What is meant by "two-wire" vs "four-wire" in HART terminology?

• A. Two-wire devices use the same pair for power and signal (loop-powered); four-wire devices have a separate power supply for the device.
• B. Two-wire devices have twice the data rate of four-wire devices.
• C. Four-wire devices are only for analog signals; two-wire for digital.
• D. Two-wire devices require no external power; four-wire require battery.

Answer: (B)