HART why called a TRANSDUCER?

Hello friends, i know a transducer is a device that convert one form of energy to another and HART is a device which can communicate digitally over 4-20 ma analog signal, but why its called a HIGHWAY ADDRESSABLE REMOTE TRANSDUCER? in what way its a transducer what it converts?

It converts the analog data and some diagnostics measured by the transmitter to a FSK ( frequency shift Keying) signal. See link below for more info on the Hart protocol.

http://www.hartcomm.org/protocol/about/aboutprotocol_how.html