The malfunction of a vibrator as a drawback of a conventional independent vibrator type portable terminal is obviated. A communication system of a portable communication terminal comprises a portable communication terminal capable of movably communicating with another communication terminal via radio communication with a base station, and peripheral equipment which performs a predetermined operation via radio communication with the portable communication terminal. The portable communication terminal transmits a radio signal to the peripheral equipment by using a time division multiplex access system for exchanging signals by putting data on a time slot as the radio communication between the portable communication terminal and the peripheral equipment and using the time slot in a time zone excluding other time zones in which the portable communication terminal is transmitting a radio signal to the base station. Thus the radio wave transmitted from the portable communication terminal to the peripheral equipment is prevented from being jammed by the radio wave transmitted from the portable communication terminal to the base station.