Highway Addressable Remote Transducer Protocol

The HART Communications Protocol (Highway Addressable Remote Transducer) is an early implementation of Fieldbus, a digital industrial automation protocol. Its most notable advantage is that it can communicate over legacy 4-20 mA analog instrumentation wiring, sharing the pair of wires used by the older system. According to Emerson, due to the huge installed base of 4–20 mA systems throughout the world, the HART Protocol is one of the most popular industrial protocols today. HART protocol has made a good transition protocol for users who were comfortable using the legacy 4–20 mA signals, but wanted to implement a "smart" protocol. Industries seem to be using Profibus DP/PA and Foundation fieldbus (also by Rosemount) more as users become familiar with later technology and look to take advantage of the enhanced diagnostics they can provide.