Abstract: A system for testing seismic signal recording equipment wherein a test signal is generated which simulates the output of at least one seismic sensing device, and, thereafter, the test signal is applied to the seismic signal recording equipment. The test signal is recorded by the seismic signal recording equipment and the recorded signal is compared with the generated test signal to evaluate the performance characteristics of the seismic signal recording equipment. The system can include circuitry to vary component elements of the test signal to test different performance characteristics of the seismic signal recording equipment, as well as ability to generate a random noise signal for addition to the test signal.

Abstract: An interface for coupling a computer to a plurality of magnetic tape transports, including dual-density transports and combinations of high and low density transports. The interface includes an automatic density selector for detecting the density of data stored on a tape prior to reading and for storing this information for as long as the tape is being used. A read-only memory and other logic circuitry translate computer operating commands into commands readable by a transport formatter. The interface also couples digital data between the computer and the formatter and converts formatter status information into language readable by the computer.

Abstract: This disclosure describes a decoding system for decoding and formatting digital data recorded on magnetic tape in the STR ("speed-tolerant recording") format. The digital words are stored in cells of about equal width except that the leading cell of each word, called a "sync" cell, is of double width. Each cell starts with a positive pulse, and a cell detector provides a signal each time this occurs. The apparatus includes a data detector, which analyzes the width of this positive pulse relative to the cell width to determine whether the cell is a 1 bit or a 0 bit. Since the measurement is relative, cell length, i.e., total cell time, is not important. The bit determination is loaded into a shift register. Other apparatus determines the width of the cell, so that a sync cell detector can determine whether a sync cell is present or not. When a sync cell is detected, a pulse is generated which actuates the output buffer register to load the bits from the shift register. Data flows from buffer to a computer.

Abstract: The analog signals provided by a seismic-velocity well logger, resulting from the transmission of seismic impulses from a transmitter to a receiver in a logging sonde in a well by paths that include travel through the rock walls of the borehole, are digitally recorded. These seismic impulses and the resulting received seismic signals, or traces, are repeated approximately 20 times per second. The recording apparatus digitizes these analog traces by determining signal amplitudes at intervals of approximately 10 microseconds and temporarily stores the digital values. The apparatus includes a programmable-gain amplifier, an analog-to-digital converter, a computer, and a memory in which are, in addition to the data, also stored the values of gain which are to be used in digitizing the next signal. That is, on each digitizing interval a stored gain "program" is read out of the computer and sets the gain of the amplifier.