I have a T1 card in my system which allows my phone system to used the trunks like stem cells.

I can make the system route the call to any extension I want just by the number dialed or use the trunk or outbound calls.

I have a SLI card in my system that allows me to attach fax machines and other analog devices to my phone system.

Bottom line is that if you configure your system right, you can use 1 PRI(23 trunks) more effectively than 80 POTS line which would normally be dedicated to fax machines and private phone in offices, etc....

I'm not good at explaining but basically I use to have 84 trunks and after I got my sytem configured right, I now just have 23 trunks which can handel the same traffic without any busy signals before of more efficient system.

Thanks.