A) Railroad companies in the beginning of the 19th century, required means for long distance signaling and communication between stations for safety and keeping the train schedule. This necessity was a motivation for Cooke and Wheatstone, the inventors of the Galvanometer or Needles Telegraph in the beginning of the 19th century.

 

 

 

 

 

 

 

 

B) Realizing that signals and messages can be transmitted over electric wires, caused a necessity  for a single wire telegraph system, instead of the multiple wire needles Telegraph. The inventor Samuel Morse  with his team, responded to this necessity with the Electromagnetic Telegraph that operated with a single wire line.

 

 

 

 

 

 

 

 

C) Electromagnetic Telegraph required skilled Morse Code Operators at every station. There was a necessity for a telegraph system that can be operated by less skilled operators. It led the inventors House, Hughes and Phelps, to develop the Character Printing Telegraph, which during the 20th century became the Teleprinter and later on the TELEX.

 

 

 

 

 

 

 

D) The tremendous success of the Electric Telegraph from the mid 19th century, raised the idea of sending speech voice over the telegraph wire lines. This necessity was the drive for the inventors Elisha Gray and Alexander Bell to develop in 1876 the Liquid Transmitter. It enabled to convert acoustical sound waves to electrical signals. This was the first step towards the development of a complete Telephone Set.

 

 

 

 

 

 

 

E) At the beginning of the Telephone History, Magneto and Common Battery Telephones were in use. These telephones required the intervention of  operators at the Central Office Switchboard, to connect between subscribers. In 1889, Almon Strowger had a problem with a switchboard operator, which did not connect telephone calls to his business. There was a necessity to find a way to enable the subscriber to route a call to a second party, without the switchboard operator. Strowger was obliged to becaome an inventor that developed the Rotary Dial Telephone and the Strowger Selector Unit at the Central Office.

 

 

 

 

 

 

 

 

F) The Wire Telegraph and Telephone networks caused a great revolution in human communication. In many cases, remote and far areas were not connected to these networks, due to the extreme costs of routing the wire lines along difficult terrains. No means of communication existed with ships at distances longer than the line of sight. There was a necessity for sending telegraph signals to long distance without electric wire lines. Marconi The inventor developed the early apparatus  for sending electromagnetic waves and to detect them at long distances.  The resuls of his efforts were the practical Wireless Telegraph around 1900.

 

 

 

 

 

 

 

 

 

G) The main problem of the Wireless Telegraph was the DETECTOR quality at the receiving point. The most popular detector at the beginning of the 20th century was the Crystal Detector, but it was not so stable and not sensitive enough to detect far distance low level signals. There was a necessity for a reliable and sensitive Detector. John Ambrose Flaming invented the Vacuum Tube Detector (Diode), based on the Edison Effect. This was the first step on the path that enabled Lee de Forest to develop the Audion. It was further developed by Armstrong and became the practical amplifying vacuum tube Triode. The Triode started the Vacuum Tubes Era, which made the 20th century a turning point in the technological history of mankind.

 

 

 

 

 

 

 

H)  Another breakthrough was in 1947 when the inventors William Shockley, John Bardeen and Walter Brattain, discovered the Trans-Resistance Effect in semiconductor materials. This led to the development of the Transistor at Bell Labs. The Transistors replaced the Vacuum Tubes and became the Building

Blocks of every electronic circuit from the 1960’s until these days.