title: could the iPhone's headphone jack be used as an input for a device?
body: <p>I am working on a Remote Controller via Headphone jack of iPhone. It requires:</p>
  
  <ul>
  <li>In Sending mode, Send signal (19kHz) and signal (10kHz) as 1 and 0 respectively</li>
  <li>In Learning mode, it receive corresponding signal from other remote controller</li>
  </ul>
  
  <p>I read a site that it introduces AudioUnit (http://cocoawithlove.com/2010/10/ios-tone-generator-introduction-to.html) to do tone generation for sending</p>
  
  <p>But How about Learning mode ? How can my application detect 19kHz and 10kHz as 1 and 0 ?</p>
  
  <p>Thanks.</p>