The Lie Detector Circuit

Here is the figure that shows to us about design circuit of the lie detector circuit;

In this circuit, it has the two probes shown are held in the hands and the skin resistance applies bias to the transistor. The 5 k ohm pot is set for zero deflection on the meter. When the "subject" is embarrassed or lies, sweating on the hands takes place, increasing the bias to the transistor and upsetting the bridge balance.[Circuit diagram source: Seekic.Com]