Advances in Communication Technology

A variety of inventors developed versions of the telegraph in the early 1800s, although Samuel Morse's design was one of the most practical. The system was a simple electrical circuit consisting of a battery, a switch and an electromagnet. Pressing the switch key closed the circuit; this energized the electromagnet which produced a clicking sound from a piece of metal. Operators sent messages as a series of coded key taps; the receiving station heard the corresponding clicks produced with virtually no delay. Telegraph wires eventually connected cities across the country, carrying news, commerce and personal messages.

In the late 1800s, further experiments in electricity led inventors to develop the telephone. As with the telegraph, the telephone sends electrical signals through wires to a distant receiver; in place of staccato clicks which take training to understand, telephone wires carry the sounds of actual speech. Although telephones and telegraphs coexisted for several decades, telegraphs are now mostly museum pieces; in 2012, telephones continue to be a dominant form of personal communications.

Radio systems send voice, data and video by means of wireless signals. Not long after Bell developed the telephone, other inventors such as Nikola Tesla and Guglielmo Marconi experimented with sending signals over the air using high-frequency electronic circuits and antennas. Radio systems introduced the concept of broadcasting, in which thousands of listeners hear speech and music sent by a single transmitter. Today, the concept of radio extends from traditional broadcast stations to cell phones and wireless data networks.

Although radio waves carry signals reliably, long-distance transmissions are complicated by the ionosphere, a layer of thin, energetic gas that lies above the breathable atmosphere. Satellites solve the distance problem by receiving radio signals in space, amplifying and retransmitting them to ground-based receivers thousands of miles from the original source. In the 1960s, networks of satellites permitted the first instantaneous, world-wide communications.

The Internet had its beginnings in a military research project called the Advanced Research Projects Agency Network in the 1960s. It was an early data network which permitted computer users at different locations to share information. ARPANET was a testing ground for ideas such as dividing large amounts of data into same-size chunks called packets. In addition to the user's data, the packet has the network addresses of the sender and receiver. Devices called routers pass packets along from one system to another until they arrive at their destination. Users added more computers to the network, and in the early 1980s, the ARPANET became the larger Internet. Originally, researchers used the Internet for data and simple emails, but in the late 1980s, Tim Berners-Lee developed a standard format for linked pages of text, and the World Wide Web was born. Today, the Internet continues to grow and develop, both in the services it offers and the speed of the network hardware which carries data.