The ST75185 contains three drivers and five receivers. The pinout matches the DB9S connector design in order to decrease the part count, reduce the board space required and allow easy interconnection of the UART and serial port connector of IBM PC/ATTM and compatibles. The bipolar circuits and processing of the ST75185 provides a rugged low-cost solution for this function at the expense of quiescent power and external passive components relative to the ST75C185.