Abstract: A fluid control valve includes a valve member movable into engagement with a seating to prevent the flow of fluid through the valve, and an actuating member which is biased in one direction by a return spring and is moved against the action of the return spring by the armature of the actuator when the winding thereof is energized. The movement of the actuating element is transmitted to the valve member through an under travel spring which yields to allow continued movement of the actuating element when the valve member engages the seating.

Abstract: A lithospheric electromagnetic telemetry system specifically adapted for telemetry of oil well drilling parameters from well bottom to surface of the earth. Sensors measure such parameters as pressure, temperature, salinity, direction of well bore, bit conditions, as well as the standard well logging parameters. The sensor outputs are converted to digital form and stored in a local memory until they are transmitted upon a triggering signal from a surface station. Transmission is accomplished by phase shift modulating an ELF (Extra Low Frequency) or ULF (Ultra Low Frequency) carrier, preferably in the range of 1-30 Hz. Repeater stations which delay and retransmit the signal are spaced along the oil well drill pipe as required. Both the well bottom station and repeaters are mounted inside the oil well drill pipe without substantially decreasing clearance for mud flow.