Abstract: A pressure detector for particular use in a system for administering parenteral fluid to a human patient. The pressure detector includes a conventional pressure diaphragm having a flexible membrane that is movable in accordance with the pressure of the fluid being administered. The pressure detector further includes a special receptacle for retaining the pressure diaphragm, and a special follower assembly that is moved in a prescribed fashion by installation of the diaphragm in the receptacle and by movement of the diaphragm membrane due to variations in fluid pressure. A pair of electrical contacts are controllably moved together and apart by the follower assembly, to provide an electrical signal whenever the diaphragm is not installed or, if it is installed, whenever the fluid pressure exceeds a prescribed threshold.

Abstract: A device for measuring distances to a target includes electronic circuits for generating a light which is amplitude modulated by three selectable frequencies. Also included are optics for focusing the amplitude modulated light onto the target, and for receiving reflection of the light therefrom. Additional circuits convert the received light to electrical signals representative thereof, and compute the phase angles between these signals and the amplitude modulating signals. The distance to the target is then calculated based on these phase angles and the wavelength of frequencies equal to the differences between the three selectable frequencies. Another circuit uses an accelerometer to measure vertical angle to the target, and further distance measurements are made based thereon. Still other circuits compensate for a variety of potential error causing conditions, such as signal waveform asymmetry and component tolerance.