title: ios pjsip - play a sound during sip call
body: <p>When I am on sip call, sometimes I want to send dtmf digits.<br/>
  To do this I created a custom dial pad which when a key is pressed should play a sound of that key, but it is not playing that sound during a sip call (when there is no call, sound is played). <br/>
  These sounds are played with functions from <code>AudioToolbox.h</code> library (<code>AudioServicesPlaySystemSound(soundID)</code>).</p>
  
  <p>Is there some property that I need to set up in pjsip (pjsua) or in AudioToolbox library to enable a sound be played during a sip call?<br/>
  I know this is possible (<a href="http://www.counterpath.com/bria-iphone-edition.html" rel="nofollow">Bria</a> has this, <a href="http://www.acrobits.cz/11/acrobits-groundwire-for-iphone" rel="nofollow">Groundwire</a> also, not sure if they are using pjsip to implement sip).</p>