Inside the Box: Switches and Signals

Big idea: Everything a computer does is built from millions of tiny switches that can only be on or off. Two choices — on and off — are enough to store every word, picture, and sound a computer knows.

A light switch has two settings: on or off. A computer is packed with switches just like that — only it has billions of them, far too small to see. Each switch holds one tiny piece of a message. We write the two settings with numbers: 1 means on and 0 means off. A message made only of 1s and 0s is called binary.

How can on and off spell a word or paint a picture? By using a code. People agreed on a plan called ASCII, where each letter gets its own pattern of 1s and 0s — the letter A is 1000001. Colors work the same way: every color on a screen is a mix of Red, Green, and Blue light, and the computer stores how much of each as numbers. The kind of data — a letter, a number, or a color — decides which code the computer uses.

A computer is a system with three jobs. First it takes something in (an input, like a key you press or a tap on a screen). Then the processor in the middle works on those 1s and 0s. Then it sends something out (an output, like a letter on the screen or a sound). Input → processor → output. Computers also pass these signals to each other across wires and the internet, which is how a message you type reaches a friend far away.

Essential question: How can a computer build everything it does out of just two choices — on and off?

Teacher Guide — Inside the Box: Switches and Signals

Sessions: 2 × 30-40 min (see grade-banded pacing) · Format: mostly unplugged — no devices required. An optional block-based color check is offered but never needed; no student logins, no student data collected.

At a glance

• Big idea: Everything a computer does is built from tiny on/off switches. Two choices — 1 (on) and 0 (off), called binary — are enough to store any letter, number, or color. A computer is a system: it takes data in, a processor works on it, and it sends data out — and computers pass data to each other, too.
• Essential question: How can a computer build everything it does out of just two choices — on and off?
• You do not need to be a computer scientist to teach this. Every move is scripted below; every material is a common classroom item or a printable in this unit's Printable Materials.

Learning targets (kid language)

1. I can show how a row of on/off switches (1s and 0s) stores a piece of information.
2. I can name the parts of a computer system — input, processor, output — and trace a signal through them.
3. I can pick the right kind of code for the data: ASCII for letters, RGB for colors, plain binary for numbers.
4. I can explain that computers send and receive data — to a screen, a speaker, and to other computers.

Standards (what each target proves)

Target	VA CS SOL (2024)	Plain gloss
Trace input → processor → output	3.CSY.1	model how devices in a computing system work (processor, inputs, outputs, sensors)
Choose the data type / code for the job	4.DA.1	identify the appropriate type of data to answer a question (incl. binary/ASCII/RGB)
Computers collect and exchange data	5.CSY.1	explain how computing systems are used to collect and exchange data

VDOE AI Guidance: Empower Student Success.

Materials (all common, all reusable)

• The switch strips (5-bit and 7-bit), ASCII letter key, RGB color cards, and the system board (input → processor → output) — print/cut from this unit's Printable Materials (one set per pair or small group).
• Two-color counters, coins, or double-sided cards (one side marked ●/ON, one side ○/OFF) so a child can flip a "switch."
• Chart paper for the class "Binary Wall" (the alphabet your class encodes together).
• Optional (never required): one classroom device to show a color picker's R/G/B sliders.

Pacing by grade

	Active time	Adjust
3	2 × 25-30 min	Use 5-bit strips; encode a 1-letter initial; trace input→output with the system board
4	2 × 30-35 min	Use 7-bit ASCII; encode a short word; add "which code fits this data?" (4.DA.1)
5	2 × 35-40 min	Encode a word and an RGB color; add the "send it to another computer" beat (5.CSY.1)

If you only have 15 minutes: do the Hook (human switches) + a 5-bit group encode of one letter using the switch strips and the a-z code key. That alone meets the core of 3.CSY.1.

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Lesson plan

1. Hook — "We are the switches" (5 min)

Pick five volunteers to stand in a row. Each is one switch: hands up = ON = 1, hands down = OFF = 0. Call a pattern — "on, off, off, off, on" — and have them set their hands. Read the row aloud: "1, 0, 0, 0, 1." Then say: "That single row of five choices is how a computer remembers one tiny thing. A real computer has billions of these, far too small to see." Flip one student's hands and show the pattern is now different — one switch changed the whole message.

Why this works: it makes "binary" a body idea before it's a word — each child is a bit. It also previews the 6-8 jump to transistors and logic gates: the human switch becomes a silicon switch.

