The lie detector we presented was created by a professional detective and found in a 1982 publication. We do not need to comment, therefore, on its efficiency ... The working principle, however, needs to be explained: this detector is based on variation of the resistance of the skin of an interrogated individual, in function of his state of nervous tension. Small variations in resistance can be detected by the very sensitive instrument. The potentiometers P1 and P2 are used to adjust the ideal operating point, so that resistance variations can be better accused by the instrument. This instrument must be a sensitive 0 - 1 mA milliammeter or a 200 uA VU meter.
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