In a radio calling system in which a user carrying a radio receiver is called by a base station by means of a radio wave and the receiver returns an answer signal to the base station upon receiving the call signal sent to the receiver, the answer signal from each radio receiver can be transmitted with low power and the frequencies can be utilized effectively even when the number of the radio receiver increases by returning the answer signal through direct diffusion modulation using a base station identification signal which is inserted into a call signal train transmitted from the base station and made different for every base station or a code which is uniquely determined by the order of individual call signals in the call signal train. <IMAGE>
