Patent ID: 8614957

Claim:
An extension connection method for establishing an extension connection between a first mobile terminal and a second mobile terminal, the extension connection method comprising: transmitting an extension connection request for an extension call placed from the first mobile terminal to the second mobile terminal, from the first mobile terminal to a first route selection device; selecting a first extension connection route from among a plurality of extension connection routes for an extension call between the first mobile terminal and the second mobile terminal; transmitting a type of the first extension connection route and calling-side address information used on the first extension connection route from the first route selection device to a second route selection device; selecting a second extension connection route from among the plurality of extension connection routes for the extension call between the first mobile terminal and the second mobile terminal; transmitting a type of the second extension connection route and called-side address information used on the second extension connection route from the second route selection device to the first route selection device; and determining whether the second extension connection route coincides with the first extension connection route; wherein when the second extension connection route coincides with the first extension connection route, establishing the extension connection between the first mobile terminal and the second mobile terminal via the first extension connection route.