Panasonic KX-TDA0484 Getting Started page 56

A1 VoIP Requirements
Is there only a single IP network between two ends of a call?
A huge degradation in speech quality will be produced when calls are made through multiple
IP networks as shown below; therefore, it is recommended that you avoid establishing a VoIP
network in this fashion.
IP Network 1
56 Getting Started
PSTN
IP Network 1
IP Network 2
IP Network 2