SSA-1 is a fully self-contained, 3 channel digital recording Strong Motion Accelerograph of 12 bits of resolution, or >72 dB dynamic range at 200 sps. The unit contains electronics, sensors, battery power and data storage all in a water- tight enclosure.

  Acceleration data from the three sensors are digitized by the A/D converter on the Analog-to-Digital Converter/Power Supply (ADCPS) board and are continuously monitored for signals that satisfy event detection criteria. When these criteria are satisfied, the event is stored in CMOS battery-backed-up RAM until later retrieval by the user.

   The RAM board can optionally be expanded up to 2 megabytes of CMOS RAM. The SSA-2 can be operated as a single unit, or interconnected in sets of several units for large multi-channel applications.

  A micro-power, low accuracy, time-of-year clock is included for event time identification. Optional time code generators or radio receivers can be installed to provide common timing for interconnected units as well as for higher basic timing accuracy. For field data retrieval and control of the SSA-1 an IBM compatible PC is required.