Patent ID: 7945297

Claim:
A headset comprising: at least one circuit element; a capacitive sensor operable to provide a capacitance measurement signal; a control circuit to enable at least one charge transfer cycle to the capacitive sensor; and a charge sensing circuit coupled to the control circuit and operable to generate a user presence signal responsive to values of the capacitance measurement signal for the at least one charge transfer cycle, the values indicating whether the headset is being worn by the user, and wherein the charge sensing circuit is operable to control the at least one circuit element dependent on said user presence signal and output an external output signal that is dependent on said user presence signal for receipt by another device to which the headset is connected wherein the charge sensing circuit includes a sample capacitor and is further operable to transfer charge from the capacitive sensor to the sample capacitor to generate an electric potential at the sample capacitor for measuring; and at least one switch within the control circuit, the at least one switch being operable to transfer a burst of charge packets sequentially from the capacitive sensor to the sample capacitor prior to any measurement of the electric potential being made, wherein the at least one switch includes: a first switching element to drive electric charge through the capacitive sensor and the sample capacitor when the first switching element is closed; a second switching element to clear voltage across the capacitive sensor to permit measurement of the sample capacitor when the second switching element is closed; and a third switching element to reset the charge on the sample capacitor when the third switching element is closed.