2. I do — from switches to a letter (6-8 min)

Hold up a switch strip and the ASCII letter key. Think aloud: "Two choices per switch isn't much. But line up seven switches and you get enough patterns for every letter. People agreed on a plan called ASCII. Look — capital A is 1000001." Set your switch strip to 1000001 (flip cards/counters) and find A on the key. Then make the data-type point: "If I wanted to store a color instead of a letter, I'd use a different code — RGB, three numbers for red, green, blue. The kind of data tells me which code to reach for." (3.CSY.1 + the seed of 4.DA.1.)

Keep it to one letter. The goal is "on/off patterns stand for things," not memorizing ASCII. Grade 3 may stay at 5 bits (enough for a small a-z code on the printable).

3. We do — encode a letter together (7-9 min)

Put the system board (input → processor → output) where all can see. Narrate the system: "The input is the letter I want — say, the first letter of our school. My brain is the processor that looks up the code. The output is the row of 1s and 0s." As a class, pick one letter, find it on the ASCII key, and set a strip together. Model the sentence: "The letter ____ is the input; its code is ____; that's the output." (3.CSY.1.)

4. You do — pairs encode and exchange (8-12 min)

Pairs encode their own initial (Gr 3: a-z 5-bit code; Gr 4-5: 7-bit ASCII) onto a switch strip and lay it on the output square of their board. Grade 5 adds the exchange beat: Partner A builds a strip and passes it to Partner B, who decodes it back to a letter using the key — "You just sent data from one computer to another. The wire is the hand-off; the code is what makes the message readable on the other side." (5.CSY.1.) Circulate and ask one child per pair: "Which code did you use, and why that one for this data?" (4.DA.1.)

5. Closure — the Binary Wall (4 min)

Each pair adds their encoded initial (letter + its 1/0 strip) to the class Binary Wall. Close with a quick whip-around: "Name one thing — a letter, a number, or a color — and tell me which code a computer would use to store it." That single sentence is the 4.DA.1 check.

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Common misconceptions

• "Binary is a different number for every letter — I have to memorize it." → No. It's a lookup: the ASCII key does the remembering. Students choose patterns, not recall them.
• "The 1s and 0s are the actual letters inside." → They're a code people agreed on. A different agreement (a different code) would store the same letter with a different pattern.
• "On/off is too simple to hold a picture." → A photo is just millions of tiny color dots, and each color is three numbers (RGB) made of switches. Simple parts, huge totals.
• "The processor is the whole computer." → The processor is the middle step. Without an input and an output, a computer has nothing to work on and nowhere to send it.

Background (teacher notes)

"On/off" is the physical truth under all of computing: a transistor is a switch that's either conducting (1) or not (0). Binary is base-2 counting; ASCII is one agreed mapping from 7-bit patterns to characters; RGB stores a color as three intensity numbers. You are not teaching base-2 arithmetic or the full ASCII table — only the powerful idea that two states, combined and coded, represent anything. The input → processor → output frame is the computing-system spine (3.CSY.1) and the data-exchange idea (5.CSY.1) is the same loop scaled to two machines over a wire. This is the literal foundation the rest of the band builds on: algorithms (Unit 2) are instructions the processor runs; data and ML (Units 3-4) are what those signals come to mean.

Safety & privacy note

This unit is unplugged by default and collects no student data. If you use the optional color picker, show it on the teacher's device only — students don't log in or enter anything. Keep encoded examples to initials or school-safe words; don't ask students to encode home addresses, phone numbers, or other personal information.

Spiral — where this goes next

• Unit 2: the processor follows step-by-step instructions (algorithms, loops) on these signals.
• Unit 3: those signals become data the computer finds patterns in to make guesses.
• 3-5 → 6-8: the human switch becomes a transistor and logic gate; ASCII/RGB become representation. → 9-12: representation becomes numbers, vectors, and embeddings — meaning turned into math.

Printable Materials — Inside the Box: Switches and Signals

How to use: Print one set per pair or small group on cardstock if you can, cut along the lines, and reuse all year. Pair each printable with two-color counters or coins so a child can flip each switch ON (●/1) or OFF (○/0). Nothing here needs a device. (Grade 3: use the 5-bit strip + the short a-z key. Grades 4-5: use the 7-bit strip

• the ASCII key. Grade 5: add the RGB color cards.)

Material A — Switch strips (cut apart; one per child)

Place a counter on each box: ●/1 = ON, ○/0 = OFF (write the 1 or 0 in the box, or flip a two-color counter). Read the row left to right.

