Abstract: A hands-free device for a mobile-phone handset includes: a read unit that detects connection of a mobile-phone handset and reads identifying information of the mobile-phone handset connected; a phone book creation unit that creates a phone book for each piece of the identifying information; and a change unit that changes the identifying information assigned to the phone book to identifying information of another mobile-phone handset.

Abstract: A navigation device includes: a hands-free call unit that is connected to a mobile-phone handset and provides a hands-free call; an acquisition unit that acquires from the mobile-phone handset data related to a phone number stored in the mobile-phone handset; a display control unit that displays a screen based upon the data related to the phone number acquired by the acquisition unit; a storage unit in which the screen displayed by the display control unit when power is turned off is stored; and a redisplay control unit that calls and redisplays the screen stored in the storage unit when the power is turned on again after having been turned off.