MoPR Mobility Minute: US Patent 2,292,387

The patent for "Secret Communications System" was granted August 11, 1942 to H.K. Markey, et al. The patent is often referred to as the “Markey-Antheil” patent for the two principal inventors.

The primary purpose of the invention was for the remote control of torpedoes from aircraft. The problem it solved was the jamming of radio frequencies that could disrupt communication between an aircraft and the dirigible craft (torpedo) it was guiding.

The technology applied to overcome radio jamming is called signal hopping. Both the remote craft and the guiding craft had radios that were synchronized using a paper roll, not dissimilar from the paper rolls used in player pianos such as the Pianola. Eight different frequencies were coded onto the paper roll, and as it turned it caused the radio signal to switch frequencies simultaneously at both ends of the transmission.

This particular patent was never built into a product, and the patent eventually expired in 1959. However, the technological concepts of the patent continued to inspire engineers. In 1957, engineers in Sylvania’s laboratories replaced the paper roll with electronics and created a more advanced means of transmitting signals over multiple radio frequencies. This time, the technology was used for secret communications, utilized on US Navy ships during the Cuban Missile Crisis as just one example.

Today, more than 1200 patents refer to this original patent, all based on “signal hopping” or, as it is better known today, “spread spectrum.” The technology originally meant for military application to send a single data stream over multiple radio frequencies is now used to break data up into small packets that can travel on multiple frequencies or even multiple networks. US Patent 2,292,387 contains the basic technology for such everyday modern mobility technologies as digital cellular phone systems like CDMA (code division multiple access) and Wi-Fi (IEEE 802.11) wireless Internet.

Who was H.K. Markey? Markey was her married name (one of her six married names). The inventor of spread spectrum technology was actress Hedy Lamarr (1913 – 2000). Co-inventor George Antheil (1900 - 1959) was a concert pianist and composer; hence the paper roll resembling one in a Pianola and eight different frequencies like the eight notes in an octave.