5-bit strip (Grade 3):

☐	☐	☐	☐	☐
switch 1	switch 2	switch 3	switch 4	switch 5

7-bit strip (Grades 4-5 — full ASCII):

☐	☐	☐	☐	☐	☐	☐
1	2	3	4	5	6	7

Material B — Short a-z code key (Grade 3, 5-bit)

Each letter is just its place in the alphabet, written in 5 switches.

Letter	Switches (1/0)		Letter	Switches (1/0)
A	00001		F	00110
B	00010		G	00111
C	00011		H	01000
D	00100		I	01001
E	00101		J	01010

(Full a-z key continues on the printable sheet, A=00001 … Z=11010.)

Material C — ASCII letter key (Grades 4-5, 7-bit, capitals)

Letter	ASCII (1/0)		Letter	ASCII (1/0)
A	1000001		N	1001110
B	1000010		O	1001111
C	1000011		P	1010000
D	1000100		R	1010010
E	1000101		S	1010011
H	1001000		T	1010100
I	1001001		Y	1011001

(Full A-Z key continues on the printable sheet; capitals run A=1000001 … Z=1011010.)

Material D — RGB color cards (Grade 5, "which code fits the data?")

A color is not a letter, so it uses a different code: three numbers for Red, Green, Blue (0 = none, high = lots).

Color	R	G	B
🟥 Red	255	0	0
🟩 Green	0	255	0
🟦 Blue	0	0	255
⬜ White	255	255	255
⬛ Black	0	0	0
🟨 Yellow	255	255	0

Material E — System board (one per pair; input → processor → output)

Lay the switch strip on the OUTPUT square. Move a counter along the arrows as you talk through the system.

📥 INPUT	➡️	⚙️ PROCESSOR	➡️	📤 OUTPUT
the letter / color you want		looks up the code		the row of 1s and 0s

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Teacher answer key (do not print for students)

• 5-bit a-z (Grade 3): A=00001, B=00010, C=00011 … each letter is its alphabet position in base-2 (count the place: A is 1st, so 00001). Z = 26 = 11010.
• 7-bit ASCII capitals (Grades 4-5): A=1000001, B=1000010, C=1000011 … each next letter adds 1; H=1001000, I=1001001, O=1001111, S=1010011, T=1010100, Y=1011001, Z=1011010.
• Sample encodes: HI → 1001000 1001001. CAT → 1000011 1000001 1010100.
• RGB (Grade 5): Red = (255,0,0); Yellow = Red + Green = (255,255,0); White = all three full; Black = all three zero. The point isn't the exact numbers — it's that a color needs a color code, while a letter needs a letter code (4.DA.1).
• A child has it if they can (1) set a strip to match a letter on the key (3.CSY.1) and (2) say which code they'd use for a letter vs. a color and why (4.DA.1). Accept a decoded strip read back to a partner as evidence of data exchange (5.CSY.1).

Vocabulary — Inside the Box: Switches and Signals

Six grade-sized words. Post them on the word wall; they spiral forward — algorithm (Unit 2), data and pattern (Unit 3), and fair data (Unit 4) all run on the signals you name here.

Word	Kid-friendly meaning	Say it in a sentence
switch	A part with only two settings: on or off.	"A computer has billions of tiny switches."
binary	A message made of only 1s and 0s (on and off).	"The letter A in binary is 1000001."
input	The data that goes into a computer.	"Pressing a key is an input."
processor	The part in the middle that works on the data.	"The processor looks up the code."
output	The data the computer sends out.	"Letters on the screen are the output."
code (ASCII / RGB)	An agreed plan that says which 1s and 0s mean what.	"We used the ASCII code to spell a word."

Anchor pair / section

Keep returning to the spine of the whole unit: in → process → out, all built from on/off (1/0). Every later band adds depth to this base — the switches get smaller and faster, but the idea never changes: two choices, combined and coded, can represent anything.

Spiral note (for teachers)

Switch is deliberately concrete here (a light switch you can see). In 6-8 it becomes the transistor and logic gate — the real silicon switch — and binary/ASCII/RGB become representation. In 9-12, representation deepens into numbers, vectors, and embeddings (meaning turned into math). Teaching the plain words now prevents re-teaching later: the definition deepens, it never gets undone. Keep input/processor/output intact all the way up — it is the computing-system frame every unit returns to.

Differentiation & Access — Inside the Box: Switches and Signals

Designed against Universal Design for Learning: multiple means of representation, expression, and engagement. The activity is hands-on and language-light by default — a child can show mastery by flipping switches, with no reading or speaking required.

