network client 28 may exchange data with other devices on the internet 12 through its associated nat server 26 referring briefly to fig2 exemplary structure of a telephony client 23 in accordance with this invention is shown the telephony client 23 is useful as both an internet client 22 fig1 and as a private network client 28 fig1 for purposes of this invention the telephony client 23 may be a desk top computer which includes a processing unit 40 for operating a plain old telephone service pots emulation circuit 42 a network interface circuit 44 a driver 46 for the pots emulation circuit 42 a driver 48 for the network interface circuit 44 and an internet telephony application 58 each of the pots emulation circuit 42 and the network interface circuit 44 may be cards that plug into the computer expansion slots the pots emulation circuit 42 includes an rj 11 female jack 50 for coupling a traditional pots telephone handset 52 to the emulation circuit 42 a tip and ring emulation circuit 54 emulates low frequency pots signals on the tip and ring lines for operating the telephone handset 52 an audio system 56 interfaces the tip and ring emulation circuit 54 with the internet telephony application 58 more specifically the audio system 56 operates to digitize audio signals from the microphone in the handset 52 and present the digitized signals to the internet telephony application 58 and simultaneously operates to receive digital data representing audio signals from the internet telephony application 58 representing the.