a contact detector having power switches for disconnecting power to portions of the contact sensor when an over current is detected is disclosed . the power switches thus protect the contact sensor from over - current as the result of latch - up or other current - generating conditions . these current - generating conditions are often the result of esd events on a surface of the contact detector . a contact detector comprises an exposed surface for detecting the presence of an object , an insulating surface , and a protection element disposed under the insulating surface for controlling power to the contact detector . the protection element is configured to disconnect power to the contact detector when a current to the contact detector is detected above a threshold . preferably , the contact detector is a finger swipe sensor , but it can be a finger placement sensor or any other type of device that functions on contact with a finger or other patterned object .