Tone transmission conveys measurements by encoding the duration of the tone; which option describes that?

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

Answer: (C)

Tone duration encoding means the value is carried by how long the tone is audible. When the measurement is represented by the length of time the tone lasts, the receiver converts that duration into a numerical value. The option that describes a pure audible tone whose duration represents the measured value matches this idea directly. It’s not about sending a stream of binary bits, or a time-stamped digital packet, or modulating a carrier’s amplitude; those methods convey information differently—via bits, packets, or amplitude rather than the length of the tone.