Penn’s Telephone & Voice Mail Services uses VoIP (Voice over IP) technology. VoIP offers a host of features and benefits not available with traditional analog phone service. Penn’s VoIP service is called PennNet Phone.  If you have any trouble with your VOIP phone you should contact your LSP at manager@math.upenn.edu or DRL-3N5.

PennNet (VOIP) Phone Getting Started - FAQ & Getting started guide for PennNet phones

PennNet Phone Services - Change settings related to your phone line

The model 320/321 and 550 are the single line sets and the one that most people in the math department will find in their office.  The 650 supports up to 6 lines.