US Patent 7778238 IP telephone apparatus

A source IP telephone apparatus obtains, from an ENUM server, NAPTR records of a call destination based on a telephone number of the call destination, the telephone number being input by dialing. The source IP telephone apparatus then selects, from the obtained NAPTR records, a NAPTR record to be used for transmitting a call, based on a priority order, and transmits a call to the call destination based on an access method and a destination number included in the selected NAPTR record. When a destination IP telephone apparatus is busy, the second priority NAPTR record is selected and another call is made by automatically switching the access method.