1、This module give full consideration to the 485 bus lightning protection design and anti-interference design, high EMC and high performance of EMI; For outdoor long-distance transmission, the earth end of module is connected to the earth, that can have ve 2、With standard 54 spacing pin header, it is convenient for your secondary development. 3、With 120 ohm match resistor, short circuit of R0 can enable matching resistor; short circuit is suggested for long-distance transmission. 4、It supports communication of multiple machines that the same network can be connected to at least 40 nodes. 5、Anti-interference type wiring and copper laying method prevent signal interference. Features: This module give full consideration to the 485 bus lightning protection design and anti-interference design, high EMC and high performance of EMI; For outdoor long-distance transmission, the earth end of module is connected to the earth, that can have very good anti-interference and lightning protection, making the 485 bus more security;For indoor short-distance transmission, the earth end can be disconnected from earth. With standard 2.54 spacing pin header, it is convenient for your secondary development. With 120 ohm match resistor, short circuit of R0 can enable matching resistor; short circuit is suggested for long-distance transmission. It supports communication of multiple machines that the same network can be connected to at least 40 nodes. It supports hot plugging, while signal will not jam. Anti-interference type wiring and copper laying method prevent signal interference. Compatible with 3.3 V and 5.0 V signal, can match with module. With high performance of EMC and EMI. Using imported chip, industrial design, with strong anti-interference ability; using powerful 485 lightning protection design that can be used in industrial field and harsh environment; within the temperature of 40 ℃ to + 85 ℃, the transmission distance can be up to 1km (tested with 850m 2* 1.5 cable, it is suggested to use within 800 meters; please add repeater if more than 800 meters). With insulated wire and terminals, very convenient to use. Designed with RXD, TXD signal indicator lights for easy checking of sending and receiving status. Specification: Wide voltage power supply: 3.0V ~ 30V        Limiting voltage: 33 V( it is recommended to use within 30 V, the minimum voltage should be higher than 2.8 V) Size: 52 * 23 * 11mm / 2 * 0.9 * 0.4in Package list: 1 * Module 1 set * Cable