Abstract: A measuring and telemetry system is disclosed adapted to measure the ambient pressure and temperature in a downhole environment, and to telemeter signals representative of such measurements to the wellhead for demodulation and display. Only two wires are used in the system between the wellhead and the measuring location downhole. The two wires are used for both the power applied downhole and measurement signals transmitted uphole. A current balance circuit is provided for a downhole iron core transformer through which the DC power is provided through one winding. The current balance circuit senses a signal representative of the DC current flowing through the one winding and applies an equal in magnitude but opposite in direction current through the other winding of the transformer to prevent magnetic saturation of the transformer.

Abstract: A remote sensing and indicating system for monitoring and displaying at a central operating location the state or position of a remotely located multiple state element. The multiple state element may be a subsea valve which may be either in an open state or a closed state. The system electronically scans valve position switches, stores data indicating the position and drives lamps to display valve position. Switches at the remotely located valve are selectively closed in response to the state of the valve. The switches are connected to the central location by only two leads.