US Patent 9041510 Capacitive data transfer in an electronic lock and key assembly

An electronic key may include a partial capacitor comprising a capacitive metal plate in communication with a processor. The capacitive metal plate of the partial capacitor is configured to form a capacitor with a corresponding capacitive metal plate of a lock when brought into proximity with the metal plate of the lock. Data may be transferred from the key to the lock using a capacitor formed by combining the two metal plates, wherein a common ground is established between the metal plate of the key and the metal plate of the lock through a parasitic capacitance present between the key and lock circuitry.