Abstract: A monitoring system for continuously monitoring the ground conductor of an electrical cable having power conductors and a pilot wire in addition to the ground conductor. An a.c. test signal is connected onto a loop comprised of the ground conductor and pilot wire and a terminating impedance. A current transformer samples the test signal on the ground conductor and checks its magnitude. By making the transformer impedance considerably lower than the mutual inductance between the ground conductor and pilot wire, large, expensive blocking impedances are not required to prevent the test signal from following sneak paths from the test loop to earth ground.

Abstract: A ground monitoring circuit for detecting the existence and proper connection of the ground wires in an electrical power cable of a type commonly used at a surface mining site. A complete conductive loop is established between the ground conductor, or conductors, and the ground check, or pilot, wire of the cable. A sensing signal at a frequency higher than the power frequency is coupled onto the ground monitoring loop. The voltage and current in the loop are separately sampled. Various comparisons of the voltage and current samples are made to detect any deviation in the resistance and/or reactance characteristics of the loop. Any deviation from desired conditions in the loop produce one or more output signals that change the condition of a trip relay. The trip relay initiates action that ultimately opens circuit breakers to remove power from the cable.

Abstract: In accordance with the present invention, light from tungsten lamps is directed onto tomatoes moving in parallel rows on a conveyor belt. Above each row of tomatoes three photodetectors having different spectral responses are employed for looking at three different wavelengths of light reflected from the tomatoes. One of the wavelengths is the visible red color, the second one is the so-called "water dip" wavelength in the near infra red, and the third one is a reference wavelength in the near infra red. By means of logic circuitry operating in response to the three photodetector output signals, red tomatoes are separated from all other articles on the conveyor, including dirt and rocks. The logic circuitry "asks" the following questions. Is an article present? Is the article vegetable matter? Is the article red? If all questions are answered in the affirmative the article is processed as a desired red tomato. If any one of the questions is answered in the negative the article is rejected as undesirable.

Abstract: A synchronizing system is provided to produce gating pulses which occur only when a pocket between adjacent convoluted rollers is directly under the optical system. These gating pulses control operation of the circuitry of the grading apparatus and the ejection apparatus. With this arrangement, the rollers are in effect blanked out of the field of view of the optical system and the grading system can "see" only articles and objects in the pockets between rollers.

Abstract: A produce grader that includes first and second signal paths for producing first and second signals corresponding to respective detected characteristics of an article of produce being graded. Each signal path includes chopper means for converting d.c. signals to a.c. signals, a.c. amplifier means, and means including synchronous detector means for reconverting amplified a.c. signals to d.c. signals. The reconverted signals are compared and/or evaluated to establish a basis for grading. Means are provided for adjusting the duty cycle of the gating signal controlling at least one synchronous detector thereby adjusting the gain of the corresponding signal path and adjusting the calibration of the grader.