Polygraph, model 5D, Grass Instrument Company, United States, 1960-1970.

Polygraphs are popularly known as ‘lie detectors’, but this was not their intended function. This polygraph recorded important information about a hospital patient which included blood pressure, temperature, heart rate and oxygen levels. It was made by Grass and Co. Machines like this can diagnose an illness, or monitor a patient’s condition during an operation. The polygraph records this information simultaneously. It saves medical professionals regularly checking the various life signs.