To enable telephone speech communication utilizing the Internet, together with extension and outside line speech communication via the existing data communication network.

This system consists of a matching device 60 of a data communication network, which disassembles and interprets packet data via the data communication network and classifies voice data and the matching device 70 of a telephone subscriber, which performs digital conversion and compression of a voice signal inputted from a telephone network, converts the voice signal into packet data by referring to an IP address corresponding to the telephone number of each telephone set, subsequently transmits the packet data to the device 60 of the data communication network, restores or performs analog conversion the voice data inputted by the device 60 of the data communication network to transmit the voice data to the device 70 of the telephone subscriber. An IP address, corresponding to the telephone number, is dialed by using specific buttons of the telephone set, i.e., '#' and '*' buttons, so as to classify the extension speech communication, the outside line speech communication and telephone speech communication using the Internet, and a telephone exchange function is conducted by the IP address.