When a radio communication is made between a predetermined base station and a communication terminal, the communication terminal is allowed to make a communication if a predetermined registration processing is made. If the above registration processing is not executed, then predetermined functions other than a communication function of the communication terminal are limited. Moreover, when a predetermined operation mode is set by an operation means, at least a transmission processing at a radio communication means is stopped and an execution of predetermined functions other than the radio communication processing is not restricted. Thus, when a communication terminal apparatus incorporates therein other functions than an audio reproducing function, operation of such function can be limited properly. Moreover, when other functions such as an audio reproducing function are incorporated into a communication terminal apparatus, operations of the functions thus incorporated can be limited properly and the communication functions can be stopped properly.