TV Channel Selector (4-to-1 MUX) Circuit Simulator

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JavaScript を有効にするとライブ回路が読み込まれます。下の真理値表で動作を確認できます。

学べること

Apply a 4-to-1 MUX as a channel selector.
Use a 2-bit select to address 4 input channels.
Read the MUX truth table for the application.
Recognize MUXes in HDMI switches, KVMs, and audio routing.
Scale to wider channel counts by adding select bits.

仕組み

A 4-to-1 multiplexer makes an excellent TV channel selector: four channel inputs, two select bits, one output to the screen. The select code (S1, S0) picks which channel reaches the output: - 00 → Channel 1 - 01 → Channel 2 - 10 → Channel 3 - 11 → Channel 4

This is the same circuit as the textbook 4-to-1 MUX, just with the application labelled. Real TVs are far more complex (RF tuners, digital decoders) but the principle of "select one of N input streams to display" is the same — multiplexers are the underlying primitive.

The select bits in a real remote control come from button presses encoded into a 2-bit (or wider) channel-number register. Each button press updates the register; the MUX immediately routes the new channel through. The user sees an instant switch.

For 16 channels you'd need a 16-to-1 MUX with 4 select bits; for 256 channels, an 8-bit select. MUXes scale efficiently — the select width is logarithmic in input count.

真理値表

Selecting one of 4 channels with a 2-bit select code. Showing each channel's selection.

入力		出力
S1	S0	Channel
0	0	1	S=00 → Channel 1
0	1	1	S=01 → Channel 2
1	0	1	S=10 → Channel 3
1	1	1	S=11 → Channel 4

ブール式

Y = \overline{S_1}\overline{S_0} C_1 + \overline{S_1}S_0 C_2 + S_1\overline{S_0} C_3 + S_1 S_0 C_4

Standard 4-to-1 MUX expression — each channel ANDed with its select-code minterm.

順を追って試す

上の埋め込み回路で入力を設定し、期待される結果と一致するか確認しましょう。

1

S1 = 0 S0 = 0 C1 = 1

期待値: Output = 1 (showing C1)

観察ポイント: Select 00 → Channel 1 plays. Other channels are tuned out.
2

S1 = 0 S0 = 1 C2 = 1

期待値: Output = 1 (showing C2)

観察ポイント: Flip S0 — switch to Channel 2 instantly.
3

S1 = 1 S0 = 0 C3 = 1

期待値: Output = 1 (showing C3)

観察ポイント: Channel 3 selected. The MUX routes the new channel through immediately.
4

S1 = 1 S0 = 1 C4 = 0

期待値: Output = 0

観察ポイント: Channel 4 selected, but C4 input is 0. Output reflects the actual channel content — 0 means "channel currently dark."

使用コンポーネント

実世界での応用

Analog TV channel selection. Older TVs used analog MUXes (or selectable RF tuners) to pick between input bands. The select control was the channel knob.

HDMI input switching. Modern TVs use multiplexers (or active switches) to route one of N HDMI sources to the display pipeline. The remote's input button drives the select.

Audio/video matrix routing. Conference room AV systems route multiple inputs to multiple outputs via crossbar switches — fundamentally an array of MUXes.

KVM switches. Keyboard/Video/Mouse switches use multiplexers to share peripherals across multiple computers based on a select knob.

Radio frequency selection. Radios with preset buttons use small MUXes to select between stored frequency-tuning configurations.

よくある質問

Why is a TV channel select called a multiplexer?

Multiplexer is a generic term for "select one of N to route to a single output." TV inputs are a specific application — channel select. Same circuit, different application labels.

How do real digital TVs handle channel select?

Modern TVs decode encoded RF or HDMI signals digitally; the channel selector is internal to the digital signal processor. But conceptually it's still a MUX — picking which decoded stream feeds the display pipeline.

What if I want to switch between 8 channels?

Use an 8-to-1 MUX (3 select bits). For 16, a 16-to-1 (4 select bits). MUXes scale logarithmically in select width.

How is fast channel-changing implemented?

MUX-level selection is microseconds-fast — the slow part of TV channel change is RF tuning or decoder buffer flush. Pure MUX selection happens in nanoseconds; modern TVs add buffering and de-noise transitions for visual smoothness.

Could I MUX between video signals (multi-bit) instead of single bits?

Yes — for an 8-bit-per-pixel video signal, use 8 parallel 4-to-1 MUXes (one per bit), all sharing the same select. The select picks which channel's full 8-bit pixel reaches the output. This is how real video switches work — banks of MUXes one per data line.