The Standalone Data Acquisition System (SDAS) is a portable digital data recording system for geophysical field data collection. This report describes the SDAS, giving special emphasis to the SDAS signal conditioning subsystem, which uses custom-designed active filter modules for signal filtering and amplifications. Detailed descriptions of the active filters, including design equations and software, are provided. This subsystem, together with software for its configuration and performance verification, provides an improved capability for analog signal conditioning. This report also provides a functional description of the SDAS. It documents the system hardware and such software as is needed for system configuration and checkout. Each subsystem in the SDAS is described via functional descriptions and such diagrams and schematics as are necessary to understand subsystem functioning. Detailed schematics, parts lists, software listings, and subsystem specifications are covered in appendices.