Patent ID: 7142838

Claim:
A radio communications system comprising: a master receiver circuit having a sleep mode and an active mode, the master receiver circuit being configured to consume less power in the sleep mode than in the active mode; a switch circuit configured to control when the master receiver circuit switches between the sleep mode and the active mode; a receiver input configured to receive radio signals; and a wake-up detector circuit, coupled to the receiver input, including: circuitry configured to reject any of said radio signals not having a data rate equal to a single, specific, predetermined, first data rate, and to generate a wake-up mode signal when the receiver input receives a radio signal having a data rate equal to said first data rate; wherein the switch circuit switches the master receiver from the sleep mode to the active mode in response to the data rate detector circuit generating said wake-up mode signal; and wherein the switch circuit does not switch the master receiver from the sleep mode to the active mode in response to the receiver input receiving a radio signal having a data rate not equal to said first data rate.