US Patent 8378967 Wearable electrical apparatus

A wearable input device includes a pair of ring-shaped signal electrodes and a current sensor arranged in parallel in the direction of the axis of a finger. The current sensor is provided outside an area sandwiched between the signal electrodes. An alternating current signal is applied between the signal electrodes. When the top end of the finger with this device worn thereon is brought into contact with any other body site, a current flows through the current measure point of the current sensor. When the top end of the finger is not in contact with any other body site, no current flows through the measurement point of the current sensor. Based on the measured current, it is determined whether the finger is in contact with any other body site. A command is outputted to an external device according to the result of the determination.