PURPOSE: To easily identify the number of starting times for respective general exchange stations by giving identification information inherent to respective general exchange stations, adding said identification information with regular subscriber number information which the general exchange stations transmit so as to transmit them to a special exchange station at the time of connecting to the special exchange station different in an operation company.

CONSTITUTION: It is assumed that plural general exchange stations 11-13 and the special exchange station 16 connected from the general exchange stations 11-31 through a public network 15 are operated by the different operation companies. When an originating call for the special exchange station 16 is judged at the time of connecting the originating call of the general exchange stations 11-13, identification information given to respective general exchange stations 11-13 are added to subscriber number information so as to transmit them to the special exchange station 16 at the time of transmitting subscriber number information by the general exchange stations 11-13. Thus, the number of starting times for respective general exchange stations 11-13 can easily be identified without using a processor such as a computer in the special exchange station 16.