In about 1955, the Stoelting Company of Chicago, Illinois which has been producing polygraph instruments since 1935, introduced the Deceptograph model 22500. This model contained vacuum tubes in its amplifier which required approximately thirty minutes of warm up time before use. It contained three recording channels, cardio, pnuemo and G.S.R., which provided a continuous recording of changes in relative blood pressure, heart rate, pulse wave amplitude, respiration and electrical skin resistance. The A.C. component unit was packaged in an aluminum Halliburton case with sectionalized components and a built-in microphone cartridge. The 22500 also had an individual inking system which consisted of a pen tip, fork, counter balance, plastic tubing, ink reservoir and ink reservoir receptacle. The 22500 weighs approximately thirty-one pounds with its accessories, and its dimensions are 18" x 9" x 6". The 22500 uses the standard 110 volt, 60C alternating current.
The 22500 model displayed here was advertised as the most widely used polygraph instrument in the world, and was primarily used in the United States Military.
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