Support (emerging learners & IEP)

• Use the 5-bit strip and pre-fill all but one switch, so the child completes a single on/off choice and reads the result.
• Offer a pre-set "answer card" the child can match their strip against, then fade it.
• Pair each child with the human-switch memory from the Hook: "hands up = 1, hands down = 0" — let them use their own hands before the counters.
• Pre-teach one letter the child already cares about (their initial) so the first encode is familiar and successful.

English learners

• Display picture + word together on the word wall: a light switch for switch, ●/○ for binary, arrows for input/processor/output.
• Allow responses in the home language, then echo the English term back; cognates help (input/output are near-universal tech words).
• Use total physical response with the whole class: input = hands pull in; processor = tap the head; output = hands push out. A motor anchor for the system frame helps everyone, not only ELs.
• Give a sentence frame: "The ____ is the input; its code is ____; that's the output."

Extension (advanced learners) — classroom-anchored

• Encode a short word (not just a letter) and challenge a partner to decode it from the key — no home tech needed, just the printable.
• Ask: "Our class has 24 students. How many switches would we need to give everyone their own number?" (Explore how few switches cover many things — the power of combining.)
• Find something in our classroom that is an input, something that is an output, and name what the processor would do between them (links to 3.CSY.1).
• Decode an RGB card challenge: "Which color is (255,255,0)?" and explain why a color needs a color code, not ASCII (4.DA.1).

Access & accommodations

• Fine-motor: use large floor switches (paper plates flipped over) or magnetic ●/○ tiles on a board instead of small counters; a partner may place tiles on the child's spoken or pointed direction.
• Vision / color: never rely on color alone — use the shape + word (● and the word "ON"; ○ and the word "OFF"), high-contrast strips, and read each switch position aloud. RGB cards carry the color name in words, not just the swatch.
• Hearing: pair every spoken cue with a held-up strip or a gesture; face the child when speaking; the entire encode can be done visually with the system board and key.
• Non-speaking / AAC: accept mastery shown by switch placement alone — a child can encode a letter and trace input→output by pointing or eye-gaze, with no speech required; decoding can be shown by matching the strip to the key.
• Sensory / attention: keep each encode to one letter; offer a quiet "show me on the board" option instead of a verbal share; let restless learners be the human switches in the Hook so movement is built in.

Inside the Box: Switches and Signals — Assessment

3-5 assessment is observational and performance-based, with a short written/drawn exit ticket. Use the look-fors during the Unit 1 encode-and-exchange activity. Each look-for names the standard it gives evidence for, so the alignment is verifiable at a glance.

Learning targets

A student who has met this unit can:

1. Set a row of on/off switches (1s and 0s) to match a letter on the code key, and trace it through input → processor → output. (3.CSY.1)
2. Name the right code for the data — ASCII for a letter, RGB for a color, plain binary for a number — and say why. (4.DA.1)
3. Send an encoded strip to a partner and have them decode it, explaining that computers collect and exchange data this way. (5.CSY.1)

Observational checklist (circle one per student)

Look-for	Standard	Not yet	Developing	Got it
Sets a switch strip to match a letter on the key (1/0 placed correctly)	3.CSY.1	○	○	○
Points to input → processor → output on the system board and names each	3.CSY.1	○	○	○
Picks the right code for given data (letter→ASCII, color→RGB) and gives a reason	4.DA.1	○	○	○
Passes an encoded strip and partner decodes it back to the letter	5.CSY.1	○	○	○
Says why the code lets the message be read on the other computer	5.CSY.1	○	○	○

Performance task — "Encode, trace, and send" (6-8 min, pairs)

Give each student a switch strip, the code key, and a system board.

1. Encode (3.CSY.1): "Set your switches to the first letter of your name. Show me the input, the processor, and the output on your board."
2. Choose the code (4.DA.1): Show two slips — one says the letter B, one shows a red square. "Which code does each one need, and why?" (Expected: B → ASCII letter code; red → RGB color code, because a color isn't a letter.)
3. Send (5.CSY.1): "Pass your strip to your partner. Partner, decode it — what letter did they send? How did the code let you read it?"

• Meets: encodes one letter correctly and matches each data type to the right code and partner decodes the strip and names the code as the reason it was readable.
• Approaching: encodes with one switch off, or matches codes but the reason is "I guessed" / "it looks right."
• Reteach: flips switches at random or can't locate input/output → return to the human- switch Hook and re-encode one letter on the system board together.

