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Morse telegraphs (1838 AD) 

In the United States, the telegraph was developed by Samuel Morse

and Alfred Vail. Samuel F. B. Morse independently developed an

electrical telegraph in 1836, an alternative design that was capable of

transmitting over long distances using poor quality wire. His assistant,

Alfred Vail developed the Morse code signaling alphabet with Morse.

This was a practical electrical telegraph system, and subsequently

electrical telegraph came to refer to a signaling telegram - a system

where an operator makes and breaks an electrical contact with a

telegraph key, which results in an audible signal at the other end

produced by a telegraph sounder, which is interpreted and transcribed

by a human.

 

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Telephone (1876)

The telephone , often colloquially referred to as a phone, is a

telecommunications device that transmits and receives sound, most

commonly the human voice. Telephones are a point-to-pointcommunication system whose most basic function is to allow two

people separated by large distances to talk to each other. It is one of

the most common appliances in the developed world, and has long

been considered indispensable to businesses, households and

governments.

A landline telephone is connected by a pair of wires to the telephone network,

while a mobile phone or cell phone is portable and communicates with the

telephone network by radio. A cordless telephone has a portable handset which

communicates by radio with a base station connected by wire to the telephone

network, and can only be used within a limited range of the base station.

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Radio (1896)

Radio is the transmission of signals by modulation of  electromagnetic

waves with frequencies below those of  visible light. Radio became

more useful after the invention of  electronic devices such as thevacuum tube and later the transistor, which made it possible to amplify

weak signals. Today radio systems are used for applications from

walkie-talkie children's toys to the control of  space vehicles, as well as

for broadcasting, and many other applications.

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Television (1927)

Television (TV) is a telecommunication medium for transmitting and

receiving moving images that can be monochromatic (shades of grey)

or multicolored. Images are usually accompanied by sound. 

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