Patent ID: 7668556

Claim:
A communication system comprising: a communication terminal apparatus; and a wireless key apparatus, wherein the communication terminal apparatus and the wireless key apparatus are in wireless communication, said communication terminal apparatus comprising: a communication unit operable to receive a first wireless signal from the wireless key apparatus, and a control unit operable to determine a distance between the communication terminal apparatus and the wireless key apparatus based on the received first wireless signal, wherein the control unit limits a predetermined function of the communication terminal apparatus based on the determined distance being longer than a first predetermined distance; and said wireless key apparatus comprising: a communication unit operable to receive a second wireless signal from the communication terminal apparatus, and a control unit operable to determine the distance between the communication terminal apparatus and the wireless key apparatus based on the received second wireless signal, the control unit decreasing transmission power associated with the communication unit based on the determined distance being longer than the predetermined first distance, wherein the limited predetermined function is released and the transmission power is increased when the distance is determined to be shorter than a second predetermined distance, and wherein the second predetermined distance is less than the first predetermined distance.