Abstract: A directional coupler transformer insensitive to data bus termination failures, includes a ferrite toroid core about which first through fourth windings are wound, the first and second windings being for connection in series with each conductor, respectively, of a data bus for sensing or generating data signal current, the third winding being connected in parallel with the data bus conductors for sensing or generating data signal voltage, and a fourth winding inductively coupled to the other three windings for either coupling data signals traveling in one direction from the data bus to a receiving unit, or coupling data signals from a transmitting unit to the data bus for transmission along the data bus in a given direction.

Abstract: In portable seismic data acquisition units, an adaptive seismic signal processor and method for resampling and bandpassing selected frequencies of an input digital signal. The adaptive seismic signal processor and method provide an output digital signal having a frequency domain and resampling rate which can be selected from one of a plurality of predetermined frequency domains and sampling rates during the course of acquisition of the input digital signal without substantial loss or deterioration thereof.