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

We talked about the use of Morse code by flashlight, because the flashlight can provide binary code, only light and extinguish, there is no third state. So for the flashlight, we can do further research.
The flashlight consists of a light bulb, a wire, a battery, a switch, a metal sheet, and a plastic housing containing a battery. Then we'll analyze them all.
The current in the circuit is like the flow of water and water, but the properties of electricity cannot be described by other models. So we have 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 electricity is introduced by "Amber". Because rubbing through the amber and the fur will make the fur get electrons. But in the end it tends to be a balanced state.
Strength: The power of a proton in the nucleus to be bound together.
Then we start to introduce electricity from the lightning, and why is there lightning? Because the lower layers of the cloud get electrons and the upper layer of the cloud loses electrons, a bolt of lightning is used to balance this imbalance. Lightning is the rapid movement of electrons from one end to the other.
And the flashlight's current is because of the chemical reaction in the battery, so that the cathode quickly get the electrons, the cathode quickly lose the electrons, in order to maintain the balance, the cathode needs to transfer electrons to the positive, the formation of the current.
Without an absolute insulator, any substance can conduct electricity by adding enough voltage.

Understanding the principle of the flashlight, we can use the characteristics of the flashlight to do something, imagine that the Morse code through the flashlight is the premise must be face-to-face, and distance can not be too long. If I need to communicate with my neighbors, which means I need to communicate with people who are not next to each other, we need to find another way to do this, using the principle of a flashlight.
Like I need to send messages to my neighbors, then put the battery and switch on my side, the light bulb on the neighbor side, through the wire to train them into a loop, so that at my end with the switch to the closure and communication, the same, neighbors can also use a reverse way to make neighbors send messages to me.
Improvement 1:
We used 4 wires before, and if you use a public connection, you can use only 3 wires.
Improvement 2:
Because the earth is a very large conductor, because the section is very large, so the impedance is very small, so we can use the natural conditions, but we need to use a very large battery, rather than the average 1.5-volt battery, so that only need 2 wire.
In real life, wire is based on the AWG that the United States line by standard measurement, the smaller the AWG, the more coarse the wire, the smaller the resistance.
There are two ways to solve a long distance:
(1) Increase the section to reduce the resistance.
(2) High voltage.

Morse had mentioned earlier that in fact his exploits were not only encoded, 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 have a group of people standing on the peak waving flags, as intermediate transmission. But it's still inconvenient. The Telegraph was invented to solve the problem.

The principle of the Telegraph is to make some changes at the other end by doing some action at one end. The example of the turn communication we talked about earlier is the example of the Telegraph, but unfortunately, when the telegraph was invented, the light bulb was not invented, so Morse was replaced by electromagnetism. The structure of our telegraph is made up of a maintains, a battery, a generator. By moving the maintains, the generator emits a tick-and-clatter sound for binary encoding. This instant communication is resolved. But if it's long enough, the wire will cause the current to be so small that it won't be able to achieve the effect. So we put the repeater every 200 miles, the repeater is made up of a generator and a maintains, because the repeater position is near, so the generator can emit sound and pass to maintains, so it can play a magnifying role.