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For many years scientists have attempted to develop a successful lie detector. In the seventies American researchers developed the Psychological Stress Evaluator (PSE) and the Voice Stress Analyser (VSA). These two principles have now been incorporated into the Truth Machine.

Micro tremors in the voice, which are often not detected by the human ear, produce frequency modulations, which are measured. The amplitude of the upper and lower sidebands of the frequency spectrum of the voice is also measured.

The results are analysed and shown visually by the columns of LED lights which range from green (low tension) to red (high tension). The Truth Machine accurately measures changing stress levels in the voice but as each individual's voice reacts differently it is not infallible; the lighting of red LEDs, high stress, is indicative of lying however!

Not only is the Truth Machine great fun when used in general conversation, it can also be used to test against the TV, radio or even the telephone. The Truth Machine operates most effectively when there is no background noise. Noise such as music, traffic and air conditioning generally light up red LEDs, so it may be difficult to accurately test people in such environments.

• Includes instructions
• 11 LEDs to give a high resolution readout
• Dimensions 140 x 77 x 21mm approx