In the early days of the telegraph, people soon found that it suffered from a problem caused telegraph distortion that limited the speed at which signals could be transmitted. As the length of cables increased it soon became apparent that signals suffered distortion during transmission. A sharply rising pulse at the transmitter end of a cable was received at the far end as a highly distorted pulse with long rise and fall times. The 1866 transatlantic telegraph cable could transmit only 8 words per minute. The diagram illustrates the effect of this so-called telegraph distortion. 

Telegraph distortion

The effects of telegraph distortion worried the sponsors of the transatlantic cable project and the problem was eventually handed to William Thomson at the University of Glasgow. In overcoming this problem, the theories of electronics were developed that describe how signals behave in all circuits. Without these theories, it would be impossible to construct today’s high-speed computers.

 Thomson, who later became Lord Kelvin, was one of the 19th Century's greatest scientists. He published more than 600 papers, developed the second law of thermodynamics, and created the absolute temperature scale. The unit of temperature with absolute zero at 0° is called the Kelvin in his honor. Thomson also worked on the “dynamical theory of heat” and carried out fundamental work in hydrodynamics. His mathematical analysis of electricity and magnetism provided the basic ideas for the electromagnetic theory of light. 

In 1855 Thomson presented a paper to the Royal Society analyzing the effect of pulse distortion that became the cornerstone of what is now called transmission line theory. The cause of the problems investigated by Thomson lies in the physical properties of electrical conductors and insulators. At its simplest, the effect of a transmission line is to reduce the speed at which signals can change state. Thomson's theories enabled engineers to construct data links with much lower levels of distortion.

Thomson contributed to computing by providing the theory that describes the flow of pulses in circuits, which enabled the development of the telegraph and telephone networks. In turn, the switching circuits used to route messages through networks were used to construct the first electromechanical computers.