The only requirement for the interaction computer is that it allows you to connect to a telephony call or web conference. A headset should be used to optimze audio quality, but it does not need to be a USB microphone.  The Streaming computer connects to the same telephony call or conference with microphone or audio input muted. Volume properties should be set to record 'stereo mix', 'what u hear', or 'wave out mix' - not 'microphone.  The streaming computer then connects to a streaming service (e.g. Ustream, Shoutcast, or Livestream).  It may be necessary to mute the volume on external speakers or headsets on the streaming computer in order to avoid echo.