To obtain experimental data, the latest step-scan design from Manning Applied Technology was used. This instrument is based on a P5-90 PC controlling a Mattson Polaris-type optical bench. The detector signal is demodulated by a 33 MHz digital signal processor mounted in the PC's accessory bus. The only system component other than the computer and optical bench is a rack box containing amplifiers to take low-level signals from the computer to levels suitable for driving the interferometer motors.