In digital electronics and data communication, which statement best characterizes a digital signal with respect to its voltage interpretation and binary values?

Introduction / Context:
Digital systems encode information as discrete symbols, typically binary 0 and 1, represented by electrical voltage ranges or logic levels. Understanding how physical voltages map to logical values is essential for reliable digital circuit design, noise margins, and interfacing between devices that may use different logic families (TTL, CMOS, LVDS, etc.).

Given Data / Assumptions:

• Binary logic uses two symbols: 0 and 1.
• Voltage thresholds define valid logical regions for 0 and for 1.
• Signal shape is not inherently sinusoidal; it is usually approximated as square or pulse-like.

Concept / Approach:

A digital signal maps a continuous physical quantity (voltage) into discrete logic levels via thresholds (e.g., VIL and VIH). Values within noise margins are still correctly interpreted. While a digital waveform can be analyzed in the frequency domain and does have spectral content, the defining property is the discrete mapping of voltage to symbols, not the waveform being sinusoidal.

Step-by-Step Solution:

Verification / Alternative check:

Interface specifications (for example, CMOS or TTL datasheets) cite VIH min and VIL max, establishing the exact thresholds for 1 and 0 recognition.

Why Other Options Are Wrong:

Sinusoidal shapes describe analog carriers; digital edges are not inherently sinusoidal.

“Exactly three levels” confuses general digital with multi-level line coding.

“Do not have a frequency” is false; any time-varying signal has spectral content measured in hertz.

Common Pitfalls:

Ignoring noise margins and assuming any intermediate voltage is valid; undefined regions can cause metastability in logic circuits.

Final Answer:

Digital signals are assigned values of 1 or 0 depending on the voltage level (within defined thresholds)