A.A.
Here's what we are teaching our children (4 and 21mos) to do when they need to talk to us and we are already in a conversation. They can come up to us and put their hand on us so that we know they need to say something. If we can stop the conversation for a minute we do in order to talk with them. Otherwise we will put our hand on top of their hand so that we acknowledge them and they are learning to wait until we can stop the conversation to talk with them. This can be used for live conversation or for the phone or while you are reading them a story as well.