"Another quick example. An audio signal from the laptop tells the Picaxe 18X when to turn the LED on and off.
Note that in the example, the longest period of the LED is well beyond the period of any waveform that a computer could produce (~0.5Hz). The LED could be on or off for as long as the user wishes, or play any pattern. In the example, the smallest period is ~50ms.
Of course, the LED might as well be a relay or something else entirely. And a computer / audio playback device has two channels, so multiple chips or outputs on a single chip could be easily controlled via an ipod shuffle or something similar. ( more )"