To enable outputting a ringing tone in discrimination according to a calling type to a mobile nurse call master unit, without complicated registration work to a telephone directory.

To an IP mobile telephone 10, different ringing tones are set to a plurality of predetermined telephone numbers which are registered in a telephone directory storage. When a call is made from a nurse call sub-unit, an IP adaptor 7 identifies a predetermined telephone number corresponding to a calling type included in a calling signal output from a controller unit 5. By the transmission of the calling signal, which includes the identified predetermined telephone number as a calling party, from an SIP server 8 to the IP mobile telephone 10, the IP mobile telephone 10 recognizes the predetermined telephone number included in the calling signal, as the calling party. By enabling outputting the ringing tone which is set to the telephone number of the calling party through the telephone directory storage, it becomes sufficient only to register the predetermined telephone numbers as many as the number of calling types into the telephone directory of the IP mobile telephone 10.