Abstract: A digital marine seismic system employes a plurality of data acquisition control modules which simultaneously digitize analog seismic signals. The control modules also are selectably addressable in that each module is uniquely programmed to respond only to a particular control word. The system allows a large number of channels, such as 480 channels, on a simple transmission system, such as a twisted pair of wires. Each module includes a power switch to sequentially apply power to downstream modules. Selective addressing of the switches allow testing of specific modules for power malfunctions.

Abstract: A processor responsive to multiple AC analog signals has individual sampling circuits to sample and hold each AC analog signal in DC form. After the DC signals are multiplexed, a single error correction circuit calculates correction voltages individualized for each sampling circuit and sums them with the DC signals. An instantaneous floating point amplifier amplifies each signal in 12 db increments up to a preselected limit, and then a second sampling circuit holds the amplified signal before an analog-to-digital converter generates a digital signal representative of the amplified signal.

Abstract: Disclosed is a cable leveling device for a seismic marine cable. The cable leveling device features a motor which controls diving planes by way of direct mechanical linkage. The motor is controlled by a stored program digital processor connected in a closed loop feedback circuit. Optical reflective sensors are employed in the feedback loop to monitor the position of the mechanical linkage to directly determine the angle of the diving planes. A telemetry unit is provided to telemeter data from the cable leveling device to shipboard via the marine cable.

Abstract: Sensors mounted in detachable modules are located at selected positions along a cable, such as one used in marine seismic exploration, adapted to be towed behind a vessel in a body of water. The sensors are selectively addressable, either individually or as a group, by coded signals sent through the cable. When addressed, the sensors provide readings of the earth's magnetic field vector. The readings are used to provide an indication of the position of the sensors and thus the cable relative to the towing vessel. Cable depth readings may also be made by the sensors.