What is a key characteristic of a continuous wave in radiocommunications?

A continuous wave (CW) is primarily characterized by its use in transmitting Morse code. This is because CW consists of a single frequency that is turned on and off to create a signal, which can be effectively used for encoding information in the form of dots and dashes. This method of transmission is well-suited for simple, long-distance communication, especially in conditions where other forms of modulation may not perform optimally.

While the other options may relate to various aspects of communication systems, they do not define the core characteristic of a continuous wave. For example, digital communication techniques typically involve different modulation methods and are not synonymous with CW transmission. Similarly, while CW could be modulated for clarity, the key defining feature remains its application in Morse code rather than the modulation itself. Voice clarity in phone calls is achieved through other modulation techniques and is not relevant to the operation of continuous waves as used in Morse code. Thus, its primary attribute lies in its function for Morse code transmission, making it a fundamental concept in the study of radiocommunications.