Telecommunication


1. Introduction

Computer and telephone networks inflict a gigantic impact on today\'s
society. From letting you call John in Calgary to letting you make a withdraw
at your friendly ATM machine they control the flow of information. But today\'s
complicated and expensive networks did not start out big and complicated but
rather as a wire and two terminals back in 1844. From these simple networks to
the communication giants of today we will look at the evolution of the network
and the basis on which it functions.

2. The Beginnings

2.1. Dot Dot Dot Dash Dash Dash Dot Dot Dot

The network is defined as a system of lines or structures that cross.
In telecommunications this is a connection of peripherals together so that they
can exchange information. The first such exchange of information was on May 24,
1844 when Samuel Morse sent the famous message "What hath God wrought" from the
US Capitol in Washington D.C. across a 37 mile wire to Baltimore using the
telegraph. The telegraph is basically an electromagnet connected to a battery
via a switch. When the switch is down the current flows from the battery
through the key, down the wire, and into the sounder at the other end of the
line. By itself the telegraph could express only two states, on or off. This
limitation was eliminated by the fact that it was the duration of the connection
that determined the dot and dash from each other being short and long
respectively. From these combinations of dots and dashes the Morse code was
formed. The code included all the letters of the English alphabet, all the
numbers and several punctuation marks. A variation to the telegraph was a
receiving module that Morse had invented. The module consisted of a
mechanically operated pencil and a roll of paper. When a message was received
the pencil would draw the corresponding dashes and dots on the paper to be
deciphered later. Many inventors including Alexander Bell and Thomas Edison
sought to revolutionize the telegraph. Edison devised a deciphering machine.
This machine when receiving Morse code would print letters corresponding to the
Morse code on a roll of paper hence eliminating the need for decoding the code.

2.2. Mr. Watson, Come Here!

The first successful telephone was invented by Alexander Graham Bell.
He along with Elisha Gray fought against time to invent and patent the telephone.
They both patented their devices on the same day-February 14, 1876- but Bell
arrived a few hours ahead of gray thus getting the patent on the telephone. The
patent issued to Bell was number 174,465, and is considered the most valuable
patent ever issued. Bell quickly tried to sell his invention to Western Union
but they declined and hired Elisha Gray and Thomas Edison to invent a better
telephone. A telephone battle began between Western Union and Bell. Soon after
Bell filed suit against Western Union and won since he had possessed the basic
rights and patents to the telephone. As a settlement Western Union handed over
it\'s whole telephone network to Bell giving him a monopoly in the telephone
market. During his experiments to create a functional telephone Bell pursued
two separate designs for the telephone transmitter. The first used a membrane
attached to a metal rod. The metal rod was submerged in a cup of mild acid. As
the user spoke into the transmitter the membrane vibrated which in turn moved
the rod up and down in the acid. This motion of the rod in the acid caused
variations in the electrical resistance between the rod and the cup of acid.
One of the greatest drawbacks to this model was that the cup of acid would have
to be constantly refilled. The second of Bell\'s prototypes was the induction
telephone transmitter. It used the principle of magnetic induction to change
sound into electricity. The membrane was attached to a metal rod which was
surrounded by a coil of wire. The movement of the rod in the coil produced a
weak electric current. An advantage was that theoretically it could also be
used both as a transmitter and a receiver. But since the current produced was
so weak, it was unsuccessful as a transmitter. Most modern day telephones still
use a variation of Bell\'s design. The first practical transmitter was invented
by Thomas Edison while he was working for the Western Union. During his
experiments Edison noticed that certain carbon compounds change their electrical
resistance when subjected to varying pressure. So he sandwiched a carbon button
between a metal membrane and a metal support. The motion of the membrane
changed the pressure on the