Patent ID: 7577447

Claim:
A communication system comprising: a communication terminal apparatus; and a wireless key apparatus capable of a wireless communication with the communication terminal apparatus by a predetermined wireless communication system and limits a function of said communication terminal apparatus in response to a communication state between said communication terminal apparatus and said wireless key apparatus, wherein said predetermined wireless communication system is a system in which one of two apparatuses carrying out a communication each other becomes a master and the other one becomes a slave such that a signal from the master is detected by the slave so as to carry out a wireless connection between the two apparatuses; each of said communication terminal apparatus and said wireless key apparatus comprises communication means for carrying out a wireless communication by said predetermined wireless communication system, and control means for controlling the communication state in said communication means; when the wireless communication state between said communication terminal apparatus and said wireless key apparatus is a non-connection state, the communication means on the side which becomes said master decreases a transmission period in a plurality of steps in response to the non-connection time period and transmits a signal asking for a response from said slave intermittently; and the communication means on the side which becomes said slave decreases a reception period in a plurality of steps in response to the non-connection period and carries out a reception for searching for the signal from said master intermittently.