title: iOS: How to choose which microphone (inbuilt/external) to use?
body: <p>Let us say I have an audio iPhone app which takes input from the microphone.</p>
  
  <p>Now, although I haven't tried this myself, I believe the user could use an external microphone that plugs into the phonojack socket.</p>
  
  <p>This means my audio unit could be receiving its input from the internal or the external microphone.</p>
  
  <p>My guess is that iOS will automatically route from an external microphone if it is connected.</p>
  
  <p>But what if I don't want that?</p>
  
  <p>Is there a way to specify which microphone should be used?</p>
  
  <p>I have looked in the audio session guide, I can find some setting regarding a Bluetooth headset. But that is as close as I can find.  It appears that it is not possible. But I find that difficult to believe.</p>
  
  <p>PS Also I am curious how it detects an external microphone...  if I plug my headphones in,  it should continue routing from the internal microphone.  my headphones are just plain stereo headphones.   but if I used my mobile phone's headphones ( on extra band on the Jack...  they have a microphone built onto the cable where the individual earpiece strands meet ) I would expect it to pick up this source instead.</p>