Turtle Art is programmed to produce two different frequency sounds. The headphone output of the XO is connected to a pair of [http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS006975.PDF LM567] tone decoders, each of which lights a LED when its input signal frequency is present. With this principle we could control any device based on the frequency emitted by the XO.
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[http://sites.google.com/site/solymar1fisica/fisica-con-xo-investigacion- "Physics with XO."] [http://www.youtube.com/watch?v=IVzVlAZsz1w video] by Guzmán Trinidad.