Controlling circuit for configuring ring indicator pin of communication port

摘要

A controlling circuit for a communication port having a ring indicator (RI) pin is provided. The controlling circuit includes a first selection circuit and a second selection circuit. The first selection circuit is controlled by a basic input/output system (BIOS) for determining whether an RI signal is transmitted to the RI pin. The second selection circuit is controlled by the BIOS for determining whether a first voltage or a second voltage is transmitted to the RI pin.