optical sensors and corresponding retro-reflective targets; and finite state-machine processing logic to discriminate a specific sequence of sensor responses.

Abstract: Device for guiding flows of individuals in mass transportation systems, containing at least the following components: A) a guidance system in embarking and disembarking areas interacting with at least one of the following devices: a) a guidance system in the means of transportation. b) a blocking device between the embarking/disembarking areas and the means of transportation.

Abstract: An opto-electronic apparatus for the monitoring of a protection area which has at least one protection device, which works in a non-contact manner, is described. The protection device, which works in a non-contact manner, has an evaluation unit for the generation of an object detection signal on the intrusion of an object into the protection area. An image detection unit is coupled to the protection device, which works in a non-contact manner, for the detection of an areal or spatial image detection area, with a secondary monitoring area disposed close to the protection area, but outside the protection area, being detected by the image detection unit. The protection device, which works in a non-contact manner, is controllable by the image detection unit.

Abstract: A portal access control system is disclosed for preventing unauthorized entry from a public area into a secure area. The system utilizes input from several different sensors, including: passive IR sensors, motion detectors, photo detectors and authentication devices. Also, the passage time of an individual through the open portal may be determined. Based on selected combinations of one or more sensor inputs, the portal access control system can detect passage into the secure area by a lone perpetrator and also by tailgating behind an authorized user.

Abstract: To provide an anti-thief security sensor assembly wherein an optical axis adjustment of a beam projector can be accurately achieved merely by physically opening a cover of a beam projecting unit while a cover of a beam receiving unit is not opened physically, the anti-thief security sensor assembly includes a beam projecting unit (1) for emitting an infrared beam IR and having a projector cover (21A) mounted on a projector base (20A) so as to cover and protect a sensor circuit. This beam projecting unit (1) includes an opening detecting switch (7) for detecting the physical opening of the projector cover (21A) and a transmission request generating circuit (8) operable in response to the detection by the opening detecting switch (7) to output a received beam level transmission request signal B to the beam receiving unit (2).

Abstract: Communicating apparatus to be provided between an intermediate line and transmission lines to establish data communications, the intermediate line and the transmission lines having in combination data pass therethrough, the transmission lines including first line and second line, comprises: first receiving means 111 for receiving the data via the first line, second receiving means 121 for receiving the data via the second line, interface means 101 for transmitting via the intermediate line the data received by the first receiving means via the first line and the data received by the second receiving means via the second line, and for receiving the data transmitted by an other communicating apparatus via the intermediate lines, first transmitting means 112 for transmitting via the second line the data transmitted via a first receiving means of the other communicating apparatus, first detecting means 113 for detecting the data transmitted via the second line, first controlling means 114 for controlling the firs

Abstract: An object detection system for use in detecting the presence of an object within a space, such as in an aisle of a mobile storage system bounded by at least one mobile storage unit, includes a pair of pivotable light emitter/receiver unit located outwardly of each side of the space and a series of reflectors located outwardly of each side of the space. Each emitter/receiver unit includes a pivotable emitter which emits a beam of light which passes across and through the space and impinges upon the reflectors located outwardly of the opposite side of the space. A receiver associated with each emitter/receiver unit receives reflected light from the reflectors. The presence of an object within the space prevents the light beam from reaching one or more of the reflectors, and the absence of one or more reflected light beams is detected such that operation of the mobile storage unit is prevented until the object exits or is removed from the space.

Abstract: A vehicle door stop safety system for preventing closing of a door of a vehicle when an object moves between the open door and the body of the vehicle. The vehicle door stop safety system includes a field producing assembly for producing a field adjacent to the latch end of the door. The field producing assembly is mountable on the latch end of the door, and the field producing assembly is adapted for operatively connecting to the switch of the vehicle such that the field producing assembly produces the field when the switch is actuated by opening of the door. A sensing assembly produces a block signal when an interruption of the field is sensed. The sensing assembly is mountable on the latch end of the door of the vehicle. A blocking assembly is provided for blocking closure of the door when the sensing assembly detects an interruption of the field produced by the field producing assembly. The blocking assembly is mountable on the body of the vehicle adjacent to the door opening.

Abstract: An adapter (10) for a light fixture (F) has a socket (16) into which the base of the light bulb (L) is screwed. The adapter has a base (12) sized to be inserted in a socket of the light fixture for attaching the adapter to the light fixture. The adapter further includes a housing (14) in which is installed an audio alarm (20) for a security system. The audio alarm is electrically operated and connected in parallel with the light bulb. Electrical current routed to the adapter through the light fixture simultaneously illuminates the light bulb screwed into the socket of the light holder and the audio alarm.

