title: Asterisk does not detect inband DTMF tones
body: <p>Asterisk 14 (from Packages @ tucny.com)
  Connected to Twilio SIP trunk</p>
  
  <p>Asterisk does not detect inband DTMF tones. 
  Other ways(INFO, rfc2833) to send DTMF works correctly.
  I've played with tone duration and volume without success.
  In DTMF debug I can see the asterisk reaction to incoming INFO or rfc2833 events, but nothing happens when inband tone is coming.
  Seems like asterisk does not "hear" the line at all.</p>
  
  <p>I couldn't find any information about modules requeried to detect inband DTMF.
  Installed modules:
    <code>
    - asterisk
    - asterisk-odbc
    - asterisk-pjsip
    - asterisk-hep
    - asterisk-sounds-core-en-alaw
    - asterisk-sounds-core-en-ulaw</code></p>
  
  <p>Will be very thankfull for any information.</p>