By executing a ring-tone determination program and so on, a handsfree device transmits range information to a mobile phone handset connected with the handsfree device. When the handsfree device receives information of frequency ranges used by ring-tone signals in the handset, it makes a determination according to the received information. If the received information indicates that the handset is compatible with the range information, it transmits a signal for directing not to restrict a frequency range. If the received information indicates that the handset is not compatible with the range information, it transmits either of a signal for directing to restrict a frequency range or a denial signal denying the reception of ring-tone sound, depending on a setting in the handsfree device.