Abstract: A keyless access sensor system for use with a keyless access control mechanism (KACM) is described for controlling the operation of a locking device. The KACM receives a signal from a sensor device for keyless access to create a first output signal before the user has begun any action on the handle in order to open the door. The first output signal is sent to a general processor, which initiates a recognition process and, after recognition of the authorized user the processor then generates an unlocking signal which unlocks the locking device before the authorized user will have fully accomplished the action of opening the door. Thus the authorized user is allowed to open the door without any specific un-ergonomic and time-consuming additional action to the simple action of actuating the handle to open the door.

Abstract: A coupling system allows interconnection of multiple light curtains segments but prevents interconnecting dissimilar segment types. A first connector half mounts to a segment while a second connector half mounts to another segment, such that mating the two halves interconnects the two segments. The two mating sections of the connector or coupling system may be formed as matched mating blocks that are mounted in different orientations, depending upon whether they are attached to transmitter or receiver type light curtain segments. One or both mating sections may rotatably mount to its respective segment, thereby providing an articulated connection between the joined segments. In other implementation, one mating section may be formed as a reversible coupler, with the other mating section formed as a mating receptacle that may be conveniently keyed to accept only a particular orientation of coupler.

Abstract: An attachment for a light unit, which attachment comprises light-detecting means adapted to generate an output signal corresponding to the intensity of light incident thereon, and adjustable attaching means for removably attaching said attachment to an existing light unit such that the light detecting means are positioned within a beam of light emitted by the light unit when operated and are adapted to detect light that is directed towards the light unit, said attaching means being adjustable to allow the attachment to be selectively fitted to a range of different existing light units. Particularly, said light sensing means are adapted to sense light from the light unit that is retro-reflected back towards the light unit.

Abstract: A method for monitoring two or more movable objects in a monitoring region. A substantially horizontal light barrier grid having a plurality of parallel light barriers monitors the region. To permit a plurality of objects to simultaneously move in the monitored region without deactivating the monitoring function of the system, the system controls an entry area for the objects, the size of the objects as well as the distance between the objects to ascertain that predetermined criteria therefor are met. If one or more of these criteria is not met, a control signal is generated which can be used, for example, to deactivate the machinery and/or prevent access to the monitored region.

Abstract: A method and apparatus for an event detector using an array of passive infrared detector elements, which uses interchangeable spectral filters and lenses to permit detection of a range of event types, which normally each require individual detectors with specific spectral/optical designs.

Abstract: According to one embodiment of the invention, the optical security system consists of a first laser beam generation and feedback signal receiving station on one end of the security zone and a second laser beam receiving and feedback signal transmitting station on the other end of the security zone. The first station consists of a laser source that generates a modulated low-divergence laser beam and a first optical signal receiver. The second station consists of a second optical signal receiver that receives the aforementioned modulated low-divergence laser beam emitted from the laser source and a feedback optical signal transmitter which is connected to the aforementioned second optical signal receiver via a signal processing unit which codes the received signal and forms it into a feedback signal to be sent to the first optical signal receiver of the first station from the transmitter of the second station. In the system of the second embodiment the feedback signals are in the form of IR, MW, or RF signals.

Abstract: A mixed architecture light curtain system comprises a mix of flexibly and rigidly interconnected light curtain segments. For example, a number of light curtain segments may be rigidly interconnected in series at desired connection angles using one or more types of rigid connectors to form a set of rigidly connected segments. Another set of rigidly connected segments may be flexibly connected to this first set, or one or more individual segments may be flexibly connected in series with this first set. In general, a series of interconnected segments may be formed in any desired combination of rigidly and flexibly connected segments. In any such combination, differing types of rigid and flexible connectors may be used, such that rigidly and flexibly interconnected segments may be fixed at essentially any desired angle, offset, or relative spacing, allowing the mixed architecture light curtain to conform to complex and even disjointed protection zone shapes.

Abstract: A perimeter monitoring system is arranged to detect passage across a perimeter of an area. The system primarily includes an emitter, a retroreflector, a detector and an alarm. The emitter provides a modulated visible laser beam. The retroreflector is arranged to direct the beam along a segment of the perimeter and return the beam along the segment. The detector includes a device that blocks reception of light outside an angle of less than 5 degrees. One or more local or remote alarms are activated in response to the signal. For example, a remote alarm is located on the inside of a residence window where it is activated by another visible laser beam. Alignment of the peripheral monitoring system is less costly and false alarms are less likely than with known systems.

