Demonstrating multiplexer behavior with mechanical switches Which single mechanical device most clearly demonstrates the basic principle of a digital multiplexer (selecting one of many inputs to connect to a single output)?

Introduction / Context:
A multiplexer (MUX) selects exactly one of multiple inputs and connects it to a single output. Mechanical analogies help students visualize this behavior before moving on to IC-based multiplexers such as the 74HC151 or CMOS analog switches.

Given Data / Assumptions:

• We want a one-of-N selection using a single output contact.
• The device should offer multiple selectable inputs.
• The selection mechanism should be unambiguous and exclusive.

Concept / Approach:
A rotary switch presents many input positions around a dial, with a common wiper that connects exactly one selected position to the common terminal. This is the mechanical equivalent of a k-to-1 digital multiplexer. Other switches either select between only two inputs or provide different functions.

Step-by-Step Solution:

Verification / Alternative check:
Mapping: rotary switch positions ↔ multiplexer inputs; wiper common ↔ multiplexer output; knob position ↔ select lines.

Why Other Options Are Wrong:

• Single-pole relay: acts like an SPST/SPDT, not many-to-one.
• DPDT switch: two inputs per pole only.
• Linear stepper: an actuator, not a selector.

Common Pitfalls:
Confusing demultiplexing (one-to-many) with multiplexing (many-to-one); the rotary switch models the latter perfectly.

Final Answer:
rotary switch