One word of caution with the sign....I always tell the folks on my team that you train people how to work with you so if you put up a sign but you're chatting with other folks while your DND sign is up, people will see this as OK to chat with you when that sign is up. We don't have signs but our internal chat system has an "in a meeting status". I advise my team to put themselves in this status when they are in meetings but caution them not to interact with folks while they are in that status because you're telling people that you don't even respect your own sign so it's OK for them to ignore it too.
Hope this helps.
"Life is not the harbor. Life is the boat."