RS485 is an industrial standard for long-distance, anti-interference, and reliable communication. The Arduino RS485 shield, specially designed for the Arduino Uno board. It converts UART/Serial protocol to the RS485 protocol. This RS485 board allows Arduino talk to industrial devices.
In contrast to RS-422, which has a single driver circuit that cannot be switched off, RS-485 drivers use three-state logic allowing individual transmitters to be deactivated. This allows RS-485 to implement linear bus topologies using only two wires. The equipment located along a set of RS-485 wires is interchangeably called nodes, stations, or devices.
What is RS485?
"RS-485 enables the configuration of inexpensive local networks and multidrop communications links. It offers data transmission speeds of 35 Mbit/s for distances up to 10m and 100 kbit/s up to 1200 m. Since it uses a differential balanced line over twisted pair (like RS-422), it can span relatively large distances up to 1,200 m (4,000 ft). A rule of thumb is that the speed in bit/s multiplied by the length in meters should not exceed 10^8. Thus a 50-meter cable should not signal faster than 2 Mbit/s." From Wiki.
