Abstract: An apparatus for flicker protection when a servo motor driven sewing machine starts utilizing comparators. Setting the original voltage as the reference voltage and the dropped voltage as the monitor voltage, the comparator compares the voltages and, if the difference exceeded more than the predetermined value, signals for setting the maximum electric current to the servo motor are attenuated such that the voltage drop of the electric source will be reduced.

Abstract: The control device for an earthwork machine according to the invention is designed for reducing the manufacturing cost of the earthwork machine by eliminating some of the calculating circuitry and the control circuitry. According to the control device, one of the cylinders necessary for carrying out straight excavation is directly manually controlled without using calculating circuitry, and the operations of the cylinders are respectively detected by detecting circuitry. The other two cylinders are also controlled by the arithmetic unit provided in the control device for performing calculation necessary to move the sharp edge of the bucket along a straight line of predetermined inclination in accordance with detected pivoted angles of the boom, arm and bucket.

Abstract: In apparatus for detecting the degree of contamination of liquid of the type wherein the quantity of light transmitting through a liquid sample is detected, a combination of a transparent flat plate and a convex lens is interposed between a light source and a light receiver. The flat plate is in contact with the convex lens at the top of the convex lens so as to define an annular gap for accommodating the liquid sample.