Exit ticket (whole class, 2-3 min — short write/draw)

On a half-sheet, each student answers one prompt (their choice):

• Draw a row of 5 boxes. Shade the ones that are ON to spell the first letter of your name, using the key. (3.CSY.1)
• Write the data and the code it needs: "A letter uses the ____ code. A color uses the ____ code." (4.DA.1)

Evidence to keep: a photo of the class Binary Wall documents the whole class against targets 1 and 3 at once; the half-sheet exit tickets give a written record for target 2.

Family Letter — Inside the Box: Switches and Signals

Dear family,

This week your child looked inside a computer. They learned that everything a computer does is built from millions of tiny switches that are only ever on (1) or off (0) — a code called binary. They also traced how a computer works as a system: it takes data in, a processor works on it, and it sends data out — and computers pass data to each other, too.

Try this together — no device needed: play "secret switches." Draw 5 boxes on paper. Agree that a shaded box = ON and an empty box = OFF. Use this tiny code (A=1, B=2, …, each letter is its number in the alphabet written as on/off boxes) to send your child a one-letter secret, and have them send one back. Ask: "How many letters could we spell with just 5 switches?" No paper handy? Use your hands — hands up for ON, hands down for OFF — and "send" a switch pattern across the room.

One key habit: when you see a screen at home, in a store, or on the bus, ask your child, "What's the input here, and what's the output?" Naming the in-and-out makes the invisible machine visible.

Thank you for learning alongside us.

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This letter is available in other languages — just ask your child's teacher. Esta carta está disponible en otros idiomas — pregunte al maestro de su hijo/a.

Sand to Circuits: A Paper Switch Lab

The real-world fact behind the lesson: the switches inside a computer chip are made from silicon, and silicon is refined from ordinary sand. Melt sand down, purify it, and slice it into thin wafers, and you have the raw material every chip starts as — before it is etched with the billions of tiny on/off switches your class learned about.

Build a paper switch. No electricity needed — this models exactly what an electrical switch does: it either completes a path (on / 1) or breaks a path (off / 0).

What you need: one strip of paper, a paperclip, and two brass fasteners (or two more paperclips).

What to do:

1. Poke the two fasteners through the paper about two inches apart. These are your contacts.
2. Attach the paperclip loosely to one fastener so it can swing like a hinge.
3. Switch ON: swing the paperclip so it touches both fasteners — the path is complete.
4. Switch OFF: swing the paperclip away from the second fastener — the path is broken.
5. Flip your switch on and off five times. Each flip is one bit: write down the pattern as 1s and 0s (on = 1, off = 0).

Spell a letter in binary. Using the ASCII idea from class (the letter A is 1000001), flip your paper switch seven times, once per digit, and have a partner read your on/off pattern back as 1s and 0s. Can they guess which pattern you built?

Essential question: How can a computer build everything it does out of just two choices — on and off?

Talk about it: A real computer chip does this same on/off trick with wires far too small to see — and it does it billions of times a second. Ask a grown-up: what everyday object do you think started out as sand? (Hint: glass is sand, melted and cooled — and so, in a very different way, is the chip in your phone.)

Practice Set — Inside the Box: Switches and Signals

How to use: One copy per student. Parts 1–3 fit every grade 3-5 reader. Part 4 adds the 7-switch ASCII code and choosing the right code for the data (Grade 4). Part 5 adds RGB colors and sending data to another computer (Grade 5). No device needed. Answers are in the Answer Key.

Remember: a switch is ON (● = 1) or OFF (○ = 0). A computer is a system: input → processor → output.

Part 1 — On or off?

1. Rows a and b show switches. Write each row as 1s and 0s. Rows c and d show 1s and 0s. Draw ● or ○ in each box.

Row	Switch 1	Switch 2	Switch 3	Switch 4	Switch 5	Written as 1s and 0s
a	●	○	○	○	●
b	○	●	●	○	●
c						00110
d						10100

Part 2 — Use the short code key

Short code key (5 switches — each letter is its place in the alphabet):

Letter	Switches		Letter	Switches
A	00001		F	00110
B	00010		G	00111
C	00011		H	01000
D	00100		I	01001
E	00101		J	01010

2. Decode this message. Write one letter under each pattern.

00110	00001	00011	00101
___	___	___	___

The word is: ______________

3. Encode the word HEAD. Write the 5 switches for each letter.

H	E	A	D
________	________	________	________

4. The letter E is 00101. Flip switch 4 only (switches are counted from the left).

New pattern: ______________ New letter: ______

Why did flipping just one switch change the letter?

