[Freeswitch-users] Implementing emergency calls ... or call priority ?

Whats are best practicies to implement emergency calls ? I can identify such a call by regexp but how to handle those calls ? Is there some build param to be set ? How I can set priority for call ? e.g. I have limited capacity for outgoing and incoming call to 10. I need to drop some calls with small priority to allow emergency call, but I have no idea where to start. Can somebody give me right direction for this ? Thank you very much PS: Google does not helped me :(