1. An instrument to obtain simultaneous tracings from several different sources; radial and jugular pulse, apex beat of the heart, phonocardiogram, electrocardiogram. The ECG is nearly always included for timing.
2. An instrument for recording changes in respiration, blood pressure, galvanic skin response, and other physiologic changes while the person is questioned about some matter or asked to give associations to relevant and irrelevant words; these physiologic changes are presumed to be indicators of emotional reactions, and thus whether the person is telling the truth.
The information shown above for polygraph is provided by Stedman's.
* Stedman's, part of Lippincott Williams & Wilkins, provide a comprehensive line of health-science publications for healthcare professionals and medical students.