Apparently Pentax DSLR cameras have a remote shutter option that used infrared signals. [Pies for you] gathered up several different hacks and built a method of triggering the camera using custom audio. He put together the dongle above, just a headphone extension cord and two IR LEDs, which plugs into the headphone jack of any audio device like an iPod or an Android phone. When you play back a file the audio signals drive the IR LEDs. This is completely worthless unless you craft your own audio file using the correct frequency, duty cycle, and bit encoding. [Pies for you] did just that and got things up and running. Looks like the system doesn’t do so well with MP3 compression, but take a look at the waveform analysis that he posted and then make sure you’re using a lossless format.