US Patent 8648837 Active capacitive control stylus

A data transfer device comprising: a body; a tip coupled to the body, wherein the tip has a dielectric constant value suitable for interacting with a capacitive touch screen of a separate device; a control unit mounted to the body; and an electronic switch mounted to the body and operatively coupled to the control unit, wherein the switch is disposed to connect the tip to a ground source when the switch is in a closed configuration and to break the connection between the tip and the ground source when the switch is in an open configuration.