Explanation: A NOT gate, also known as an inverter, is a fundamental building block in digital logic circuits, commonly found in amateur radio equipment for control, processing, and modulation. Its defining characteristic is to output the opposite logic state of its input. Therefore, if the input is a logic "1" (high voltage), the output will be a logic "0" (low voltage). Conversely, if the input is a logic "0," the output will be a logic "1." This inversion is precisely what option B describes. Options A and C describe characteristics more aligned with a gate that enables or disables data flow based on an input condition, not the direct logical inversion performed by a NOT gate. Option D describes a buffer or a direct connection where the output mirrors the input, which is the opposite function of a NOT gate.