Combinational logic terminology: In multiplexing, a “data selector” refers to a circuit that routes one of many data inputs to a single output. Is it correct to say that a data selector is the same as a demultiplexer?

Introduction / Context:
Digital designers often use the terms multiplexer (MUX), demultiplexer (DEMUX), and data selector. While they sound similar, they describe different signal-routing functions. This question checks whether you can distinguish a “data selector” (another common name for a multiplexer) from a demultiplexer, which performs the opposite routing direction.

Given Data / Assumptions:

• “Data selector” is a term used in many datasheets for multiplexers.
• A multiplexer selects one of N inputs and forwards it to a single output using select lines.
• A demultiplexer takes a single input and routes it to one of N outputs, chosen by select lines.

Concept / Approach:
The core difference is the direction of data flow with respect to fan-in/fan-out. A multiplexer has many inputs and one output (many-to-one). A demultiplexer has one input and many outputs (one-to-many). Both use select lines, but their roles are inverse. Therefore, a “data selector” is not a demultiplexer; it is a multiplexer.

Step-by-Step Solution:

Verification / Alternative check:
Check classic parts: 74HC151 is titled “8-channel data selector/multiplexer” (8-to-1 MUX). Demultiplexer examples include 74HC138/139 used in address decoding (1-to-8 or 1-to-4 demux-like functions). The nomenclature in vendor datasheets confirms the distinction.

Why Other Options Are Wrong:

• Correct: Would imply data selector equals demultiplexer, which is not the case.
• Only correct for active-LOW devices: Signal polarity does not change the fundamental function.
• Only correct when tri-stated / Applies only to analog switches: Tri-state or analog implementation details do not redefine MUX vs. DEMUX roles.

Common Pitfalls:
Assuming symmetric interchangeability due to similar select lines; overlooking that many IC titles explicitly pair “data selector” with “multiplexer.”

Final Answer:
Incorrect