Abstract: A use prohibition system which can disable a cellular phone or any other device if it separates more than a predetermined distance from the user, and at the same time give a warning to the user. It includes an identification signal transmission unit and a use prohibition mode canceling unit attached or mounted to the cellphone. Each unit has a transmitter and a receiver. The receiver of the canceling unit receives an ID code signal from the transmission unit and produces, based on the ID signal received, a use prohibition canceling signal. The canceling unit returns a confirmation signal to the transmission unit. If the two units separate more than a predetermined distance from each other, the levels of the ID signal and the confirmation signal received by the respective units drop below a predetermined value. Thus, the canceling unit stops producing the canceling signal to disable the cellphone, while the transmission unit sounds an alarm.