Fast sample collection for the Autogen 1700 (EMG) and Apple II.

Autogenic systems Inc. (ASI) sells an EMG unit that filters the EMG signal through a band-pass filter, full-wave rectifies it, then processes that signal with an envelope circuit. The time constant of this envelope circuit can be varied from 10, 20, 50, 100, 200, 500 to 1,000 seconds. These long time constants may be desirable for obtaining baseline values during biofeedback therapy, but they will filter out the majority of any transient phenomena in the signal that may be meaningful. This is particularly true for work with mental rehearsal. Permission was obtained from ASI to reduce the time constant of the envelope circuit by changing the capacitor (C79) from 1.0 MFD to .05 MFD. This produced time constants of 1, 2, 5, 10, 20, 50, and 100 seconds, respectively. The front panel was also altered to reflect these changes. One should contact ASI for permission to alter the equipment and for the capacitor location.