ATC-107N photoelectric isolation interface converter is compatible with RS-232C, RS-422, RS-485 standards, and can convert single-end RS-232 signal into balanced differential RS-422 or RS-485 signal. The built-in photoelectric isolator can provide 3500V isolation voltage, and the grade 2 rapid transient voltage suppressor (TVS) can effectively inhibit lightning and ESD, provide 1000W lightning strike and surge protection power on each line, and prevent lightning strike and common code interference. Connect PC, IPC, or portable computer via a DB9 female connector at RS-232 interface, and connect RS-422, RS-485 end via convenient 6-bit plug-in terminal. RS-485 supports dual-line half duplex, namely, the only two lines of RS-485 shall both send and receive data. Handshake signal (e.g. RTS, Request To Send) usually controls the data direction. The inner circuit of ATC-107N photoelectric isolation interface converter can detect data direction and switch to control it automatically, conveniently to form a RS-485 network without any shake hand signal. This kind of RS-485 control is fully transparent and need no software amendment for the former working modes basing on RS-232. ATC-107N photoelectric isolation interface converter can provide credible connection for point to point, point to multi-point communication. The point to multi-point communication is to connect many terminal devices to the same network, and they can communicate with each other. ATC-107N photoelectric isolation interface converter can automatically configure the function to automatically identify the communication address of the terminal device and automatically configure the terminal device to the RS-485 bus.