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Part 3 — Input → processor → output

5. Write input, processor, or output for each one.

What happens	Input, processor, or output?
You press a key on a keyboard.
A letter shows up on the screen.
The part in the middle works on the 1s and 0s.
You tap a picture on a tablet screen.
Music plays from a speaker.
A microphone picks up your voice.

6. Fill in the system board for this job: you press the B key, and the letter B shows up on the screen.

INPUT	→	PROCESSOR	→	OUTPUT

7. Sam says, "The processor is the whole computer." Name the two parts a computer would be missing with only a processor. What goes wrong without each one?

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Part 4 — ASCII and the right code (Grade 4)

ASCII key (7 switches, capital letters):

Letter	ASCII		Letter	ASCII
A	1000001		N	1001110
B	1000010		O	1001111
C	1000011		P	1010000
D	1000100		R	1010010
E	1000101		S	1010011
H	1001000		T	1010100
I	1001001		Y	1011001

8. Decode this ASCII message: 1011001 1000101 1010011

The word is: ______________

9. Encode the word DATA in ASCII.

D	A	T	A
__________	__________	__________	__________

10. Which code does each kind of data need? Write ASCII, RGB, or binary number.

Data	Code it needs
the letter B
a red square
the word CAT in a message
a yellow sun in a drawing
the number 7 (a game score)

Pick one row. Why does that data need that code?

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11. In the short code, A is 00001. In ASCII, A is 1000001. Jada says one of them must be wrong. Is she right? Explain.

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Part 5 — RGB colors and sending data (Grade 5)

12. A color is stored as three numbers: Red, Green, Blue light. 0 means none; 255 means the most. Fill in the blanks.

Color	R	G	B
__________	255	0	0
__________	0	0	0
__________	255	255	255
Blue	____	____	____
Yellow	____	____	____

13. Partner A builds this message and passes it to Partner B: 1001110 1001111

a. Use the ASCII key. What did Partner A send? ______________

b. What made it possible for Partner B to read the message?

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c. Suppose Partner B picks up the short code key instead of the ASCII key. What goes wrong?

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14. You type HI on a tablet, and it shows up on a friend's tablet far away. Number the steps 1–5 in order.

Order	Step
___	Your friend's screen shows the letters.
___	You press keys to type HI.
___	The 1s and 0s travel across wires and the internet.
___	Your tablet's processor turns each letter into 1s and 0s using a code.
___	Your friend's computer uses the same code to turn the 1s and 0s back into letters.

Which step is the first input? Step ____ Which step is the last output? Step ____

Challenge — How many patterns?

15. Every switch you add gives you more patterns to use.

Switches	Patterns you can make
1	2 (0, 1)
2
3
4
5

a. List all the patterns you can make with 2 switches: ______________________

b. The short code uses 5 switches for 26 letters. Why not just 4?

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c. A class has 24 students. What is the fewest switches that gives every student their own pattern? ______

In-Class Project — Postcard Network

How to use: Groups of 3-4, about 45 minutes, no devices. Each group needs the switch strips, code keys, RGB color cards, and system board from Printable Materials, plus two-color counters (or coins), pencils, and crayons or markers. Pair up the groups so every group has a partner group to send to. One Project Sheet per group. Grade 3 does Missions 1–2. Grade 4 adds Mission 3. Grade 5 adds Mission 4. A mixed room can run all of them at once.

The mission

Your group is one computer in a network. Your partner group is another computer across the room. You will send them secret postcards — a word, then a picture — using only 1s and 0s.

The network rules: the paper that travels between groups may only show 1s and 0s (or RGB numbers in Mission 4). No talking, no pointing, no drawing on the paper that travels. If the other computer can rebuild your postcard exactly, your message got through.

Group roles

Role	Job
Input	Chooses what to send and says it to the Processor.
Processor	Looks up the code on the key and sets the switch strips with counters.
Wire	Copies the 1s and 0s onto a slip of paper and carries it to the partner group. Silent!
Output	When a slip arrives from the partner group, decodes it and shows the result.

In a group of 3, the Input also acts as the Output. Switch roles after each mission.

Mission 1 — Send a secret word (everyone)

1. The Input picks a 3-letter word that uses only letters A–J. Try BAD, CAB, HID, DIG, FIG, or JAB — or find your own.
2. The Processor sets one 5-switch strip for each letter, using the short a-z code key.
3. Lay the strips on the OUTPUT square of the system board. Every group member points to the INPUT, PROCESSOR, and OUTPUT squares and says what is there right now.
4. The Wire copies the three patterns onto a slip and delivers it.
5. When a slip arrives, the Output decodes it and writes the word on the Project Sheet. Walk over and check: did the word get through?

