[asterisk-users] only ring phones that are not on a call

[Jon Weisman]

is there anything i can do in my dialplan to only ring phones which are not 
on a call at the time someone dials in?

its for a call center, they do not want to use queues, but they are 
complaining that the call waiting beep is annoying.

i tried call-limit in the sip.conf but then it just busy out all phones when 
a call comes in.

any thoughts?

thanks,
jon