Telephone applicable to PSTN and IP network and call connection control method

A telephone applicable to a public switched telephone network (PSTN) and an Internet Protocol (IP) network, comprising:

• a first interface for transmitting and receiving analog signals over the PSTN;
• a second interface for transmitting and receiving packet data over the IP network;
• means for communicating with a telephone number translation server connected to the IP network through said second interface when a call is originated by entering a PSTN telephone number and obtaining from the telephone number translation server an IP network telephone number of a destination telephone corresponding to the PSTN telephone number;
• means for communicating with a call agent connected to the IP network through said second interface to obtain IP address information of the destination telephone corresponding to said IP network telephone number, and establishing a call connection with the destination telephone via the IP network by using the IP address information;
• and
• means for establishing a call connection with the destination telephone via the PSTN through said first interface if the IP network telephone number of the destination telephone corresponding to said PSTN telephone number cannot be obtained from said telephone number translation server.