The early version reported in the journal produced power
at microvolt levels.
The output from these temperature sensors, and the solar radiation sensor, were recorded by a datalogger with one
microvolt resolution.
Thus, when the arousal threshold is highest (i.e., sleep is «deepest»), the EEG shows slow - wave sleep with a frequency of 0.5 to 2.0 Hz and an amplitude of 75
microvolts or greater.
Because the response amplitude is so small (fractions of
a microvolt) it is necessary to average the responses to multiple stimuli (clicks) to unmask them from the other unrelated electrical activity that is also present on the scalp (EEG, muscle activity, etc).