2. Flashlight principle, Flashlight Principle application: Turning communication and Telegraph

We talked about the application of Morse code by flashlight, because the flashlight can provide binary code, only light and out, there is no third state. So for the flashlight, we can do further research.
The flashlight consists of a bulb, a wire, a battery, a switch, a metal sheet and a plastic housing containing a battery. Next we analyze each of them.
Current flows in circuits are like water and water pipes, but the characteristics of electricity cannot be described by other models. So we've introduced "Electronic theory." Everything is made up of atoms. Atoms are made up of neutrons, electrons, and protons.
The number of electrons in a balanced atom is the same as the number of protons. And the electricity is introduced by "Amber". Because rubbing through amber and fur causes the fur to get electrons. But eventually it tends to be a balanced state.
Strength: Protons in the nucleus are bound together.
Then we start by introducing the electric current from the lightning, why is there lightning? Because the lower clouds get electrons and the upper layers lose electrons, a bolt of lightning is used to balance this imbalance. Lightning is the rapid movement of electrons from one end to the other.
The electric current of the flashlight is due to the chemical reaction in the battery, which makes the cathode quickly get electrons, the cathode loses the electron quickly, in order to maintain the balance, the cathode needs to transfer electrons to the positive, forming the current.
There is no absolute insulator, as long as sufficient voltage is added, any substance can conduct electricity.

Understanding the principle of the flashlight, we can use the characteristics of the flashlight to do something, imagine that the torch for Morse code, the premise is to face, and distance can not be too long. If I need to communicate with a neighbor, that is, to communicate with a non-adjacent person, then we need to find a different method, which is based on the principle of flashlight.
For example, I need to send a message to the neighbor, then put the battery and switch on my side, the light bulb on the neighbor side, through the wire to practice them into a circuit, so that in my end to use the switch closure and disconnection to communicate, similarly, the neighbor can also use a reverse method to enable neighbors to send messages to me.
Improvement 1:
We used 4 wires previously, and if we took advantage of a public connection, we could use only 3 conductors.
Improvement 2:
Since the earth is a very large conductor, because of the large cross-section, so the impedance is very small, so we can take advantage of the natural conditions, but we need to use a very large battery, rather than the general 1.5-volt battery, so that only 2 wires are required.
In real life, The wire is based on the AWG, the American line by the standard measurement, the smaller the AWG, the thicker the wire, the smaller the resistance.
There are two solutions for long distances:
(1) Increase the cross section to reduce the resistance.
(2) High voltage.

Morse has mentioned earlier that his merits are not only coded, but he invented the Telegraph.

In order to complete real-time long-distance communication, we used a lot of methods, the most typical way is to let a group of people standing on the top of the mountain waving flags, as intermediate transmission. But it's still inconvenient. The Telegraph was invented to solve the problem.

The Telegraph's principle is to make some changes at the other end by doing some action at one end. The example of the turn-by-turn communication in front of us is an example of the Telegraph, but unfortunately, the invention of the Telegraph did not invent the bulb, so Morse replaced it by electromagnetism. The structure of our telegraph is made up of a locking, a battery and a generator. By moving the locking, the generator emits a beep and a sound, which is used for binary coding. This will solve the instant communication. However, if the long distance, the wire will lead to a very small current, so that the effect can not be achieved. So we place repeaters every 200 miles, the repeater is composed of a generator and a locking, because the repeater placement is near, so the generator can emit sound and pass to locking, so it can play a role in amplification.