Four channels, all extracted in this browser: cardiac pulse recovered from colour changes in facial skin, body motion from frame differencing, vocal pitch from the microphone, and response latency from question onset to first speech.
This is the same channel set a field polygraph records. What it measures is arousal. Arousal rises with fear, guilt, anger, surprise, arithmetic, caffeine, and being accused of something you didn't do — the instrument cannot tell those apart, and neither can anyone reading its output. It is labelled honestly throughout for that reason.
NEUTRAL — uncontested facts. These set the baseline; you need at least four.
RELEVANT — the questions at issue.
CONTROL — unrelated but uncomfortable, and near-universally true. “Have you ever lied to someone who trusted you?” Everyone reacts to these. They are the honest part of the procedure: they show you what a reaction looks like from someone who isn't concealing anything about your actual subject.
Video and audio are processed frame-by-frame and discarded. Nothing is recorded, stored, or transmitted.