6.1 (The Telegraph)

-> Samuel Morse also invented the telegraph

In the early 1800’s you could communicate instantly, and you could communicate over long distances, but you couldn’t do both simultaneously.

Telegraph literally means ‘far writing’.

The principle behind an electrical telegraph is:

You do something at one end of a wire that causes something to happen at the other end of the wire.

• this time, instead of a long-distance-flashlight, (a practical lightbulb couldn’t be used as a signaling device because it wouldn’t be invented for another forty years)

• Instead, Morse relied on the phenomenon of electromagnetism

6.2 (Electromagnets)

If you:

• wrap an iron bar with a few hundred turns of wire,

• and then run a current through that wire,

• then the iron bar becomes a magnet – an electromagnet

The electromagnet is the foundation of the telegraph.

• turning the switch on and off causes it to do something at the other end.

Morse’s initial prototypes involved actually writing something on paper -> producing a hard copy, whether it’s with dots, dashes, etc

Like Valentin Haüy being stuck with the notion that books for the blind required raised letters of the alphabet, Morse was stuck in a paradigm that required paper and reading.

Anatomy of a Telegraph

1. Key

2. It’s really just a switch designed for maximum speed

3. Some wires

4. An electromagnet pulling a metal lever

5. It originally controlled a pen

6. It progressed to controlling a sounder

   1. The electromagnet (in the sounder) pulled a movable bar down to make a ‘quick’ noise. When the bar was released, it sprang back to its normal position, making a ‘clack’ sound.

      1. A fast ‘click-clack’ was a dot.

      2. A slower ‘click-clack’ was a dash

7. A battery

Anatomy of a Bidirectional Telegraph System

Apply everything you learned about bidirectional systems in the previous chapter, and apply it here.

• Just replace the lightbulb with a sounder remote telegraph station.

• And replace the switch with a key.

The invention of the telegraph marks the beginning of modern communication.

6.3 (Morse’s Triumph)

Morse’s system prevailed because it was resilient against bad line conditions.

• people were finally able to communicate

  • farther than the eye can see

  • farther than the ear can hear

  • faster than a horse can gallop

Later forms of electrical and wireless communication that abandoned binary codes include:

• telephone

• radio

• television

Even later forms of electrical and wireless communication that re-adopted binary codes include:

• computers

• compact discs

• digital videodiscs

• digital satellite tv broadcasting

• high-def TV

Overcoming Limitations of Telegraphs

Length of wire couldn’t extend indefinitely.

• resistance of long lengths of wire becomes too great

-> One solution to this problem is relays

Relay / Repeater:Like a sounder in that an incoming current is used to power an electromagnet that pulls down a metal lever. The lever, however, is used as part of a switch connecting a battery to an outgoing wire, so a weak incoming current is amplified to make a stronger outgoing current.

• the relay is remarkable because it’s a switch, but one that’s turned on and off not by humans hands, but by a current.