Which option correctly defines tone transmission?

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

Answer: (A)

Tone transmission encodes information in the duration of a pure audible tone. A single, steady tone is emitted, and the length of time it is present corresponds to the measured value. This time-based encoding is what defines tone transmission, as opposed to using changes in frequency or amplitude, or packing data into digital packets or a continuous stream of bits. In essence, the longer the tone, the higher the value being conveyed, within the defined measurement range.