The siemens optipoint 420 s familyall models belonging to the optipoint 420 s families are based on the sip protocol session initiation protocol for effective communication with all components in the network this enables the terminal devices to support a multitude of sip based communication systems in addition they are optimized for use of the features of the siemens hipath 8000 communication system power can be supplied either locally or via power over ethernet poe in accordance with the