RS-232 to RS-485/422 Converter schematic. It can support RS-422 and RS-485 to change only two jumppers. And it used general devices. 75176 can be replaced max485, 65LBC184 etc.

The Document Gives the basic idea about RS485 communication with the PC. It shows basic hardware arrangement of Rs-232 to 485 converter

一个详细描述了USB到232接口转换硬件电路设计的文章-A article which detailed descr iption of the USB to 232 interface converter hardware circuit design.