Mission 2 — Send a picture (everyone)

A screen picture is made of tiny dots called pixels. In a black-and-white picture, each pixel is one switch: 1 = colored in, 0 = blank.

1. Draw a picture on the 5 × 5 Our picture grid. Keep it simple — a heart, an arrow, a letter. Here is a heart:

	1	2	3	4	5	Switches
Row 1	○	●	○	●	○	01010
Row 2	●	●	●	●	●	11111
Row 3	●	●	●	●	●	11111
Row 4	○	●	●	●	○	01110
Row 5	○	○	●	○	○	00100

2. The Processor turns each row into 5 switches. Your picture is now 25 switches — 5 rows of 5.
3. The Wire delivers only the five rows of 1s and 0s. No hints about what it is!
4. The partner group's Output colors in the Picture we received grid, then guesses what it shows.
5. Put the two grids side by side. Circle any pixel that doesn't match, and find which row it was in.

Mission 3 — Real ASCII and the right code (Grade 4)

1. Send a new word using the 7-switch ASCII key. Pick from HAT, SEA, TOP, PEN, STAR, or RAIN (every letter is on the key).
2. Count before you send: how many switches does your whole word need? (Each letter is 7.)
3. Build a full postcard with three parts: your ASCII word, your picture from Mission 2, and a color you want the picture to be. In the Project Sheet's Which code? table, write the code each part needs — ASCII, black-and-white pixels, or RGB — and why that kind of data needs that code.
4. Trade tables with the partner group. Do they agree with every choice?

Mission 4 — Color pixels and a noisy wire (Grade 5)

1. Color postcard. Draw a 2 × 2 picture using only colors from the RGB color cards. Each pixel is sent as three numbers (R, G, B). The Wire delivers 4 pixels × 3 numbers = 12 numbers, in order: top-left, top-right, bottom-left, bottom-right.
2. The partner group's Output looks up each set of three numbers on the RGB cards and colors the Color picture we received grid.
3. Noisy wire. Send one more ASCII word, but this time the partner group's Wire secretly flips one switch before delivering. The Output decodes it. Which letter came out wrong? (A pattern that isn't on the key counts as wrong, too.) Can your group find the flipped switch?
4. Discuss and write on the Project Sheet: How did both computers read the same message? What went wrong when one switch flipped, and why can a real network not let that happen?

Project Sheet

Word postcards

Mission	Word sent	Switches sent	Word received	Got through?
1
3
4 (noisy)

Our picture (color in the pixels, then write each row)

	1	2	3	4	5	Switches
Row 1
Row 2
Row 3
Row 4
Row 5

Picture we received (color in the pixels from the switches)

	1	2	3	4	5	Switches
Row 1
Row 2
Row 3
Row 4
Row 5

Which code? (Grade 4)

Part of the postcard	Code it needs	Why that code?
The word
The black-and-white picture
The color

Color picture we received (Grade 5)

Pixel	R	G	B	Color
top-left
top-right
bottom-left
bottom-right

Noisy wire notes (Grade 5)

The letter that came out wrong: ______ The switch that flipped: ______

Why both computers could read the message: _______________________________________________

How you'll know you did it

	Not yet	Getting there	Got it
Encode	Switches don't match the key.	Most letters match; one switch is off.	Every letter and every pixel row matches exactly.
System	Can't say which part is input, processor, or output.	Names the parts with help.	Points to input → processor → output and says what each one did.
Send and decode	The partner group can't rebuild the message.	The word or the picture gets through, but not both.	The partner group rebuilds the word and the picture exactly.
Right code (Grade 4)	Codes are missing or mixed up.	Right codes, but no reasons.	Each part has the right code and a reason tied to the kind of data.
Color + noise (Grade 5)	The color picture doesn't come through.	Colors come through; the flipped switch isn't found.	Colors match, the flipped switch is found, and the group explains why both computers need the same code.

Share-out: each group holds up the picture they sent next to the picture their partner group received, and tells the class whether every pixel got through.

Answer Key — Inside the Box: Switches and Signals

How to use: Answers for the Practice Set, question by question. Where more than one answer works, the key says what to accept. The codes are lookups, not memory work: a student who finds the right row on the key and copies the pattern carefully has done it right.

Part 1 — On or off? (3.CSY.1)

1.

