9-15 Communications Exercise, LED Circuits, Victrola

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6 minute Communications Exercise:

Using LED 'telegraph', create a code and communicate a message to a team in another room. The remote team needs to do what you instruct in the message.

Issues:

• Establishing a communication channel
• Agreeing on an information protocol
• How do we agree on what is being said?

Basic messages:

• "Are you there?"
• "Yes I am"
• "1,2,3"
• "Start Over"
• "Message accurately received"
• "Echo"
• "Echo Back"

Common Error Detection Techniques

Parity Check: Adds a single parity bit (even or odd) to make the total count of 1s even or odd; detects single-bit and odd-numbered errors. [1, 2, 3]
Checksum: Sums up segments of data using one's complement arithmetic and appends the result for verification; commonly used in internet protocols like TCP and UDP. [1, 2]
Cyclic Redundancy Check (CRC): Treats data blocks as binary polynomials and appends a remainder calculated via polynomial division; highly effective at catching burst errors in networks like Ethernet and USB. [1, 2]
Cryptographic Hashes / Digital Signatures: Advanced mathematical algorithms that protect against both random noise and intentional tampering. [1, 2]

Codes:

 

           ASCII Code https://en.wikipedia.org/wiki/ASCII

         MORSE Code. https://en.wikipedia.org/wiki/Morse_code 

Half duplex vs Full Duplex:

Full-duplex allows devices to send and receive data at the same time, while half-duplex allows data to move in both directions, but only one direction at a time. [1]

Most users on Reddit agree that half-duplex is like a single-lane bridge where cars must take turns, whereas full-duplex is like a two-lane bridge where traffic flows both ways simultaneously. [1]

Half-Duplex

How it works: Two-way communication happens, but devices take turns. If both try to send data at the same time, a data collision occurs. [1, 2]
Real-world example: A walkie-talkie. Only one person speaks while the other listens. [1, 2]
Pros and Cons: It has lower cost and simpler setup, but features higher latency and lower throughput. [1]
Example: I2C Protocol- all devices share same wires( serial clock and serial data). I2C is used extensively by sensors.


Why I2C is Half-Duplex
Single Data Line: I2C uses only one shared wire for data—the Serial Data Line (SDA)—alongside the clock line (SCL). [1, 2]
One Direction at a Time: Because data travels back and forth on the exact same wire, devices can send or receive data, but they cannot do both simultaneously. [1, 2]
Turn-Based Control: The controller (master) dictates the communication flow, addressing a target device and switching the line direction depending on whether it is writing data or requesting a read. [1]

Full-Duplex

How it works: Separate channels or paths let devices transmit and receive data at the same time without waiting or collisions. [1, 2]
Real-world example: A standard telephone call. Both people talk and hear each other at the same time. [1, 2]
Pros and Cons: It provides faster speeds, higher throughput, and better efficiency, making it the standard for modern Ethernet networks. [1, 2]

If you want, I can explain how a duplex mismatch affects network performance or how auto-negotiation sets these modes.

Every Hardware Protocol Explained Simply in 10 Minutes:

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LED Circuits

Ohms' Law: V= I x R

V(electrical force): measured in volts

I(Current): measured in amperes or milliamperes( 1/1000 ampere) ( I stands for intensity)

R (Resistance): Measured in ohms or kilo-ohms(1000 ohms)

Small LEDs should have their current limited to 20 mA(Milliamperes)

Calculation for current limiting resistor:

Schematic Symbols:

Discussion of Diode Circuits:

Victrola uses back-driven worm gear:

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"His Master's Voice"

Up above is what we Americans think of as the RCA logo, having grown up seeing it everywhere. But the logo first belonged to British entertainment company HMV, which is in fact named after the original painting on which the logo is based, called "His Master's Voice."

Francis Barraud was a Liverpudlian painter who had a brother named Mark. In the late 1800s, after Mark died, Francis inherited a bunch of his stuff: An early cylinder phonograph player, cylinder recordings of Mark's voice, and Mark's dog, a fox terrier named Nipper.

Francis observed that when he played the records of his dead brother's voice, the dog would run over to the phonograph and listen intently. Francis painted the scene, calling it "His Master's Voice" .

Becoming a Global Logo

The Painting: Francis painted the scene in 1898–1899, originally featuring an Edison-Bell cylinder phonograph. [1, 2]

The Change: The Gramophone Company bought the painting in 1899 on one condition: Francis had to paint over the cylinder machine and replace it with their disc-based gramophone holding a shiny brass horn. [1, 2, 3]

The Trademark: The image became an international symbol for quality after being adopted by the Victor Talking Machine Company in the United States, and later by RCA. [1, 2]