What is a communications relay?

A communications relay is fundamentally a device designed specifically to enhance communication range by receiving a signal and retransmitting it. This process allows for signals to be passed along from one point to another, effectively overcoming obstacles or distances that would otherwise inhibit direct communication. By extending the reach of signals, relays play a pivotal role in maintaining communication networks, especially in tactical operations where reliability and distance can be significant challenges.

In contrast, the other choices represent different concepts entirely. Broadcast communication typically relates to spreading a signal to a broad audience rather than extending range through relay. Measuring signal strength is important for assessing communication quality, but it does not involve retransmission functionalities. Tools for data encryption serve a different purpose focused on securing information rather than facilitating communication through signal relay. Thus, the definition of a communications relay distinctly aligns with option A.