Indy, I should have studied your course before I started. I am sure a telecommunications guy would laugh at my system.
After some research, I went for a local solution in a very hybrid way. The design goals were redundancy, control, and separation of incoming, outgoing, and fax traffic. I have three Comcast rollover voice lines for incoming calls (some days maxed); one Qwest voice line, and two VOIP lines for outgoing. There is a separate Comcast fax line for outgoing faxes. The box is a Talkswitch. I looked at AccessLine switches but decided against them. I have VOIP phones for the heavy users (billing, MAs) and legacy analog 4-line phones wired in parallel for incoming. The box allows me to manage voice messages, menus, log calls, and switch lines (e.g. when Comcast went down). I have QoS for VOIP but not a separate LAN for VOIP phones. Performance seems ok even when all VOIP phones are in use.
I also have both Qwest and Comcast internet service, and am thinking of adding Verizon 4G for more redundancy. I use Accessline for virtual fax of admin stuff, and UpDox for clinical.
