Persisting Dynamic Meetme conferences

Hello all,

I am using the following in extensions.conf…I found this here I believe.

exten => _X.,1,MeetMe(${CONF}|dTMps)

How can I Implement this.
In a standard MeetMe conference I can dial 8200 and join that conference.
What is dialed for the dynamic meetme?
How long does this dynamic conference persist?
Is is destroyed after everone has left?

If there is a better explanation of dynamic meetme confs somewhere, a URL would be appreciated.