The Difference Engine, Point-Contact Transistor, and TAT-1: The June 2018 Hardware History Roundup

June 24, 2018 by Chantelle Dubois

Learn about three key points in EE history and how they changed the world: the invention of the Difference Engine, the introduction of the first point contact resistor, and the laying of the first transatlantic cables.

This month’s hardware history roundup highlights a few significant events in the history of hardware computing in electronics:

  • 1822: The Difference Engine, which is credited as the first calculating mechanical device, is announced.
  • 1948: The first point contact resistor is demonstrated for the first time, moving electronics from the vacuum tube to the transistor era.
  • 1955: The first transatlantic cable is laid out across the ocean floor to connect two rival superpowers.


1822: Babbage Introduces Designs for the Difference Engine

Charles Babbage was a mechanical engineer, inventor, mathematician, and philosopher who is often given credit as being one of the founding fathers and pioneers of computing. Among his most well-known inventions are the Difference Engine and Analytical Engine.

In June 14, 1822, Babbage announced the invention of the Difference Engine Royal Astronomical Society—a mechanical device that could calculate polynomial functions and populate tables of numbers using the divided differences algorithm.

Mathematical tables are often used for engineering, scientific, and navigational applications, and at the time were populated manually by humans who are prone to error during such a tedious task. The Difference Engine was meant to automate this process, remove human error, and speed up calculations. By turning a handled crank, the machine’s many mechanical parts (approximately 25,000) would work together to calculate, and print, the results. 



A year later, the British government funded the building of the first Difference Engine, providing 1700 GBP (approximately 196,532.86 GBP in 2018, or $260,975.59 USD). However, problems with the construction were encountered due to the fact that the parts needed to be much more precise than what could be manufactured with the technology at the time. 

Babbage would iterate on the design of the Difference Engine over the years but never complete a fully working one. In 1842, the government stopped funding the project and declared it a failure, although everything Babbage learned from the process was then applied to the more comprehensive Analytical Engine.

In 1991, the London Science Museum built the first fully complete Difference Engine based off of Babbage’s well-documented designs of Difference Engine #2. The project was led by museum curator, Doron Swade, and took nearly 18 years. The final product worked exactly as Babbage envisioned. A second one was built and put on display at the Computer History Museum in Mountain View, California.


1948: First Point Contact Transistor Demonstration

The transistor is to electronics as the cell is to the living organism; they are the foundational blocks to nearly all of our electrical hardware today, acting as switches and amplifiers. 

The first point-contact transistor is credited as the work of William Shockley, John Bardeen, and Walter Brattain who were all working at Bell Laboratories in 1947. The company began funding research in solid state physics starting in 1945, led by Shockley. All three men were physicists and focused their work on the pn-junction—the region between a material with an excess of electrons and a region lacking in electrons.

At the time, they were exploring alternatives to the vacuum tube, which were somewhat unreliable and required a lot of power, which Bell was hoping to eventually replace.

One of their first models of the transistor was rather bulky and large, consisting of a plastic triangle with a thin layer of gold on two edges leading to a point. At the point of the triangle, the gold layer was sliced so that it wasn’t continuous and each side was isolated. The point of the triangle was pressed into a block of germanium that had a layer containing excess electrons, held in place with a spring. 


Image courtesy of the Smithsonian Chip Collection.


What the team discovered was that if they input a low current on one side, the other side would experience a current that was greater—effectively and amplifier. The team even demonstrated the amplification of speech.

This first experiment was carried out in December 1947, and a press conference was held on June 30, 1948, in New York where the device was demonstrated. The team knew they had something that would make a significant impact on the electronics world.

Shortly after, the junction transistor would be invented by the lab, and materials would be swapped out from germanium to silicon. The transistor didn’t catch on right away, but by the 50s the significance of the component was realized and Bell began licensing out the component. With the transistor, computers quickly became smaller, faster, and more energy-efficient.


1955: The Telephone Transatlantic Cable Begins Construction

The history of electronic transatlantic communications dates as far back as the mid-1800s when the first telegraph cable was laid out across the ocean floor, connecting the North American and European continents.

A successful telegraph cable took several attempts due to various challenges. In September 1958, the engineers struggled to provide enough voltage to successfully transmit messages as boosting the voltage from 600V to 2000V would damage the cable, making it inoperable. They also struggled with issues with speed (a single character took more than two minutes to send), as well as the ability to ensure that the cable could withstand its environment.

Despite these challenges, submarine cables would eventually connect the world, providing near-instant communication via telegraph, transforming industries globally.

The technology for telephone and the eventual transatlantic telephone cable wouldn’t come to fruition until the 1940s. Among those technologies would be the coaxial cable, which was patented for the first time by Bell Labs in 1931. By 1941, it was being used in commercial telephone systems in the USA. Better vacuum tube technology would also help with repeaters, a device that re-broadcasts a signal to help maintain signal strength over long distances, and the advent of polyethylene which would be used in cable insulation.

With all the right technology now available, the construction of TAT-1 (Transatlantic No. 1) would begin in June 1955 in Oban, Scotland and connect to Clarenville, Newfoundland (Canada). Two cables would be laid out for bi-directional communications, each spanning over 1,500 nautical miles in the main section of the cable. Bell Labs provided 51 repeaters that were installed every 37 nautical miles.

When finally completed, the cable provided 36 channels at 4 kHz. The line was inaugurated in September 1956 with a call between important figures in the telecommunications industry in the US, Canada, and England who were calling in from New York, Ottawa, and London respectively.  


Exposed layers of the TAT-1 cable. Image courtesy of Geni [CC BY-SA 4.0]


TAT-1 would also be used to set up a hotline between Washington DC and Moscow during the height of the Cold War after the Cuban Missile Crisis. This was in an attempt to ensure that urgent communication between the USA and USSR could happen quickly, reducing the time that teleprinter messages took to receive, decode, interpret, and respond to. 



Thanks for joining us for this month's history roundup! If you'd like to see more history articles, let us know in the comments below.

  • Morvan June 26, 2018

    Very good article, but I did mention Julius Edgar Lilienfeld as a pioneer into semiconductors, having direct impact on transistor history. He is the true precursor of transistor, FET or bipolar one.

    Like. Reply
  • E
    electricalstudent1 July 02, 2018

    I must get a vist to The London Science Museum into my bucket list. I want to see this up close.
    Thanks for this great article.

    Like. Reply