RS485 (also written RS-485 or EIA-485) is an electrical standard for serial communication that supports multi-point connections over distances up to 1,200 metres. It uses differential signalling for noise immunity, making it ideal for electrically noisy industrial environments.
RS485 is the physical layer underlying MODBUS RTU — the most common industrial communication protocol. A single RS485 bus can connect up to 32 devices (or 256 with repeaters), allowing one gateway to aggregate data from many sensors.