I have been tinkering with a personal VoIP system in my spare time over the last couple of months. At this point, I have rescued the 3 lines of house wiring in my 1970s house and connected them to Asterisk on a VM via a Cisco MC3810 and a Adit 600 channel bank. This has involved messing with T1s which was a childhood dream of mine. I have 12 phones connected to the system, using my house wiring, a few point-to-point wires, and some SIP VoIP phones over ethernet. In turn these connect to Phreaknet, C*NET, and of course the normal PSTN via a pair of different ITSPs. I now feel almost qualified to build an early 2000s business voice phone system, for what very little that is worth. More importantly, I have a rotary phone on my desk. ;)