Which statement describes the 4-20 mA current loop principle?

• A. The loop transmits a fixed current regardless of the process variable.
• B. Two-wire loop carries power and signal; transmitter modulates current between 4 and 20 mA to represent the process variable.
• C. Current signaling is unsuitable for long distances.
• D. The loop uses voltage signaling rather than current.

Answer: (B)