Abstract: In the power system and many industrial applications, long-distance 485 communication is often encountered, which requires a long communication cable and a large amount of work. In order to solve this problem, by changing the working mode of type II collector, it has the function of RS485 and carrier two-way active data transmission, so as to build the "RS485—carrier—RS485" networking mode, and convert the wired 485 communication to the 220 V power line carrier communication. Bidirectional conversion device is divided into broadband and narrowband, which can adapt to different communication rates, self-organizing network, stable and reliable communication, simple use, strong adaptability, and has broad application prospects.

Key words: RS485 and carrier bidirectional conversion, “RS485—carrier—RS485” networking mode, collector working mode