A digital circuit that observes an applied coded input pattern and asserts exactly one related output line (often one-hot) is best described as which device?

Introduction / Context:
In digital logic, encoders and decoders perform opposite roles. A decoder observes a compact binary input and activates a corresponding output line, commonly as a one-hot signal. Recognizing this behavior is essential in address decoding, chip select schemes, and display selection.

Given Data / Assumptions:

• The input is a coded binary value.
• Only one output line should be active for any valid input.
• Outputs may be active-high or active-low depending on implementation.

Concept / Approach:
A decoder translates an n-bit input into 2^n mutually exclusive outputs. For example, a 3-to-8 decoder maps 3 input bits to one of 8 outputs. Display drivers often include decoding logic internally, but the generic device that directly performs code-to-line activation is a decoder.

Step-by-Step Solution:
Let the input be A..D representing a binary number N.The decoder asserts output YN corresponding to N; all other Yk remain inactive.Thus the circuit responds to a specific input code and produces a related digital output line.Hence, the correct identification is a decoder.

Verification / Alternative check:
Datasheets for 74HC138 (3-to-8) and 74HC154 (4-to-16) demonstrate one-hot activation controlled by enables and inputs, validating the functional definition.

Why Other Options Are Wrong:

• BCD matrix: Not a standard logic device category.
• Display driver: A broader class; may include decoding but is not the generic name.
• Encoder: Performs the inverse mapping (many inputs to compact binary output).
• Priority multiplexer: Not a standard term; multiplexers select one of many inputs to one output.

Common Pitfalls:

• Confusing decoders with demultiplexers; a DeMUX routes signals, while a decoder generates one-hot control signals from codes.
• Ignoring enable pins that gate the decoder outputs.

Final Answer:
decoder