Row	Switch 1	Switch 2	Switch 3	Switch 4	Switch 5	Written as 1s and 0s
a	●	○	○	○	●	10001
b	○	●	●	○	●	01101
c	○	○	●	●	○	00110
d	●	○	●	○	○	10100

Accept shaded and unshaded boxes, or "ON" and "OFF" written in, for rows c and d. Watch for students who read right to left — every row is read left to right.

Part 2 — Use the short code key (3.CSY.1)

2. 00110 = F · 00001 = A · 00011 = C · 00101 = E. The word is FACE.

3. H = 01000 · E = 00101 · A = 00001 · D = 00100.

4. New pattern: 00111. New letter: G. Why: the letter comes from the whole pattern, so changing even one switch makes a different pattern, and a different pattern stands for a different letter. Common mistake: flipping switch 4 counted from the right (which gives 01101). Switches are counted from the left.

Part 3 — Input → processor → output (3.CSY.1, 4.CSY.1)

5.

What happens	Answer
You press a key on a keyboard.	input
A letter shows up on the screen.	output
The part in the middle works on the 1s and 0s.	processor
You tap a picture on a tablet screen.	input
Music plays from a speaker.	output
A microphone picks up your voice.	input

On the tablet row, a student may point out that a tablet screen also shows things (output). That is true. The tap is still the input, so accept "input", and give credit to a student who explains that the screen does both jobs.

6.

INPUT	→	PROCESSOR	→	OUTPUT
pressing the B key		works on the 1s and 0s / looks up the code for B		the letter B shows on the screen

Also accept the ASCII pattern 1000010 (or the short code 00010) written in the processor box. The key idea is the order: something goes in, the processor works on it, something comes out.

7. A computer with only a processor is missing the input and the output. Without an input, it has nothing to work on. Without an output, it has nowhere to send the result, so nobody sees or hears anything.

Part 4 — ASCII and the right code (3.CSY.1, 4.DA.1)

8. 1011001 = Y · 1000101 = E · 1010011 = S. The word is YES.

9. D = 1000100 · A = 1000001 · T = 1010100 · A = 1000001. Common mistake: mixing up D (1000100) and T (1010100). They differ only in switch 3.

10.

Data	Code it needs
the letter B	ASCII
a red square	RGB
the word CAT in a message	ASCII
a yellow sun in a drawing	RGB
the number 7 (a game score)	binary number

Sample reasons: A color is not a letter, so it needs a color code: RGB. · CAT is made of letters, so it needs a letter code: ASCII. · A score is a number, so the computer stores it as a plain binary number. Accept any reason that matches the kind of data to the code. "It looks right" or "I guessed" is not yet a reason.

11. No, Jada is not right. Both patterns are correct. Each code is a plan people agreed on, and different plans can use different patterns for the same letter. What matters is that the sender and the reader use the same code.

Part 5 — RGB colors and sending data (4.DA.1, 5.CSY.1, 4.CSY.1)

12.

Color	R	G	B
Red	255	0	0
Black	0	0	0
White	255	255	255
Blue	0	0	255
Yellow	255	255	0

Yellow is the tricky row: it is red and green light together, with no blue. Black is no light at all. White is all three at the most.

13. a. 1001110 = N · 1001111 = O. Partner A sent NO. b. Both partners used the same code (ASCII). The code is what turns the 1s and 0s back into a message on the other side. c. The patterns have 7 switches, but the short code key only has 5-switch patterns, so nothing matches. Partner B can't read the message, or reads the wrong letters. Two computers exchanging data have to use the same code.

14. Order, top to bottom: 5 · 1 · 3 · 2 · 4. In order: press keys to type HI (1) → your tablet's processor turns the letters into 1s and 0s (2) → the 1s and 0s travel across wires and the internet (3) → your friend's computer uses the same code to turn them back into letters (4) → your friend's screen shows the letters (5). First input: step 1. Last output: step 5. Accept a student who notes that the traveling 1s and 0s are an output of your tablet and an input to your friend's. That shows real understanding of two computers exchanging data.

Challenge — How many patterns? (3.CSY.1)

15.

Switches	Patterns you can make
1	2 (0, 1)
2	4
3	8
4	16
5	32

Each new switch doubles the number of patterns. a. 00, 01, 10, 11 (any order). b. 4 switches only make 16 patterns, and 16 is not enough for 26 letters. 5 switches make 32 patterns, which is enough. c. 5 switches. Four switches make only 16 patterns, fewer than 24 students. Five switches make 32 patterns, enough for everyone.