The History of Communication Technology

Telephone

 
     
 
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By Chelsea Henderson, clh303@psu.edu

Communication has certainly changed a lot over the past 150 years. When our founding fathers first came to America, the only form of communication they had with one another was through letters, which could take days or even weeks to reach its destination. Sending letters to England could take months. But even before that Native Americans actually used smoke signals to communicate with one another. Native Americans are not the only group of people who have used smoke signals to communicate. The Chinese have also used smoke signals as well as the Boy Scouts of America. This form of communication is used by creating puffs of smoke using a fire and a blanket. The smoke signals must be used in an area where they will be visible to the receiver and is usually transmitted on top of a hill or mountain (http://www.indians.org/articles/smoke-signals.html).

It was evident that something had to be developed to make communicating with one another easier and faster. That’s where the telephone comes in. It could actually be considered the greatest invention of the nineteenth century. It not only made communicating with others who were miles away much quicker, it also spawned the growth of many businesses since it made communication much easier.


Surprisingly, there were two people in the running to patent the telephone, not just one person as the majority of people believe. In the 1870s, two relatively unheard of inventors of this time, Alexander Graham Bell and the less known Elisha Gary, both independently designed devices that could transmit speech electrically. This would later be known as the telephone, of course. Both men rushed their respective designs to the patent office within hours of each other, but Bell patented his telephone first. Elisha Gray and Alexander Graham Bell entered into a famous legal battle over the invention of the telephone, which as most people know, Bell won.


 

Some of the first telephones



The telephone was actually discovered by Bell accidentally in his attempts to improve the telegraph. The telegraph was a highly successful system with its dot-and-dash Morse code, but it was basically limited to receiving and sending one message at a time. Bell's extensive knowledge of the nature of sound and his understanding of music enabled him to conjecture the possibility of transmitting multiple messages over the same wire at the same time. Although the idea of a multiple telegraph had been in existence for some time, Bell offered his own harmonic approach as a possible practical solution. His "harmonic telegraph" was based on the principle that several notes could be sent simultaneously along the same wire if the notes or signals differed in pitch (http://inventors.about.com/od/bstartinventors/a/telephone.htm).


The definition of the telephone is, “An instrument which converts sound, specifically the human voice, to electrical impulses of various frequencies and then back to a tone that sounds like the original voice (http://www.ideafinder.com/history/inventions/telephone.htm).”


Cellular phones are one of the fastest growing and most demanding telecommunications applications. Today, it represents a continuously increasing percentage of all new telephone subscriptions around the world. Currently there are more than 45 million cellular subscribers worldwide, and nearly 50 percent of those subscribers are located in the United States. It is predicted that cellular systems using a digital technology will become the universal method of telecommunications. By the year 2005, forecasters predicted that there would be more than 100 million cellular subscribers worldwide (http://www.visualtron.com/gsm_topic01.htm). Cell phones are more common today than landlines. It is impossible to go out to the grocery store or to a restaurant and not see someone on a cell phone.


 

Today's modern celluar phones



Even before cell phones, however, there was something called a satellite phone. Satellite phones were very similar to cell phones in that they could be used almost anywhere, but satellite phones weren’t transmitted by towers they were transmitted by satellites orbiting the earth. Originally the Iridium satellite constellation consisted of 77 active satellites that orbited the earth from pole to pole. The name Iridium came from the element iridium which has the atomic number of 77. Today the Iridium satellite constellation consists of a system of 66 activate satellites in low earth orbit at a height of 485 miles. The Iridium satellites traveling at 17,000 miles an hour will orbit from pole to pole in 100 minutes. Unlike the Globalstar constellation the Iridium constellation communicate with each other using intersatellite links. This allows for the total planetary coverage only Iridium can offer. Each satellite had four intersatellite links two to communicate with satellites on either side and tow to communicate to other satellites for and aft in the same orbital plane.


 

Satellite phones



The LM700 satellite was first used in the Iridium system. The system used L-Band to provide the global communications. The Iridium system employs L-Band FDMA/TDMA signal at 4.8 kbps for voice and 2400 bps for data. 125 spacecraft built by Lockheed were used to place the satellites in orbit at a cost of $700M. The spacecraft is three-axis stabilized using a hydrazine propulsion system. The spacecraft has two solar panels with 1-axis articulation. Each satellite uses 48 spot beams arranged as 16 beams in three sectors for earth coverage and uses Ka-Band for cross links and ground commanding.


The original design of the Iridium satellite was of the a completely static 1960s type design with control and time-triggered messages for an entire orbit that would be uploaded each time the satellite passed the poles. When it was found this design did not offer enough bandwidth to upload each satellite quickly over the poles this design was dropped in favor of a performed dynamic control of routing and channel selection which delayed the delivery of the system by one year (http://www.globalcomsatphone.com/articles/history.html).


The telephone came a long way since it was first developed in the late 1800s. There have been many changes to this form of communication and as of now, it seems like nothing is impossible. From satellite phone to cell phones to smart phones, it seems like mobile communication has just started to take off. Don’t be surprised if within the next 20 years more people have cell phones than house phones!



Sources:

http://inventors.about.com/od/bstartinventors/a/telephone.htm

http://www.ideafinder.com/history/inventions/telephone.htm

http://www.visualtron.com/gsm_topic01.htm

http://www.globalcomsatphone.com/articles/history.html