The first telegraph was developed in the 1830?s using an Electro-magnet and a crude switch. When the switch was pushed dc voltage from a battery would create a circuit and give the magnet power. This magnet would pull a strip of iron toward it and make a clicking sound. This was not very useful, though, because there was no way to send a message on it, and it did not transmit over a long enough distance to matter.
The first telegraph that could send a message over a distance was invented by Joseph henry. He invented a telegraph that used relays to transmit a message. These relays, which are a type of switch that turns on from an electric current, would replace the original current with current from another battery, so that a stronger signal could be received at a longer range. The only problems with this one were, the operator would have to touch the wire together every time he wanted to send a message. The second was that there was still no code to use.
The first practical telegraph was created by Samuel Morse. A device called a key operated it. The key was a device that had an arm with a contact on the bottom suspended slightly above another contact. When the button was pushed, an electric current went through the wire. It used Joseph Henry?s idea of the relays, but when the current reached the destination, it used an Electro magnet to make a pencil contact a moving strip of paper.
Morse also developed a code for use with the telegraph. This code was based on the idea that letters could be represented by a series of dots and dashes. The operator could then deliver the message within a few hours, instead of a few days.
Samuel Morse was granted $30,000 dollars to create a link between Washington D.C. and Baltimore. The message was received, and the telegraph became a popular mode of communication in the United States.