Chelsea Henderson, email@example.com
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).
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.
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
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.
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.
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!