Multifunction terminal circuit

摘要

A multifunction terminal circuit having an optional circuit (12) a signal terminal (10) connected to the optional circuit; an unidirectional conductor means (14) connected to the signal terminal; and a circuit means (16) whose coupling node (A) is coupled with the signal terminal through the unidirectional conductor means. The circuit means determines a conduction state of the unidirectional conductor means in accordance with a potential difference between the signal terminal and the coupling node.