Which of the following statements is true about digital signals?

Digital signals are characterized by their ability to maintain quality over transmission due to their discrete levels, which help in reducing the impact of noise and distortion. This inherent structure allows digital signals to be easily regenerated. Regeneration involves reconstructing the original signal from received data, which is crucial in long-distance communication where the signal may degrade. By converting the digital signal back to its original form at intervals, the integrity and accuracy of the information can be preserved, making digital systems more reliable in maintaining signal quality.

In comparison, other statements present characteristics that do not align with the properties of digital signals. For instance, options mentioning noise reliability and continuous voltage variations are indicative of analog signals, which suffer more in noisy environments and utilize varying voltages to convey information. Thus, the correct statement highlights the clear advantage of digital signals in regeneration and quality maintenance during transmission.