service is accessed for example when power is initiated from the first battery 22 to the communication module 32 the controller 38 can check whether the pda is currently being used step s 35 if the pda is currently used the controller 38 can then turn on the pda module 30 and the communication module 32 steps s 36 and s 37 if however the pda module is not used the controller 38 can turn off the pda module 30 and turn on only the communication module 32 thereby reducing the power consumption of the first battery 22 steps s 38 and s 39 thereafter if the remaining capacity of the first battery is below the first level the controller 38 can turn off the first relay switch 26 to cut off power from the first battery 22 to the pda module 30 so that the pda module 30 is turned off as a matter of course since the second relay switch 28 is maintained in the on state power can be continuously supplied from the first battery 22 to the communication module 32 so that the user can continuously use the call service also as a further way to minimize power consumption power to a display of a terminal can be limited in a preferred embodiment by power being limited to only the communication module 32 and only a portion of the whole display the display unit may also be dividedly constructed into sections as where only specific sections i e relating to the communication module 32.