Abstract: A passenger detecting apparatus including a sensor unit of a small size heightwise which can be manufactured inexpensively includes a light emitting means (21a, . . . , 21h) for emitting light rays in a substantially horizontal direction, a beam forming means (22a, 22b) for transforming light rays emitted from the light emitting means into a collimated or converged light beam in a substantially horizontal direction, a downward reflecting means (23a, 23b) for reflecting the light beam in a direction toward a lower seat disposed in the compartment, and a light receiving means (24a, 24b) for receiving the light beams scattered upon striking on the passenger for thereby detecting the state of the passenger.

Abstract: An optical position detecting device includes side frames on three sides, which are composed of slide parts and guide parts for guiding the slide parts and provided with light retro-reflectors; and a side frame on one side, which is composed of a slide part and a guide part for guiding the slide part and incorporates two optical units including light emitting elements, polygon mirrors and light receiving elements, and the optical position detecting device is externally fixed to a display apparatus by moving the slide parts.

Abstract: A method for monitoring an entrance to a hazardous area comprising sensing a signal pattern generated by light barriers when an object passes the entrance and comparing the sensed signed pattern with at least one predetermined signal pattern. The object is admissible if the signal patterns are identical and under certain other conditions.

Abstract: Method for configuring the operating mode of an optical detector, by recognition, following an emission in a first operating mode M1, by means of the receiving system. The latter then confirms the detector in the first operating mode or switches it over into a second operating mode M2 according to whether there is recognition of the first mode. Automatic validation or validation carried out by the operator confirms the recognized operating mode. Application to multimode optical detectors able to operate in barrier, reflex, proximity, background suppression proximity mode.

Abstract: The present invention relates to a method for detecting fire with light section image to sense smoke. Infrared radiation arrays (1) and infrared cameras (2) are provided in a monitored area. The images of the infrared light spots transmitted by the infrared radiation arrays (1) are converted into video signals by the infrared cameras (2), and transferred to a video switcher (3). The video switcher sends the video signals received from the infrared cameras to a computer (4) one by one. The computer processes the signals. If fire is sensed, the computer controls the alarm unit (5) to alarm by a linkage.

Abstract: A display monitor is provided for a multi-optical-path photoelectric safety apparatus including a plurality of multi-optical-path photoelectric sensor units. The user can determine whether a special function such as blanking is set for each optical path in a group which comprises a plurality of indicator lamps placed in a row along a longitudinal direction. The user can check the light incidence/light block status for each optical path on an indicator lamp group. The display monitor includes the plurality of indicator lamps placed in a row in the longitudinal direction. First and second switches allow the user to select the unit and the optical path to be shown on the two indicator lamp groups.

Abstract: A pool alarm system for alerting when an object such as a child has entered a pool filled with water. The pool alarm system includes, a sensor assembly for detecting when an object has entered the water in a pool. The sensor assembly includes a housing that is mountable on a side wall of the pool. A first sensor is mounted on the housing for detecting movement of the surface of the water. In one embodiment of the present invention, the first sensor is designed to detect surface movement of the water in the pool caused by an object entering and disturbing the surface of the water. A warning assembly is provided for warning an individual in a vicinity of the pool that the sensor has been activated. The warning assembly preferably includes a speaker that is mounted on the housing for emitting sound to audibly warn an individual in a vicinity of the pool that the sensor has been activated.

Abstract: An occupant sensor has a photodetective portion having a photosensitive surface capable of receiving a reflection R of a light curtain (two-dimensional light) projected from a light projecting portion. Masks cover part of the photosensitive surface. The apparatus can quickly detect presence/absence of an occupant, because the masks block entry of unwanted light. Control of an airbag is carried out based on the presence/absence of occupant.

Abstract: A coordinate input apparatus includes light sources, a reflecting member, light receiving members, a signal analyzing mechanism, and a coordinate determining mechanism. Each light source is fixed around a perimeter of a predefined input region at a fixing position different from others and is configured to emit light extending in a deltaic form centered at the fixing position and approximately in parallel to the input region. The reflecting member is fixed around the perimeter of the input region and is configured to recursively reflect the light so that the light returns towards the light sources. The light receiving members are fixed around the perimeter of the input region and are configured to receive the light recursively reflected from the reflecting member and to convert the light into an electric signal. The signal analyzing mechanism analyzes the electric signal to detect a position of an obstacle when the obstacle is placed in the input region and blocks the light.

Abstract: An infrared detection and alarm system for the bottom shelf of shopping carts having attached to the bottom shelf an infrared emitter which shall emit therefrom infrared light which shall be received by an infrared detector when no merchandise is located on the bottom of the cart and if a piece of merchandise is located on the bottom shelf the light shall be interrupted. Upon interruption of the light, a transmitter shall communicate a code to a receiver mounted on the checkout stand at which point said receiver shall activate an LED warning light to communicate to the sales clerk the presence of merchandise on the bottom shelf of the shopping cart.