From Bioinformatics.Org Wiki
The "virtual hub" model is described in the following publication:
Gichora, N.N., et al. 2010. Ten Simple Rules for Organizing a Virtual Conference--Anywhere. PLoS Comput Biol 6(2):e1000650. (http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1000650)
The hub manager should be able to communicate during conference on behalf of the hub. A webcam can be placed such that the audience is captured via video. A video projector will be needed to project the conference video on a wall that is visible to all participants. And a public address system will be needed to project the conference audio to the audience.
For hubs with presenters: to prevent problems with audio feedback, you may need to temporarily turn off the public address speakers during the presentation. This is the simplest approach. Otherwise, the presenter should be in a different location from the audience, and you would of course need a separate computer for the presenter.