Real-world analogy for a multiplexer (data selector): Which everyday control most closely illustrates the function of a multiplexer by selecting exactly one of several available signal sources to pass onward?

Introduction / Context:
A multiplexer (MUX) is a data selector that routes exactly one of several inputs to a single output based on select lines. Drawing accurate real-world analogies helps solidify intuition about digital building blocks. This item asks which common stereo receiver control most faithfully mirrors a MUX’s behavior.

Given Data / Assumptions:

• A MUX chooses one source among many; it does not mix or scale signals.
• Only one channel is passed at a time to the downstream stage.
• Other controls (volume, balance, tone) operate on the chosen signal rather than selecting among discrete sources.

Concept / Approach:
The source or function selector (e.g., PHONO/AUX/TUNER/BT) on a receiver is a hardware switch that connects one of several inputs to the amplifier path. That is exactly what a multiplexer does, albeit electronically and under digital control. Volume corresponds to gain (scaling), balance changes relative channel gains, and tone controls apply frequency-dependent filtering—none of which involve selecting among multiple input sources.

Step-by-Step Solution:

Verification / Alternative check:
Classic receiver schematics show the input selector routing the chosen jack to the preamp, confirming the selection-only behavior matching a MUX.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing selection (one-of-many) with mixing (many-to-one simultaneous) or with gain/tonal adjustments that act on the already selected path.

Final Answer:
the function/source selector switch on a stereo receiver