Abstract: A marine depth sounding apparatus including a floatable housing carrying a sonic transducer for emitting sound waves toward the bottom of a body of water and for detecting the reflections of such sound waves, and a sound transmitter for emitting an audible signal when the information provided by the sonic transducer indicates that the depth of the water is less than a predetermined depth. The apparatus may be cast away from the vessel to provide information concerning the depth of water at locations remote from the vessel. A circuit is disclosed for comparing the time period required for sound waves to travel a distance corresponding to the predetermined depth with the actual time elapsed between the emitting of the sound waves by the sonic transducer and their detection by the sonic transducer.

Abstract: A pilot operated stepping valve where an electrical pulse motor drives a pilot valve spool which controls the flow of hydraulic fluid driving a main valve spool which actuates a hydraulic motor or actuator. The main valve spool follows the pilot spool and is hence sensitive to the pulses received by the pulse motor.