Abstract: The acoustic data communication system includes an acoustic transmitter and receiver wherein low frequency acoustic waves, propagating in relatively loss free manner in well drilling string piping, are efficiently coupled to the drill string and propagate at levels competitive with the levels of noise generated by drilling machinery also present in the drill string. The transmitting transducer incorporates a mass-spring piezoelectric transmitter and amplifier combination that permits self-oscillating resonant operation in the desired low frequency range.

Abstract: A system is disclosed for transmitting information during a borehole drilling operation wherein a section of the drill string near the drill bit is utilized as a transmitting element of an electromagnetic wave propagation system. A receiving system at the surface uses a section of the drill string as one electrode and a metallic ring or ring of probes which penetrate the earth's surface at a given radius from the drill string as another electrode between which signal voltages are detected. In another embodiment, the receiving system comprises metallic rods at the surface which extend radially from the drill string. Signal currents induced in these radially extending rods are detected by a receiver coupled between the rods and the drill string.

Abstract: A base band radio speed sensor, for use with the path of travel of the craft whose speed is to be sensed advantageously disposed at right angles to the antenna patterns, utilizes a transmitter flanked by equally spaced receivers for determining the times of passage of the craft with respect to symmetrically disposed receiver antennas.

Abstract: A detector which is subject to temperature variations and power supply drift including a tunnel diode circuit having first and second stable states and a variable threshold that is sensitive to noise and input signals within a useful frequency band and produces output signals when the amplitude of the noise or the input signals exceeds the instantaneous value of the variable threshold to cause the tunnel diode to switch from its first low voltage stable state to its second high voltage stable state. A control circuit coupled to the tunnel diode produces a square range-gate pulse having a pulse width which determines the interval during which the detector is sensitized and produces a reset pulse in response to the leading edge of the square range-gate pulse which sets the tunnel diode in its first stable state.