Patent ID: 8254871

Claim:
A method for playing ring back tone comprising: transmitting, by a calling side mobile switching center, a route request message to a called side home location register after the calling side mobile switching center receives a calling request transmitted from a calling terminal to a called terminal; receiving, by the calling side mobile switching center, a response to the route request message returned from the called side home location register, wherein a roaming number field in the response to the route request message is filled with an identifier of a ring back tone service, wherein the identifier of the ring back tone service is an identifier returned to the calling side mobile switching center when the called side home location register acquires an absence response message of the called terminal and determines that the called terminal has customized the ring back tone service; identifying, by the calling side mobile switching center, whether the roaming number field in the response to the route request message includes the identifier of the ring back tone service to determine whether to instruct the playing device to play the ring back tone to the calling terminal; and instructing, by the calling side mobile switching center, a playing device to play the ring back tone to the calling terminal when the roaming number field in the response to the route request message includes the identifier of the ring back tone service.