SIP RTP ports

can I specify the range of the sip RTP ports and if so how would I do this?

I think the default is 10,000 -20,000 udp right ?

from my understanding sip 5060 sets up the call and picks a random rtp port correct?
how can I tell the system to use 10,000 -60,000 or something like that?

Edit the file rtp.conf in /etc/asterisk (or wherever you keep your configuration files). Look for the lines labeled rtpstart= and rtpend=.