If you are talking about a meeting for 1000 people you are talking about Skype for Business BROADCAST. In a broadcast meeting there is an inner meeting (participants) and an outer meeting (audience). The inner meeting would typically be a small number of people. However, it can be up to the normal SfB meeting limit of 250. What view from the inner meeting gets shown to the audience is selected by the producer. So, lets say you have offices in 15 countries. You could have 1 representative from every country as part of the "inner meeting" and they could ask questions (either audio / visual or just IM). The producer could either choose to show the questioner and "broadcast" them or just let the "panel" or CEO or whatever read the IM questions and answer them -- "Question from our office in Singapore...... " style. BEWARE though - every person on the "inner" meeting has producer controls and right now you cannot change that. So, you need to ensure that the people in your inner meeting are trusted - they could seriously screw up your meeting if someone started messing with the producer controls (This is an issue which MS needs to address - feedback has been given on it). Also there will be a 20 - 30 second audio lag between the inner meeting and what is broadcast. That would seem very odd if the e.g. the director of the Singapore office is standing up in front of his office staff asking the questions in front of actual people who are then also watching the broadcast with its delay. There are various ways around that by running parallel "meetings" with the audio visual piped from one to another - you could set it up so that you get synced audio and video projected onto a large screen in a lecture theatre from the "inner" meeting for those physically in the theatre (the projector is an inner meeting passive participant) and yet they guys down the hall in the singapore office and also in the office in London are getting the broadcast - 20 seconds later. As long as you can't see / hear both the inner meeting and the broadcast at the same time it should work fine. With this set up you could have a globally distributed multi site "town hall" and the producer can switch between a questioner in Singapore - to the CEO's answer in London and then another questioner in Australia. Personally, if I was doing a meeting on this scale I would also run a third meeting in parallel as the "control meeting" and use this so that the producer can privately say to the guy in Australia - ok, have your question ready, we are coming to you and you will be live "on Air" when the CEO has finished with the question from Singapore. I guess you could also do that via IMs without the extra "control" meeting but it would be a bit clunky - if you want the producer to be able to say "Singapore - we are coming to you in 5 - 4 - 3 - 2 - 1 you will need a control meeting. The control meeting is not something that is currently built into SfB broadcast but it is just another SfB meeting - you would just need a few extra basic SfB licenses and devices to run that extra parallel meeting on - even mobile clients would do for the control meeting. I hope that is helpful. I haven't actually tried any of this but I have a similar issue for a conference coming up and having given it some thought this was what I came up with and is the basis I am working on for my plannning.
