Most people are at least vaguely familiar with the early history of modern digital computers, particularly their importance in breaking the Nazi Enigma codes during WWII. Less familiar is the computing machines that preceded them.
In response to the need for more and faster computation, researchers developed a series of analog computers that did the job but were complicated and difficult to maintain. Inspired by (and in some cases actually using) the switches used to connect telephone calls, digital computers using relays were developed that used base 2 arithmetic. As useful as they were these relay computers would end up mostly being forgotten, replaced by machines based on vacuum tubes.