PURPOSE: To provide a Lissajous type display from a single vocal source.

DESCRIPTION: The signal from a microphone is amplified and fed into a circuit which produces two signals which are different in phase, and these two signals are fed into the X and Y coordinates of the oscilloscope to create a type of Lissajous pattern. The circuit makes the two signals exactly 90 degrees apart at 300 Hz, producing a circle. For other frequencies the phase shift is different and various figures are formed.

SUGGESTIONS: This device makes a nice hallway demonstration.

REFERENCES: (PIRA unavailable.) See Demonstration Reference File for article describing this apparatus and for circuit details.

EQUIPMENT: Microphone, phase circuit, and oscilloscope.

SETUP TIME: 5 min.

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