What best describes tone transmission?

• A. A pure audible tone whose duration represents a measured value.
• B. A digital packet containing time-stamped data.
• C. A radio frequency carrier with amplitude encoding the value.
• D. A continuous stream of binary bits conveying the measurement.

Answer: (A)

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.