Conference lock is a feature on many conferencing systems that allows you to lock a conference after you start. It's particularly helpful after you have done a number count and roll call to establish that everyone on the call is who you want to be on the call. After that you do the “lock down”. No one can get into the call at that point not even an operator can get in or listen to your call. All this is wonderful unless you need an operator to identify and clean up a line situation or a quality issue. Of course you can unlock and summon an operator with *0. The truly frustrating thing would be if you as host were disconnected from the call you could not get back into your own call. While land lines seldom disconnect you, a cell phone might. This happens while travelling while on the call and enter a dead spot, etc. Also disconnected guests cannot jump on board again unless you unlock the call. Those are the joys and sorrows of conference lock.