Patent ID: 7065391

Claim:
A communication system comprising: a master and a slave that can communicate with each other, said master including a first communication section for transmitting a start request signal to said slave, said slave including a second communication section for receiving the start request signal transmitted by said master, wherein said slave can take any of a start state in which said slave can communicate with said master, a communication control state in which at least said slave can receive the start request signal transmitted by said master and makes a transition to the start state upon reception of the start request signal, or a standby state in which power is less consumed than in the start state or the communication control state, wherein said slave further comprises a state control section for repeatedly operating so that said slave in the standby state is switched, independently of any signal from the master, to the communication control state at a predetermined timing and is switched to the standby state when the communication control state continues for a predetermined time period without receiving the start request signal, and wherein said slave further comprises a sensor communicating section which produces a communication state request so that the slave in the standby state is switched to the communication control state.