Abstract: A photodetector is provided with two light sources and a light sensitive component. The use of two light sources significantly reduces the opportunity of a surface feature, or abnormality, from focusing light back toward the light sensitive component in a manner that could possible cause the photodetector to misinterpret the intensified light as being indicative of the absence of an object in the detection zone. The light sources and light sensitive component can be arranged along an axis which is either parallel to the path of the objects to be detected or perpendicular to their path.

Abstract: A photoelectric sensor is provided with the capability of calculating a threshold magnitude based on a maximum light intensity received by a light sensitive device. The maximum value of the light intensity is determined during a preselected period of time when no object is blocking the path of a light beam. A second threshold magnitude is used to assist the present invention in determining the leading edge and trailing edge of a transparent object. The values of the first and second threshold magnitudes are updated dynamically as bottles pass through the path of the light beam. This permits the photoelectric sensor to react to changes in light intensity without providing false signals of bottles within the light path or missing bottles that are within the light path.

Abstract: An overcurrent protection circuit is provided with a counter which permits a preselected number of reinitiations of current following the detection of an overcurrent condition. Each stoppage of current in response to the detection of an overcurrent condition is followed by a predetermined time delay and a subsequent reinitiation of current. After the predetermined number of reinitiations, current is permanently stopped from flowing between first and second circuit points until a manual reset occurs.