(CT) Key Developments in Communications Technology Lesson

Telephone Technology 

Everyone in modern society knows the significance of the telephone. Alexander Graham Bell was among other scientists and inventors trying to create devices to transmit audio over wire. Bell’s team was successful in implementing the first patented telephone in America. His focus and ultimate success was the re-creation and transmission of multiple voice tones to ensure recognizable speech clarity at the receiver.  

Telephones were initially point to point communication systems. That means a dedicated phone to another phone. Of course, over time the phone instruments and landline communication included dialing from the phone set and switching networks that would communicate worldwide through interface of different transmission methods. These technologies grew into the field of telephony; which is the design, development, application and deployment of electronic information (voice, fax, data- ISDN, DSL) via a twisted pair of wires.  

The technology behind the telephone communications network is more sophisticated than the telephone set itself. Technologies evolved, and surely continue to evolve, to carry the services and end user features desired for the highest quality and reliability, but lowest cost. Landline telephone circuits have been critical for business, government, and life emergencies and thus needed to always be available. Unlike other communication networks, the telephone networks have been built with specifications for redundancy which ensures continued operation during foreseeable events. This includes automatic redundancy for components in equipment, automatically switchable transmission paths, and emergency power backup. Emergency switching is generally automatic because it is based upon electronic error correction sensing technologies and software. The telephone communication system is often called a “self-healing” network.  

Wireless Technology

In the decades following the teletype, engineers and scientists experimented with emerging knowledge to develop possible applications for non-wired signal flow through electromagnetic radiation or radio waves. Guglielmo Marconi was a clear leader in the field with many solid accomplishments. In 1896 he patented the wireless telegraph. He further developed long wave wireless communications and in 1900 was successful in transatlantic wireless communication. These innovations enabled communications that saved lives. Marconi wireless devices were used to signal for assistance by many who had accidents at sea, including the RMS Titanic in 1912.  

Wireless technologies have enabled long distance communications with terrestrial microwave systems, satellite systems, television broadcast, broadcast radio, shortwave radio, walkie-talkies, pagers, and modern radio and wireless applications. A key use has been dedicated mobile radio communications for workers such as first responders, utility workers, and construction.  

The advent of wireless applications caused the US Government to create the Federal Communications Commission (FCC) to oversee frequency allocations and to regulate use of the public airwaves.  

Vacuum Tube Technology 

While developing the filament light bulb, Thomas Edison made an interesting discovery. He learned that putting an additional element in the bulb that was positive to the filament would attract electrons and cause current flow to that element. He noted that it did not happen when polarities were reversed. This occurrence was further researched and documented as the Edison Effect, because Edison was first to note the pattern. This revolution was the beginning of vacuum tubes and the application of diodes for signal rectification.  

John Ambrose Fleming took Edison’s discovery and developed the two-electrode vacuum tube, called the thermionic valve. The two-electrode tube, or the diode, was used in radio receivers to convert an alternating current (AC) signal to a direct current (DC) signal. Lee De Forest developed a vacuum tube capable of amplification. His three-electrode tube was used to amplify radio signals.  

Vacuum tube technology became crucial in the development of radio broadcasting, television, microwave communications for long distance telephony, and computers.  

Semiconductors Technology 

Semiconductors are solid state electronic devices created on the principle that electrons will flow from a negative material to a positive material. During World War II, Bell Laboratories developed diodes from semiconductor material. The purpose was to replace the two-electron tube for certain military applications. From the success of the solid state diode, Bell Laboratories continued investigation and research in the attempt to create a semiconductor device to replace the three element vacuum tube, the triode. This device was invented in 1947 -1948 by Bell Laboratories scientists John Barden, Walter Brattain, and William Shockley. The device was named a transistor.  

The benefit of the transistor is small size, weight, high reliability, low cost, and reduced power requirements. Transistors were used in electronic devices for amplification, switching circuitry, and other functions. Semiconductor devices developed and include diodes, light-emitting diodes (LEDs), transistors, integrated circuits (ICs), random access memory (RAM), and microprocessors. This technology has improved and resulted in miniaturization of electronics that we see today. The speed and efficiency of data networking and computers we see today would not be possible without the development of semiconductor technologies.  

Challenge 

Take Away

The research for communications technologies and growth of the telecommunications network in the United States was largely driven by the corporation American Telephone and Telegraph (AT&T). AT&T Bell Laboratories (Bell Labs) was the engineering think tank for research and development of critical and leading edge communications technologies in America and the world. Bell Labs established standardization for performance of electrical equipment and physical plant (buildings, electrical) standards for the industry implementation of communication networks within the United States. In 1984 AT&T was considered a monopoly and was forced to break apart into separate companies due to the legal divestiture agreement with the US government. Bell Labs has been owned by several companies since divestiture.

Name five technological breakthroughs discovered and developed by Bell Labs:

• • Cellular Telephony (wireless communications)
  • Data Networking
  • Transistor
  • Laser
  • Digital Transmission and Switching
  • Communications Satellites
  • Solar Cells
  • Touch Tone Telephone
  • Unix Operating System and C Language
  • Digital Signal Processing
  • Lightwave Communications (fiber optics)
  • Transatlantic Telephone Vable
  • Radio Astronomy
  • Fax Machines,
  • Long Distance Television
  • Digital Radio

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