An earphone microphone 1 is connected to a mobile terminal 10 by radio waves. A user can preset each of levels of volume and tone quality that he/she considers as appropriate for each of the predetermined use states inside his/her mobile terminal via a volume setting section 15 and a tone quality setting section 16. When a change in an internal use state is followed by the acquisition of a use state after the change, volume setting information 32 and tone quality setting information 33 both associated with the use state are read out from a memory. Volume and tone quality are each adjusted individually for each of a mobile terminal microphone 11, a mobile terminal ear receiver 12, an external microphone 2, and an earphone 3.