If there is a delay, then the speaker should take breaks to allow interruptions and ask for questions. Microphone issues Students did not like push-button microphones. Asking a question or making a comment bordered on a competition. The more sites and participants the greater the need for instructor leadership. Check for understanding by giving time to capture thoughts, doing a summary session, Provide clear time out for reflection.
Time management creates a professional respectful atmosphere.
Allow each site to work by itself on various things and bring people back at a specified time and with a specified signal. Prepare a bag of trick to use under various situations such as later in a session that runs for several hours or if there is down time. Timing Video conferencing can cause extreme fatigue. More intense concentration is required. Video conferencing should not be used to cram all contact time into one session but should be spread through out the duration of a course.