Abstract: A system for point-level detection of material within a vessel includes a transmission line probe adapted to be mounted to a wall of the vessel so as to extend within the vessel for contact with material when the material reaches a preselected level within the vessel. Electronics are operatively coupled to one end of the probe for launching microwave energy along the probe. The electronics are responsive to a change in microwave energy reflected from the free end of the probe within the vessel when the material is in contact with the probe, employing time-domain reflectometry techniques, for indicating that the material is in contact with the probe. This change in reflected microwave energy may comprise a change in phase or, more preferably, a change in apparent length of the probe resulting from contact with material having a higher dielectric constant than that of air when air surrounds the probe.

Abstract: A normally closed, three-way valve comprises a housing having a supply passage, a control passage, and an exhaust passage. A valve assembly controls communication between the passages. The valve assembly includes a valve in the supply passage to open and close communication between the supply and control passages. The valve assembly also includes a second valve in the exhaust passage to open and close communication between the control and exhaust passages. The supply passage valve is normally held closed by the pressure of hydraulic fluid in the supply passage. A solenoid, when activated, moves the exhaust passage valve to closed position. A pintle between the two valves is shifted in one direction by the closing of the exhaust passage valve to open the supply passage valve against the pressure of fluid in the supply passage. The pintle is shifted in the opposite direction by the supply passage valve when the solenoid is de-activated, to move the exhaust passage valve to its open position.