Digital signals are robust against this interference.

• A. Noise
• B. Fading
• C. Crosstalk
• D. Echo

Answer: (A)

Digital signals are defined by discrete voltage levels and a clear decision boundary. What makes them robust is that small random fluctuations from interference—noise—often stay within the margin around a level and don’t change which level is detected. Once the received value is above or below the threshold, a clean decision can be made, and, if you have error-detecting or error-correcting codes, you can detect and fix occasional misreads. That resilience to random noise is a hallmark of digital communication.

Interferences like fading, crosstalk, or echo can distort amplitude, delay, or mix signals, and while they can be mitigated with techniques such as equalization, shielding, or coding, the fundamental reason digital signals endure is their threshold-based detection and the ability to use redundancy to recover the original data.