Abstract: A method of searching and maintaining data elements in memory which are stored in a doubly-linked list. A logically related address component array is used to access data elements in the list. The list is divided into list segments which are dynamically maintained to decrease overall access time.

Abstract: I provide a combination land/bay cable capable for simultaneous use on land and in water-covered areas. When the cable section is placed in a water-covered area suitable for hydrophone use, a polarized plug containing an impedance matching transformer is detachably connected to a polarized socket. The transformer connects the hydrophones to a transmission line. If the cable is to be used on land, the transformer is unplugged deactivating the hydrophones and at least one geophone having a substantially identical plug is inserted in the socket. The plug connects the geophone to the transmission line and leaves the hydrophones inactive.

Abstract: A cross country vehicle for seismic exploration is provided wherein a first drive means, such as wheels can be conveniently interchanged, in the field, for a second drive means having a different configuration such as endless tracks. The interchange is enabled by use of a pre-existing lifting means associated with a seismic acoustic source.

Abstract: The resistive sensor consists of a pair of electrodes separated by an impervious insulating material. The sensor is mounted adjacent to an exhaust port of an airgun, in the path of the air blast that results when the gun is fired. When the air gun is submerged and not activated, the surrounding water creates a low-resistance path between the electrodes. When the gun is fired, the air blast blows the water away from the electrodes and the resistance between them abruptly increases substantially. A bridge circuit detects the instant of resistance change and generates an electrical transient to mark the time that the gun fired.