Patent ID: 7518984

Claim:
An Internet protocol private branch exchange comprising: a software-based built-in control unit; at least one card slot into which a control card is plugged; and a data bus connecting said software-based built-in control unit and said card slot, wherein said software-based built-in control unit includes: a first management unit managing up to a first number of Internet protocol terminals; and an Internet protocol terminal registering unit connected to said first management unit and said card slot, wherein said control card includes a second management unit managing up to a second number of Internet protocol terminals, wherein said Internet protocol terminal registering unit compares a current number of Internet protocol terminals managed by one of said first management unit and said second management unit with a corresponding one of said first number and said second number when an Internet protocol terminal requests communication, said Internet protocol terminal having an identification number and an Internet protocol address, wherein, if said current number is smaller than said one number, said Internet protocol terminal registering unit associates said one management unit with said identification number and said Internet protocol address, and said one management unit manages said Internet protocol terminal, and wherein, if said current number is equal to said one number, said Internet protocol terminal registering unit associates another of said first management unit and said second management unit with said identification number and said Internet protocol address, and said another management unit manages said Internet protocol terminal.