RS-485 is a simple, inexpensive, reliable communications specification. It is a widely used protocol for POS, industrial, and telecom applications. Its wide common-mode range enables data transmission over longer cable lengths and in noisy environments such as the floor of a factory. Also, the high input impedance of the receivers allows more devices to be attached to the lines.
Lots of factors limit the maximum data rate of RS-485, including cable length, cable construction (shielding enhances noise immunity), driver output impedance, receiver input impedance, terminations, driver slew rate, and more.
Poll Question: What is the maximum data rate that has been achieved by an RS-485 transceiver to date?