What can be the visual observation of a condition whereby it may be possible to initiate a reliable TELEX transmission but a voice transmission may not be possible?

Correct Answer: Option D — An indication on a meter or on the terminal of low receiver signal strength.

Low receiver signal strength indicates poor link quality. While digital TELEX (data) can often be recovered through error correction protocols even with a weak signal, voice communications require a higher signal-to-noise ratio to maintain intelligibility. Thus, a weak signal may support data transmission while rendering voice communication impossible.