asterisk users - Jan 2005 - Limit max calls & call duration

Hello,

I was wondering if there is a simple way to limit the number of simultaneous
calls in an Asterisk PBX ?
I've seen that we can make this easily per channel (like in SIP.CONF) :
incominglimit=X, but I'm looking to limit the maximum calls all channels 
together.

Another thing. Working with asterisk-perl, I need to get the call 
duration, currently
I use $AGI->get_variable('DIALEDTIME'). Is it possible to have a
better
precision,
because DIALEDTIME is only 1sec precise.

Thank you.