The Preliminary Credibility Assessment Screening System, or PCASS, captures less physiological information than a polygraph, and uses an algorithm, not the judgment of a polygraph examiner, to render a decision whether it believes the person is being deceptive or not.
When a person takes a polygraph test, four to six sensors are attached to him. A polygraph is a machine in which the multiple ("poly") signals from the sensors are recorded on a single strip of moving paper ("graph").