To solve a problem that it is necessary to temporarily disconnect a call, to dial a third person, to listen to the opinion and to report the result to the first speaking party again when it is necessary to listen to the opinion of the third person in a one-to-one interactive style.

When either one of portable telephone subscribers under one- to-one talking is to perform a dial connection to the portable telephone terminal of a third person as it is without disconnecting the call, a portable telephone base station, to which the portable telephone subscriber dialing the third person is connected, connects another line while connecting the call to a portable telephone base station connected to the portable telephone terminal of the third person and when talking is enabled, the voices of the third person are mixed on a one-to-one speaking line by an analog signal mixer located on a transmitting/receiving path so that speaking is enabled.