It is a little known fact that Nikola Tesla is the acknowledged inventor of the electronic AND logic gate circuit, a critical element of every digital computer. In New York City in the mid 1890s Tesla's work was focused on the development of an independent remotely-controlled device, the "telautomaton." These efforts led him to devise methods for selectively activating any of several wireless receivers (he called this "the art of individualization") that involved multiple transmissions on separate frequencies. At the receiving end, each one of the individual frequency components had to be tuned in, in order for the receiver to responding the AND logic function. In June of 1899 Tesla established an experimental station at Colorado Springs where he continued his studies. Realizing the importance of his ground-breaking techniques he gave instructions upon his return to New York that patent applications be prepared and submitted. During the review period, the Patent Office told Tesla that another patent application for a similar concept had been received from Reginald Fessenden, and in 1902 a U.S. Patent Interference investigation was conducted concerning Tesla's wireless communications system. In the end, Tesla's claims were supported and he was granted protection under the "System of Signaling" and "Method of Signaling" patents, both describing the AND-gate circuit. After World War II when computer hardware manufacturers attempted to patent digital logic gates in general, the U.S. Patent Office asserted Tesla's turn-of-the-century priority in their electrical implementation. These same patents also describe essential features of the spread-spectrum wireless communications techniques known as frequency-hopping and frequency-division multiplexing.
