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.