wezm.net/content/technical/2009/01/the-iphone-headphones-have-a-button.html

Before Christmas I was speaking with two colleagues and recent iPhone adopters about headphones. They were examining my <a href="http://www.amazon.com/Sony-MDR-EX71SLA-Fontopia-Bud-Style-Headphones/dp/B000JKHXPQ/ref=sr_1_3?ie=UTF8&s=electronics&qid=1231211983&sr=1-3">Sony MDR-EX71s</a> (white, short cable) connected to <a href="http://www.griffintechnology.com/products/smarttalk">Griffin SmartTalk</a>. I mentioned the SmartTalk gives third-party headphones a button and microphone. I was asked if you could answer calls with the button to which I said, "yes, it does all the same things as the included headphones". To which the reply was, "the included ones have a button?". Yep they certainly do.
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<blockquote>The headset included with iPhone features a microphone and an integrated button that allows you to answer and end calls easily, and control audio and video playback.
Plug in the headset to listen to music or a phone call. Callers hear you through the headset microphone. Click the mic button to control music playback and answer or end calls, even when iPhone is locked.</blockquote>

<img src="/images/2009/01/iphone-headphones.png" alt="Stereo Headset with mic" width="384" height="185" class="aligncenter size-full wp-image-79" />

These are the functions that can be performed with the mic button:
<table class="left_headers">
  <tr>
    <th>Pause a song or video</th>
    <td>Click the mic button once. Click again to resume playback.</td>
  </tr>
  <tr>
    <th>Skip to the next song</th>
    <td>Click twice quickly.</td>
  </tr>
  <tr>
    <th>Skip to the previous song</th>
    <td>Click three times quickly.</td>
  </tr>
  <tr>
    <th>Answer an incoming call</th>
    <td>Click once.</td>
  </tr>
  <tr>
    <th>End the current call</th>
    <td>Click once.</td>
  </tr>
  <tr>
    <th>Decline an incoming call</th>
    <td>Press and hold for about two seconds, then let go. When you let go, two low beeps confirm you declined the call.</td>
  </tr>
  <tr>
    <th>Switch to an incoming or on-hold call and put the current call on hold</th>
    <td>Click once. Click again to switch back to the first call.</td>
  </tr>
  <tr>
    <th>Switch to an incoming or on-hold call and end the current call</th>
    <td>Press and hold for about two seconds, then let go. When you let go, two low beeps confirm you ended the first call.</td>
  </tr>
</table>