In the last few years we have seen a relevant transformation of the te
lephone network, with an extensive digitalization of the voice transmi
ssion and switching able now to reach the subscriber In the meanwhile
various techniques have been implemented to exploit data transmission
in an environment designed for voice only. This paper will review this
important transformation and its future perspective from the point of
view of the IC industry by considering several analog/digital basic r
ealization in PCM, analog modem, ISDN and radio-communication fields.