A polygraph created by C.W. Darrow in the 1930s. It was one of the most elaborate polygraphs of that era, recording relative blood pressure, skin resistance, breathing, reaction time, and bilateral hand tremors. It had two stimulus markers, one activated by hand and the other was a voice key. Costing upwards of $2,000 and requiring a separate technician to operate, Darrow’s photopolygraph was primarily a laboratory instrument and was not used extensively by the PDD community. Also called the Darrow Photopolygraph. See: Darrow (1932).