VISUAL ZERO-BEAT INDICATOR
Schematic:
Notes:
Light-emitting
diodes connected with reverse polarity provide a visual indication of zero-beat
frequency. Each LED is on for only half cycle of the input. When the input
frequency is more than 1 kilohertz away from the zero-beat frequency, both LEDs
appear to be on all the time. As the input frequency comes within about 20
hertz of zero beat, the LEDs will flicker until zero beat is reached. Both LEDs glow or flicker until zero beat is reached, when
they go out.
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