In digital logic, what is the primary function of an encoder device?

Introduction / Context:
Encoders and decoders are fundamental building blocks in digital systems. Recognizing the direction of conversion—one-hot or multi-line inputs to compact binary codes—helps when designing keypads, priority circuits, and address generators.

Given Data / Assumptions:

• An encoder takes multiple mutually exclusive inputs (e.g., keys 0–9) and outputs a binary code representing the active input.
• A decoder performs the inverse operation, expanding a binary code into multiple output lines.
• We identify the correct functional description of an encoder.

Concept / Approach:
A classic example is a 10-to-4 keypad encoder that maps one pressed key to a 4-bit binary output. Additional features like 'priority' handle simultaneous inputs. Telegraphy is unrelated, and an encoder’s number of inputs is not restricted to four.

Step-by-Step Solution:

Verification / Alternative check:
Digital design texts specify n-to-log2(n) encoders and log2(n)-to-n decoders, validating the function described.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing encoders with multiplexers; while related concepts exist, their functions differ.

Final Answer:
It converts an input (from one of many lines or keys) into a binary number