I wish I could, I'll see if I can dig up my old report from class, but that was from 2007. Very simply, I literally just wired the laser in series with the hea

I wish I could, I'll see if I can dig up my old report from class, but that was from 2007. Very simply, I literally just wired the laser in series with the headphones, like, attached directly to the battery of the laser pointer so the audio +/- 5v would jiggle the laser's brightness around that value (the laser was also +5v so this "just works" if I recall. I might have had a resistor in there, and at some point, current leaked back into my iPod and fried it :) On the receiving end, same deal, PC speaker audio jack attached to a photodiode and power. It's remarkably analog, but it's also the same reason that things like the now anachronistic CD-player cassette adapter work, throwing 5V AM signals around :)