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Abstract

Equipment was designed and constructed to monitor automatically and unobtrusively up to twelve physiological variables on a human subject engaged in a prolonged field exercise. Inputs from transducers are sampled in turn, and are encoded into 7-digit PCM. They are then recorded on a small tape-recorder worn by the subject. All equipment is battery-operated, but the recorder and digital circuitry is energized for only 1/2 second every 30 seconds. This, permits recording for over 24 hours without interruptions for a change of battery or tape cassette. A decoder and de-commutator were built so that the tapes can be played back later in the laboratory. Selected parameters can be viewed on an oscilloscope or plotted on a chart-recorder. Overall accuracy of the system is 1%. Two types of transducers have been developed: one measures the heart rate and the other the skin temperature. Other transducers remain to be developed. Component circuits were tested at varying environmental temperatures, and a prototype of the whole system was tested on an arctic exercise.