PURPOSE: To enable the transmission of various signal tones to a telephone set, by storing a digital data corresponding to various analog signals in a packet exchanger.

CONSTITUTION: After a packet exchanger 30 receives a dial information from this telephone set 8 at the detection time of off-hook of a telephone set 8, a digital data 25 for dial tone, digital data 26 for ring back tone, and digital data 27 for dial tone stored in the exchanger are outputted to an audio digital converter VOCODER7 during calling of other party, relay line 9 in busy, or detection time of the party in busy. Further, the digital data are converted into an analog signal at the VOCODER 7 and transmitted to the telephone set 8.