Function identification – the logic device that takes a single input data line and routes it to exactly one of several outputs under control of select lines is called a ________.

Introduction / Context: In digital systems, you often need to distribute a signal to one of many destinations under programmable control. The primitive that performs this fan-out selection is not a decoder (which maps binary codes to one-hot outputs) nor a multiplexer (many inputs to one output), but the device that effectively performs the inverse of a multiplexer with respect to signal routing.

Given Data / Assumptions:

• There is one data input signal D.
• There are multiple output lines Y0…YN−1.
• Select inputs choose which single output should carry D.
• Only the chosen output follows D; others are forced inactive.

Concept / Approach: A demultiplexer (DEMUX) sends the single input to one selected output. If D toggles, the selected output mirrors those toggles while nonselected outputs remain at their inactive level. In some families outputs may be active-low; the routing principle remains unchanged. DEMUXes are used in time-division distribution, addressable control lines, and DAC channel selection when a separate sample-and-hold captures the routed signal downstream.

Step-by-Step Solution:

Verification / Alternative check: Compare to a multiplexer: a MUX performs N inputs → 1 output, the directional opposite of DEMUX. Decoder: code → one-hot outputs, no routed data line. This confirms naming and functional differences.

Why Other Options Are Wrong: Multiplexer is the inverse routing element; comparator evaluates magnitudes; counter produces sequences; priority encoder selects among many inputs to produce an encoded index, not to route a separate data stream.

Common Pitfalls: Confusing DEMUX with decoder due to similar select lines; forgetting active-low conventions that might invert apparent logic levels on outputs.

Final Answer: demultiplexer