Simultaneous Ring Behaviour

[fruvous]

Can anyone tell me what happens when simultaneous ring is selected when I pick up a call? Will the call simply be transferred to the first number that picks up? Do I need to press a button to answer the call?

I'm also wondering how people deal with the voice mail issue if it's left to whichever one picks up first as there is no guarantee which number will be first to answer due to latency and other factors.