As it turns out, our friend Danielle had written about something similar two years ago. <a href="http://www.daniellemorrill.com/2010/06/how-i-built-a-multi-user-door-buzzer-for-our-apartment/" rel="nofollow">http://www.daniellemorrill.com/2010/06/how-i-built-a-multi-u...</a><p>Great minds :D