HART Protocol And 4–20 MA Loop Communication Fundamentals Practice Test

Tone transmission encodes information by how long a tone lasts. The measured value is mapped to a specific duration, so the receiver interprets the length of the audible tone and converts it back into a value. This is a straightforward time-based encoding: the signal is a single pure tone whose on-time conveys the data, rather than sending structured packets, modulating a carrier, or streaming continuous binary data. Why this fits best: the essence of tone transmission is using the duration of the tone itself as the carrier of information, which matches the description of a pure audible tone whose length represents the value. The other methods describe different signaling schemes—digital packets imply discrete messages with formatting and overhead; a RF carrier with amplitude encoding uses amplitude (and typically binary or modulated data) over a wireless link; a continuous stream of binary bits conveys information as a sequence of bits rather than the duration of a single tone.