Due to the acoustic feedback introduced by long delays and the lack of echo cancellation, speaker and microphone are, in many cases, not appropriate for interactive conferencing. To reduce background noise (and triggering of the silence detector), the microphone must be held close to the speaker's mouth. Some alternatives that combine an earphone/headset with a microphone include the following. Dance instructors have similar needs...
IEEE 1394 interconnect
(R): recommended by somebody using them for Internet conference applications.
Unlike professional audio gear, the audio interfaces in workstations are unbalanced (ground and signal). This may cause hum due to ground loops. This is particularly noticeable when connecting house audio (such as a mixer) to the workstation. An audio transformer may be useful to remove hum caused by ground loops: Sound localization