To telegraph from one place to another it is necessary to stretch between the two places a wire, over which the electric current may flow. Iron wire is generally used, because it is stronger and cheaper than copper wire. In the United States, wires arc usually stretched upon high poles. As the electricity would run down the poles to the earth if the wire touched them, the wire is fastened to a glass knob. Glass being a non-conductor, the electricity is thus insulated and flows freely between the places connected by the wire.

Fig. 97. - A Telegraph System.

Figure 97 shows the actual arrangements of a telegraphic system. If the operator at one end of the line desires to send a message he opens the switch connected to his key, which is always kept closed except when sending a message. He then begins to operate his key. Every time he touches his key he closes the circuit and the electricity flows through the line causing his own sounder and the one at the other end to click. Because of the great resistance to the current, the electricity by the time it reaches the end of the line is so feeble that it is necessary to place in the local circuit a battery and a second electromagnet, called a sounder. On the main line there is another electromagnet, called a relay. This has a greater resistance, due to its fine wire, than the sounder, which has a small resistance.

When the telegraph operator at one end of the line presses on the key so as to close the circuit, the magnets at the other end of the line become magnetic, the end of the lever is attracted and drawn down by the magnets, the other end is pushed up and the steel point presses against the paper and dents a line in it. This line is made so long as the key is kept pressed down in the sending office.

As soon, however, as the sending operator takes his fingers from the key, the circuit is broken. The magnets in the register at the receiving station then lose their power on the lever, the end drops down, and a blank space is left on the paper. When the operator in the sending station taps on the key so as to close the circuit only for an instant, a dot or very short line is made on the paper in the receiving station as shown on the table below. By pressing on the key a little longer time, or not at all, the operator can make dots, lines, or blank spaces on the paper in the receiving station. By putting together these lines and dots in different ways all the letters of the alphabet may be made, so that any kind of a message may be sent.

The alphabetical application of the dot-and-dash code invented by Morse was made in 1837 by Alfred Vail, though it is universally known as the Morse alphabet. This alphabet, which is used in the United States and Canada, and in a modified form all over the Continent of Europe, is made up wholly of dots and lines, the letters most used having the simplest symbols.

Morse Alphabet

Morse Numerals

Morse Punctuation, etc.

Period,

Comma,

Interrogation,

Exclamation,

Colon,

Semicolon,

&,