Rockwell Automation 1770-HT8 SMART TRANSMITTER - Manual (Page 11)

Preface
P-4
Point-to-point: one HART field device per channel on a terminal block
RIO: Remote Input Output link that supports remote, time-critical, I/O
and control communications between a master PLC controller and its
remote I/O and adapter mode slave processors
Transducer/Transmitter: any one of several field devices that can
measure pressure, temperature, level, flow, density or other process control
variables, and then transmit the value of that variable as a 4-20 mA signal.
Transducers that support the HART protocol are designated as being
“smart”.