A system is provided for communication between a mobile device and an Enterprise Network. The method according to the present invention is to restrict the trigger of the NACK signaling, by setting the condition of the UE feeding back the NACK signaling when the UE received the error block. The method further allows creating changeable keys on the input device, and assigning functions to the keys from various sources. The control portion supplies a second signal in response to a second display data.