Patent US 4,359,724

An eyelid movement detector, includes one electrode to be placed above each eyebrow of an individual and a third electrode to serve as a ground or reference. The electrodes sense eyelid muscle activity and produce a voltage in response to eyelid movement, indicative of a state of awareness. The sensed voltage produced is amplified and compared to a threshold reference voltage by a comparator, which produces a control signal if the sensed voltage is greater than the threshold voltage. The control signal resets a timer. If the timer is not reset within a predetermined time interval, an alarm is activated to warn an individual.