PURPOSE: To save the public network utility charge and to improve the utilizing efficiency of a public network.

CONSTITUTION: The system is provided with a dial number reception means 4 receiving a dial number dialed from a terminal equipment 2 to a public network 8 and with dial number analysis means 5,6 analyzing the received dial number as to whether or not the destination is connected to other extension terminal equipment 3 or via a relay line network 9. Moreover, an exchange 1 is provided with a means 7 editing numeral information to be dialed to the public network 8 or the relay line network 9 and sending it. When the destination dialed from the terminal equipment 2 to the public network 8 is discriminated to be a destination to pass through the relay line network 9 or to be connected to the other extension terminal equipment 3 by the dial number analysis means 5,6, the relay line network or the extension terminal equipment 3 of its own station is selected as a dial route and the exchange 1 edits a proper number and sends it.