Which description best fits tone transmission?

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

Answer: (B)

Tone transmission conveys information by how long a tone lasts. The best description is a pure audible tone whose duration represents the measured value, because the data is encoded in the length of time the tone is present rather than in changes to frequency, amplitude, or in digital packet structures. This highlights duration as the encoding parameter: a single, steady tone that is heard longer or shorter to indicate larger or smaller measurements. The other descriptions describe different signaling methods—varying frequency or amplitude on a carrier, digital packets with time stamps, or a continuous binary bit stream—none of which match the idea of information carried by tone duration.