[Asterisk-Users] Wait for X rings before answering?

[Robert La Ferla]

How do I set up extensions.conf to wait for "x" rings (ringing all 
extensions) before answering?  I'm trying to mimic a regular answering 
machine on an multiple analog phone system.  Currently, Asterisk picks 
up after 1 ring and just tries to dial one extension.  I want all 
extensions to ring.

[incoming]
exten => s,1,Dial(SIP/myext,25,t,r)
exten => s,2,Voicemail(myext)
exten => s,3,Hangup()

Also, I couldn't find documentation on the "r" option for Dial().