To limit utilization to the third person of a portable telephone set or the like without requiring any special operation concerning an electronic device required to limit the utilization to the third person.

An identification device 5 is provided having an oscillator 6 separated from a main body 4 of portable telephone set (main body device) and in the main body 4 of portable telephone set, a distance to the oscillator 6 is measured by a measuring instrument 3 on the basis of a signal oscillated from the oscillator 6. When the distance to the oscillator 6 is longer than prescribed one, the main body 4 of portable telephone set is disabled to originate a telephone call and warning is performed. Besides, when the distance to the oscillator 6 is longer than prescribed one, the destination to contact of an owner is displayed on a display means on the main body 4 of portable telephone set.